What is plexiglass made of?

Per Wikipedia: "Poly(methyl methacrylate) (PMMA) poly(methyl 2-methylpropenoate) is a thermoplastic and transparent plastic. Chemically, it is the synthetic polymer of methyl methacrylate. It is sold by the trade names Plexiglas, Vitroflex, Limacryl, R-Cast, Per-Clax, Perspex, Plazcryl, Acrylex, Acrylite, Acrylplast, Altuglas, Polycast, Oroglass, Optix and Lucite and is commonly called acrylic glass, simply acrylic, perspex or plexiglas. Acrylic, or acrylic fiber, can also refer to polymers or copolymers containing polyacrylonitrile. The material was developed in 1928 in various laboratories and was brought to market in 1933 by Rohm and Haas Company." This is not the same as Lexan, which is far more rigid and impact resistant ... for instance, retrofit of automobile glass (race cars: shatterproofing, weight reduction) would call for Lexan rather than Plexiglas.