Constitution, Configuration and Conformation in Amorphous Polymers

We consider a general bisubstituted vinyl polymer (Fig. 8.a) with two different sidegroups. For the characterization of its geometry, the following notions must be recognized. A more detailed account can be found in many textbooks on organic chemistry or polymer science, e.g. [8]. 

Constitution refers to the binding situation, i.e. the sequence of atoms in a molecule. Systems which have the same sum formula, but different structural formulae are called constitutional isomers. The transformation of one constitutional isomer into another requires breaking and forming chemical bonds with activation energies 1 eV (96.5 kj/mol). Polymerization defects like head-head-addition (in place of the desired head-tail-addition) introduce constitutional isomers which sometimes have pronounced effects on the material properties. For simplicity however, an ideal, defect-free constitution of the systems inquired will be assumed throughout this review, and constitutional isomerism will not be discussed. 

In FClBr-methane (b), the central carbon atom is asymmetric (or chiral), and the molecule and its mirror image can be transformed one into another only by a chemical reaction or the influence of a catalyst. The two molecules are said to differ in configuration. 

In extended vinyl polymer chains, only relative chiralities can be distinguished. In a meso diad (c), two consecutive pseudoasymmetric carbon atoms (C2, C4) have the same configuration, whereas in syndiotactic diads (d) the configuration is opposite 

The presence of various configurations in a sample gives rise to a configurational splitting in the solution NMR spectrum. This aspect will be discussed in some more detail in Sect. 3.7. 

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