A novel polymethyl methacrylate (PMMA) with excellent optical and thermal properties-bearing hydroxyadamamtyl substituent

Polymethyl methacrylate (PMMA) is an important thermoplastic polymer and a versatile lithographic resist. However, the low heat resistance and low dry-etch resistance seriously restricts the application of PMMA in high-end devices and advanced nanolithography. Herein, methyl methacrylate (MMA) was copolymerized with two comonomers 1-adamantyl methacrylate (AdMA) and 1-acryloyloxy-3-hydroxyadamantane (HAdMA), and a series of copolymers P(AdMA-co-MMA) and P(HAdMA-co-MMA) with different contents of HAdMA were prepared. The UV–Vis, ellipsometer, DSC, TG, and TG–MS techniques were employed to investigate the effects of adamantyl and hydroxyadamantyl substituents on the optical and thermal properties of PMMA. The introduced hydroxyadamantyl not only significantly enhanced the refractive index, but also maintained the high transparency and low dispersion of PMMA. The glass transition temperature and thermal stability of PMMA were also greatly improved by the hydroxyadamantyl. The initial decomposition temperature of PMMA increased from 160 to about 260 ℃ after introducing 5% HAdMA. HAdMA was more effective than AdMA in improving the optical and thermal properties of PMMA. The novel P(HAdMA-co-MMA) copolymer has overcome the shortcomings of traditional PMMA and is anticipated to significantly broaden its range of applications.