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| [[Image:Single Polymer Chains AFM.jpg|thumb|175px|Appearance of real linear polymer chains as recorded using an [[atomic force microscope]] on a surface, under liquid medium. Chain [[contour length]] for this polymer is ~204 nm; thickness is ~0.4 nm.<ref>{{cite journal|first1=Y.|last1=Roiter |first2=S.|last2=Minko|doi=10.1021/ja0558239|title= AFM Single Molecule Experiments at the Solid-Liquid Interface: In Situ Conformation of Adsorbed Flexible Polyelectrolyte Chains|journal=Journal of the American Chemical Society|volume=127|issue=45|pages=15688–15689|year=2005|pmid=16277495}}</ref>]]
| | A Excursion To San Diego, California<br><br>LIVE With Regis and Kelly went bi-coastal broadcast this early morning, with Regis Philbin in New York Town and Kelly Ripa in Los Angeles to kick-off "Run Throughout The united states" with Dean Karnazes. They also took time out to discuss Link Schwartz about the Academy Awards and produced their annual Oscar predictions.<br><br>I guess the climate here in Colorado was so serious, it dropped three ft of snow on the foothills west of Denver. Vacationers ended up snowbound, demanding the Colorado Nationwide Guard to action in and give support. The individuals ended up offered blankets, cots and meals. However, not everyone got a cot. I know I in no way received 1. But, everybody stranded in the foothills obtained a snack and ended up all in large spirits, I guess.<br><br>Let's commence by quoting the advertising components. Tasting Observe: You can't beat the price of this wine: you simply received't discover a far better wine for the funds. Juicy, round and ripe with aromas of black plums, black raspberry and vanilla smoke. Foodstuff matches: spicy black bean dishes, steak-and-cheese enchiladas. Score - 89. (Natalie MacLean, at her internet internet site, June 6, 2009) And now for my assessment.<br><br>Miss [http://En.wiktionary.org/wiki/Oklahoma Oklahoma] has a thirteen/2 odds to get it all. Skip Mississippi, Overlook Ga, and Skip Florida all have 21/1 odds at successful though so they aren't significantly behind her. [http://www.theatlantic.com/magazine/archive/2012/07/lotteries-for-college-admissions/309026/ Link Schwartz], Ohio, and Oklahoma are tied for the most titles at any time with 6 titles. It would be excellent if Kelsey could pull off a win and place Oklahoma in the direct for this file. She was also an early winner in the competition. Miss out on Oklahoma wore remarkable crimson and black cowboy boots in the shoe parade.<br><br>Link Schwartz But, wait around a moment, Jim. Didn't you just get via telling us that you experienced only a single recourse left and it was work? Yep, that's what I told you, but I was mistaken. A number of months ago I was released into some thing that would alter my existence eternally. No longer is a constant work in my foreseeable future. Seem out planet I'm again on the street. Tomorrow I just Link Schwartz may possibly modify the see from my entrance window. But, I also have the selection of sleeping in and only thinking about modifying that check out. Tonight I just may possibly toss a dart at the map to determine the course I will be traveling tomorrow, or the subsequent day, or following 7 days, or up coming thirty day period.<br><br>I'm a little bit hesitant to share what I know and what has set me back again on the highway and permit other people reach their desires. Why the hesitancy? Do I fear laughter? I don't think so. What I worry most is that I may possibly not be ready to support everybody achieve their dream. What transpires to people that get remaining by the wayside? Can I truly feel very good about asking other people to support me in my objective of spreading good wellness, happiness and very good fortune? Is this too considerably for 1 particular person to handle? Oh, so several questions and nevertheless I know the place I can discover the responses. All I have to do is dig out that minor enterprise card that was handed to me so a lot of months in the past and all the help I need is a call away. No, I am not left out in the entire world to fend for myself.<br><br>In the organization and financial globe, I guess GM and Chrysler are getting more cash from the treasury. They want to better their firms. But, they don't mind placing taxpapers in even deeper personal debt. How wonderful. Delta and United Airways rose in US trading considering that saying initial-quarter losses that conquer estimates. Last but not least, financial institutions throughout the globe will have to sooner or later compose down belongings by $4.1 trillion just to get finances again on keep track of around the globe. Recognize, it states trillion.<br><br>Several times went by and I obtained curious. Following a single particular stress loaded day at work I went house and determined I had had adequate. I really needed to discover one thing to replace that "job" I just know I was likely to eventually stroll away Link Schwartz from. I rummaged about and discovered that little company card and commenced to do some study. The pc and I stayed up really late that night. What I located intrigued me. What I didn't find shocked me. How could this globally firm be so different than all the rest? It's not like it's a household identify, but more than the past three a long time it has quietly identified its way into the homes of more than nine million [http://Www.Google.com/search?q=people+close&btnI=lucky people close] to the world.<br><br>If you're looking to lose fat artichokes are a fantastic concept. Not only are they delicious, but they supply a good deal vitamins and fiber. The only drawback is that they get a little on the other vegetables of equivalent dietary worth. Even so, their flavor is worth it! Find out how to make a minimal-calorie sauce to go with the artichokes. I frequently serve this with a little lean portion of steak and pink wine. Bon Apetite! |
| {{Quote box
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| |title = IUPAC definition
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| |quote = Substance composed of [[macromolecules]].
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| ''Note'': Applicable to substance macromolecular in nature like cross-linked<br/>systems that can be considered as one macromolecule.
