Thermal Degradation and Synthesis of Block Copolymers of Styrene and n-Butyl Methacrylate by Atom Transfer Radical Polymerization

Poly(n-butyl methacrylate) (PnBMA)-b-polystyrene (PS) (diblock), PnBMA-b-PS, and PnBMA-b-PS-b-PnBMA (triblock copolymers) were synthesized by atom transfer radical polymerization (ATRP), using PnBMA and PnBMA-b-PS with C-Br-end-group as macroinitiators. The diblock and triblock copolymers were characterized by 1H-NMR, FT-IR spectroscopy, and differential scanning calorimetry (DSC). The molecular weight and molecular weight distributions were obtained by gel permeation chromatography (GPC). Polymerization was controlled up to a molecular weight of 46,200, and the polydispersity index was 1.33. The experimental results showed that the polymerization was controlled/living. The thermal degradation behavior of the block copolymers was studied using thermogravimetry (TG) and a single line vacuum system consisting of a degradation tube with a condenser for product collection and a liquid nitrogen trap (−196°C). The block copolymers were heated from ambient temperature to 500°C. The products of degradation were collected at two different fractions, which are cold ring fraction (CRF) and volatile liquid fraction (VLF) trapped at −196°C. All the fractions of diblock and triblock copolymers were investigated by means of IR, 1H-NMR, and GC-MS. In this study, n-butyl methacrylate and styrene are given as major products of degradation. On the other hand, the most important minor products are benzene, ethyl benzene, ethyl methacrylate, and toluene.