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No abstract

The phase structure of a series of random ethylene copolymers with 1-butene, 1-hexene, or 1-octene as comonomers, which have narrow molecular weight and composition distributions, has been studied by treating both the counit content and molecular weight as independent variables. Essentially no difference in behavior has been found between the three types of branches in most of the properties analyzed. However, the interfacial content of the ethylene-octene copolymers showed consistently higher values than the others. The interphase is shown to be a relatively important component of the copolymeric lamellae, with thicknesses varying from 10 to «45 Á. The melting temperatures and the levels of crystallinity of these copolymers adhere to the reference curves established for the model hydrogenated polybutadienes and random copolymers. It is found to be very important to separate and distinguish the influence of molecular weight and of copolymer composition on the phase structure.

Insoluble films of trisilanolisobutyl-POSS and octaisobutyl-POSS at the air/water interface are investigated by means of surface pressure - area per molecule isotherm (Pi - A) and Brewster angle microscopy (BAM). Analysis of the experimental results shows the partial cage molecule, trisilanolisobutyl-POSS, is a surface-active molecule that self-assembles into uniform monolayer upon compression; but the fully condensed cage molecule, octaisobutyl-POSS, is nonamphiphilic.