Regulation of Vinyl Acetate Polymer Stereoregularity through Solvent–Monomer Hydrogen Bonding

This study systematically investigates how solvent–monomer hydrogen bonding influences the stereoregularity of chain segments in the free-radical polymerization of vinyl acetate (VAc). Combining density functional theory (DFT) calculations, Fourier transform infrared spectroscopy (FTIR), and polymer property analysis, we examined the correlation among solvent hydrogen bond strength, polymer stereoregularity, and material performance. Three solvents with different hydrogen bond donor abilities—methanol (MeOH), trifluoroethanol (TFE), and hexafluoroisopropanol (HFIP)—were selected for study. FTIR spectra reveal that stronger hydrogen bonding causes a gradual red shift in the C=O absorption peak, confirming solvent–monomer complex formation. DFT results further show that increasing solvent fluorination shortens the solvent–VAc coordination distance and enhances hydrogen bond energy (MeOH < TFE < HFIP), consistent with the observed rise in syndiotactic stereoregularity of the resulting poly(vinyl alcohol) (PVA). Experimentally, stronger hydrogen bonding yields PVA with higher molecular weight, crystallinity, and improved thermal and mechanical properties. By integrating theoretical insight with experimental validation, this work demonstrates that solvent design can effectively regulate stereoregularity in free-radical polymerization, offering a feasible strategy toward synthesizing high-performance PVA materials.