The physical properties of well-defined alternating copolymers poly (methyl methaerylate-alt-styrene) and poly(n-butyl methacrylate-alt-styrene), prepared by reversible addition-fragmentation chain transfer polymerization in the presence of Lewis acids, were investigated with differential scanning calorimetry, wide-angle X-ray scattering, and dynamic mechanical measurements. The properties were compared with those of random copolymers of the same overall composition and the corresponding homopolymers. Wide-angle X-ray scattering data showed that the alternating copolymers possessed a more regular comonomer sequence than the random copolymers. The thermomechanical properties of alternating copolymers and random copolymers were quite similar and typical for amorphous polymers, but in one of the cases studied the glass-transition temperature for alternating copolymer was remarkably higher than for the random copolymer. (c) 2005 Wiley Periodicals, Inc.