Spectra of methyl methacrylate polymers in chloroform solution at 90° show three α‐methyl proton peaks. Measurements of their areas in spectra of polymers prepared with free radical and anionic initiators indicate that these may be attributed to (1) isotactic sequences (ddd or lll), (2) syndiotactic sequences (ldl or dld), and (3) heterotactic sequences (ldd, dll, ddl, or lld). The conformation and stereochemical configuration of the chains may thus be examined with considerable discrimination; degrees of regularity, block sizes, etc. appear to be determinable. Free radical polymers of methyl methacrylate are found to be predominantly syndiotactic, whereas those produced with anionic initiators. such as n‐butyllithium, are shown to be predominantly isotactic, in agreement with the findings of others. The backbone methylene resonance also shows striking changes with chain stereochemical configuration, such as to provide absolute, independent confirmation of the assigned structures.

The adsorption parameters (R) of polyalkoxy alkanes CH 4-z Z z , CH 3-z Z z (CH 2 ) n H, and Z(CH 2 ) n CH 3-z Z z , in which Z is either CH 3 O or CH 3 CH 2 O, were established experimentally in the usual way. 1-10 In the cases of those homologous series that comprise the structural classifications CH 3-z Z z (CH 2 ) n H or Z(CH 2 ) n CH 3-z Z z , the R n -values for only two or three of the lower members (n < 5) in a given series were determined experimentally; the rest were established by extrapolation or interpolation using the appropriate log R n Vs n linear relationship, as described in the text. The results obtained thereby support the conclusions derived earlier from similar studies 6 in which Z was either a chloro or a bromo substituent, namely, that liaison between the adsorbed molecule and the polymer at liquid-saturation is monodentate rather than polydentate. The other Z-substituents on the carbon atoms adjacent to the adsorption site affect R in a manner that reflects not only the net influence of electronic and steric contributions at this site but also the affinity of these substituents for the mobile sorbed-but-not-adsorbed molecules in the liquid-saturated system. Hence, systematic incrementation of these Z-substituents to the allowable limit at constant n does not afford a linear log R z Vs z relationship but rather reflects one that exhibits a maximum at z ) 2 or 3, depending upon the series. On the other hand, similar systematic incrementations of Z on carbon atoms further removed from the adsorption site do exhibit log R z Vs z linear relationships at constant n in the manner previously noted for log R n Vs n relationships at constant z.

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Many polymers in solution exhibit well‐resolved NSR spectra, in contrast to the broad peaks observed for the solid state. The peaks for polystyrene dissolved in carbon tetrachloride are not very much broader than those of cumene and other small organic molecules. When segmental motion is restricted or prevented, polymer peaks may become very broad even in solution. This is observed for poly‐γ‐benzyl‐L‐glutamate in trichloroethylene, in which it probably exists as large aggregates of α‐helices. It is shown that the α‐helical conformation itself is not responsible for this broadening. Many proteins also show poorly resolved spectra in the native state, but well‐resolved peaks in the unfolded state. Large “anomalous” shifts observed in the positions of the proton peaks in the NSR spectra of polystyrene and substituted polystyrenes are interpreted in terms of a π‐current model of the benzene ring. It is concluded that where sequences of 10 or more phenyl groups are present on a polymer chain, they tend to cluster together in a quasi‐crystalline arrangement.

The NMR spectrum of polytrifluorochloroethylene in 3,3′‐bistrifluoromethylbiphenyl solution at 150°C. consists of two doublets having unequal components. Those at lower field correspond to CF2 chain units, while those at higher field correspond to CFCL units. In the CF2 doublet, the weaker component (at lower field) is found to have half the area of the stronger (at higher field), for polymers prepared over a 120°C. range of polymerization temperatures. By comparison to the spectra of the model compounds meso‐ and dl‐CF2ClCFClCF2CFClCF2Cl, the peaks of which closely coincide with those of the polymer when both are compared at 150°C., it is concluded that of the two CF2 peaks in the polymer spectrum, the weaker one represents CF2 groups which are between monomer units in isotactic dyads whereas the stronger one represents CF2 groups which are between monomer units in syndiotactic dyads. It follows that in trifluorochloroethylene propagation, syndiotactic dyad formation is twice as probable as isotactic dyad formation. This preference for syndiotactic placement corresponds to an activation entropy for isotactic propagation 1.38 e.u. more negative than that for syndiotactic propagation; there is no difference in the activation enthalpies. This behavior is in contrast to that previously found for methyl methacrylate propagation; here, preference for syndiotactic placement is entirely dictated by a greater activation enthalpy for isotactic placement.