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We discuss the applicability of forced Rayleigh scattering (FRS) as a means of a direct determination of possible diffusional anisotropies on the block copolymer systems with lamellar morphology. We report a first result which directly indicates the anisotropy of diffusion in this system. For this purpose the diffusion measurements were conducted on a bulk poly(styrene-6/ocfe-isoprene) copolymer (Mn = 2.12 X 104) in the ordered state and in directions parallel and perpendicular to the surface of an oriented film at temperatures higher than the glass transition temperature of polystyrene microdomains.

ABSTRACT:In the presence of 2,6-dimethylpyridine as an added base, living cationic polymerization of isobutyl vinyl ether was achieved in n-hexane at O to +40°C with the 1-(isobutoxy)ethyl acetate (3)/ethylaluminum dichloride [CH3CH(OiBu)-OCOCH3/EtAICl2] initiating system. A low concentration of the pyridine, 4 times that of the cationogen 3 ( or the active end), was sufficient for the living process. Without the added amine, the polymerization was almost instantaneous and nonliving. The use of triethylamine and less hindered pyridines (pyridine, 2-methylpyridine, and 2,4-dimethylpyridine), in place of the 2,6-dimethyl derivative, failed to induce living polymerization but instead resulted in chain termination. In contrast, highly crowded 2,3-dit-butylpyridine could not affect the polymerization by 3/EtAICl2 at all. It is proposed that 2,6-dimethylpyridine stabilizes the otherwise unstable growing carbocation via a nucleophilic interaction to endow it with livingness. The effects of the pyridine structures showed not the basicity but the steric crowding around the nitrogen to play a critical role in the nucleophilic stabilization of the growing cation.