Study On Relationship Between Glass Transition Temperature Of Copolymer And Conversion

Glass transition temperature (Tg) determines the basic properties of polymers. Polymers'glass transition temperature can be changed through copolymerization. In earlier study, a new equation proposed in view of additivity of chemical bond, which describes the relationship between binary copolymer glass transition temperature and composition. The new equation was applied to study the relationship between composition and glass transition temperature of copolymers at low conversion. While the composition and structure of the copolymer will drift along copolymerization, Tg will also change. The relationship between conversion and glass transition temperature of the copolymers of styrene-butyl acrylate and methyl methacrylate-butyl acrylate were studied in this paper.Styrene-butyl acrylate and methyl methacrylate-butyl acrylate copolymers at different conversions under different monomer feed compositions were obtained via radical copolymerization in benzene at 60℃. The compositions of copolymers at low conversion have been measured with 1H-NMR. The glass transition temperature have been measured by using (differential scanning calorimetry)DSC. Feed ratio and reactivity ratio was used to calculate the content of every instantaneous fraction, the Tg of every instantaneous fraction were calculated by using Tg-composition equation proposed earlier, respectively. FOX equation was used to calculate Tgs of accumulative copolymers It is found that the relationship between the binary random copolymer Tgs and conversion could be described adaptively by using the method proposed here.Monomer feeding mode will effects glass transition temperature and Tg distribution of copolymers even though the cumulate compositions of copolymers are equal. Tg distribution of copolymer have been calculated from DSC curve of St-BA copolymer obtained with different monomer feeding mode. Copolymers with different Tg distribution can be synthesized by using monomer feeding mode.