The effect of size and concentration of nanoparticles on the glass transition temperature of polymer nanocomposites

Abstract

Numerous studies have reported a possibility of alteration of the polymer glass transition temperature (Tg) by the introduction of nanoscale particles. Here we use model nanocomposites based on polystyrene and polyphenylene dendrimers to show both theoretically and experimentally that inclusion of rigid nanoparticles of 2.3-5 nm size into the polymer leads to a negligible Tg increase, not exceeding the experimental measurement error. Furthermore, we establish a strategy for preparation of the polymer nanocomposites with Tg modified significantly from a practical point of view. We find that to form a uniform distribution in the polymer matrix the size of thermodynamically compatible nanoparticles should not exceed 2.3 nm. An increase of the particle diameter by 2 nm inevitably leads to the formation of filler aggregates.