Butadiene and styrene copolymerize to form styrene-butadiene rubber.
Tips
usage
Two distinct registers: in everyday speech 共聚 means 'to come together' (typically family or old friends - fixed phrase 共聚一堂 'all gathered under one roof'). In chemistry 共聚 = 'copolymerize', and 共聚物 = 'copolymer'.
memory
共 (together) + 聚 (gather) - semantically transparent. The chemistry sense is a calque of 'co-polymerize' built on the same 共- prefix.
