Conformation of single polymer chain in rubbed thin film observed by fluorescence imaging

The conformation of poly(methyl methacrylate) (PMMA) chains in a thin film after the rubbing process was investigated through the direct observation of the single chains by scanning near-field optical microscopy (SNOM) and excitation polarization modulation microscopy (EPMM). The rubbing at room temperature hardly changed the dimension on the whole chain scale in spite of the increase in orientational order on the segmental scale. The increase in the chain dimension along the rubbing direction was observed in the film rubbed at the higher temperature, which showed a surface morphology with fine groove. The extension ratio of the whole chain in the rubbed film was much smaller than that in the uniaxially stretched film. This indicates that the rubbing process mainly induces the conformational change on the length scale of the monomer unit rather than for the whole chain.