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| A '''polymer''' {{IPAc-en|ˈ|p|ɒ|l|ɨ|m|ər}}<ref>{{cite web|title=polymer - definition of polymer|url=http://www.thefreedictionary.com/polymer|publisher=[[TheFreeDictionary.com|The Free Dictionary]]|accessdate=23 July 2013}}</ref><ref>{{cite web|title=Define polymer|url=http://dictionary.reference.com/browse/polymer|publisher=[[Dictionary.com|Dictionary Reference]]|accessdate=23 July 2013}}</ref> is a large [[molecule]], or [[macromolecule]], composed of many repeated subunits, known as [[monomer]]s. Because of their broad range of properties,<ref name="PC1">{{Cite book | last1 = Painter | first1 = Paul C. | last2 = Coleman | first2 = Michael M. | title = Fundamentals of polymer science : an introductory text | year = 1997 | publisher = Technomic Pub. Co. | location = Lancaster, Pa. | isbn = 1-56676-559-5 | page = 1 }}</ref> both synthetic and natural polymers play an essential and ubiquitous role in everyday life.<ref name="MBB1">{{Cite book | last1 = McCrum | first1 = N. G. | last2 = Buckley | first2 = C. P. | last3 = Bucknall | first3 = C. B. | title = Principles of polymer engineering | year = 1997 | publisher = Oxford University Press | location = Oxford ; New York | isbn = 0-19-856526-7 | page = 1 }}</ref> Polymers range from familiar synthetic [[plastic]]s such as [[polystyrene]] (or [[styrofoam]]) to natural [[biopolymers]] such as [[DNA]] and [[proteins]] that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via [[polymerization]] of many monomers. Their consequently large [[molecular mass]] relative to [[small molecule]] [[Compound (chemistry)|compounds]] produces unique physical properties, including [[toughness]], [[viscoelasticity]], and a tendency to form [[glass]]es and [[Crystallization of polymers|semicrystalline]] structures rather than crystals.
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| The term "polymer" derives from the ancient Greek word πολύς (polus, meaning "many, much") and μέρος (meros, meaning "parts"), and refers to a [[molecule]] whose structure is composed of multiple repeating units, from which originates a characteristic of high [[relative molecular mass]] and attendant properties.<ref>http://goldbook.iupac.org/M03667.html; accessed 7 October 2012. Per the IUPAC Gold Book and PAC sources referenced therein, "In many cases, especially for synthetic polymers, a molecule can be regarded as having a high relative molecular mass if the addition or removal of one or a few of the units has a negligible effect on the molecular properties." However, they note that the "statement fails in the case of certain macromolecules for which the properties may be critically dependent on fine details of the molecular structure."</ref> The units composing polymers derive, actually or conceptually, from molecules of low relative molecular mass.<ref>{{GoldBookRef | title = macromolecule (polymer molecule) | file = M03667}}</ref> The term was coined in 1833 by [[Jöns Jacob Berzelius]], though [[Jöns Jacob Berzelius#New chemical terms|with a definition]] distinct from the modern [[IUPAC]] definition.<ref>If two substances had empirical formulae that were integer multiples of each other -- e.g., acetylene (C<sub>2</sub>H<sub>2</sub>) and benzene (C<sub>6</sub>H<sub>6</sub>) -- Berzelius called them "polymeric". See: Jöns Jakob Berzelius (1833) "''Isomerie'', Unterscheidung von damit analogen Verhältnissen" (''Isomeric'', distinction from relations analogous to it), ''Jahres-Bericht über die Fortschitte der physischen Wissenschaften …'', '''12''' : 63-67. [http://books.google.com/books?id=1vs4AAAAMAAJ&pg=RA1-PA64#v=onepage&q&f=false From page 64]: "Um diese Art von Gleichheit in der Zusammensetzung, bei Ungleichheit in den Eigenschaften, bezeichnen zu können, möchte ich für diese Körper die Benennung ''polymerische'' (von ''πολυς'' mehrere) vorschlagen." (In order to be able to denote this type of similarity in composition [which is accompanied] by differences in properties, I would like to propose the designation "polymeric" (from ''πολυς'', several) for these substances.)<br>Originally published in 1832 in Swedish as: Jöns Jacob Berzelius (1832) "Isomeri, dess distinktion från dermed analoga förhållanden," ''Årsberättelse om Framstegen i Fysik och Kemi'', pages 65-70 ; the word "polymeriska" appears on [http://books.google.com/books?id=PZUHAAAAcAAJ&pg=PA66#v=onepage&q&f=false page 66].</ref><ref>See also: William B. Jensen (2008) "Ask the Historian: The origin of the polymer concept," ''Journal of Chemical Education'', '''88''' : 624-625. Available on-line at: [http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/141.%20Polymer.pdf University of California.edu].</ref> The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by [[Hermann Staudinger]], who spent the next decade finding experimental evidence for this hypothesis.<ref>{{cite book|last1=Allcock|first1=Harry R.|last2=Lampe|first2=Frederick W.|last3=Mark|first3=James E.|title=Contemporary Polymer Chemistry|publisher=Pearson Education|edition=3|year=2003|page=21|isbn=0-13-065056-0}}</ref>
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| Polymers are studied in the fields of [[biophysics]] and [[macromolecule|macromolecular science]], and [[polymer science]] (which includes [[polymer chemistry]] and [[polymer physics]]). Historically, products arising from the linkage of repeating units by [[covalent]] [[chemical bond]]s have been the primary focus of polymer science; emerging important areas of the science now focus on non-covalent links. [[Polyisoprene]] of [[latex]] [[rubber]] and the [[polystyrene]] of [[styrofoam]] are examples of polymeric natural/biological and synthetic polymers, respectively. In biological contexts, essentially all biological [[macromolecules]]—i.e., [[proteins]] (polyamides), [[nucleic acids]] (polynucleotides), and polysaccharides—are purely polymeric, or are composed in large part of polymeric components—e.g., isoprenylated/lipid-modified glycoproteins, where small lipidic molecule and oligosaccharide modifications occur on the polyamide backbone of the protein.<ref>{{cite journal | author1 = Ten Feizi | author2 = Wengang Chai | title = Oligosaccharide microarrays to decipher the glyco code | journal = Nature Reviews Molecular Cell Biology | volume = 5 | pages = 582–588 | year = 2004 | doi = 10.1038/nrm1428 | issue = 7}}</ref>
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| ==Common examples==
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| Polymers are of two types:-
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| *[[Natural polymer|Natural polymeric materials]] such as [[shellac]], [[amber]], [[wool]], [[silk]] and natural [[rubber]] have been used for centuries.A variety of other natural polymers exist, such as [[cellulose]], which is the main constituent of wood and paper.
