AbstractAnionic copolymerizations of styrene (M1) with excess 1‐(4‐dimethyl‐aminophenyl)‐1‐phenylethylene (M2) were conducted in benzene at 25°C for 24h, usingsec‐butyllithium as initiator. Narrow molecular weight distribution copolymers with M̄;n= 16.1 × 103g/mol (M̄w/M̄n= 1.04) and 38.2 × 103g/mol (M̄w/M̄n= 1.05), and 24 and 38 moles of M2per macromolecule, respectively, were characterized by size exclusion chromatography,1H NMR spectroscopy and DSC. The monomer reactivity ratio, r1= 5.6, was obtained from the copolymer composition at complete consumption of M1, assuming that the rate constant k22=0,i.e. r2=0. The polymers exhibitedTgvalues of 128 and 119°C, respectively, which correspond to an estimatedTg= 217°C for the hypotheti