a process for preparing lactam - polyol - polyacyl lactam or acyl polylactam terpolymers having ester end group termination and both ester linkages and amide linkages between the monomeric segments . the terpolymers are prepared by initiating the anionic catalyzed polymerization with a polyester initiator formed from dicarboxylic acid esters and aliphatic polyols and / or aliphatic polyether polyols . this is a division of application ser . no . 482 , 532 filed june 24 , 1974 , u . s . pat . no . 3 , 944 , 629 .