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| *The [[list of synthetic polymers]] includes [[synthetic rubber]], [[phenol formaldehyde resin]] (or [[Bakelite]]), [[neoprene]], [[nylon]], [[polyvinyl chloride]] (PVC or vinyl), [[polystyrene]], [[polyethylene]], [[polypropylene]], [[polyacrylonitrile]], [[Polyvinyl butyral|PVB]], [[silicone]], and many more.
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| Most commonly, the continuously linked backbone of a polymer used for the preparation of plastics consists mainly of [[carbon]] atoms. A simple example is polyethylene ('polythene' in British English), whose repeating unit is based on [[ethylene]] [[monomer]]. However, other structures do exist; for example, elements such as silicon form familiar materials such as silicones, examples being [[Silly Putty]] and waterproof plumbing sealant. [[Oxygen]] is also commonly present in polymer backbones, such as those of [[polyethylene glycol]], [[polysaccharide]]s (in [[glycosidic bond]]s), and [[DNA]] (in [[phosphodiester bond]]s).
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| ==Polymer synthesis==
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| {{main|Polymerization}}
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| [[File:Polypropylene.svg|thumb|right|200px|The repeating unit of the polymer polypropylene]]
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| Polymerization is the process of combining many [[small molecules]] known as monomers into a covalently bonded chain or network. During the polymerization process, some chemical groups may be lost from each monomer. This is the case, for example, in the polymerization of [[polyethylene terephthalate|PET polyester]]. The monomers are [[terephthalic acid]] (HOOC-C<sub>6</sub>H<sub>4</sub>-COOH) and [[ethylene glycol]] (HO-CH<sub>2</sub>-CH<sub>2</sub>-OH) but the repeating unit is -OC-C<sub>6</sub>H<sub>4</sub>-COO-CH<sub>2</sub>-CH<sub>2</sub>-O-, which corresponds to the combination of the two monomers with the loss of two water molecules. The distinct piece of each monomer that is incorporated into the polymer is known as a [[repeat unit]] or monomer residue.
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| Laboratory synthetic methods are generally divided into two categories, [[step-growth polymerization]] and [[addition polymerization|chain-growth polymerization]].<ref>{{Cite book | last1 = Sperling | first1 = L. H. (Leslie Howard) | title = Introduction to physical polymer science | year = 2006 | publisher = Wiley | location = Hoboken, N.J. | isbn = 0-471-70606-X | page = 10 }}</ref> The essential difference between the two is that in chain growth polymerization, monomers are added to the chain one at a time only,<ref>Sperling, p. 11</ref> such as in [[polyethylene]], whereas in step-growth polymerization chains of monomers may combine with one another directly,<ref>Sperling, p. 15</ref> such as in [[polyester]]. However, some newer methods such as [[plasma polymerization]] do not fit neatly into either category. Synthetic polymerization reactions may be carried out with or without a [[catalyst]]. Laboratory synthesis of biopolymers, especially of [[peptide synthesis|proteins]], is an area of intensive research.
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| ===Biological synthesis===
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| [[File:ADN animation.gif|thumb|right|220px|Microstructure of part of a DNA [[double helix]] '''biopolymer''']]
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| {{main|Biopolymer}}
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| There are three main classes of biopolymers: [[polysaccharides]], [[polypeptides]], and [[polynucleotide]]s.
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| In living cells, they may be synthesized by enzyme-mediated processes, such as the formation of DNA catalyzed by [[DNA polymerase]]. The [[Protein biosynthesis|synthesis of proteins]] involves multiple enzyme-mediated processes to [[Transcription (genetics)|transcribe]] genetic information from the DNA to [[ribonucleic acid|RNA]] and subsequently [[Translation (biology)|translate]] that information to synthesize the specified protein from [[amino acid]]s. The protein may be [[Posttranslational modification|modified further]] following translation in order to provide appropriate structure and functioning.
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| ===Modification of natural polymers===
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| Naturally occurring polymers such as cotton, starch and rubber were familiar materials for years before synthetic polymers such as [[polyethene]] and [[perspex]] appeared on the market.
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| Many commercially important polymers are synthesized by chemical modification of naturally occurring polymers. Prominent examples include the reaction of nitric acid and cellulose to form [[nitrocellulose]] and the formation of [[vulcanized rubber]] by heating natural rubber in the presence of [[sulfur]].
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| Ways in which polymers can be modified include [[oxidation]], [[cross-link]]ing and end-capping.
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| Especially in the production of polymers, the gas separation by membranes has acquired increasing importance in the petrochemical industry and is now a relatively well-established unit operation.
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| The process of polymer degassing is necessary to suit polymer for extrusion and pelletizing, increasing safety, environmental, and product quality aspects. Nitrogen is generally used for this purpose, resulting in a vent gas primarily composed of monomers and nitrogen.<ref name="Improvement Economics Program">{{cite web|url=http://www.slideshare.net/intratec/membranes-on-polyolefins-plants-vent-recovery|title= Membranes on Polyolefins Plants Vent Recovery, Improvement Economics Program|publisher=by Intratec, ISBN 978-0615678917}}</ref>
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| ==Polymer properties==
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| Polymer properties are broadly divided into several classes based on the scale at which the property is defined as well as upon its physical basis.<ref>{{cite journal|author=S.A. Baeurle|doi=10.1007/s10910-008-9467-3|title=Multiscale modeling of polymer materials using field-theoretic methodologies: a survey about recent developments|journal=Journal of Mathematical Chemistry |volume=46|issue=2|pages=363–426|year=2009}}</ref> The most basic property of a polymer is the identity of its constituent monomers. A second set of properties, known as [[microstructure]], essentially describe the arrangement of these monomers within the polymer at the scale of a single chain. These basic structural properties play a major role in determining bulk physical properties of the polymer, which describe how the polymer behaves as a continuous macroscopic material. Chemical properties, at the nano-scale, describe how the chains interact through various physical forces. At the macro-scale, they describe how the bulk polymer interacts with other chemicals and solvents.
