【正确答案】The polymerization approaches to improving the properties of polymers include copolymerization, terpolymerization, and multicomponent polymerization. For example, butyrene is tough but weak, and polystyrene is a brittle polymer that has limited toughness and poor chemical resistance. But through copolymerization of acrylonitrile with styrene, it is possible to obtain a chemically resistant, more rigid, and stronger plastic. Copolymerization of butadiene and styrene results in an elastomer, and theterpolymerization of acrylonitrile, butadiene, and styrene produces ABS plastics that are though and elastomeric, and have good chemical resistance.