No abstract

Multiblock copolymers poly(l-lactic acid)-block-poly(butylene succinate-co-butylene adipate)s (abbr. P(LLA-mb-BSA)s) are synthesized via a polycondensation/chain extension/coupling method using binary chain extenders. A poly(l-lactic acid) (PLLA) prepolymer synthesized via direct melt polycondensation of l-lactic acid is rapidly chain extended with a bis (2-oxazoline) to form hydroxyl terminated dimer, and the dimer is then chain extended/coupled with a hydroxyl terminated poly(butylene succinate-co-butylene adipate) (PBSA) prepolymer by a diisocyanate. The microstructure is characterized with GPC, 1H NMR and FTIR, and the thermo-mechanical properties are investigated with DSC, TGA, DMA, tensile, and impact testing. In the copolymers, the PLLA hard segments are crystallizable and the PBSA soft segments are amorphous, and only melting of PLLA segment was detected. Two independent glass transitions corresponding to both segments are observed, suggesting incompatibility between the two kinds of segments. The tensile modulus and strength decrease while the elongation at break and impact strength increase with increasing the weight percentage of PBSA segment (ϕw,PBSA). The mechanical properties can be tuned in wide range by ϕw,PBSA, from toughened thermoplastics with excellent tensile modulus, strength and impact strength to thermoplastic elastomers with high elongation at break.

It is indispensable to investigate hydrolytic degradation behavior to develop novel (bio)degradable polyesters. Biobased and biodegradable copolyesters poly(butylene adipate-co-butylene furandicarboxylate) (PBAF) and poly(butylene succinate-co-butylene furandicarboxylate) (PBSF) with BF molar fraction (/ BF ) between 40 and 60% were synthesized in this study. The hydrolytic degradation of film samples was conducted in a pH 7.0 PBS buffer solution at 25 8C. Slight mass loss (1-2%) but significant decrease in intrinsic viscosity (35-44%) was observed after 22 weeks. The apparent hydrolytic degradation rate decreased with increasing / BF and initial crystallinity. Meanwhile, PBAFs degraded slightly faster than PBSFs with the same composition. The / BF and crystallinity increased slowly with degradation time, suggesting the aliphatic moiety and the amorphous region are more susceptible to hydrolysis. And high enough tensile properties were retained after hydrolysis degradation, indicating PBAF and PBSF copolyesters are hydrolytically degradable, with tunable hydrolytic degradation rate and good balance between hydrolytic degradability and durability. V C 2016Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44674.