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| ===Monomers and repeat units===
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| The identity of the monomer residues (repeat units) comprising a polymer is its first and most important attribute. Polymer nomenclature is generally based upon the type of monomer residues comprising the polymer. Polymers that contain only a single type of repeat unit are known as [[homopolymer]]s, while polymers containing a mixture of repeat units are known as [[copolymer]]s. Poly(styrene), for example, is composed only of styrene monomer residues, and is therefore classified as a homopolymer. [[Ethylene-vinyl acetate]], on the other hand, contains more than one variety of repeat unit and is thus a copolymer. Some biological polymers are composed of a variety of different but structurally related monomer residues; for example, [[polynucleotide]]s such as DNA are composed of a variety of [[nucleotide]] subunits.
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| A polymer molecule containing ionizable subunits is known as a [[polyelectrolyte]] or [[ionomer]].
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| ===Microstructure===
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| {{Main|microstructure}}
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| The microstructure of a polymer (sometimes called configuration) relates to the physical arrangement of monomer residues along the backbone of the chain.<ref>Sperling, p. 30</ref> These are the elements of polymer structure that require the breaking of a covalent bond in order to change. Structure has a strong influence on the other properties of a polymer. For example, two samples of natural rubber may exhibit different durability, even though their molecules comprise the same monomers.
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| ====Polymer architecture{{Anchor|Intermolecular forces}}====
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| {{main|Polymer architecture}}
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| [[Image:Polymer Branch.svg|thumb|right|200px| Branch point in a polymer]]
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| An important microstructural feature of a polymer is its architecture and shape, which relates to the way branch points lead to a deviation from a simple linear chain.<ref name="PP6">{{Cite book | last1 = Rubinstein | first1 = Michael | last2 = Colby | first2 = Ralph H. | title = Polymer physics | year = 2003 | publisher = Oxford University Press | location = Oxford ; New York | isbn = 0-19-852059-X | page = 6 }}</ref> A [[branching (chemistry)|branched polymer]] molecule is composed of a main chain with one or more substituent side chains or branches. Types of branched polymers include [[star polymers]], [[comb polymers]], [[brush polymers]], [[dendronized polymers]], ''ladders'', and [[dendrimers]].<ref name="PP6"/> There exist also [[Two-dimensional polymers (2DP)|two-dimensional polymers]] which are composed of topologically planar repeat units.
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| A polymer's architecture affects many of its physical properties including, but not limited to, solution viscosity, melt viscosity, solubility in various solvents, glass transition temperature and the size of individual polymer coils in solution.
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| A variety of techniques may be employed for the synthesis of a polymeric material with a range of architectures, for example [[Living polymerization]].
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| [[Image:RAFT Architecture.png|thumb|400px|Right|Various polymer architectures.]]
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| ====Chain length====
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| The physical properties<ref>{{Cite book | last1 = De Gennes | first1 = Pierre Gilles | title = Scaling concepts in polymer physics | year = 1979 | publisher = Cornell University Press | location = Ithaca, N.Y. | isbn = 0-8014-1203-X }}</ref> of a polymer are strongly dependent on the size or length of the polymer chain.<ref name="PP5">Rubinstein, p. 5</ref> For example, as chain length is increased, melting and boiling temperatures increase quickly.<ref name="PP5"/> [[Impact resistance]] also tends to increase with chain length, as does the [[viscosity]], or resistance to flow, of the polymer in its melt state.<ref>McCrum, p. 37</ref> Melt viscosity <math>\eta \,</math> is related to polymer chain length Z roughly as <math>\eta \,</math> ~ Z<sup>3.2</sup>, so that a tenfold increase in polymer chain length results in a viscosity increase of over 1000 times.<ref>Introduction to Polymer Science and Chemistry: A Problem-Solving Approach
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| By Manas Chanda</ref> Increasing chain length furthermore tends to decrease chain mobility, increase strength and toughness, and increase the [[glass transition temperature]] (T<sub>g</sub>){{Citation needed|date=May 2009}}. This is a result of the increase in chain interactions such as [[Van der Waals attraction]]s and [[Reptation|entanglements]] that come with increased chain length{{Citation needed|date=May 2009}}. These interactions tend to fix the individual chains more strongly in position and resist deformations and matrix breakup, both at higher stresses and higher temperatures{{Citation needed|date=May 2009}}.
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| A common means of expressing the length of a chain is the [[degree of polymerization]], which quantifies the number of monomers incorporated into the chain.<ref>McCrum, p. 30</ref><ref name="PP3">Rubinstein, p. 3</ref> As with other molecules, a polymer's size may also be expressed in terms of [[molecular weight]]. Since synthetic polymerization techniques typically yield a polymer product including a range of molecular weights, the weight is often expressed statistically to describe the distribution of chain lengths present in the same. Common examples are the [[number average molecular weight]] and [[weight average molecular weight]].<ref>McCrum, p. 33</ref><ref name="PP23">Rubinstein, pp. 23-24</ref> The ratio of these two values is the [[polydispersity index]], commonly used to express the "width" of the molecular weight distribution.<ref>Painter, p. 22</ref> A final measurement is contour length, which can be understood as the length of the chain backbone in its fully extended state.<ref name="PP50">Rubinstein, p. 50</ref>
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| The flexibility of an unbranched chain polymer is characterized by its [[persistence length]].
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| ====Monomer arrangement in copolymers====
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| {{main|copolymer}}
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| [[Image:Copolymers.svg|right|400px|Different types of copolymers]]
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| Monomers within a copolymer may be organized along the backbone in a variety of ways.
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| *'''Alternating copolymers''' possess regularly alternating monomer residues:<ref name="PC14">Painter, p. 14</ref> [AB...]<sub>n</sub> (2).
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| *'''Periodic copolymers''' have monomer residue types arranged in a repeating sequence: [A<sub>n</sub>B<sub>m</sub>...] m being different from n .
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| *'''Statistical copolymers''' have monomer residues arranged according to a known statistical rule. A statistical copolymer in which the probability of finding a particular type of monomer residue at a particular point in the chain is independent of the types of surrounding monomer residue may be referred to as a truly '''random copolymer'''<ref name="PC15">Painter, p. 15</ref><ref>Sperling, p. 47</ref> (3).
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| *'''Block copolymers''' have two or more homopolymer subunits linked by covalent bonds<ref name="PC14"/> (4). Polymers with two or three blocks of two distinct chemical species (e.g., A and B) are called diblock copolymers and triblock copolymers, respectively. Polymers with three blocks, each of a different chemical species (e.g., A, B, and C) are termed triblock terpolymers.
