| Several sets of novel polydiacetylenes bearing photoactive azobenzene chromophores were synthesized and characterized, which are difference in alkylene spacer and the substituents of azobenzene ring or connecting modes. In the thesis, the nonlinear optical properties and the thermochromism of the azobenzene functional polydiacetylenes were investigated detailedly. The main contents of this dissertation consist of the following points:1. The mechanism of polymerization of the diacetylenic compounds and the mechanism of chromic properties of polydiacetylenes were presented, and the recent development of the research and the application on polyacetylenes were reviewed systematically.2. A series of polydiacetylenes containing azobenzene chromophores with different terminal groups poly-{CH3-(CH2)11-C≡C-C≡C-(CH2)8-COO-(CH2)2-O-C6H4-N= N-C6H4-R, where R = NO2, CN, CH3 and labeled as 3a, 3b and 3c, respectively} were synthesized. The polymers were no longer soluble in common organic solvents and thermally stable (≥285℃). The thermochromic behavior of the polymers was evaluated with UV, Raman, X-ray diffraction analyses, it was found from results that all of the polymers possessed large temperature ranges of thermochromism. The temperature ranges between the low and the high critical temperature for the red phase were obtained to be 60-160℃, 57-162℃and 50-154℃for P3a, P3b and P3c, respectively, which are larger than those reported before for other polydiacetylenes.3. A series of main chain azobenzene polymers containing diacetylene moieties with different lengths of the spacer {-[C≡C-CH2-O-C6H4-OCO-(CH2)m-O-C6H4-N=N-C6H4-O-(CH2)m-OCO-C6H4-O-CH2-C≡C]n-, where m = 3, 6, 11} were synthesized by oxidative coupling polymerization. All the polymers could be cross-linked at the elevated temperatures due to the polymerization reactions of the diacetylene groups in the polymer backbone, and the cross-linked polymers showed dramatically modified properties, such as their thermal stability and solvent resistance. The third-order nonlinear susceptibilities of the cross-linked polymers were investigated by an 13 ns Nd:YAG laser system at 532 nm wavelength. Results showed that the third-order nonlinear susceptibility of the polymers was as high as 10-9 esu and the optical limiting and nonlinear optical performances were affected by the spacer length .The polymers having longer spacer lengths on the azobenzene ring show inferior properties.4.A series of azopolymers{-[C≡C-CH2-O-C6H4-OCO-C2H4-O-(N-C6H4-N=N-C6H4-R)-O-C2H4- OCO- C6H4 -O-CH2-C≡C]n-, R = NO2, OCH3} with diacetylene main chain and azobenzene side moieties were prepared by oxidative coupling polymerization. It was found that the optical absorption of azobenzene showed a gradually shifting to blue with development of the thermal curing reaction, and based on that, we defined an apparent cross-linking degree. The photo-induced birefringence (Δn) and grating of the cross-linked polymers were evaluated by a He-Cd laser system at 442 nm wavelength. We also found that the maximum value ofΔn increased with a decreasing in the cross-linking degree, and when two parallel linearly polarized beams at 442 nm were interfered in the film, no diffraction beam was observed. However, when two orthogonal linearly polarized beams were allowed to interfere in the film, a polarization grating was formed and the value of diffraction efficiency reached about -1.70×10-2 within 15 min. The repeated "writing" and "erasing" experiments were made and the value of maximum transmittance kept constant for cross-linked films, which indicated that cross-linking could effectively improve the stability of the photo-induced birefringence in the new materials.5.A series of poly-(pentacosa-10,12-diynoic acid)/diacetylene-containing mainchain azopolymer(PDA/PAzo6) and poly-(pentacosa-10, 12-diynoic acid) /polymethy lmethacrylate(PDA/PMMA) hybrid films were prepared. The photo-polymerization of films was carried out by irradiation at 254 nm under monitoring the optical absorption in the visible region. It was found that PDA/PAzo6 showed maximum absorption at 663 nm, which was 30 nm higher than that of PDA/PMMA. Through the TEM and XRD analyses, we proposaled the obviously red-shift of absorption maximum in visible region came of the phase-separated domains of PDA/PAzo6. In addition, the PDA/PAzo6 showed unusual thermochromism and interesting photochromism, Investigation into thermochromism and photochromism of these novel materials were in progress.
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