Patent ID: 7151155

Claim:
A copolymer polymerized from monomers including, (i) a cyclic ester of at least a five membered ring; and (ii) a cyclic formal of a substituted or unsubstituted diol having at least 3 atoms between the hydroxyl groups of the diol; wherein the cyclic ester and the cyclic formal monomers comprise at least 50 wt. % of the total monomers based on the total weight of the copolymer; wherein the copolymer is polymerized in the presence of a polymerization initiator selected from the group consisting of ethylene glycol; 1,4-butanediol; 1,6 hexanediol; 1,3-propanediol; 2,2-dimethyl-1,3-propanediol; diethylene glycol; triethylene glycol; glycerol; 2-ethyl-2-hydroxymethyl-1,3-propanediol; 2-methyl-2-hydroxymethyl-1.3-propanediol; 2-methyl-2-ethyl-1,3-propanediol; 2-ethyl-2-butyl-1,3-propanediol; 1,3-bis(hydroxymethylcyclohexane); 1,4-bis(hydroxymethylcyclohexane); and mixtures thereof.