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| *'''[[Copolymer#Graft copolymers|Graft or grafted copolymers]]''' contain side chains that have a different composition or configuration than the main chain.(5)
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| ====Tacticity====
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| {{main|Tacticity}}
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| Tacticity describes the relative [[stereochemistry]] of [[chirality (chemistry)|chiral]] centers in neighboring structural units within a macromolecule. There are three types: [[isotactic]] (all substituents on the same side), [[atactic]] (random placement of substituents), and [[syndiotactic]] (alternating placement of substituents).
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| ===Polymer morphology===
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| Polymer morphology generally describes the arrangement and microscale ordering of polymer chains in space.
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| ====Crystallinity====
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| When applied to polymers, the term ''crystalline'' has a somewhat ambiguous usage. In some cases, the term ''crystalline'' finds identical usage to that used in conventional [[crystallography]]. For example, the structure of a crystalline protein or polynucleotide, such as a sample prepared for [[x-ray crystallography]], may be defined in terms of a conventional unit cell composed of one or more polymer molecules with cell dimensions of hundreds of [[angstrom]]s or more.
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| A synthetic polymer may be loosely described as crystalline if it contains regions of three-dimensional ordering on atomic (rather than macromolecular) length scales, usually arising from intramolecular folding and/or stacking of adjacent chains. Synthetic polymers may consist of both crystalline and amorphous regions; the degree of crystallinity may be expressed in terms of a weight fraction or volume fraction of crystalline material. Few synthetic polymers are entirely crystalline.<ref>{{cite web|url=http://www.iupac.org/publications/books/pbook/PurpleBook-C4.pdf|title=IUPAC Purple Book: Definition of terms relating to crystalline polymers (1988) See Sec.1.3 Degree of Crystallinity|format=PDF}}</ref>
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| The crystallinity of polymers is characterized by their degree of crystallinity, ranging from zero for a completely non-crystalline polymer to one for a theoretical completely crystalline polymer.
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| Polymers with microcrystalline regions are generally tougher (can be bent more without breaking) and more impact-resistant than totally amorphous polymers.<ref>{{cite book|last1=Allcock|first1=Harry R.|last2=Lampe|first2=Frederick W.|last3=Mark|first3=James E.|title=Contemporary Polymer Chemistry|publisher=Pearson Education|edition=3|year=2003|page=546|isbn=0-13-065056-0}}</ref>
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| Polymers with a degree of crystallinity approaching zero or one will tend to be transparent, while polymers with intermediate degrees of crystallinity will tend to be opaque due to light scattering by crystalline or glassy regions. Thus for many polymers, reduced crystallinity may also be associated with increased transparency.
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| ====Chain conformation====
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| The space occupied by a polymer molecule is generally expressed in terms of [[radius of gyration]], which is an average distance from the center of mass of the chain to the chain itself. Alternatively, it may be expressed in terms of [[pervaded volume]], which is the volume of solution spanned by the polymer chain and scales with the cube of the radius of gyration.<ref>Rubinstein, p. 13</ref>
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| ===Mechanical properties===
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| [[Image:stable neck MDPE.jpg|50px|thumb|right|A polyethylene sample [[Necking (engineering)|necking]] under tension.]]
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| The bulk properties of a polymer are those most often of end-use interest. These are the properties that dictate how the polymer actually behaves on a macroscopic scale.
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| ====Tensile strength====
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| The [[tensile strength]] of a material quantifies how much stress the material will endure before suffering permanent deformation.<ref>{{cite book|authorlink=M. F. Ashby|last1=Ashby|first1=Michael|last2=Jones|first2=David|title=Engineering Materials|pages=191–195|publisher=Butterworth-Heinermann|year=1996|edition=2|isbn=0-7506-2766-2}}</ref><ref>{{cite book|first1=M. A.|last1=Meyers|first2=K. K.|last2=Chawla|title=Mechanical Behavior of Materials|publisher=Cambridge University Press|year=1999|page=41|url=http://www.toodoc.com/Mechanical-Behavior-of-Materials-ebook.html|isbn=978-0-521-86675-0}}</ref> This is very important in applications that rely upon a polymer's physical strength or durability. For example, a rubber band with a higher tensile strength will hold a greater weight before snapping. In general, tensile strength increases with polymer chain length and [[Cross-link|crosslinking]] of polymer chains.
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| ====Young's modulus of elasticity====
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| [[Young's Modulus]] quantifies the [[elasticity (physics)|elasticity]] of the polymer. It is defined, for small [[Deformation_(mechanics)#Strain|strain]]s, as the ratio of rate of change of stress to strain. Like tensile strength, this is highly relevant in polymer applications involving the physical properties of polymers, such as rubber bands. The modulus is strongly dependent on temperature. [[Viscoelasticity]] describes a complex time-dependent elastic response, which will exhibit [[hysteresis]] in the stress-strain curve when the load is removed. [[Dynamic mechanical analysis]] or DMA measures this complex modulus by oscillating the load and measuring the resulting strain as a function of time.
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| ===Transport properties===
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| Transport properties such as diffusivity relate to how rapidly molecules move through the polymer matrix. These are very important in many applications of polymers for films and membranes.
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| ===Phase behavior===
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| ====Melting point====
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| The term ''[[melting point]]'', when applied to polymers, suggests not a solid-liquid phase transition but a transition from a crystalline or semi-crystalline phase to a solid amorphous phase. Though abbreviated as simply ''T<sub>m</sub>'', the property in question is more properly called the crystalline melting temperature. Among synthetic polymers, crystalline melting is only discussed with regards to [[thermoplastics]], as [[thermoset]]ting polymers will decompose at high temperatures rather than melt.
