Topology-Directed Siloxane-Based Thiol–Ene Photoresists for Ultraviolet Nanoimprint Lithography

The ultimate resolution and pattern fidelity in ultraviolet nanoimprint lithography (UV-NIL) are fundamentally determined by the physicochemical properties of the photoresist used. To overcome the intrinsic limitations of traditional organic UV-NIL resists─namely, high volumetric shrinkage, inadequate thermal resistance, and severe oxygen inhibition─this paper designed the Vi-T series, a class of siloxane-based thiol–ene photoresists featuring a tunable branching architecture, and systematically elucidated the dual regulatory mechanisms by which stoichiometry and topological structure govern photopolymerization kinetics, rheological behavior, and pattern fidelity. Spectroscopic and thermodynamic analyses revealed that enforcing a precisely optimized off-stoichiometric ratio (C═C/–SH = 1:1.2) effectively suppressed parasitic vinyl homopolymerization. Notably, the degree of branching exerted a nonmonotonic influence on the curing rate, arising from the competition between local functional group enrichment and steric hindrance. Among the synthesized series, the Vi-T-4 formulation exhibited an optimal kinetic balance. By leveraging the flexible buffering effect of the siloxane backbone with the delayed gelation inherent to the step-growth polymerization mechanism, the optimized network achieved low volumetric shrinkage (1–3%) and high thermal stability ( T d5% up to 346.2 °C). Furthermore, the Vi-T-4 system demonstrated a synergistic balance between rheological flowability and cohesive strength during the NIL process, effectively circumventing common defects such as cohesive failure and incomplete mold filling. This study established a critical structure–property relationship for high-fidelity nanograting replication, positioning the Vi-T system as a robust candidate for the manufacturing of high-temperature micro- and nano-devices.