Copolymerization of MMA With HEMA Together With Their Transesterification to Yield Tough and Transparent PMMA

ABSTRACT Poly(methyl methacrylate) (PMMA) possesses high optical transparency but suffers from insufficient mechanical strength. Most toughening methods compromise optical clarity, processability, or industrial scalability. Herein, we present a scalable toughening strategy based on copolymerization of methyl methacrylate (MMA) with 2‐hydroxyethyl methacrylate (HEMA), combined with transesterification between their units. The resulting random MMA‐co‐HEMA copolymers retain excellent visible‐light transmittance (above 90.0%, 5 mm) while achieving remarkable mechanical enhancements, including increases of 74% in tensile strength and 22% in impact strength compared with linear PMMA. Further studies reveal that the transesterification between HEMA and MMA units induces a lightly cross‐linked network. This approach not only offers advantages in simplicity, cost‐effectiveness, and compatibility with industrial processes such as casting molding, but also effectively prevents uncontrollable autoacceleration during bulk polymerization. These findings provide new insights for the designing of high‐performance optical thermoplastics with promising potential in structural optical applications.