Thermal degradation of hydroxyalkylated poly(dimethylsiloxane)s and poly(dimethylsiloxane)-poly(trialkylsilyl methacrylate) based block copolymers synthesized by RAFT polymerization

Thermal degradation of hydroxyalkylated poly(dimethylsiloxane)s (PDMS-OH), poly(dimethylsiloxane)s bearing a chain transfer agent moiety (PDMS-CTA) for RAFT polymerization and block copolymers based on these poly(dimethylsiloxane)s containing tert-butyldimethylsilyl methacrylate (MASi) and butyl methacrylate (BMA) monomer units was investigated using thermal gravimetric analysis (TGA). The results showed that the hydroxyl end group in PDMS-OH takes part to the PDMS chain degradation in nitrogen atmosphere, the higher hydroxyl group concentration in the samples the lower thermal degradation temperatures. The degradation of the PDMS block (5000 g mol−1 and 10,000 g mol−1) in PDMS-block-PMASi, PDMS-block-poly(MASi-stat-BMA) and poly(MASi-stat-BMA)-block-PDMS-block-poly(MASi-stat-BMA) copolymers with similar molar mass values and similar PDMS block molar mass started at lower temperatures when the amount of MASi in the second block increased. The thermal degradation temperature of the methacrylic block whose number-average molar mass is in the range of 10,000 g mol−1 to 50,000 g mol−1 was inversely proportional to its length. Moreover, TGA results were useful to demonstrate that the thermal degradation of triblock copolymers starts at a lower temperature in comparison with diblock copolymers prepared from trithiocarbonate-based PDMS RAFT agents of similar molar masses.