Engineering Branching Architecture in Ionic Polysulfides for Enhanced Piezoelectric Sound Absorption of <i>Eucommia ulmoides</i> Gum Composites

Traditional acoustic materials have poor absorption capacity for low- and middle-frequency sound waves. Extending the propagation path of sound waves can ameliorate this issue. Ionic polysulfides with branched and linear structures, namely, BImS and LImS, were synthesized via inverse vulcanization. They were subsequently used to modify Eucommia ulmoides gum (EUG), yielding BImS-EUG-xs and LImS-EUG-xs . Both materials exhibited stable piezoelectric performance, and BImS-EUG-xs displayed much higher output capability. Additionally, the carbon-enhanced material BImS-EUG(C)-xs could deliver a maximum voltage of 5.90 V and a current of 30.5 nA. The introduction of polysulfides significantly enhanced the damping properties, and with the increase of polysulfide content, the sound absorption tended to shift toward lower frequencies. The modified EUG (0.2 mm in thickness) could realize efficient sound absorption with a maximum absorption coefficient of 0.987.