Glass transition of crosslinked polystyrene shells formed on the surface of calcium carbonate whisker

Glass transition of core/shell capsules consisting of calcium carbonate whisker as a core and crosslinked polystyrene as a shell was studied by differential scanning calorimetry. The thickness of the crosslinked shell was in the range of 26–81 nm. The crosslinked shells were revealed to show higher glass transition temperatures ( T g ) than the corresponding bulk values. It was revealed that a thicker shell exhibits a lower T g than a thinner shell, and that capsules without core (hollow capsules) exhibit lower T g 's than the corresponding core/shell capsules. These results suggest that the interfacial molecular interaction plays a role in the segmental relaxation, which is responsible for the glass transition. The difference in T g between the core/shell and hollow samples was reduced when a coupling agent, methacrylic acid 3‐(trimethoxysilyl)propyl ester, was not included. This also suggests the interfacial effect on T g . However, the results still suggest that the enhancement of T g for the present crosslinked shells is not only due to the interfacial effect but also to the effects of chain configuration and heterogeneous crosslink. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2475–2485, 2006