Changhui Tan

Photochromism and holographic recording in polymer film containing chiral azo molecules derived from amino acid

Abstract A kind of chiral azo molecule derived from amino acid, N-[4-(4-octyloxyphenylazo)benzoyl]- l -glutamic acid (C8-Azo- l -Glu), was synthesized and the photochromism, photoinduced birefringence, and holographic recording in C8-Azo- l -Glu doped poly(methyl methacrylate) (PMMA) films were studied. C8-Azo- l -Glu underwent a reversible trans–cis–trans isomerization in the polymer matrix. The photoinduced birefringence was investigated at various intensities of Ar laser (488 nm) beam. A reversible hologram was recorded in this media and the dependence of the first order diffraction efficiency on the recording beam intensities was also presented.

Synthesis of hyperbranched poly(amine-ester)-protected noble metal nanoparticles in aqueous solution

The synthesis of Au and Ag metal nanoparticles stabilized by G4, G5, and G6 hyperbranched poly(amine–ester) (HPAE) is reported. The reduction of hydrogen tetrachloroaurate and silver nitrate in the presence of HPAE resulted in the formation of stable, uniform, water-soluble nanoparticles. The average particle sizes are (2.4 ±0.5)–(4.1 ±0.4) nm for Au and (2.5 ±4.9)–(10.3 ±1.7) nm for Ag, depending on the generation of HPAE and metal ion-to-end tertiary amine of HPAE (M:N) used. All of the obtained colloidal solutions are stable for a long period of time. The results from ultraviolet–visible absorption spectra and Fourier transform infrared absorption spectroscopic investigations confirm the interactions between metal and HPAE.

Atomic force microscopy study of self-organization of chiral azobenzene derived from amino acid

Abstract A kind of chiral azobenzene amphiphile, N -[4-(4-dodecyloxyphenylazo)benzoyl]- l -glutamic acid (C 12 -Azo- l -Glu; as shown in Fig. 1), was synthesized and the self-organization properties on solid substrates were investigated. C 12 -Azo- l -Glu underwent a reversible trans – cis photoisomerization in dilute solution. While the photoisomerization was suppressed on solid substrate because of the H-aggregation, indicating the formation of compact film. When C 12 -Azo- l -Glu was cast from ethanol solution onto the hydrophilic surface of mica, a stable flat-layered structure formed spontaneously in large scale. High-resolution images allowed the identification of the relative orientation of molecular rows in the ordered thin film and the crystal lattice of mica. A molecular packing model of the layered structure was proposed. There was a template effect of mica to the self-organization process. Hydrogen bonding, π–π interaction and the chiral center in the molecule played the important roles in the self-organization process. The cooperative competitive effect between them led to the highly ordered structure.