聚甲基丙烯酸甲酯Poly(methyl methacrylate)

每个重复单元的季碳上连有甲基和甲氧羰基，空间位阻大使链段刚硬，工业品为无规立构、非晶态，玻璃化温度约 105 °C。没有结晶区散射光，因此高度透明，可透过可见光并部分透过紫外线（波长 300 nm 以上）。耐候性好，户外使用多年不发黄。表面硬度低于玻璃，易划伤；能溶于丙酮、氯仿等溶剂，可用溶剂黏接。

Each repeat unit carries a methyl and a methoxycarbonyl group on a quaternary carbon, and the steric bulk stiffens the chain; commercial PMMA is atactic and amorphous with a glass transition near 105 °C. With no crystallites to scatter light it is highly transparent, passing visible light and some UV above about 300 nm. It weathers well without yellowing for years outdoors. It scratches more easily than glass and dissolves in acetone and chloroform, so it can be solvent-welded.

1877 年菲蒂希和保罗合成了甲基丙烯酸甲酯并观察到其聚合。1928 年起德国罗姆-哈斯公司的奥托·罗姆研究丙烯酸酯，1933 年以 Plexiglas 商标推出 PMMA 板材；英国 ICI 以 Perspex 推出类似产品。二战期间 PMMA 被大量用于战斗机座舱罩和炮塔。医生发现飞行员眼中的 PMMA 碎片几乎不引起排斥反应，由此在 1949 年发明了人工晶状体。

Fittig and Paul made methyl methacrylate in 1877 and saw it polymerise. From 1928 Otto Röhm of Röhm & Haas studied acrylates, and in 1933 the company launched PMMA sheet as Plexiglas, while ICI in Britain launched it as Perspex. In the Second World War PMMA was used massively for fighter canopies and gun turrets. Doctors noticed that PMMA splinters in pilots' eyes caused almost no rejection, which led to the intraocular lens in 1949.

PMMA 用于广告灯箱、展示柜、水族馆观察窗、汽车尾灯罩、光导纤维、骨水泥、假牙和硬性隐形眼镜。PMMA 的上限温度约 220 °C，加热到 300–400 °C 可解聚回收单体，回收率超过 90%，是少数可高效化学回收的塑料。

PMMA is used in illuminated signs, display cases, aquarium windows, car tail-light lenses, plastic optical fibre, bone cement, dentures and rigid contact lenses. With a ceiling temperature near 220 °C, heating to 300–400 °C depolymerises it back to monomer with over 90% recovery, making it one of the few plastics that can be chemically recycled efficiently.