Talk:Polymer/Archive 1

Cleanup
There are a handful of orphaned paragraphs in this article that have nothing to do with their section headings (esp the last two). I'll rewrite when I have time unless someone beats me to it. Irene Ringworm 19:26, 19 January 2007 (UTC)

Are proteins polymers?
Please, someone edit this thing because I need some information for school project, does any of it make sense? The awnser is no. If you want any information about polymers then go too www.pslc.ws/macrog/kidsmac/natural.htm because this site is no help at all. Hope it helps. Polymers are very confusing and are hard too split apart when out together. Proteins are not polymers. The amide linkages of protein molecules have pendant groups that do not repeat and as such are not chains of repeating monomer units. The chain lengthening process for polyamides is also far more sophisticated and exact than is the polymerization of monomers. tRNA shuttle amino acids to growing polypeptides according to the template DNA strand, while addition polymerization is governed primarily by statistical considerations and is driven by large concentration gradients. Industrial polymerization catalysts do not offer the fantastic control over the polymer chain sequence that the cellular machinery does over the polypeptide sequence, and likely never will. For these reasons, the classification of proteins (or polypetides) as polymers is misleading and inaccurate.

-Kc

That is really a matter of definition. A more broad term sometimes used is macromolecule. Some people prefer to save the term polymer for chains similar to what we can create synthetically and prefer to put species such as proteins and DNA into the larger category of macromolecules. I don't think it is fair to pull proteins out of the polymer category strictly because of their propagation method. Polymeriization includes many different propagation methods, some providing more control over the propagation than others. Certain forms of living polymerization may soon allow us to control specific addition to polymer chains in similar fashion to the protein construction. In fact, a lot of research is going into making our own proteins. I believe that currently it is possibly, but incredibly slow (i.e. a few monomer units per hour). That being said, there are some other reasons to classify non-polymer macromolecules. Exactly what those are is still a good discussion.

-TM

Protthor believes all proteins are enzymes or transport proteins. Not all are. Some are purely structural proteins, and the notion of active region (isn't the more precise term an active site?) versus structural region is meaningless in this context. Of course, structural proteins are often evolutionarily scavenged enzymes (classic example being the crystallins of the eye, which tend to be derived from various and sundry proteases), so maybe it isn't all that important ;) Dwmyers 18:03, 18 Sep 2003 (UTC)

Proteins are polymers, they're just block copolymers with many different monomers, and very small blocks :) TM - we can already synthesise custom polypeptides, eg via the polystyrene tethered approach of the Merrifield synthesis (for which the 1984 Nobel Prize was awarded). Iridium77 00:17, 9 Mar 2004 (UTC)

Although vandalism is bad and I do not like, I must admit I laughed out loud when I read "dog shit is a common polymer that people like to eat". Well done, whoever put that, it was quite funny (at least I thought so) but don't do it on wikipedia please... Borb 22:49, 8 Apr 2005 (UTC)

In my opinion proteins or the DNA are not polymers and the term macromolecule is more suitable because they are not the repetition of units called monomers. I also disagree with the term block-copolymers for proteins because, in my opinion, this term is used for the macromolecules in which every block is a polymer itself, it means it is formed with teh repetition of identical units. Nevertheless nowadays some polypeptides exist as polymers, for expample poly(Glu) or poly(Ala), or even more complex as the elastin-like polymers, (GVGVP)n, or the silk-like polymers.donjavi.

Many aspects of protein behavior can be effectively modeled within a polymeric framework. For the purposes of these aspects of protein behavior, it is entirely appropriate to consider them polymers. It is, however, important to preserve the caveat that proteins possess certain complexities beyond those that models for synthetic polymers often encompass. For example, aspects of mixing thermodynamics of polymers apply strongly to proteins. In this realm, proteins may be seen as a high complexity limit to standard polymers - they simply have many different monomer units and strong intermonomer interactions that lead to additional behavioral complexities. This complex behavior is not a reasonable basis for exclusion from a polymer classification. Nearly comparable differences exist between materials that are certainly considered polymers. In fact, polyampholytic synthetic polymers may possess many of the same behavioral complexities as proteins due to the presence of both positive and negative charges.

