Free radical copolymerization of methyl methacrylate with methacrylic monomers derived from salicylic acid. Microstructural analysis, chain flexibility and hydration behaviour of the prepared copolymers

Copolymers of methyl methacrylate (MMA), and the methacrylic monomers deriv ed from salicylic acid, 2-hydroxy-4-methacrylamidobenzoic acid (4-HMA), and 2-hydroxy-5-methacrylamidobenzoic acid (5-HMA), were prepared by free radi cal polymerization in N, N-dimethylformamide, DMF, solution at 50 degrees C using 2, 2'-azobisisobutyronitrile (AIBN), as initiator. Fineman-Ross and Kelen-Tudos linearization methods, as well as the Tidwell and Mortimer non- linear least-squares treatment were used to calculate the monomers reactivi ty ratios, giving the Tidwell and Mortimer values from the 95% confidence d iagrams, the most probable ones r(4) = 0.83, r(M) = 1.52 and r(5) = 0.29 r( M) = 2.15, The microstructural analysis of the prepared copolymers was perf ormed by C-13 (75.5 MHz) nuclear magnetic resonance (NMR) spectroscopy, in terms of sequence distribution and stereochemistry of monomeric units along the copolymer chains. The stereochemical parameters sigma* = sigma(4M) = s igma(M4) = 0 21 and sigma* = sigma(5M) = sigma(M5) = 0.19 were determined f rom the C-13 NMR spectra of the copolymers 4-HMA-MMA and 5-HMA-MMA, respect ively. Also the T-g of the corresponding homopolymers and copolymers, were analysed by differential scanning calorimetry (DSC) in terms of the Fox equ ation. Hydration degree of the prepared copolymers was studied in compariso n to poly (4-HMA), poly (5-HMA) and poly (MMA). (C) 1999 Elsevier Science L td. All rights reserved.