Design, Synthesis and Property Study of Side‐Chain Siloxane‐Modified Polyurethanes Using a Hydroxyl‐Terminated Siloxane Chain Extender

ABSTRACT In this study, a side‐chain silane‐modified polyurethane (SPU‐BK) was designed and synthesized by incorporating a dihydroxy siloxane chain extender (BK) into polyurethane segments. BK , containing siloxane groups, was synthesized via Michael addition using 1,4‐butanediol diglycidyl ether ( BDG ) and γ‐mercaptopropyltrimethoxysilane (KH‐590) as raw materials. SPU‐BK resin can be cured in moisture through a dual‐curing mechanism, which involves moisture curing of the terminal –NCO groups on the main chain with water and moisture‐curing crosslinking of the side‐chain siloxane groups with water. The introduction of organosilicon via the side chains enhanced the thermal stability, hydrophobicity, and mechanical properties of the SPU‐BK elastomer; the residual carbon rate of the elastomer rises from 0.27% to 4.97% with the increase of BK content; the static water contact angle elevates from 75° to a maximum of 108.1° and remains above 90° at all BK loadings; and the tensile strength of SPU‐BK40 reaches over 1.4 MPa with the elongation at break remaining above 250%. Notably, the incorporation of organosilicon eliminated the crystallization of the material's soft segments, further enhancing the material's structural homogeneity. These findings demonstrate that side‐chain silane modification via the designed chain extender is an effective strategy for optimizing polyurethane performance.