Nitrogen-free crosslinked poly(vinylbenzyl chloride) fibers with retained benzyl chloride reactivity

Poly(vinylbenzyl chloride) (PVBC) structures are often prepared by crosslinking benzyl chloride functionalities with nitrogen-containing crosslinkers, a process that is undesirable in applications sensitive to heteroatom content. Consequently, developing nitrogen-free PVBC structures that retain benzyl chloride reactivity remains an important challenge. Here, we report a nitrogen-free approach for preparing crosslinked PVBC fibers through complementary polymer modification and thermal curing. PVBC was independently functionalized with epoxy and anhydride groups via atom transfer radical addition-mediated grafting of epoxy-containing groups and Friedel-Crafts modification with methyl-5-norbornene-2,3-dicarboxylic anhydride. Mixtures of the complementary polymers were drawn into fibers and thermally cured to promote crosslinking, with ATR-FTIR spectroscopy and combustion elemental analysis providing complementary qualitative and quantitative evidence of successful polymer modification and compositional changes before and after curing. The resulting fibers were insoluble in chloroform while retaining approximately 83% of the original benzyl chloride groups after crosslinking. Subsequent reaction with trialkyl phosphites demonstrated the retained chemical reactivity of the crosslinked fibers, with trimethyl phosphite treatment yielding an apparent degree of functionalization of 19.0% based on elemental chlorine analysis. Direct elemental phosphorus analysis of fibers modified with triethyl phosphite confirmed successful phosphonate incorporation. Nitrogen was not detected in the analyzed phosphonated fibers. This approach provides a nitrogen-free route to crosslinked PVBC fibers that retain substantial chemical reactivity for subsequent functionalization, making it attractive for separations, sensing, and heteroatom-sensitive analytical applications.