SPATIAL-DISTRIBUTION OF ADDED HOMOPOLYMER WITHIN THE MICRODOMAINS OF A MIXTURE CONSISTING OF AN ABA-TYPE TRIBLOCK COPOLYMER AND A HOMOPOLYMER

The ordered structure was investigated in binary mixtures of an ABA-ty pe triblock copolymer acid a homopolymer. For the study, we employed ( a) binary mixtures of polystyrene-block-polybutadiene-block-polystyren e copolymer (Kraton D-1102, Shell Development Co.) (hereafter abbrevia ted as K1102) and homopolymer poly(alpha-methylstyrene) (P alpha MS4) having the number-average molecular weight (M(n)) of 3200 and (b) bina ry mixtures of K1102 and homopolymer polystyrene (PS4) having M(n) of 2800. Emphasis was placed on the effect of the chemical structure of a dded homopolymer on the spatial distribution within the microdomains o f the mixtures. The morphology of the mixtures was investigated as a f unction of the volume fraction of added homopolymer (P alpha MS4 or PS 4) and temperature by small-angle X-ray scattering (SAXS) and transmis sion electron microscopy(TEM). The SAXS profiles obtained were analyze d by using one-dimensional paracrystal analysis. It was found that add ed homopolymer, P alpha MS4 or PS4, was solubilized in the PS microdom ains of K1102 but the spatial distribution of the added homopolymer wi thin the PS microdomains was different. Specifically, both the results of TEM and SAXS indicate that the added P alpha MS4 was not distribut ed uniformly within the PS microdomains of K1102, showing a tendency o f being localized at the center of the PS microdomains, whereas the ad ded PS4 was distributed uniformly within the PS microdomains of K1102. The localization observed in the K1102/P alpha MS4 mixtures was ascri bed to the: repulsive interaction between the PS chains in K1102 and a dded homopolymer P alpha MS chains. However, we observed a tendency th at added P alpha MS was distributed uniformly within the PS microdomai ns of K1102 as the temperature was raised. This was explained by the t emeperture dependence of the interaction parameter between PS and P al pha MS.