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| ====Glass transition temperature====
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| A parameter of particular interest in synthetic polymer manufacturing is the [[glass transition]] temperature (T<sub>g</sub>), at which amorphous polymers undergo a transition from a rubbery, viscous liquid, to a brittle, glassy amorphous solid on cooling. The glass transition temperature may be engineered by altering the degree of branching or crosslinking in the polymer or by the addition of [[plasticizer]].<ref>{{cite book|last1= Brandrup|first1=J.|last2=Immergut|first2=E.H.|last3=Grulke|first3=E.A.|title=Polymer Handbook|edition= 4|publisher=Wiley-Interscience|year=1999|isbn= 0-471-47936-5}}</ref>
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| ====Mixing behavior====
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| [[Image:LCST-UCST plot.svg|thumb|350px|Phase diagram of the typical mixing behavior of weakly interacting polymer solutions.]]
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| In general, polymeric mixtures are far less [[miscible]] than mixtures of [[small molecule]] materials. This effect results from the fact that the driving force for mixing is usually [[entropy]], not interaction energy. In other words, miscible materials usually form a solution not because their interaction with each other is more favorable than their self-interaction, but because of an increase in entropy and hence free energy associated with increasing the amount of volume available to each component. This increase in entropy scales with the number of particles (or moles) being mixed. Since polymeric molecules are much larger and hence generally have much higher specific volumes than small molecules, the number of molecules involved in a polymeric mixture is far smaller than the number in a small molecule mixture of equal volume. The energetics of mixing, on the other hand, is comparable on a per volume basis for polymeric and small molecule mixtures. This tends to increase the free energy of mixing for polymer solutions and thus make solvation less favorable. Thus, concentrated solutions of polymers are far rarer than those of small molecules.
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| Furthermore, the phase behavior of polymer solutions and mixtures is more complex than that of small molecule mixtures. Whereas most small molecule solutions exhibit only an [[upper critical solution temperature]] phase transition, at which phase separation occurs with cooling, polymer mixtures commonly exhibit a [[lower critical solution temperature]] phase transition, at which phase separation occurs with heating.
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| In dilute solution, the properties of the polymer are characterized by the interaction between the solvent and the polymer. In a good solvent, the polymer appears swollen and occupies a large volume. In this scenario, intermolecular forces between the solvent and monomer subunits dominate over intramolecular interactions. In a bad solvent or poor solvent, intramolecular forces dominate and the chain contracts. In the [[theta solvent]], or the state of the polymer solution where the value of the second virial coefficient becomes 0, the intermolecular polymer-solvent repulsion balances exactly the intramolecular monomer-monomer attraction. Under the theta condition (also called the [[Paul J. Flory|Flory]] condition), the polymer behaves like an ideal [[random coil]]. The transition between the states is known as a [[coil-globule transition]].
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| ====Inclusion of plasticizers====
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| Inclusion of plasticizers tends to lower T<sub>g</sub> and increase polymer flexibility. Plasticizers are generally small molecules that are chemically similar to the polymer and create gaps between polymer chains for greater mobility and reduced interchain interactions. A good example of the action of plasticizers is related to polyvinylchlorides or PVCs. An uPVC, or unplasticized polyvinylchloride, is used for things such as pipes. A pipe has no plasticizers in it, because it needs to remain strong and heat-resistant. Plasticized PVC is used in clothing for a flexible quality. Plasticizers are also put in some types of cling film to make the polymer more flexible.
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| ===Chemical properties===
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| The attractive forces between polymer chains play a large part in determining a polymer's properties. Because polymer chains are so long, these interchain forces are amplified far beyond the attractions between conventional molecules. Different side groups on the polymer can lend the polymer to [[ionic bonding]] or [[hydrogen bonding]] between its own chains. These stronger forces typically result in higher tensile strength and higher crystalline melting points.
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| The intermolecular forces in polymers can be affected by [[dipole]]s in the monomer units. Polymers containing [[amide]] or [[carbonyl]] groups can form [[hydrogen bond]]s between adjacent chains; the partially positively charged hydrogen atoms in N-H groups of one chain are strongly attracted to the partially negatively charged oxygen atoms in C=O groups on another. These strong hydrogen bonds, for example, result in the high tensile strength and melting point of polymers containing [[Carbamate|urethane]] or [[urea]] linkages. [[Polyester]]s have [[intermolecular force#Dipole-dipole interactions|dipole-dipole bonding]] between the oxygen atoms in C=O groups and the hydrogen atoms in H-C groups. Dipole bonding is not as strong as hydrogen bonding, so a polyester's melting point and strength are lower than [[Kevlar]]'s ([[Twaron]]), but polyesters have greater flexibility.
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| Ethene, however, has no permanent dipole. The attractive forces between polyethylene chains arise from weak [[van der Waals force]]s. Molecules can be thought of as being surrounded by a cloud of negative electrons. As two polymer chains approach, their electron clouds repel one another. This has the effect of lowering the electron density on one side of a polymer chain, creating a slight positive dipole on this side. This charge is enough to attract the second polymer chain. Van der Waals forces are quite weak, however, so polyethylene can have a lower melting temperature compared to other polymers.
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| ==Standardized polymer nomenclature==
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| There are multiple conventions for naming polymer substances. Many commonly used polymers, such as those found in consumer products, are referred to by a common or trivial name. The trivial name is assigned based on historical precedent or popular usage rather than a standardized naming convention. Both the [[American Chemical Society]] (ACS)<ref>CAS: Index Guide, Appendix IV ((c) 1998)</ref> and [[IUPAC]]<ref>{{cite journal|author=IUPAC|title=Nomenclature of Regular Single-Strand Organic Polymers|journal=Pure Appl. Chem.|year=1976|volume=48|pages=373–385|doi=10.1351/pac197648030373|issue=3}}</ref> have proposed standardized naming conventions; the ACS and IUPAC conventions are similar but not identical.<ref>{{cite web|url=http://www.polyacs.org/nomcl/mnn18.html|title=Macromolecular Nomenclature Note No. 18}}</ref> Examples of the differences between the various naming conventions are given in the table below:
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| {| class="wikitable"
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| |-
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| ! Common name
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| ! ACS name
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| ! IUPAC name
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| |-
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| | [[Poly(ethylene oxide)]] or PEO
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| | Poly(oxyethylene)
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| | Poly(oxyethene)
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| |-
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| | [[Poly(ethylene terephthalate)]] or PET
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| | Poly(oxy-1,2-ethanediyloxycarbonyl-1,4-phenylenecarbonyl)
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| | Poly(oxyetheneoxyterephthaloyl)
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| |-
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| | [[Nylon 6]]
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| | Poly[amino(1-oxo-1,6-hexanediyl)]
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| | Poly[amino(1-oxohexan-1,6-diyl)]
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| |}
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| In both standardized conventions, the polymers' names are intended to reflect the monomer(s) from which they are synthesized rather than the precise nature of the repeating subunit. For example, the polymer synthesized from the simple alkene [[ethene]] is called polyethylene, retaining the ''-ene'' suffix even though the double bond is removed during the polymerization process:
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| [[Image:Ethene polymerization.png]]
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| [[Image:polyethene monomer.png]]
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| ==Polymer characterization==
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| {{main|Polymer characterization}}
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| The characterization of a polymer requires several parameters which need to be specified. This is because a polymer actually consists of a [[statistics|statistical]] distribution of chains of varying lengths, and each chain consists of monomer residues which affect its properties.
