Glass Transition Behavior of Dendritic Polymers Containing Mobile Aliphatic Polyether Cores and Glassy Peripheral Polystyrenes

Abstract

The linear PSs show a typical growth of Tg up to 92.5 o C as the molecular weight increases to 8300 g/mol, while the dendrons display nearly constant Tg values of 58-61 o C, despite the increase of molecular weight with each generation. The striking contrast of Tg behavior would be mainly attributed to the fact that the dendrons keep the ratio of Ne /M (Ne: number of peripheral chain ends, M: molecular weight) over all the generations. Additionally, for the influence of dendritic spacers on glass transition temperature we prepared dimeric PSs with different linkage groups such as aliphatic ether, ester and amide bonds. We found that the dimer with the ether spacer exhibited the lowest glass transition at 55.4 o C, while the amide linked dimer showed the highest glass transition temperature at 74.2 o C. This indicates that the peripheral PS chains are effectively decoupled by the conformationally flexible ether spacer. The results from this study demonstrated that polymeric architecture and dendritic core structures play a crucial role in the determination of glass transition behavior, providing a strategy for the systematic engineering of polymer chain mobility.