Synthesis of acyl chitin derivatives and miscibility characterization of their blends with poly(ε-caprolactone)

Chitin derivatives having a normal acyl group (side-chain carbon number, N = 2–6) at different degrees of substitution (DS) were synthesized by a homogenous reaction of crab-shell chitin with various acyl chlorides in N,N-dimethylacetamide–LiCl solution. NMR analysis quantitatively demonstrated the acylations not only for C3/C6 hydroxy protons but also for C2 amino proton(s). Solution cast blend films of the acyl chitin products with poly(ε-caprolactone) (PCL) were provided for the miscibility characterization by differential scanning calorimetry. The critical total-DS required for attaining a miscibility of the blending polymer pair decreased with an increase in N. The degree of miscibility was enhanced definitely with an increase in ester-DS, but it made less correlation with amide-DS. In analogy with cellulose ester/PCL blend systems, a structural affinity of the ester side-group of the chitinous component considered with a repeating unit of PCL may be a crucial factor for the miscibility attainment.