Latent microcapsule catalysts from ATRP-derived copolymers for heat-triggered curing of one-component silicone rubbers

Abstract

Microencapsulated curing agents (MCA) offer a novel solution with considerable industrial promise. In this study, we synthesized various polymethyl methacrylate-polybutyl methylacrylate (P(MMA-co-BMA)) random copolymers with a narrow molecular weight distribution via atom transfer radical polymerization (ATRP), adjusting the monomer ratios of methyl methacrylate and butyl methylacrylate. Subsequently, MCAs termed Kar/P(MMA-co-BMA) were prepared utilizing the solvent evaporation method, wherein P(MMA-co-BMA) served as the wall material and the Karstedt catalyst as the core material. The glass transition temperature of the resulting polymers ranged from 83 to 99 °C, easily modifiable by varying the monomer feed ratios. Characterization revealed an average particle diameter of approximately 7 µm and a core content of about 20 wt%. Additionally, we evaluated the curing characteristics of one-component silicone rubber incorporating different MCAs, finding that the formulation achieved complete curing at 100 °C within one hour. Notably, decreased BMA content significantly increased ambient latency time, exhibiting a latency of 10 weeks.