Copolyesteramides—IV. Anionic copolymers of ε-caprolactam with ε-caprolactone. Molecular and chain structure

Abstract

The chain structures of copolyesteramides formed by anionic ring-opening copolymerisation of ε-caprolactam with ε-caprolactone have been investigated. The copolymers are shown to possess random multiblock structures with chains composed of O(CH 2) 5CO[NH(CH 2) 5CO] n groups (having relatively small values of n) intercalated with sequences of O(CH 2) 5CO groups. The distributions of structural units in the chains are significantly affected by reaction time and by the method of introducing lactone into the copolymerising system. A mechanism is proposed to explain the formation of the multiblock structures. The nature of an additional absorbance in the NH-stretching region of the i.r. spectra of the copolyesteramides has been investigated with the aid of model compounds and attributed to hydrogen-bonding between amide and ester groups in the amorphous regions of the copolymers. This bonding may be the cause of the anomalous mechanical properties found at high ester contents.