Electronic Absorption Spectroscopy Probed Side-Chain Movement in Chromic Transitions of Polydiacetylene Vesicles

Abstract

Thermochromism, solvatochromism, and alkalinochromism of a poly-10,12-pentacosadiynoic acid (poly(PCDA)) vesicle solution are studied by electronic absorption spectroscopy. The spectroscopic profiles reveal different sequences of side-chain movement during the chromic transitions. The gradual hypsochromic shift and reversibility of the purple solution at low temperature in the thermochromic transition indicates that the transition starts with reversible conformational alteration of methylene side chains leading to metastable purple vesicles. Further heating to 80 degrees C or higher eventually causes the hydrogen bonds at the carboxylic head groups to break and turns the vesicle solution to red. The irreversibility of the red vesicles indicates that it is the most thermodynamically stable form. In the ethanolochromism and alkalinochromism, the processes are however induced at the vesicle-media interface, directly bringing about the hydrogen bond breaking. The purple solutions observed in the ethanolochromism and alkalinochromism cannot reverse back to the blue one. The absorption spectra clearly demonstrate that they are mixtures of the blue and red vesicles.

Preparation of Reversible Thermochromism Supramolecules of 4-Aminophenol-Modified Polydiacetylene

“…However, the blue-to-red color changes undergo an irreversible colorimetric transition upon heating, preventing the use of polydiacetylenes repeatedly [21]. Investigations suggested that the blue-colored conformation is substable with that the carbon atomic orbital changes from sp hybridization into sp 2 hybridization and that the bond angle changed from 180 • to 120 • .…”

Preparation of optical active polydiacetylene through gelating and the control of supramolecular chirality

“…Polydiacetylene (PDA), as one of the most investigated polymers, exhibited many potential applications as biosensors, pathogenic agents, and functional materials [8][9][10][11]. It is well known that diacetylene undergoes topochemical reactions upon UV-irradiation by 1,4-addition reactions when the monomer units are aligned appropriately [12,13]. Strict steric conditions in the arrangement of diacetylene monomers are usually required in such topochemical reactions, which are largely depended on the substituent group in the monomeric diacetylene [14][15][16][17][18][19][20].…”

Role of Gel to Fluid Transition Temperatures of Polydiacetylene Vesicles with 10,12-Pentacosadiynoic Acid and Cholesterol in Their Thermochromisms

“…It was suggested that the change in the conformation of the conjugated ene-yne backbone or the conjugated p-orbital arrays (from planar to partially distorted) varied the conjugation length, which was primarily responsible for the color change of the polydiacetylenes. [36][37][38][39] Regarding factors affecting conformation change in the π-bond, head group interactions, arising from hydrogen bonds/lateral stacking between aromatic rings or the flexibility of head groups, were suggested to play important roles. 30,[33][34][35]40 Meanwhile, melting of the unreacted monomers was also suggested to be a factor for the conformation change of the backbone.…”