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A model set of 1,4-polybutadiene-l,2-polybutadiene diblock copolymers has been prepared and molecularly characterized. Physical characterization by differential scanning calorimetry (DSC) and qualitative identification of the flow behavior (liquidvs. solid-like) over a period of several days have established die critical degree of polymerization for this system as Nc = 1.20 (± 0.14) X 103. Below the microphase separation transition the polymers exhibit a single broad glass transition, as measured by DSC, which has been attributed to local segment density fluctuations. This effect was found to be dependent on the degree of polymerization, as predicted from theory.

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Solubility (S) and diffusion (D) of water in low-density polyethylene have been studied by means of desorption experiments. The dependence of S and D on the state of oxidation of the polymers has been measured. A model has been developed to describe the bound-oxygen dependence of S and D. Physically the oxygen groups act as traps that are strong enough to bind the water but not so deep as to remove the water from the diffusion process. Hydroxyl, hydroperoxide, and carboxylic acid groups form the strongest traps, ketone groups are weaker, and ester groups exhibit negligible trapping. Permeation is unaffected by bound oxygen. Trap volumes deduced from the analysis lie in the range of a few cubic angstroms. Some restriction of rotational motion of the trapped water is required by the analysis, and independent NMR evidence is presented to support this result.

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