Structure/Glass Transition Temperature Relationship of PVAc-b-poly(MA-co-MMA) Terpolymers with Theoretical and Topological Methods
The glass transition temperature of several PVAc(1)-b-poly(MA-co-MMA) (2) terpolymers with different fractions of methyl acrylate (MA) and methyl methacrylate (MMA) repeating units in random copolymer (block 2) were calculated with Barton, Kwei and topological equations. The calculation was on the basis of the correlation between the fraction of repeating units in random copolymers and theoretical equations and linear correlation of topological index of VAc, MA and MMA atomic structures in topological equations. The experimental values of the glass transition temperature of block 2 show a positive deviation from linearity in both Barton and Kwei theoretically calculated values. Therefore, agreement between the theoretical and experimental values were reached with summation of the effects of sequence distributions in random copolymer (R, calculated with 1H NMR and statistical methods) to the linear theoretical data in Barton equation and the effect of interactions between the copolymer chains in Kwei equation (q = 14.9). The glass transition temperature of 308 K was calculated for PVAc block with topological equation and it was near to the experimental value (310 K). Furthermore, the calculated glass transition temperatures of the block 2 with linear method were considerably close to the experimentally obtained data and increased with mole fraction of MMA in random copolymer.