Certainly typical models of industrial polymerization do not adequately encompass biological molecules. However, it is unreasonable to remove protein from the polymer classification because of their synthesis. If someone were to engineer a bacteria or yeast that produced polyethylene, would this ‘biological’ polyethylene be categorized differently than 'synthetic' polyethylene, despite being structurally identical? I also think that it is somewhat unreasonable to assume that artificial polymerization will never match the specificity of biological polymerization. While that is certainly possible, rapid improvements in nanoscale technologies and in polymer synthesis make it hard to say what limits artificial polymerization will reach.

Neither complex behavior nor synthetic mechanisms are appropriate criterion for rejection of proteins from the polymer classification. In fact, proteins should be classified as polymers inasmuch as polymer models for molecular behavior can contribute to an understanding of protein behavior. Since polymer theory is applicable to proteins (with some added complexities) this classification is entirely appropriate for most uses (although perhaps not all).

-DS

Nylon
If memory serves correctly the nylon example is inaccurate - the more reactive acid chloride is used and hydrogen chloride gas the byproduct. --ThomasWinwood 00:12, Apr 19, 2005 (UTC)

There are actually different routes to synthesize nylon. The example where the polyamide is synthesized with the acid chloride is called the "Schotten-Baumann" reaction. It's a form of "interfacial polymerization", also known as a "two phase reaction". It's extremely fast - the reaction rate is 104 to 108 times faster than the mechanism suggested on the page. But, acid chlorides are rather expensive, so its usually used when there are no other routes for synthesis available. However, I think the way the reaction is outlined on the page is misleading, and more work can be done in terms of illustrating the displacement and elimination of the small molecule correctly. HappyCamper 04:13, 19 Apr 2005 (UTC)

Article Improvement Drive
Contact lens is currently nominated to be improved on Article Improvement Drive. Please support the article with your vote. --Fenice 10:51, 16 January 2006 (UTC)

Branching Information Under the branching section: IPN stands for Inter-penetrating polymer networks, not integrated polymer networks. You might also want to discuss the effects of both short and long chain branching; how one affects the properties like Tm and Tg and the other influences melt properties.

-ASK

http://www.xanga.com/starrydesigns COOL!

Vandalism
Well of all articles, this one on polymers has been vandalised. Probably by one of the IP addresses on the history page but I don't know enough about wikipedia to be 100% sure. I've removed the vandalism which said this:

"Proteins are polymers of the nigger family... no one likes the proteins cos they are too cool ffor school amino acids" Changed to Proteins are polymers of amino acids. Once again, I have to add that that's probably not true, I'm just here doing a school project, but it's more likely than what's already there. --Calum Smith 13:30, 2 August 2006 (UTC)

New Polymer-related article: Polyanhydrides
I have added an article about polyanhydrides. Any feedback on that article would be appreciated. I am in the process of finding pictures or graphics for the page.

♥Thanks!♥

Cleanup time
I have removed some paragraphs from the main article to the talk page for cleanup or reclassification. Feel free to rework and reinsert into the article (in appropriate places). List below: Irene Ringworm 10:13, 24 February 2007 (UTC)

from the header
Similar monomers can have various chemical substituents. These differences between monomers can affect properties such as solubility, flexibility, and strength. In proteins, these differences give the polymer the ability to adopt a biologically-active conformation. (See self-assembly.) Identical monomers with nonreactive side groups result in a polymer chain that will tend to adopt a random coil conformation, as described by an ideal chain mathematical model. Although most polymers are organic, with carbon-based monomers, there are also inorganic polymers; for example, the silicones, with a backbone of alternating silicon and oxygen atoms and polyphosphazenes.

Rationale for removal: out of place in general introduction. Incoherent. No references.

from Polymer nomenclature
Polymers are typically classified according to four main groups:
 * thermoplastics (linear or branched chains)
 * thermosets (crosslinked chains)
 * elastomers
 * coordination polymers

Polymer signifies a chain of thousands of monomers that are covalently bonded together usually by the carbon atoms of the polymer backbone, but the backbone can consist of other atoms such as silicon. Examples of polymers include substances anywhere from proteins to stiff, high-strength Kevlar fibres. For example, the formation of poly(ethylene) (also called polyethene) involves thousands of ethene molecules bonded together to form a straight (or branched) chain of repeating -CH2-CH2- units (with a -CH3 at each terminal):

Rationale for removal: Doesn't belong in nomenclature section. Redundant. No references.

