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

摘要

Copolymers of methyl methacrylate (MMA), and the methacrylic monomers derived from salicylic acid, 2-hydroxy-4-methacrylamidobenzoic acid (4-HMA), and 2-hydroxy-5-methacrylamidobenzoic acid (5-HMA), were prepared by free radical polymerization in N,N-dimethylformamide, DMF, solution at 50 deg 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 reactivity ratios, giving the Tidwell and Mortimer values from the 95% confidence diagrams, 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 performed by ~(13)C (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) = #sigma#_(M4) = 0.21 and #sigma#~* = #sigma#_(5M) = #sigma#_(M5) = 0.19 were determined from the ~(13)C NMR spectra of the copolymers 4-HMAMMA and 5-HMA-MMA, respectively. Also the T_g of the corresponding homopolymers and copolymers, were analysed by differential scanning calorimetry (DSC) in terms of the Fox equation. Hydration degree of the prepared copolymers was studied in comparison to poly (4-HMA), poly (5-HMA) and poly (MMA).