Synthesis Of L-Malic Acid Based Poly(Ester-Thioether)S Via Thiol-Ene Click Polymerization And Their Biodegradability

Many bio-based polymers made from natural resources do not show satisfactory biodegradability, leading to micro-plastic pollution. Here, thiol-ene click polymerization of di-3-butenyl l-malate (BMA) and diallyl l-malate (AMA) with several dithiols including 1,8-octanedithiol (OD) proceeded at 80 degrees C to give poly(ester-thioether)s in excellent yields (70 %-90 %). Using an azo-type radical trigger, polymerization proceeded more rapidly to give the expected poly(ester-thioether)s with M-n ranging from 1.9x10(3) to 9.4x10(3) and a molecular dispersity index (M-w/M-n) of 2.1(9)-3.6(6). Click polymerization using 1,2-ethanedithiol (ED), ethylene bis(thioglycolate), and 2,3-butanedithiol proceeded to give similar poly(ester-thioether)s. In differential scanning calorimetry, all samples except for poly(BMA-alt-OD) had single T-g values between -37 and -47 degrees C. In biodegradation tests using activated sludge, poly(BMA-alt-OD) and poly(AMA-alt-ED) hardly showed biodegradability, but the other poly(ester-thioether)s showed 13 %-22 % biodegradation after 28 days. Our results open up new avenues in the design of bio-based polymers to reduce micro-plastic pollution.