Alkaline polymerization of 6-caprolactam. XLVIII. Fraction of acyl groups of the activator incorporated in high-molecular weight polymer

C) that approximately 90% of acyl groups from the activator become incorporated in the high-molecular weight polymer dijring polymeriza­ tion at 175-280°C. The remaining fraction of benzoyl groups is present in the extractable oligo­ meric fract ion. The relatively large fraction of oligomers can be assigned to fast side reactions which consume one part of the activator before it can participate in the growth reaction. has been suggested to evaluate the total end group concentration in a water-insoluble polymer; here, (BJ and (CJ are concentrations of basic and acidic groups which can be determined by titration methods; the fraction of neutral groups can be cal­ culated from the initial concentration of the activator ((A Jo), the conversion of monomer into water-insoluble polymer, p, and a coefficient (lA, representing the number of fragments of a molecule of the activator acting as chain end groups. The introduction of the factor p into the above term is based on earlier observations by Sekiguchi 3 who had found that during the low-temperature polymerization of 2-pyrrolidinone the activator was completely incorporated into the polymer. Activators of the acyllactam type are known to be subjected to condensation re­ actions under polymerization conditions. The subsequent side reactions can give rise to low-molecular weight compounds incapable of acting as growth centres. The fraction of the activator molecules which disappear to give inactive low-molecular