Copolyesteramides—II. Anionic copolymers of ε-caprolactam with ε-caprolactone. Preparation and general properties

Abstract The N -sodiocaprolactam-catalysed anionic polymerisation of e -caprolactam is activated by e -caprolactone which itself acts as a comonomer, yielding copolyesteramides. At lower temperatures and lower catalyst concentrations, copolymerisation of the lactone is favoured over that of lactam; higher temperatures, higher catalyst concentrations and longer reaction times cause a more equal incorporation of the two comonomers giving products with molecular weights in the order of 10 4 and with NH(CH 2 ) 5 CO and O(CH 2 ) 5 CO unit contents approximating to those in the reactant feeds. The T g 's of the products lie between those of the homopolymer extremes but the T m vs composition relationship displays a shallow eutectic minimum at ca 20% NH(CH 2 ) 5 CO group content and, for given NH(CH 2 ) 5 CO group contents, is sensitive to changes in the technique of copolymerisation. Alternatingly-sequenced NH(CH 2 ) 5 CO/O(CH 2 ) 5 CO copolymers prepared by polycondensation also differ from anionic copolymers of similar sub-unit stoichiometry. The property differences imply differences of chain-sequential order and hence complexity in the mechanism of the anionic copolymerisation.