Proteins are polymers of amino acids. Typically, hundreds of the (nominally) twenty different amino acid monomers make up a protein chain, and the sequence of monomers determines its shape and biological function. (There are also shorter oligopeptides which function as hormones.) But there are active regions, surrounded by, as is believed now (Aug 2003), structural regions, whose sole role is to expose the active regions. (There may be more than one on a given protein.) So the exact sequence of amino acids in certain parts of the chains can vary from species to species, and even given mutations within a species, so long as the active sites are properly accessible. Also, whereas the formation of polyethylene occurs spontaneously under the right conditions, the synthesis of biopolymers such as proteins and nucleic acids requires the help of enzyme catalysts, substances that facilitate and accelerate reactions. Unlike synthetic polymers, these biopolymers have exact sequences and lengths. (This does not include the carbohydrates.) Since the 1950s, catalysts have also revolutionised the development of synthetic polymers. By allowing more careful control over polymerization reactions, polymers with new properties, such as the ability to emit coloured light, have been manufactured.

Rationale for removal: Doesn't belong in nomenclature section. No references. Poorly organized.

From Constitution of polymers
Copolymerization with two or more different monomers results in chains with varied properties. There are twenty amino acid monomers whose sequence results in different shapes and functions of protein chains. Copolymerising ethene with small amounts of 1-hexene (or 4-methyl-1-pentene) is one way to form linear low-density polyethene (LLDPE). (See polyethylene.) The C4 branches resulting from the hexene lower the density and prevent large crystalline regions from forming within the polymer, as they do in HDPE. This means that LLDPE can withstand strong tearing forces while maintaining flexibility.

A block copolymer is formed when the reaction is carried out in a stepwise manner, leading to a structure with long sequences or blocks of one monomer alternating with long sequences of the other. There are also graft copolymers, in which entire chains of one kind (e.g., polystyrene) are made to grow out of the sides of chains of another kind (e.g., polybutadiene), resulting in a product that is less brittle and more impact-resistant. Thus, block and graft copolymers can combine the useful properties of both constituents and often behave as quasi-two-phase systems.

The following is an example of step-growth polymerization, or condensation polymerization, in which a molecule of water is given off and nylon is formed. The properties of the nylon are determined by the R and R' groups in the monomers used.
 * [[Image:Condensation polymerization diacid diamine.svg|400px]]

The first commercially successful, completely synthetic polymer was nylon 6,6, with alkane chains R = 4C (adipic acid) and R' = 6C (hexamethylene diamine). Including the two carboxyl carbons, each monomer donates 6 carbons; hence the name. In naming nylons, the number of carbons from the diamine is given first and the number from the diacid second. Kevlar is an aromatic nylon in which both R and R' are benzene rings.

Copolymers illustrate the point that the repeating unit in a polymer, such as a nylon, polyester or polyurethane, is often made up of two (or more) monomers.

Rationale for removal: No references. Poorly organized. String of non sequiturs, none of which have anything to do with intended subject heading.

Mechanical properties of polymers
Low coefficients of friction - In general coefficients of friction for polymers against polymers, metals or ceramics range from 0.15 to 0.6. Composites also retain the low coefficients of friction while having greater stiffness and strength.

Rationale for removal: Reference is a class project from RPI undergrads - not exactly authoritative. There are interesting things worth saying about polymers as lubricants or low-friction materials but this isn't it. Not my area of expertise. Any takers to improve this one? Irene Ringworm 20:22, 25 February 2007 (UTC)

Creep - the application of a constant (time independent) load causes a continuous displacement associated with the diffusion of the atoms or molecules within the material. This response is termed creep, the progressive deformation of a material under a sustained load. In metal alloys, creep becomes a problem at temperatures above approximately 0.6 Tm, where Tm is the melting temperature of the metal. However, in polymers, creep is an even more critical design problem because the polymers can be described as rubbery and viscous at temperatures above the glass transition temperature.


