Water-Phase Synthesis of a Biobased Allyl Compound for Building UV-Curable Flexible Thiol–Ene Polymer Networks with High Mechanical Strength and Transparency

Using water as a reaction medium to synthesize biobased monomers with high renewable carbon content for preparing biobased polymers is of great importance for environmental protection and sustainable development. Herein, a trifunctional allyl compound, tris(4-allyl-2-methoxyphenyl) phosphate (TAMPP) with 100% renewable carbon content was synthesized from renewable eugenol through one-step method using water as the solvent. TAMPP was then used to prepare flexible and transparent thiol–ene polymer networks TAMPP-SH via solvent-free thiol–ene “click” photopolymerization with various multifunctional thiols. The influences of the thiol functionality from 2 to 4 on structure and integrated performances were systematically researched. Among them, TAMPP-SH4 shows the best thermal and mechanical properties. Specifically, its glass transition temperature ( T g ) is as high as 35 °C, while its tensile strength and modulus are as high as 19.8 ± 0.6 MPa and 601.6 ± 22.4 MPa, respectively. At the same time, it still maintains high flexibility. The nature behind these outstanding integrated performances is attributed to the unique structure of TAMPP, which is rich in aromatic structure, and the very high cross-linking density of TAMPP-SH4 network. The especially high renewable carbon content and outstanding thermal and mechanical performances clearly show that the TAMPP-SH4 network has great potential in fabricating flexible products.