A kinetics study on the in situ reversible addition–fragmentation chain transfer and free radical polymerization of styrene in presence of silica aerogel nanoporous particles

Abstract

Nanoporous silica aerogel particles were synthesized via sol–gel process and modified with a hydrophobic surfactant. Batch polymerizations of styrene in presence of silica aerogel particles were studied via free radical and reversible addition–fragmentation chain transfer (RAFT) polymerizations. Monomer conversion, molecular weight, and polydispersity index of each system were monitored during polymerization to investigate the reaction kinetics. According to results, in both systems, the presence of silica aerogel particles has a sensible influence on polymerization kinetic and adding aerogels results in decreased polymerization rate, conversion, and molecular weight. Moreover, the prepared samples were characterized by Fourier transform infrared spectroscopy. Also, thermal gravimetric analysis (TGA) and differential scanning calorimetric techniques was used to observe the effect of aerogel particles on thermal properties of synthesized nanocomposites. According to TGA depiction, in free radical samples, one-stage degradation, related to random chain scission, is observed while degradation of RAFT-prepared nanocomposites occurred in two steps due to the decomposition of RAFT moieties and random chain scission.

Keywords:

• silica aerogel nanoparticles
• RAFT polymerization
• kinetics
• free radical polymerization
• styrene