Studies On Relationship Of Glass Transition Temperature Of Terpolymers With Composition Using Bonds As Additivity Units

Multicomponent polymerization could afford polymers desirable chemical, physical, and mechanical properties by changing compositions. As an important parameter, the glass transition temperature (Tg), which represent the molecular mobility of polymer chains commendably, reflects the polymer properties and determines its potential applications. Therefore, the study on relationship of Tg with composition for multipolymers has important academic significance and applied importance.In this article, basing on the thermodynamic theory of glass transition, we propose a new equation to describe the relationship of terpolymer glass transition temperature with composition using bonds as additivity units, which is smaller than either monomers or sequences, with concerning the effect of C substitutions on the bond rotation flexibility.Bulk copolymerization of methyl methacrylate (MMA) with styrene (St), methyl methacrylate with acrylonitrile (AN) and styrene with acrylonitrile were performed and series of binary random copolymers with low monomer conversion were obtained. The glass transition temperatures and compositions of these copolymers were determined by using differential scanning calorimeter (DSC) and quantitative nuclear magnetic resonance spectra (1H-NMR), respectively. A binary copolymer Tg~-composition equation proposed earlier was applied to interpret the relation of Tg's of MMA-St, MMA-AN and St-AN copolymers with their compositions. Excellent fitting result indicated the feasibility and veraciousness of this equation. Meanwhile, Tg values of nine assumed alternating and periodic copolymers were predicted by data regression. These values provided useful information for the study of relationship of MMA-St-AN terpolymers Tg's with their compositions.A series of MMA-St-AN ternary random polymers with low monomer conversion were prepared by bulk polymerization. The new equation established in this article was applied to interpret the relation of Tg's of MMA-St-AN terpolymers with their compositions. Excellent agreement of theoretical values with experimental data was obtained. This illuminated the dependability and applicability of the new terpolymer Tg~-composition equation. Meanwhile, Tg values of three assumed periodic copolymers, that didn't acquired yet, were predicted by data fitting which may provide useful information for related scientific researches.The relation of homopolymer glass transition temperature with its tacticity was also studied under the assumption of the additivity of bond stiff energy. Outstanding consistency of theoretical values with determined data were obtained and proved the correctness of the assumption when the relation of Tg of PMMA with its tacticity was studied.