Polymer chains structural elements

Chain Structure. The chemical composition of poly (vinyhdene chloride) has been confirmed by various techniques, including elemental analysis, x-ray diffraction analysis, degradation studies, and in, Raman, and nmr spectroscopy. The polymer chain is made up of vinyhdene chloride units added head-to-tail ... 

The struetural element of a eoumarone-indene resin is relatively similar to that for aromatie hydroearbon resins, as they differ only in the proportion of indene-type struetures which are present in higher eoneentration in the eoumarone-indene resins. The main monomers in the aromatie resins are styrene and indene. Styrene produces the atactic conformation of the resins, whereas indene introduees rigidity into the polymer chain. A typical structural element of an aromatie resin is given in Fig. 11. 

The polymer chains of P VP in complex 2 in comparison with chains of both the pure PVP and the PVP in complex 1 change their functional characteristics, e.g., they bind the organic ions in water more effectively. Such changes can be caused by the structural reorganization of PVP macromolecules at the final stage of the complex 2 formation destroying of the elements of internal structure of PVP chains during their interaction with C60 (Krakovjak et al., 2006). 

The elements of mirror symmetry d, m, and c can be removed in different ways, resulting in different classes of chiral polymers. Plane d containing the polymer chain is eliminated by the presence, in the main chain, of tertiary carbon atoms —CHR—), or of quaternary atoms with different substituents (—CR R"—), or with equal chiral substituents (—CR R —). Mirror glide plane c does not exist in isotactic structures, nor in syndiotactic ones in which the substituents are chiral and of the same configuration, 75 (33, 263). The perpendicular planes, m, are eliminated by the presence of chiral substituents of the same sign in syndiotactic, 75 (33, 263) or isotactic structures, 76 (263) or if the two directions of the chain are rendered nonreflective. This last condition can be realized in different ways some of which follow (264) ... 

The properties of polymers are not only determined by their primary chemical structure but also by secondary structural elements. This is also tme for the process of biodegradation. In a first step, the secondary structures of the polymer, e.g., crystals in a partially crystalline polymer, have to be dissolved during the degradation process and temporarily flexible chains formed. 

Fig. 8. Schematic representation of heteroatom-containing structural elements in polymers that are disposed for characterisation by 1H/X/Y triple resonance experiments where X = 13C and Y = 19F, 31P, 29Si, 119Sn, with possible coherence transfer pathways being indicated by single and double headed arrows.36 39 Selective observation of the correlations of the building blocks in (a)-(c) requires experiments involving out-and-back coherence transfer via Vc.h/ -A.x (a), Vc.h/ cx (b), or / . (c), whereas the simultaneous observation of all correlation signals originating from a chain of an isotope labelled sample (d) is feasible by means of a HCa(Y)-CC-TOCSY sequence.39...

Polymer chain - The chain of elements that form the basis of the structure of a polymer. The elements may be all carbon atoms, carbon and oxygen, silicone, nitrogen, etc. 

Where a melt-crystallized polymer has been processed by drawing, rolling or other means to produce an aligned structure in which lamellae as well as polymer chains have discernible order, a pseudocrystalline unit cell is present. Provided that this unit cell contains elements of the crystals as well as the boundaries between crystals and that it is entirely typical of the material as a whole then it could be considered as a RVE within the meaning defined above. The lamella crystal itself sometimes considered as embedded in an amorphous matrix would not seem to be an acceptable RVE for reasons similar to those advanced against the Takayanagi model, namely that its modulus is dependent upon the surface tractions. The boundaries between lamella crystals in the matrix must be included in an acceptable RVE. 

In practice the structure of any given polymer sample is by no means as regular as the above classification would imply and in most cases defies description in terms of recognizable structural elements. For example, Wunderlich64 shows examples of cobweb structures which can be found in polymers. Clearly, for the purposes of research specific structures have been identified and studied - but this does not mean that a regular solid of macroscopic dimensions may be contracted with these structures. In polymers therefore, we always have to deal with statistical assemblies of elements more or less precisely defined as e.g. lamellar crystal, fibrous crystals, tie chains etc. 

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