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Thickness changes in polyvinyl acetate thin films, during the temperature cycle across the glass transition temperature (Tg) has been studied in detail. Even after enough thermal treatment done at the high-temperature side of Tg, thickness increase during cooling (negative thermal expansion) is observed. On the other hand, slow thickness decrease is observed with aging at the high-temperature side of Tg. The above interesting phenomena can be well explained by the model considering the presence and changes of the interface layer.
When the radical polymerization inhibitor 1,4-naphthoquinone (NQ) acts on styrene, the radical capture reaction greatly contributes carbon atoms. In this study, the 1-phenethyl radical, which is a model for the growth radicals of polystyrene, was reacted with NQ using four radical sources, and we identified the reaction product. We confirmed that the same compound was formed upon addition of a small amount of NQ to heated styrene. The frontier orbital energy levels and reaction path energy diagrams were calculated, which provided numerical values to support our experimental results.
The solid-state structure of L2AlEt is reported by X-ray diffraction. BnOH (1 equiv. to L2AlEt) selectively reacts with ~0.5 equiv. of L2AlEt to afford free L–H (~1 equiv.) while maintaining L2AlEt (~0.5 equiv.). The stoichiometric balance suggests the formation of 0.5 equiv. of (BnO)2AlEt. The ROP of CL via the synergic catalysis of the two coexistent Al-complexes, L2AlEt (0.50 mol%) as a Lewis acid activator of CL and (RO)2AlEt (0.50 mol%) as a nucleophile, is proposed.
The chain dynamics in a spin-coated poly(methyl methacrylate) (PMMA) film in solvent annealing was studied by in situ neutron reflectivity. The absorbed solvent molecules homogeneously distributed in the spin-coated film and the PMMA chain even near the substrate showed sufficient mobility in the solvent annealing process, while the chain mobility was strongly restricted at the substrate in thermal annealing. This result indicates that the solvent annealing method enables the equilibration of a spin-coated polymer film from the surface to the substrate interface.
