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Question

Polymers are long chains ⛓️ of covalent bonds.

Can similar structures exist for ionic and/or metallic bonding? They don't have to be as useful.


I know there can be polymers with ionic bonds in them, but I am talking about the entire structure (at least the base) being ionic and/or metallic.


Just in case, could they exist for other types of bonding too?

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    $\begingroup$ Would you consider a monocrystal of a ionic compound or of a metal as a ionic or metallic polymer? $\endgroup$
    – Poutnik
    Commented Apr 6, 2023 at 13:31
  • $\begingroup$ @Poutnik Can it form a chain? Like a string. $\endgroup$
    – Aseku Vena
    Commented Apr 6, 2023 at 13:32
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    $\begingroup$ They are 3D polymers. Like classical organic covalent linked polymers. But linked much more properly. Short linear chains are possible, but I would not call them polymers. They are hard to form and easy to break. $\endgroup$
    – Poutnik
    Commented Apr 6, 2023 at 13:35
  • $\begingroup$ @Poutnik That would fit some definitions, but I was looking for something that forms a chain. $\endgroup$
    – Aseku Vena
    Commented Apr 6, 2023 at 13:36
  • $\begingroup$ There would be the problem the forces along the assumed ionic/metallic chains would be the same as between the chains. $\endgroup$
    – Poutnik
    Commented Apr 6, 2023 at 14:09

1 Answer 1

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In the case of ionic bonding, the answer would be that a stable structure is unlikely, although examples may exist among multimeric proteins. You may also check out the work of George Whitesides and others in the field of self-assembling soft matter.

However, to be clear, it is assumed that the arrangement in question is of alternating charges in a regular linear sequence (...+-+-+-+-+-+-...), that the attraction between nearest neighbors is isotropic, and that the arrangement is free of other forces (such as external fields). There could be a solvent but if it competes with the ionic interactions then stability is certainly impossible. Such an arrangement would be unstable in a vacuum as well except under exceptional circumstances. The reason is that electrostatic attraction operates over long distances, and charges will therefore experience attraction and repulsion from more than the nearest neighbors. In addition, since the bonding is assumed isotropic, there is little to interfere with bending under the influence of these forces and in the presence of thermal agitation. If one monomer can bond to more than two (coordination number>2) then a sheet or a nonlinear 3D structure will ensue.

However, if one monomer can bond stably to only two others, then an entangled, reptating polymer-like structure would result.

With regard to metallic bonding, there is such a thing as a "molecular wire". These can form electrically conductive single macromolecules. However I can't at present comment on whether bonding in these would be regarded as metallic, at least in a way comparable to bonding in traditional metal solids.

You might ask at matter modelling SE whether such models have been studied in silico.

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