Chain dynamics and thermal stability of boron-tris-containing copolymers

Poly(methyl methacrylate-co-glycidyl methacrylate-tris(hydroxymethyl)aminomethane) (PMGT) copolymers were obtained by copolymerization of methyl methacrylate (MMA) and a chelating monomer, glycidyl methacrylate-tris(hydroxymethyl)aminomethane (GMA-Tris), with potassium persulfate as an initiator. The glass transition temperature (Tg) and the proton spin-lattice relaxation time in the rotating frame (T1ρH) substantiated the formation of random copolymers. Borate-loaded PMGT (BPMGT) complexes were prepared by mixing PMGT and boric acid solution. The formation of coordination bond between PMGT and borate was studied using differential scanning calorimetry, infrared and 13C solid-state nuclear magnetic resonance spectroscopy. A single composition dependent Tg was obtained for the PMGT copolymers. The Tg value of BPMGT complex was much higher than that of PMGT copolymer with the same composition. The T1ρH of the main chains in the PMGT copolymers and BPMGT complexes had one value, and that in the complexes was higher than that in the copolymers. The apparent activation energy (Ea) of the thermo-oxidative degradation of Tris units in complexes was larger than that in copolymers, whereas the Ea value of the MMA-GMA matrix was reversed.