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Films based on π-stacked carbon nitride polymers are shown to bend rapidly and jump up to 10,000 times their thickness as a result of minimal variations—induced by changes in the ambient humidity or temperature—of absorbed water.

We report a photoresponsive polythiophene derivative containing a photocleavable coumarin group with an octyloxy side chain as a solubilizing group. This polymer enables fabrication of solution-processed polymer film owing to the solubilizing group. Photoirradiation at 313 nm gives the photocleaved side chain, yielding a carboxyl group. Formation of the carboxyl group causes insoluble polythiophene. Change in the solubility provides a photopatterned film through a photomask. In addition, the photocleaved polythiophene film exhibits a 10⁴-fold increase in the electrical conductivity by chemical doping.

The polythiophene nanoparticles exhibit multichromic responses to solvent, temperature and acid/base, which can be detected by the naked eye in tetrahydrofuran/water mixtures. As the concentration of water increases, the nanoparticles turn from yellow to violet by solvatochromism. The nanoparticles display a reversible thermochromic response between 20 and 90 °C, which originates from the morphological changes between an amorphous solid and isotropic liquid. Halochromic behavior of the nanoparticles is achieved by adding hydrobromic acid and bubbling with ammonia gas owing to p-doping and dedoping of the polythiophene nanoparticles, respectively.

The syntheses of novel copolymers containing indolo[3,2-b]carbazole (INC) moiety were carried out, and the effect of INC content on the physical properties were investigated. All the copolymers were glassy and the decomposition temperatures were nearly 400 °C. It was found that the photoluminescence intensities of the copolymer films decreased with the increase of INC content, which would be caused by the concentration quenching by the intermolecular interaction between INC components. The copolymer with low content of INC moiety exhibited the high emission property and good film-forming ability.

Photoinduced molecular switches were achieved by atropisomeric polymers containing conjugated structures of azo and binaphthyl units. trans-cis Photoisomerization of the azo unit led to molecular twisting motion of the binaphthyl unit, yielding chiroptical switching in a neat film. The atropisomeric polymers also displayed photoswitchable fluorescence by repeated irradiation of UV and visible light. Irradiation of the neat film with linearly polarized light caused selective excitation of the atropisomeric polymer, leading to anisotropic molecular orientation.

We report novel azo-carbazoles that can be applied to updatable full-color holography. We introduced a molecular design concept of updatable full-color holographic systems based on spectroscopic and optical characteristics. Taking advantage of characteristics of the designed azo-carbazoles, updatable red, yellow and green holograms can be recorded, which enabled us monochromic hologram as well as full-color hologram in the future.