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| A variety of lab techniques are used to determine the properties of polymers. Techniques such as [[wide angle X-ray scattering]], [[Small angle X-ray scattering (SAXS)|small angle X-ray scattering]], and [[Small angle neutron scattering (SANS)|small angle neutron scattering]] are used to determine the crystalline structure of polymers. [[Gel permeation chromatography]] is used to determine the number average molecular weight, weight average molecular weight, and [[polydispersity]]. [[FTIR]], [[Raman spectroscopy|Raman]] and [[Nuclear magnetic resonance|NMR]] can be used to determine composition. Thermal properties such as the glass transition temperature and melting point can be determined by [[differential scanning calorimetry]] and [[dynamic mechanical analysis]]. [[Pyrolysis]] followed by analysis of the fragments is one more technique for determining the possible structure of the polymer. [[Thermogravimetry]] is a useful technique to evaluate the thermal stability of the polymer. Detailed analysis of TG curves also allow us to know a bit of the phase segregation in polymers. [[Rheology|Rheological]] properties are also commonly used to help determine molecular architecture (molecular weight, molecular weight distribution and branching) as well as to understand how the polymer will process, through measurements of the polymer in the melt phase. Another polymer characterization technique is Automatic Continuous Online Monitoring of Polymerization Reactions ([[ACOMP]]) which provides real-time characterization of polymerization reactions. It can be used as an analytical method in R&D, as a tool for reaction optimization at the bench and pilot plant level and, eventually, for feedback control of full-scale reactors. ACOMP measures in a model-independent fashion the evolution of average molar mass and intrinsic viscosity, monomer conversion kinetics and, in the case of copolymers, also the average composition drift and distribution. It is applicable in the areas of free radical and controlled radical homo- and copolymerization, polyelectrolyte synthesis, heterogeneous phase reactions, including [[emulsion polymerization]], adaptation to batch and continuous reactors, and modifications of polymers.<ref>{{US patent|6052184}} and {{US patent|6653150}}, other patents pending</ref><ref>{{cite journal|first1=F. H.|last1=Florenzano|first2=R.|last2=Strelitzki|first3=W. F.|last3=Reed|title=Absolute, Online Monitoring of Polymerization Reactions|journal=Macromolecules|year=1998|volume=31|issue=21|pages=7226–7238|doi=10.1021/ma980876e|bibcode = 1998MaMol..31.7226F }}</ref><ref>{{cite journal|first1=A. M.|last1=Alb|first2=M. F.|last2=Drenski|first3=W. F.|last3=Reed|title= Implications to Industry: Perspective. Automatic continuous online monitoring of polymerization reactions (ACOMP)|doi=10.1002/pi.2367|journal=Polymer International|year=2008|volume=57|pages=390–396|issue=3}}</ref>
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| ==Polymer degradation==
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| {{main|Polymer degradation}}
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| [[Image:PlasticDamage.JPG|right|thumb|250px|A plastic item with thirty years of exposure to heat and cold, brake fluid, and sunlight. Notice the discoloration, swelling, and [[crazing]] of the material]]
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| Polymer degradation is a change in the properties—tensile strength, [[color]], shape, or molecular weight—of a polymer or polymer-based product under the influence of one or more environmental factors, such as [[heat]], [[light]], [[chemical]]s and, in some cases, [[Galvanic corrosion|galvanic]] action. It is often due to the scission of polymer chain bonds via [[hydrolysis]], leading to a decrease in the molecular mass of the polymer.
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| Although such changes are frequently undesirable, in some cases, such as [[biodegradation]] and [[recycling]], they may be intended to prevent environmental [[pollution]]. Degradation can also be useful in biomedical settings. For example, a copolymer of [[polylactic acid]] and [[polyglycolic acid]] is employed in hydrolysable stitches that slowly degrade after they are applied to a wound.
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| The susceptibility of a polymer to degradation depends on its structure. Epoxies and chains containing aromatic functionalities are especially susceptible to [[UV degradation]] while polyesters are susceptible to degradation by [[hydrolysis]], while polymers containing an [[Saturated and unsaturated compounds|unsaturated]] backbone are especially susceptible to [[ozone cracking]]. Carbon based polymers are more susceptible to thermal degradation than inorganic polymers such as [[polydimethylsiloxane]] and are therefore not ideal for most high-temperature applications. High-temperature matrices such as [[bismaleimide]]s (BMI), condensation [[polyimides]] (with an O-C-N bond), [[triazines]] (with a nitrogen (N) containing ring), and blends thereof are susceptible to polymer degradation in the form of [[galvanic corrosion]] when bare carbon fiber reinforced polymer [[Carbon-fiber-reinforced polymer|CFRP]] is in contact with an active metal such as aluminium in salt water environments.
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| The degradation of polymers to form smaller molecules may proceed by random scission or specific scission. The degradation of polyethylene occurs by random scission—a random breakage of the bonds that hold the [[atoms]] of the polymer together. When heated above 450 °C, polyethylene degrades to form a mixture of hydrocarbons. Other polymers, such as poly(alpha-methylstyrene), undergo specific chain scission with breakage occurring only at the ends. They literally unzip or [[depolymerization|depolymerize]] back to the constituent monomer.
