Controlled activity polymers. VIII. Copolymers of acrylic acid and isomeric N-akylacrylamide with pendent β-naphthol esters moieties: Synthesis and characterization

Abstract

Monomers possessing hydrolytically-labile bonds to the bioactive agent β-naphthol (βN) were prepared for incorporation into hydrophilic copolymers. β-Naphthyl acrylate was synthesized by an esterification reaction of β-naphthol with acryloyl chloride. 5-Acrylamido(β-naphthyl)valerate, 2-acrylamido(β-naphthyl)isovalerate, 3-acrylamido-3-methyl(β-naphthyl)butanoate, and 6-acrylamido(β-naphthyl)caproate were synthesized by esterification of βN with 5-acrylamidovaleric acid, 2-acrylamidovaleric acid, 3-acrylamido-3-methylbutanoic acid, and 6-acrylamidocaproic acid, respectively, utilizing 1,3-dicyclohexylcarbodiimide as a coupling agent and 4-dimethylaminopyridine as a catalyst. The βN monomers were free radically polymerized with acrylic acid, utilizing AIBN as initiator in benzene at 70°C to obtain polymer-bound allelopathic βN. Copolymer composition was determined by 1H-NMR, 13C-NMR, FTIR, and UV-vis. spectroscopy. The copolymerization reactivity ratios were calculated from 1H-NMR data using Fineman-Ross, Kelen-Tudos (K-T), and nonlinear least-squares methods. Copolymer microstructural predictions were determined from calculated K-T reactivity ratios. The resulting water soluble copolymers prepared in this work are potentially useful as plant growth regulators through the hydrolytic release of β-naphthol. These model structures have been utilized for the determination of structure/controlled release relationships reported in an accompanying publication.