 * Ways to resist creep in polymers: In order to make polymers more resistant to creep at room temperature, increasing the degree of cross-linking within the polymer chain will raise the Tg. Therefore, a higher glass transition temperature allows for more resistance to creep. Furthermore, as molecular mass of the polymer increases, the viscosity, η will increase and effectively reduce the rate of creep. Also, the more crystalline the polymer, the more creep-resistant it is compared to entirely glassy polymers.

Rationale for removal: A nicely referenced, well-organized section on polymer creep is already part of Creep. It probably makes sense to summarize this section in the polymer article but leave the details (including the definition of creep) to the main article.Irene Ringworm 20:22, 25 February 2007 (UTC)

J-shaped stress-strain curves - Many biological materials actually display J-shaped stress-strain curves. In other words, the material will initially experience large extensions for small stresses. Then, as the extension gets larger and larger, the material gradually becomes stiffer and more difficult to extend.

A J-shaped stress-strain curve enables biomaterials to be extremely tough. Because the lower part of the curve has large extensions for small stresses, the shear modulus in that region is very low and so any released strain energy can be prevented from contributing to fracture of the material. Furthermore, large extensions of the material require very large stresses, and so these large extensions are likely to occur only infrequently. The J-shaped stress-strain curve does not lead to the elastic instabilities which arise in S-shaped curves.

An example of biological materials with J-shaped stress-strain curves is mammalian skin tissue. If you pinch your earlobe and try to pull it downwards, it is initially easy to stretch, but then at larger extensions it becomes much more difficult to stretch.

Rationale for removal: Nonsequitur - relevant to biological materials but not clear how this relates to polymers.Irene Ringworm 20:22, 25 February 2007 (UTC)

S-shaped stress-strain curves - These occur in lightly cross-linked polymers such as rubber. A material that exhibits an S-shaped stress-strain curve is very is applied to the material, a very large stiffness occurs because at these high loads, the polymer chains are mostly aligned with the applied stress. Therefore, applying even more stress will stretch the strong intramolecular bonds.

Rationale for removal: Needs references.Irene Ringworm 20:22, 25 February 2007 (UTC)

Physical properties of polymers

 * degree of polymerization - The number of structural units in a polymer chain.
 * molar mass distribution - The relationship between a polymer fraction and the molar mass of that polymer fraction.
 * crystallinity - as well as the thermal phase transitions:
 * Tg, glass transition temperature
 * Tm, melting point (for thermoplastics).


 * Stereoregularity or tacticity - the isomeric arrangement of functional groups on the backbone of carbon chains.

Rationale for removal: Proseline. Expanded and referenced in new edit. Irene Ringworm 19:19, 28 March 2007 (UTC)

Biological Polymers
Oops. Perhaps I should have read the discussion first before making my addition.

But, under category of organic polymers, I added (back) biological polymers:

polypeptides polysaccharides polynucleotides

They do have the word poly in them. They are synthesized (by biological processes) out of sub units (peptides, saccharides, and nucleotide). I think these remarkably diverse and important compounds deserve a brief mention in this article.

I was also tempted to add fatty acids as polymers, since they are formed by the condensation of acetic acid (in the form of Acetyl-CoA). Clemwang 21:24, 26 February 2007 (UTC)


 * Addition is fine and consistent with cleanup. I have some additions in the works to expand - I don't think anyone will argue that these are polymers.  I'm hoping to have some sort of "polymers in nature" section that can discuss biopolymers in more detail and point folks to the appropriate pages on polypeptides etc.  Feel free to help out in any way you can.  My expertise is limited to physical polymer chemistry and I'll need other editors to fill in the blanks.  Irene Ringworm 22:20, 26 February 2007 (UTC)

Clean Up?
I dont really think there needs to be any clean up. I mean, its already organized, don't u think? It's pretty fluent, and the pages aren't really too short I added some info to the Polymers in Solution topic. It should be verified though. AznShark 00:59, 14 March 2007 (UTC)


 * I'm doing my best but there are still sections like "chemical properties of polymers" and "physical properties of polymers" which are rambling, unencyclopedic, and sometimes factually incorrect. If you can offer help there it would be appreciated.  Irene Ringworm 19:32, 25 March 2007 (UTC)

