Abstract: | In the cationic polymerization of isobutyl vinyl ether (IBVE) with binary initiating systems consisting of a protonic acid as an initiator and a Lewis acid as an activator/catalyst, phosphoric acid derivatives (RO)2POOH] coupled with SnCl4 gave highly isotactic poly(IBVE)s, whereas those with a bulky substituent (R), C4H9CH(C2H5)CH2O]2POOH ( 7 ) and (n‐C10H21)2POOH ( 8 ), led to the highest isotacticity meso dyad (m) = 86%]. In contrast, isospecificity was lower with IBVE–HCl and CF3COOH under the same conditions. From the effects of the polymerization temperature (?78 to 0 °C), it was concluded that the high isospecificity with 7 and 8 was due to an enthalpic factor. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1067–1074, 2001 |