Study on positron lifetime spectra of polymethyl methacrylate-methyl acrylic acid/ladder-like polyphenyl silsesquioxane in situ blends

Relationship between size or concentration of free-volume cavities in P(MMA-MAA)/ladder-like PPSQ blends and the composition was studied by the positron annihilation technique. Curves of positron lifetime vs. temperature for the blends with two different compositions indicate that there are two structural transitions, Tβ and Tg and that Tβ and Tg for Sample C5(5% PPSQ) are lower than those for Sample C1(1%PPSQ) because Sample C5 has a greater free-volume fraction than Sample C1. Effect of thermal history on the structure of P(MMA-MAA)/PPSQ was also investigated. It is shown that the relation of average lifetime and temperature is similar to that of free-volume fraction and temperature