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| The sorting of polymer waste for recycling purposes may be facilitated by the use of the [[Resin identification code]]s developed by the [[Society of the Plastics Industry]] to identify the type of plastic.
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| ===Product failure===
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| [[Image:Chlorine attack1.jpg|thumb|left|200px|Chlorine attack of acetal resin plumbing joint]]
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| In a finished product, such a change is to be prevented or delayed. Failure of [[safety-critical]] polymer components can cause serious accidents, such as fire in the case of cracked and degraded polymer [[fuel line]]s. Chlorine-induced cracking of [[acetal resin]] plumbing joints and [[polybutylene]] pipes has caused many serious floods in domestic properties, especially in the USA in the 1990s. Traces of [[chlorine]] in the water supply attacked vulnerable polymers in the plastic plumbing, a problem which occurs faster if any of the parts have been poorly [[extruded]] or [[Injection molding|injection molded]]. Attack of the acetal joint occurred because of faulty molding, leading to cracking along the threads of the fitting which is a serious [[stress concentration]].
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| [[Image:Ozone cracks in tube1.jpg|thumb|right|200px|Ozone-induced cracking in natural rubber tubing]]
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| Polymer oxidation has caused accidents involving [[medical device]]s. One of the oldest known failure modes is ozone cracking caused by chain scission when [[ozone]] gas attacks susceptible [[elastomer]]s, such as [[natural rubber]] and [[nitrile rubber]]. They possess double bonds in their repeat units which are cleaved during [[ozonolysis]]. Cracks in fuel lines can penetrate the bore of the tube and cause fuel leakage. If cracking occurs in the engine compartment, electric sparks can ignite the [[gasoline]] and can cause a serious fire.
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| Fuel lines can also be attacked by another form of degradation: hydrolysis. [[Nylon 6,6]] is susceptible to [[acid hydrolysis]], and in one accident, a fractured fuel line led to a spillage of diesel into the road. If [[diesel fuel]] leaks onto the road, accidents to following cars can be caused by the slippery nature of the deposit, which is like [[black ice]].
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| ==See also==
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| {{Commons category|Polymers}}
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| {{colbegin|3}}
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| *[[Aquamelt]]
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| *[[Biopolymer]]
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| *[[Conjugated microporous polymer]]
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| *[[DNA condensation]]
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| *[[Emulsion dispersion]]
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| *[[Electroactive polymers]]
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| *[[Ferroelectric polymers]]
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| *[[Forensic polymer engineering]]
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| *[[Gel]]
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| *[[List of important publications in chemistry#Polymer chemistry|Important publications in polymer chemistry]]
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| *[[Molecular design software]]
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| *[[Organic laser]]
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| *[[Organic photonics]]
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| *[[Polyanhydrides]]
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| *[[Polymer adsorption]]
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| *[[Polymer classes (disambiguation)|Polymer classes]]
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| *[[Polymer engineering]]
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| *[[Polymer Journal]]
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| *[[Polymer separators]]
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| *[[Polymerization]]
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| *[[Polymersome]]
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| *[[Shape memory polymer]]
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| *[[Smart materials]]
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| *[[Sol-gel]]
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| *[[Solid]]
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| *[[Thermoplastics]]
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| *[[Thermosetting plastics]]
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| *[[Sequence-controlled polymer]]
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| {{colend}}
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| ==References==
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| {{Reflist|2}}
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| ==Bibliography==
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| *{{Cite book | last1 = Cowie | first1 = J. M. G. (John McKenzie Grant) | title = Polymers: chemistry and physics of modern material | year = 1991 | publisher = Blackie | location = Glasgow | isbn = 0-412-03121-3 | pages = }}
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| *{{Cite book | last1 = Ezrin | first1 = Myer. | title = Plastics failure guide : cause and prevention | year = 1996 | publisher = Hanser Publishers : Cincinnati | location = Munich ; New York | isbn = 1-56990-184-8 | pages = }}
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| *{{Cite book | last1 = Hall | first1 = Christopher | title = Polymer materials | edition = 2nd | year = 1989 | publisher = Macmillan | location = London; New York | isbn = 0-333-46379-X | url = http://www.cmse.ed.ac.uk/PM2/PM2.html }}
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| *{{Cite book | last1 = Lewis | first1 = P. R. (Peter Rhys) | last2 = Reynolds | first2 = Ken. | last3 = Gagg | first3 = Colin. | title = Forensic materials engineering : case studi | year = 2004 | publisher = CRC Press | location = Boca Raton | isbn = 0-8493-1182-9 | pages = }}
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| *{{Cite book | last1 = Wright | first1 = David C. | title = Environmental Stress Cracking of Plastics | year = 2001 | publisher = RAPRA | isbn = 978-1-85957-064-7 }}
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| *{{Cite book | last1 = Lewis | first1 = Peter Rhys | title = Forensic polymer engineering : why polymer products fail in service | year = 2010 | publisher = Woodhead Publishing | location = Cambridge [etc.] | isbn = 1-84569-185-7 | pages = }}
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| *{{Cite book | last1 = Workman | first1 = Jerome | last2 = Workman | first2 = Jerry | title = Handbook of organic compounds: NIR, IR, Raman, and UV-Vis spectra featuring polymers and surfactants | year = 2001 | publisher = Academic Press | location = San Diego | isbn = 978-0-12-763560-6 | pages = }}
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| ==External links==
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| {{Wiktionary}}
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| *[http://www.icdd.com/resources/tutorials/pdf/How%20to%20analyze%20polymers.pdf How to Analyze Polymers Using X-ray Diffraction]
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| *[http://www.polymerchemistryhypertext.com/ Polymer Chemistry Hypertext, Educational resource]
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| *[http://www.pslc.ws/macrog/index.htm The Macrogalleria]
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| *[http://www.campoly.com/application_notes.html Application notes on the characterization of polymers]
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| *[http://openlearn.open.ac.uk/mod/resource/view.php?id=196631 Polymer Structures]
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| *[http://www.theotherpages.org/abbrev.html Glossary of Polymer Abbreviations]
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| *[http://www.sigmaaldrich.com/img/assets/3900/Glossary.pdf Sigma-Aldrich Polymer Glossary]
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| [[Category:Polymers| ]]
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