Synthesis and characterization of paramylon propionate-graft- poly(lactic acid) and paramylon propionate-graft-poly(ε-caprolactone)

• Published in: Polymer (Guilford) Vol. 228; p. 123922
• Main Authors: Seok, Jin Ho, Enomoto, Yukiko, Iwata, Tadahisa
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 16.07.2021; Elsevier BV
• Subjects: Acetylation; Chloroform; Copolymer; Copolymers; Degree of polymerization; Graft copolymers; Mechanical properties; Molecular weight; NMR; Nuclear magnetic resonance; Polycaprolactone; Polyester; Polylactic acid; Polysaccharide; Propionic acid; Solvents; Thermal stability; Polysaccharide; Polyester; Copolymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2021.123922

Paramylon propionate-graft-poly(L-lactic acid) (PaPr-g-PLA) and paramylon propionate-graft-poly(ε-caprolactone) (PaPr-g-PCL) were synthesized by grafting L-lactide and ε-caprolactone to the residual hydroxy group of paramylon propionate (degree of substitution (DS) of 1.6 or 2.0). The chemical structures of the graft copolymers were characterized by GPC, NMR, and FT-IR measurements. The molecular weight of the copolymers was 2.52–3.11 × 105 and the degree of polymerization of grafted side-chains was determined to be around 10. Melt-pressed films were formed from all copolymers but solvent-cast films were brittle and defected. The terminal hydroxy groups of the grafted PLA or PCL side-chains were subsequently acetylated. The acetylated graft copolymers showed good solubility in chloroform and formed self-standing uniform solvent-casted films as well as melt-pressed films. The decomposition temperature of the acetylated graft copolymers was 350 °C, which was 50 °C higher than that of nonacetylated copolymers, indicating that terminal acetylation dramatically improved the thermal stability of the copolymers. The mechanical properties of the films of the acetylated copolymers were investigated and discussed. [Display omitted] •Paramylon propionate -g- PLA/PCL were synthesized from low DS paramylon propionates.•The graft copolymers had Tg and Tm derived from PLA/PCL side-chains.•The graft copoylmers exhibited thermoplasticity and formed melt-pressed films.•The terminal hydroxy groups of side-chains were acetylated.•Acetylation resulted in improvement of degradation temperature of the copolymers.