Few things I noticed. The section showing examples of polymers. Shouldn't that be just mentioned and then referenced to their respective articles rather than explaining how each one was created, what properties it has, etc. LunaRain~ (talk) 06:23, 28 February 2008 (UTC)

Inorganic polymers?
Is there any inorganic polymers? Just a random question... I think glass is an inorganic polymer. Am I right? —Preceding unsigned comment added by 65.67.133.184 (talk) 20:49, 25 September 2007 (UTC)

Difference between polymer and molecule?
The definitions of polymer and molecule leave me a bit confused. So what exactly makes a polymer more than just a large molecule? Sbowers3 (talk) 05:33, 25 January 2008 (UTC)
 * A polymer is connected by covalent chemical bonds.
 * A molecule is connected by chemical bonds, which include covalent bonds.

The answer is contained in the first sentence of the article which specifies that a polymer is a large molecule "composed of repeating structural units". I have now added as a simple introductory example the structure of polypropylene which shows the repeating structural units clearly. (It is true that this definition is not always respected and that some chemists and biochemists use polymer more freely as a synonym for macromolecule.) Dirac66 (talk) 17:34, 4 February 2008 (UTC)

Excluded Volume / Pervaded Volume
There seems to be some confusion over the correct term used to quantify the size of a polymer chain in space. I changed 'excluded volume' to be 'pervaded volume' and a second editor changed it to be "excluded (pervaded) volume". Until this is resolved, I have reverted it to excluded volume, because excluded and pervaded volume are entirely different things. However, the correct term in this context is pervaded volume. The second editor has referenced Paul Flory to support his used of 'excluded'. I believe that you have misunderstood Flory's use of this word. In the Flory sense, 'excluded volume' means the part of space that is already occupied by the chain backbone that is not available to other parts of the chain. In other words, it signifies that in contrast with the ideal chain, a chain with excluded volume cannot overlap. Thus the amount of excluded volume of the chain in the Flory sense scales as the degree of polymerization of the chain times a volume per repeat unit. It does not scale directly with the gyration radius of the chain and is not a function of the chain conformation. It does not account for the amount of empty space or solvent contained within the chain. On the other hand, the pervaded volume is the volume of space required to contain the chain in a particular conformation. This does scale as the cube of the gyration radius and therefore actually relates to the size of the chain in space. Thus the appropriate volume to be used together with the gyration radius in specifying the size of a polymer chain in space is the pervaded volume. I can provide a reference for this - see Rubinstein, M and Colby, R. "Polymer Physics". 2003, 13.  They clearly state that "The pervaded volume V is the volume of solution spanned by the polymer chain." As further support see the wikipedia page on Paul Flory. It discusses the correct understanding of excluded volume as put forth by Flory in this context. If there is no disagreement with this point in the next day or so I will switch the term back to 'pervaded volume'. Excluded volume could perhaps be discussed more appropriately elsewhere.

Locke9k (talk)Locke9k

I have changed the term to 'pervaded volume' in the text. Please read and respond to this discussion before changing it again.

Locke9k (talk) 20:08, 30 May 2008 (UTC)Locke9k

OK, I see that “excluded volume” and “pervaded volume” are two different concepts, so I was clearly wrong to imply that the two are synonyms. I also see that “pervaded volume” is more correct here, although I still think that “excluded volume” is not completely incorrect, since the excluded volume does increase the end-to-end length and therefore the radius of gyration.

However I can accept “pervaded volume” provided that you add a brief definition or explanation of this unfamiliar term for the reader. My problem with your edit is that I find the term nowhere else in Wikipedia or in my 5 polymer books, which is why I assumed (incorrectly I now understand) that it is a synonym for “excluded volume”, a much more common term which is explained in 3 of my 5 books. Also, a Google search shows 62600 hits for “excluded volume” + “polymer”, and only 185 for “pervaded volume” + “polymer”.

