Synthesis of network polymers by photo-initiated thiol–ene reaction between multi-functional thiol and poly(ethylene glycol) diacrylate

Network polymers have been synthesized by thiol–ene reaction of multi-functional thiol, 1,3,4-tris(3-mercaptobutyloxethyl)-1,3,5-triazine-2,4,6- (1H,3H,5H)-trione (TEMBIC), pentaerythritol tetrakis(3-mercaptobutylate) (PTMB), tris[(3-mercaptopropionyloxy)-ethyl]-isocyanurate (TEMPIC), pentaerythritol tetrakis(3-mecaptopropionate) (PEMP), dipentaerythritol hexakis(3-mercaptpropionate) (DPMP), and poly(ethylene glycol) diacrylate (PEGDA) in toluene using a photo-radical initiator. All the reactions in toluene successfully yielded gels. Mechanical properties of the gels were investigated by compression test, and Young’s modulus of the gels increased with an increase in the number of thiol group in the multi-functional thiol compound due to high cross-linking density in the gels. The gels were also synthesized in some organic solvents including dimethyl sulfoxide (DMSO), propylene carbonate (PC), and tetrahydrofuran. Solvent affected mechanical properties of the resultant gels, and the gels prepared in DMSO or PC showed high Young’s modulus and breaking stress. The reaction systems of TEMBIC, TEMPIC, PEMP, or DPMP and high-molar-mass PEGDA in EtOH yielded porous polymers induced by phase separation during the network formation. All the porous polymers showed morphology formed by connected spheres. The porous polymers were soft and flexible, and not breakable by compression at the force of up to 500 kPa.