Silane-Modified Hyperbranched Polyurethane with High Strength, High Transparency, and Low Viscosity

Silane-modified polyurethanes (SPU-MDI, SPU-IPDI, and SPU-HDI) were synthesized by reacting various isocyanates (MDI, IPDI, and HDI) with poly(ether triol), followed by siloxane capping. The branched structures and properties of these SPUs were systematically characterized and evaluated. These SPU resins, upon moisture curing, yield elastomers exhibiting excellent mechanical properties and high transmittance (>92%). Incorporating polyether tertiary alcohol into the polymer chain markedly reduces the viscosity and average particle size of the SPUs due to its de-entangling effect. Specifically, the SPU-HDI resin displayed a low viscosity of 2548 mPa·s at 25 °C and an average particle size of 3.12 nm. Notably, elastomers derived from SPU-MDI and SPU-IPDI resins demonstrated tensile strengths greater than 10 MPa, surpassing that of SPU-HDI-based elastomer (∼5.0 MPa). This significant enhancement broadens the potential applications of these materials.