A monomer [thiophene]-[isothianaphthene]-[thiophene] was prepared by previously reported method [3] . Hydroxypropyl cellulose was obtained from Wako Pure Chemical Industries, Ltd. and used as supplied. Tetrabutylammonium perchlorate was obtained from Tokyo Chemical Industry Co., Ltd. and used as supplied. N,N-dimethylformamide was obtained from Nacalai Tesque, Inc. and used as supplied.

Electrochemical polymerization of a monomer [thiophene]-[isothianaphthene]- [thiophene], abbreviated as T-ITN-T, was carried out in hydroxypropyl cellulose (Figure 1). Constituents of electrolyte solution are summarized in Table 1. Firstly, tetrabutylammonium perchlorate (TBAP) (supporting salt) and monomer was dissolved in N,N-dimethylforma- mide (DMF) (Figure 2(a)). Next, hydroxypropyl cellulose was added to the electrolyte solution containing monomer and supporting salt (Figure 2(b)). The solution was stirred mechanically by glass rod for 1 min at room temperature (Figure 2(c)). A polarizing optical microscopy image of the lyotropic liquid crystal solution is shown in Figure 3. Then, electrochemical polymerization was carried out by using sandwich cell

^a[thiophene]-[isothianaphthene]-[thiophene]; ^bHydroxypropyl cellulose; ^cTetrabutylammonium perchlorate.

method with two ITO glass electrodes (ITO = indium tin oxide) developed by our group previously. Direct current (dc) voltage of 2.5 V was applied across of the cell for 60 min. A thin film was deposited on an anode side of the electrode. After the electrochemical reaction, the sandwich cell was soaked into the water to remove the residual HPC from the film surface. After a 30 min, the sandwich cell was disassembled easily. The resultant was washed with water, and acetone to yield a thin film deposited on the ITO coated glass, abbreviated as P(T-ITN-T)/HPC.

Optical texture observations were carried out by using an ECLIPS LV 100 high- resolution polarizing microscope (Nikon). Fourier Transform Infrared absorption was obtained with a FT-IR 4600 (Jasco) by using the KBr method. UV-vis absorption spectroscopy was carried out by using V-630 (Jasco). Cyclic voltammetory were carried out with a μAUTOLAB TYPE III (ECO Chemie). Electrolyte solution contained 0.1 M TBAP in acetonitrile. Circular dichroism spectroscopy was carried out with a J-720 (Jasco).

The polymer thus obtained shows clear fingerprint texture under polarizing optical microscopy (POM) in Figure 4. The fingerprint pattern is derived from cholesteric liquid crystal of HPC helical aggregation, indicating occurrence of transcription of helical structure of HPC during the electrochemical polymerization. In this case, HPC acts as a helical template.

Fourier transform infrared (FT-IR) absorption spectroscopy measurements of

HPC (matrix), T-ITN-T (monomer) and P(T-ITN-T)/HPC are shown in Figure 5. HPC shows broad O-H vibration absorption around 3450 cm⁻¹ due to hydroxyl group in the pyranose unit. Absorption band around 2960 cm⁻¹ is due to CH₂ and CH stretching vibration. The polymer shows absorption band at 3430 cm⁻¹ due to the O-H stretching vibration of cellulose unis. This result revealed that the resultant material is composite of P(T-ITN-T) and HPC. HPC component cannot be separated after washing of the film with solvents.

In situ UV-vis absorption measurements were carried out during cyclic voltammetry measurement. Change in the UV-vis of P(T-ITN-T)/HPC at various application potential are shown in Figure 6. The polymer shows absorption band at around 550 nm due to - transition of main chain. A new absorption band at 960 nm is derived from polaron band (radical cation) at oxidation process (Figure 6(a)). The absorption intensity of polaron band increases with application of voltages, indicating progress of electrochemical oxidation (doping). On the other hands, reduction process (Figure 6(b)) shows decrease of absorption intensity of the polaron band. The electrochemically reduced state at 0 V of the composite has a bandgap of 1.5 eV, which is in the range of low-bandgap conjugated polymers.

Changes in intensity of absorptions are repeatable through electrochemical doping/dedopoing (redox) process. To confirm the repeatable electrochromic property, change in absorption intensity at 550, 730 and 1030 nm upon repeating application of voltage between 0 and 1.0 V (vs. Ag/Ag⁺) was examined for 750 s

at a scan rate of 50 mV/s (Figure 7).

Cyclic voltammetry (CV) analysis of P(T-ITN-T)/HPC was carried out at various scan rates of 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 mV/s. The CV result is shown in Figure 8. First oxidation wave indicates that the polymer film was oxidized and polarons (radical and cation) were generated. At reduction process, reduced wave was confirmed, indicating that the polymer film was reduced. The polymer film exhibits repeatable redox behavior in the applied potential range from 0 to 1.0 V (vs. Ag/Ag⁺).

Circular dichroism (CD) absorption spectroscopy measurement was carried out for as prepared polymer film and reduced polymer film. The CD spectra of the film are shown in Figure 9. The reduced film was prepared by hydrazine vapor for 30 min. Reduction allows increase of the absorption band at around 400 nm due to decrease of fraction of polarons in the main-chain accompanied by

de-doping, indicating optical activity of the composite can be changed by the reduction.