Structural Elucidation and Impurity Profiling of Poly (N- Vinylpyrrolidone-co-Maleic Anhydride) Terpolymer Precursors via 1 H- NMR Spectroscopy

Abstract

Amphiphilic terpolymers with reactive functionalities serve as versatile precursor materials for developing functionalized biomaterial networks. In this study, lauryl/stearyl acrylates, N-vinylpyrrolidone (NVP), and maleic anhydride were employed in radical polymerization to generate two distinct series of hydrophilic oligomers known as the OLPM and OSPM series. High-resolution proton nuclear magnetic resonance ( 1 H-NMR) spectroscopy was utilized as an analytical standard to characterize chemical configurations, map monomer conversion patterns, and quantify trace processing pollutants. Spectroscopic analysis confirmed the effective integration of hydrophilic pyrrolidone heterocyclic rings, hydrophobic acrylate domains, and aliphatic backbones across various monomer feed ratios. The absolute ring-opening hydrolysis of moisture-sensitive maleic anhydride units into active dicarboxylic acid anchors, which are essential for subsequent covalent cross-linking with gelatin amino networks, was unequivocally confirmed by a persistent downfield singlet at δ 12.3 ppm. While minor monomer entrapment and processing solvent residues occurred in mid-tier formulations (OLPM 5 and OSPM 5) due to long-chain alkyl acrylate steric hindrance, optimizing composition dynamics entirely removed these impurities in the highest feed ratio variants. Conclusively, the OLPM 10 and OSPM 10 variants demonstrate refined, impurity-free crosslinking precursors suitable for downstream covalent network formation due to their structural rigidity and high density of crosslinkable dicarboxylic acid groups.

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