In addition to a brief explanation, a reference to a longer discussion would also be helpful, perhaps Witten’s article at http://jfi.uchicago.edu/~tten/Geometric/Geometric.pdf

As for “excluded volume”, I agree that it is well explained in the article on Paul Flory, but a direct search for the term is redirected to “Accessible surface area” which is not at all the same if only because surface is not volume. We could use a separate article on Excluded volume similar to the material in the Flory article. Dirac66 (talk) 20:38, 30 May 2008 (UTC)

Yes, I agree with your response. To start, I have just added a stub on pervaded volume. I also think a page on excluded volume would be quite valuable. The redirect is one excluded volume is indeed completely wrong and should probably be removed immediately, although I personally haven't learned how to do this yet.

I suspect that the reason that the term 'pervaded volume' is less common is because often researchers in this field just use the radius of gyration and consider the cube of the gyration radius. On the other hand, the concept of 'excluded volume' is a fundamental one that is a sort of instrumental physical consideration in polymer physics. There may also be many other nonstandard ways of referring to the 'pervaded volume' of the chain; I believe that it may be less standardized than the term 'excluded volume'. However, this term is used by several prominent authors and to my knowledge it is the dominant term in use right now. I will try to do some additional research to see if there are any other commonly used terms. If so, they should be added to the article on pervaded volume. I also came across the Witten link you mention. After looking at it a bit more at your suggestion I agree that it seems informative on this subject and I have added a link to it to the pervaded volume page.

Locke9k (talk) 22:18, 30 May 2008 (UTC)Locke9k

1. I have moved this discussion to the end of the talk page which should have its sections in chronological order (of first appearance). This ensures that this new section will be retained when the talk page becomes too long and the beginning is archived.

2. The Chain Size section is now very good, as is the new article on pervaded volume.

3. As for excluded volume, I have now replaced the incorrect redirect by a real article stub. I just copied the relevant section from the Paul Flory article and modified the first sentence. I would be glad to see any improvements you can make. The article on Accessible surface area is still in Wikipedia for the biochemists, but without the redirect there is no implication that excluded volume is the same thing.

4. What do you think of adding a note at the end of Excluded Volume to say See also: Pervaded Volume, and vice versa? Dirac66 (talk) 02:10, 31 May 2008 (UTC)

Reorganization of Chain Size and Chain Length sections
Good start on the new excluded volume article. Now we can work on improving / expanding it over time. I will save any discussion on that, such as on the 'see pervaded volume', for that discussion page now that it exists. I actually do have one long term objection to the current 'chain size' section though. I actually do not think that the part on gyration radius and pervaded volume should be in the same section as the rest of the material there. Both gyration radius and pervaded volume are functions of the polymer configuration and not just its size, whereas the rest of the material in that section is actually a correct description of the chain size only. I'm not going to make that change just yet, as I am still mulling over where to fit it into the overall organizational scheme of the page. People have improved on this general organization since I did a major reformat last year but I still think it can use some work to help bump it up to an 'A' article.

Locke9k (talk) 22:19, 1 June 2008 (UTC)Locke9k

Perhaps we should rearrange the two sections Chain Size (now 3.3) and Chain Length (now 4.9). The text on Mn and Mw really belongs in Chain Length, as well as the last sentence on contour length. Radius of gyration and pervaded volume should be a separate section as you say, but I would suggest calling it Molecular Volume or Molecular Size (less ambiguous than Chain Size) and placing it in Polymer Properties (rather than Polymer Structure), perhaps right after Chain Size where we could point out explicitly that molecular volume depends not only on chain length but also on configuration (or "conformation" for organic chemists). Several ideas here - what do you think? Dirac66 (talk) 01:19, 2 June 2008 (UTC)

Yes, this is a good point. I would say that the parts you mentioned belong in 'chain length'. I also think that 'chain length' belongs in 'polymer structure' rather than polymer properties. Part of the general problem I have with this page is that the distinction between 'structure' and 'properties' has not been made entirely clear and unambiguous in the article organization. I would say that the material on pervaded volume etc does belong in a separate section, but it would be better to just call it "polymer conformation" thjan "molecular volume" or "size" as these terms are not used in polymer science to my knowledge and have no clear meaning. I will go ahead and make these changes and we will see how it looks.

Locke9k (talk) 20:20, 2 June 2008 (UTC)Locke9k

Done. I still have organizational objections. When I redid the organization of this page about a year ago one of my objectives was to remove a lot of floating material about structure - property relationship and reorganize it into the structure and property sections as appropriate. As you can see, there is no still some of what I would consider 'trivia' about how they are related that is not cleanly organized in. I will work on it.

