Temperature-Dependent Coarse-Grained Force Field for Polymethacrylate-Based Copolymers: Sequence- and Composition-Dependent Glass Transition Temperatures

Polymethacrylate-based copolymers are key materials in photoresists, where the glass transition temperature Tg is a critical parameter influencing heat resistance, diffusion properties, and ultimately lithographic performance. Predicting Tg accurately remains challenging due to the complex interplay of composition, sequence, and chain length. In this study, we developed a temperature-dependent coarse-grained force field (CGFF) for poly(methyl methacrylate) (PMMA), poly(1-adamantyl methacrylate) (PAdMA), and their copolymers. The CGFF was constructed via iterative Boltzmann inversion from all-atom molecular dynamics trajectories, with the temperature across the 300–600 K range enhanced by Lagrange interpolation. The simulations with the developed CGFF reproduce a Flory–Fox relationship between Tg and reciprocal molecular weight, and a scaling relation between the mean-square radius of gyration and chain length for the homopolymer and alternating copolymers. Using coarse-grained molecular dynamics simulations, we systematically investigated the effects of chain length, composition, and sequence on Tg of P(MMA-co-AdMA) copolymers. The Tg exhibits a nonlinear composition dependence─negative deviation at low MMA content and positive deviation at high MMA content. These phenomena were further elucidated by tracking changes in persistence length, density distribution, contact probability, and free volume. This work demonstrates a robust multiscale framework for efficiently predicting Tg in complex copolymer systems.