High-Performance Polydimethylsiloxane/Lignin Photothermal Composites Benefit from the Exceptional Photothermal Conversion of Modified Lignin

To alleviate the energy crisis and reduce environmental pollution, developing high-performance photothermal elastomers from a reprocessable polymer matrix and renewable photothermal materials is an important strategy. However, the photothermal conversion performance of both renewable fillers and the obtained elastomer composites is not satisfactory yet. In this work, modified lignin (mLig-2) was prepared through silylation based on demethylation, achieving an impressive photothermal conversion efficiency of 74.9%, which is the highest value under standard 808 nm near-infrared light conditions, compared to previously reported lignins. For the first time, lignin was introduced into polydimethylsiloxane (PDMS) vitrimer, preparing reprocessable PDMS/mLig-2 composites through silyl ether linkages. With only 5 wt % mLig-2, the PDMS/mLig-2 composite exhibited excellent mechanical properties (elongation at break of 842%, tensile strength of 5.49 MPa, and toughness of 26.65 MJ/m³) and remarkable photothermal conversion capability. The temperature of the composite reached as high as 263.0 °C under 808 nm laser irradiation at 1.00 W cm^–2. Furthermore, a high-performance solar thermoelectric generator was demonstrated, which stably outputs 120 mV under standard solar radiation. In conclusion, this work is of great significance for the development of environmentally friendly PDMS/lignin photothermal elastomers with excellent performance and provides new opportunities for the photothermal application of lignin.