Ruttayapon Potai

Stable polydiacetylene/ZnO nanocomposites with two-steps reversible and irreversible thermochromism: The influence of strong surface anchoring

This contribution introduces a versatile method to prepare a new class of polydiacetylene(PDA)-based material. ZnO nanoparticle is used as a nano-substrate for spontaneous assembling of diacetylene monomer, 10,12-pentacosadiynoic acid, on its surface. An irradiation of the organized assemblies by UV light results in PDA/ZnO nanocomposites with deep blue color. Strong ionic interaction and hydrogen bonding at the ZnO surface restrict the dynamics of alkyl side chains and promote the PDA ordering, which in turn drastically affects its thermochromic behaviors. We have found that the PDA/ZnO nanocomposite exhibits two-steps color transition upon increasing temperature. The first transition of the nanocomposite in aqueous suspension, causing the color change from blue to purple, occurs reversibly at ∼90°C. The transition temperature shifts to ∼100°C when the nanocomposite is embedded in polyvinyl alcohol matrix. Further increasing temperature to 145°C induces the second transition, which causes irreversible color change from purple to red.

Fine tuning the color-transition temperature of thermoreversible polydiacetylene/zinc oxide nanocomposites: The effect of photopolymerization time.

An ability to control the thermochromic behaviors of polydiacetylene (PDA)-based materials is very important for their utilization. Recently, our group has developed the PDA/zinc oxide (ZnO) nanocomposites, which exhibit reversible thermochromism (Traiphol et al., 2011). In this study, we present our continuation work demonstrating a rather simple method for fine tuning their color-transition temperature. The PDA/ZnO nanocomposites are prepared by varying photopolymerization time, which in turn affects the length of PDA conjugated backbone. We have found that the increase of photopolymerization time from 1 to 120min results in systematically decrease of the color-transition temperature from about 85 to 40°C. These PDA/ZnO nanocomposites still exhibit reversible thermochromism. The PDA/ZnO nanocomposites embedded in polyvinyl alcohol films show two-step color-transition processes, the reversible blue to purple and then irreversible purple to orange. Interestingly, the increase of photopolymerization time causes an increase of the irreversible color-transition temperature. Our method is quite simple and cheap, which can provide a library of PDA-based materials with controllable color-transition temperature.

Conjugated polymers with m-pyridine linkages: synthesis, photophysics, solution structure and film morphology

The synthesis of two π-conjugated polymers whose structures include m-pyridyl linkages that create regularly spaced bends and disrupt π-conjugation along the polymer backbones is described. The π-conjugated segments in the two polymers were comprised of p-(2,5-dialkoxyphenylene)vinylene, p-phenylenevinylene and 2,7-carbazole subunits. Additionally, each m-pyridylene unit is enshrouded within a steric cleft provided by 2,6-diaryl substitution of the pyridyl ring, thus minimizing inter-chain interactions of these sites. The concentration-dependence of photophysical characteristics along with small angle neutron scattering (SANS) was employed to resolve solution aggregation properties and atomic force microscopy was employed to assess the surface morphology of polymer films.