Studies On Relationship Of Glass Transition Temperatures Of Copolymer With Its Composition And Sequence

The glass transition temperature is an important intrinsic characteristic that influences the material properties of a polymer and its potential applications. The glass transition temperature of polymer can be changed by copolymerization. So, the relationship of copolymer glass transition temperature of copolymer with its homopolymer Tg and composition is all through investigative hotspot. In view of bond rotation flexibility and the additivity of stiff energy, a durance is broken in this paper which chemical bond is regarded as additivity unit instead of monomer is regarded as cell. And then a new equation containing mole fractions of sequences and Tgs of periodic copolymer of the monomers is proposed. This may facilitate its convenient application compared with that of Ham equation because of its lesser parameter.In this paper, copolymers of styrene with methyl methacrylate (St-MMA), styrene with acrylonitrile (St-AN), acrylonitrile with methyl methacrylate (AN-MMA) were synthersized by bulk polymerization. The conversion was controlled less than 5%. The copolymer compositions (monomer mole fractions) were determined by 1H-NMR. The Tgs of copolymers were determined on a differential scanning calorimeter (DSC). The diad and triad fractions were obtained by reactivity ratio. The new equation is applied to St-MMA, St-AN and AN-MMA copolymers and excellent fitting is obtained. It is better than Barton and Johnston equation.Besides, the effect of substituent density and length on polymer Tg was predicted tentatvily in this paper. Series MMA copolymers and MA copolymers with different compositions were synthesized by bulk copolymerizatin at 60℃. The new equation is applied to these copolymers and excellent fitting is obtained. The Tgs of periodical copolymers were predicted. And the influence of the substituent volume as well as substituent density on the Tg of PMMA and PMA was also tentatively predicted.