Locke9k (talk) 20:24, 2 June 2008 (UTC)Locke9k

Yes, the latest changes are an improvement. The article (and all of Wiki) will never be perfect or "complete", but we can continue to make it better. I have broken this long discussion into two sections for legibility. Dirac66 (talk) 20:47, 2 June 2008 (UTC)

Synthetic polymer page
There is currently a page entitled synthetic polymer. As far as I can tell it is not referenced from here. It also contains virtually no additional information. I suggest people take a look at it a post some opinions on whether to expand it and link to it from here or to absorb it into this page somehow

Locke9k (talk) 21:13, 2 June 2008 (UTC) Locke9k

I suggest renaming ("moving" in Wikispeak) that article *List of synthetic polymers*, which is all it really is, and then linking to it in the See also section. And no, it is not referenced from the Polymer article - I checked the What links here link in the toolbox on the left of the screen. Dirac66 (talk) 21:23, 2 June 2008 (UTC)


 * Forgive my ignorance if I have missed something: a point by someone above about an whether you can have an inorganic polymer, combined with this point, begs the question as too why when I searched for "silo" or "sila" (as roots for siloxane and silane, respectively) I got no results at all. In fact the word silicone(s) only occurs once on this page at current and there are books written solely on synthetic inorganic polymers and their properties. Then we come onto the organic/inorganic hybrid systems which are becoming increasingly important. Maybe there is a good argument then for having so-called synthetic polymers separately (which could further be broken into two articles itself with the "plastics" versus inorganics - although I think this could be overdoing it). Either way, unless I missed something (which is perfectly possible), we are missing important content or at least a fair number of appropriate links. --WhirlwindChemist (talk) 20:43, 29 August 2008 (UTC)

OK. I have now addressed the above concerns by 1. Moving (renaming) Synthetic polymers to List of synthetic polymers 2. Linking to the list from this article - see second paragraph 3. Adding an inorganic section to the list with silicone and polyphosphazene to start.

Much revision of the list is still needed, but at least I have given it an identity separate from this article, and also made it accessible from this article. Dirac66 (talk) 00:18, 30 August 2008 (UTC)

Is the etymology of the word "polymer" accurate?
I was under the immpression the word had two words it originates from. "Poly" meaning many and the "mer" part is from "monomer" meaning the singular molecule form of polymers. For example the monomer of PVC is vinyl chloride and the monomer for polyethylene is ethylene etc. —Preceding unsigned comment added by 58.172.129.176 (talk) 10:26, 20 October 2008 (UTC)

Yes, the etymology of the article is accurate, as the word polymer predates the word monomer. As stated in the article, "polymer" was proposed by Berzelius in 1833 from the two Greek words "poly" and "meros". The words "monomer", "dimer", "trimer" etc. came later and are based on "polymer".

In the 20th century after the structure of polymers was understood, the English word "mer" was introduced as an occasional synonym for repeat unit. Since the shorter word mer derives from the longer word polymer, this is an example of linguistic back-formation. Dirac66 (talk) 16:42, 20 October 2008 (UTC)


 * Note that the original 19th-century definition of polymer meant something very different from the current definition: a substance was a polymer of another substance if its formula was a multiple of the formula of the "monomer". For example, benzene would be a polymer of acetylene, butene a polymer of ethene, and glucose a polymer of formaldehyde. See J. Chem. Ed. 2008, 85, 624. --Itub (talk) 15:40, 23 October 2008 (UTC)

Good point. In fact I added the glucose-formaldehyde example to the article on Berzelius last year (18 May 2007). In this article it is perhaps misleading to include Berzelius in the History section, since he was not dealing with what we now call polymers. I will move him to the Etymology section, note that his definition of polymer is different, and add a reference to the article on Berzelius for the details. (I don't want to actually present his definition in this article, where it could mislead a too-rapid reader into thinking that it is the current definition.)  Dirac66 (talk) 19:19, 23 October 2008 (UTC)

