Synthesis of L‐Malic Acid Based Poly(ester‐thioether)s via Thiol‐Ene Click Polymerization and Their Biodegradability

Abstract 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 °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 1.9×10 3 to 9.4×10 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 °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.