A copolymer composition comprises an arylate polyester unit, an aromatic carbonate unit, and a soft-block moiety, wherein individual occurrences of the soft block moiety are linked by a spacer unit comprising one or more of the arylate polyester units, one or more of the aromatic carbonate units, or a combination comprising each of these. In one embodiment, a soft block moiety comprises a polysiloxane unit. A film of the composition has a percent transmittance of greater than or equal to 60% as determined according to ASTM D1003-00. A method of forming a copolymer composition is disclosed, comprising substantially forming the bis-haloformates of a dihydroxy compound comprising an arylate polyester unit, and a dihydroxy compound comprising a soft-block moiety, and reacting the bis haloformates with a dihydroxy aromatic compound.