From: Geometric777 Date: April 25, 2009. I have added a paragraph to "Polymer Degradation" citing the article which states polymer degradation can also occur through galvanic corrosion. There are other articles which I may cite later. I have also included "galvanic action" in the first paragraph of "Polymer Degradation". Any comments or feedback on that paragraph would be appreciated. Thank you. Geometric777 —Preceding unsigned comment added by Geometric777 (talk • contribs) 10:56, 25 April 2009 (UTC)

Reorganization
I am doing some heavy reorganization of all the sections relating to polymer properties. There are several reasons for this. First, the present layout leads to a lot of redundancy and doesn't present things in a very clear and easy to follow manner for a newcomer to the subject. It needs a significant change, so I'm giving it a shot. Second, and more importantly, the categorization and presentation of the various types of properties didn't really follow the way they are defined and organized in better textbooks. Since I have a number of such textbooks, I am trying to bring the way the various properties are organized and categorized more into line with the clearest reliable sources (of which there are many, of varying literary quality on this subject). I still have a lot of work to do, so I'll ask for some patience as I get it to a more developed state. Locke9k (talk) 15:50, 19 May 2009 (UTC)

Biological synthesis
I added RNA information as intermediate step from DNA to protein synthesis. DanielGlazer (talk) 21:43, 13 June 2009 (UTC)

Degree of crystallinity and rigidity
There was a small disagreement today over whether *Increasing* or *Decreasing* degree of crystallinity tends to make a polymer more rigid and brittle, with 65.93.99.250 changing Increasing to Decreasing twice and Brian Crawford changing it back once, all without comment. Actually this is a complex question whose answer depends on the polymer and the temperature. Crystals of most small molecules and some polymers are rigid, but remember that amorphous polymers at low temperature form a glassy state which is often quite rigid and brittle.

From Allcock et al, Contemporary Polymer Chemistry, 3d ed (2003) p.546: "Microcrystalline polymers are generally tougher than totally amorphous ones. They can be bent more without breaking, they resist impact better, ..." This is simplified and not always true, but it does imply that as a general tendency, more crystallinity makes the polymer LESS rigid and brittle, in agreement with 65.93.99.250. Dirac66 (talk) 00:04, 3 August 2009 (UTC)

Further comment: the reason polymer crystals are not as rigid and brittle as small-molecule crystals is contained in the word microcrystalline (or semicrystalline) - they contain both crystalline regions which provide strength (toughness) and amorphous regions which provide flexibility. The section requires much work to get it completely right, but I think 65.93.99.250 is more right than wrong. Dirac66 (talk) 00:16, 3 August 2009 (UTC)


 * Actually, the idea that crystalline polymers are more flexible is almost certainly wrong. Firstly, I am looking at Allcock et al, Contemporary Polymer Chemistry, 2d ed (1990) p.527.  It clearly shows that both soft and hard polymers may be tough; there is not a direct correlation between the two.  It clearly enunciates that the two are separate properties.  Thus the quote above has been misinterpreted.  The fact that it can bend more without breaking does not mean that it is more flexible.  Flexibility is usually taken to be the ease of deformation; in other words, it is something like the stress per strain for bending.  This is not the same as the failure strain or stress with bending, which is more like a toughness.  As an aside, from a polymer physics standpoint, it seems very hard to believe that increased crystallinity would ever lead to increased flexibility.  The simple fact is that crystalline regions are far more rigid than amorphous regions.  These rigid regions will be attached to the amorphous regions, of course, thus pinning them in place and reducing their mobility.  This should lead to a reduction in flexibility.  Nevertheless, since this is apparently a point of contention in this discussion, I am simply removing the claim that flexibility is increased and will refrain from re-adding the counterclaim until I can find a more solid sourcing. Locke9k (talk) 17:33, 17 November 2009 (UTC)
 * OK thanks. Apparently I erred in using the word "flexible" whose definition seems to depend on source and context. Since "tough" is another word whose precise definition may not be clear to everybody (it wasn't to me), I suggest adding in parentheses after "tougher" the words "can be bent more without breaking" from Allcock et al (3d ed p.546 or 2d ed p.436): Dirac66 (talk) 23:50, 17 November 2009 (UTC)

Assessment comment
Substituted at 15:35, 1 May 2016 (UTC)