Spin-system, vinyl polymers

Figure 1. Spin Systems in Isotactic Vinyl Polymers...

Figure 5. Spin Systems in Syndiotactic Vinyl Polymers.

The closest physical realization of the system examined above would be a polymer such as poly(vinyl fluoride) doped into poly(ethylene) (observing the r resonance) or poly(trifluoroethylene) doped into poly(tetra-fluorethylene), observing H. Neither of these systems is likely to be sufficiently miscible, and there is the possibility of significant proportions of head-to-head linkages, which would dominate the experimental M2 because of the proximity of the spins on adjacent backbone atoms. 

A preferable system is poly(p-fluorostyrene) doped into poly(styrene). Since rotations about the 1,4 phenyl axis do not alter the position of the fluorine, the F spin may be regarded as being at the end of a long "bond" to the backbone carbon. In standard RIS theory, this polymer would be treated with dyad statistical weights to automatically take into account conformations of the vinyl monomer unit which are excluded on steric grounds. We have found it more convenient to retain the monad statistical weight structure employed for the poly(methylene) calculations. The calculations reproduce the experimental unperturbed dimensions quite well when a reasonable set of hard sphere exclusion distances is employed. 

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