Biodegradability of ethyl and n-octyl branched poly(ethylene adipate) and poly(butylene succinate)

Ethylene glycol/adipic acid and 1,4-butanediol/succinic acid were copolymerized in the presence of 1,2-butanediol and 1,2-decanediol to produce ethyl and n-octyl branched poly(ethylene adipate) (PEA) and poly(butylene succinate) (PBS), respectively. The chain branching reduced the crystallinity of PEA more significantly than the crystallinity of PBS. Surface tension of PEA was higher than that of PBS, though the two polyesters have identical number of methylene groups and ester groups in the repeating unit. However the modified Sturm test showed that the two polymers were assimilated to CO2 at a similar rate. As the degree of chain branching increased, the biodegradation rate of PEA increased to a greater extent than that of PBS due to the faster reduction in the crystallinity of PEA compared to the crystallinity of PBS.