Talk:Tacticity

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Isn't the stereochemistry bit rather a red herring? I think of tacticity as due to the orientations of the monomers - see my added notes on isotactic — Preceding unsigned comment added by Ewen (talk • contribs) 01:44, 28 August 2002 (UTC)

No, tacticity is defined by the stereochemistry of the pendant groups off of the chain. You seem to be describing head-to-tail vs. head-to-head and tail-to-tail addition of monomers, which is an entirely different thing. Jeff 21:34, 25 May 2005 (UTC)

Context tag

I added the context tag because I could not understand most of the terms in the introduction. And one of the critical terms (chiral) leads to a disambiguation page! --- Skapur 00:14, 21 September 2006 (UTC)

• Hi Skapur, I have added some context to the article but do realise that proper understanding of this article requires knowledge of stereochemistry and polymers and that there is really no point in re-introducing these concepts again in this article. From what page did you arrive at this article? V8rik 21:37, 21 September 2006 (UTC)

Merge the isotactic page to this one (copied from isotactic talk page)

Policy: Wikipedia:Wikipedia_is_not_a_dictionary. This page is nearly 100% redundant (including the picture) with the page labeled tacticity. Unless there are plans in the works to expand this article with, for example, multiple notable examples of isotactic polymers, I suggest we merge. Will merge in 7 days if there are no responses. Irene Ringworm 19:35, 25 February 2007 (UTC)

Article could well expand into larger technical article devoted entirely to isotactic polymers.Will take some time though and we do not wish to discourage expects in the field of isotactic polymers to have their specialist contribution added to the very general and entry-level tacticity article. I also carefully read the dictionary guidelines but really was not able to find any justification there for this merge. PS this merge discussion should take place on the tacticity talk page not here according to the merge tag V8rik 21:11, 25 February 2007 (UTC)

Unless you are prepared to expand the article I suggest that we merge it until one of these experts shows their face. The isotactic article has been floundering as a glorified dictionary entry for six years with no real work (except the picture). If you really feel strongly about this I'm okay to leave it where it is - not worth an edit war - but it seems clearcut to me. Hopefully someone else will weigh in? Irene Ringworm 21:22, 25 February 2007 (UTC)

I searched the INSPEC database for review articles, books, and book chapters with "isotactic" in the title or topics. There are several review articles discussing how tacticity impacts physical properties and a review article on the structure of i-PMMA but there are no major publications in the last four decades on the principle of isotacticity alone. I would suggest that, contrary to User:V8rik's argument, the isotactic article has no room for expansion and be merged to the main article. Irene Ringworm 00:27, 26 February 2007 (UTC)

Any argument for merging "isotactic" should also apply to the articles "atactic" and "syndiotactic". Expanding the technical discussion of the different types of tacticity, IMHO as a polymer engineer, would probably make most sense in one combined article, as tacticity is not considered a "field" but more of a characteristic that all polymers with pendant groups have, and the differences between say an isotactic and an atactic polypropylene are more interesting than discussing each separately. (Apologies in advance for errors of form - this is my first contribution to Wikipedia.) Laura-m7 20:37, 26 February 2007 (UTC)

Agreed and done. Irene Ringworm 22:25, 26 February 2007 (UTC)

It would make sense to incorporate all three within this article, as i just searched for tacticity, to find the three terms and their meanings. I think it would be an all round improvement for this article if they were merged. Fizzyfifi 22:20, 29 April 2007 (UTC)

External links

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Head-vs-tail isomerism

Regarding § Head/tail configuration and the issue raised by User:Fishsicles in this edit-summary, head-to-head and tail-to-tail are indeed factually different. The difference is visible in both the File:Tail head isomerism.svg image here in this article and in File:Ferroelectric-wiki-w1.png in the polyvinylidene fluoride article. Notice the differing distances along the polymer backbone for the substituents (the "R" or "F" in those images, respectively). This ChemLibre article illustrates and discusses it further (though that ref-site needs "case by case" analysis for purposes of citing on WP).

Now it is quite possible that some monomers and some polymerization methods only form one or the other. And the choice of what is 'head' vs 'tail' might not be scientifically defined. But given there are two structurally different options that at least gives a self-consistent terminology when discussing certain zones of the chain in specific structures.

However, none of this concept is about tacticity, the topic of this article. It is a constitutional isomeric difference, not a stereochemical one. This topic-scope concern was first mentioned 20 years ago, in the very first discussion on this talkpage, but did not lead to any further discussion or changes to the article. I'm not sure where to move this content, but it's not on-topic here at all. DMacks (talk) 17:57, 22 February 2025 (UTC)

My main reason for the edit as it was was to go with what the source I found on the matter was saying, as the existing claims were all uncited. Said source discussed H-T and H-H, but made no separate focus on T-T (though as it focused on the synthesis of polymers with only H-H bonds, with T-T bonds existing as a consequence of that structure). I agree that it's not really a matter of tacticity, but it's not a topic I'm familiar enough with to write a new page for. Fishsicles (talk) 00:59, 24 February 2025 (UTC)

Also, your listed source is about terpenes - isoprene has two different double bonds at 1 and 4, whereas the vinyl polymers discussed in this article have a single asymmetric double bond where addition is occurring. Not sure how applicable the terminology of one is to the other. Fishsicles (talk) 01:33, 24 February 2025 (UTC)

That terpene case just the first really clear example ref I found of the HH/TT issue. Isoprene polymers are potentially ridiculously more complicated than vinyls, but tacticity is definitely one of the variables in them (see doi:10.1021/acs.macromol.3c00615 for examples). Ring-opening polymerization and acyclic diene metathesis give other classes of polymers with potential head/tail isomeric variation. I'm not sure what target article this material should get. DMacks (talk) 06:26, 24 February 2025 (UTC)

My issue with the terpene case is that the polyisoprene definitions of HH/TT appear to me as qualitatively different than the vinyl definitions used in the existing article text: the polyisoprene case is describing which functional groups are linked, while the vinyl case is describing the orientation of a single functional group, and that the sense used in the vinyl is - at least in principle - applicable to any given type described by the terpene definitions. E.g., isoprene units undergoing 1,2 addition are all considered to be HH by the polyisoprene definitions, but would be distinguished as HH or HT by the vinyl definitions depending on whether the methyl/allyl carbons are adjacent (HH) or separated by CH2 (HT). Of course, this is my mathematician brain zooming in on the corner case - I suspect that the steric effects would basically never allow the double HH case in 1,2 polyisoprene in practice.

It definitely seems like something that warrants discussion somewhere, though I agree not here - but it also seems to be a very niche topic. It may simply warrant its own heading under Polymer#Microstructure, and not a dedicated page unless someone more specialised in the field sees the need to add one? Fishsicles (talk) 14:34, 24 February 2025 (UTC)