Kinetics of the Reversible Thermochromism in Langmuir-Blodgett Films of Cd2+ Salts of Polydiacetylenes Studied Using UN-Vis Spectroscopy

Abstract

The first quantitative model for the partially reversible thermochromism in Langmuir-Blodgett films of the polymerized Cd2+ salts of 10,12-tricosadiynoic acid (TCDA) and 10,12-pentacosadiynoic acid (PCD A) is presented. The visible spectrum as a function of temperature provides evidence for two parallel processes, one of which is reversible. The following kinetic model is proposed which qualitatively and quantitatively accounts for the observed reversible thermochromism: B R (kf, fer); P -* R (fe2). B and P stand for two distinct forms of the blue polymer, and R stands for the red form of the polymer. Activation barriers of E{ = 22.5 kcal/mol, Et = 21.4 kcal/mol, and E2 -23.0 kcal/mol are obtained from the TCDA spectra as a function of temperature using a "normal" preexponential factor of 1012 s-1 and Et and Et as adjustable parameters. The same model can be fit to films of PCDA and gives activation barriers of Et = 21.5 kcal/mol, Et = 21.0 kcal/mol, and E2 = 22.5 kcal/mol.

Deposition and Photopolymerization of Phase-Separated Perfluorotetradecanoic Acid–10,12-Pentacosadiynoic Acid Langmuir–Blodgett Monolayer Films

“…Neither of the pure films underwent phase transitions to liquid-like states, which is consistent with other isotherms reported in the literature for these surfactants. 15,27,37 The films exhibited collapse pressures of ∼55 mN m À1 for PF and ∼20 mN m À1 for PCDA, respectively, which again is in agreement with previous literature reports. For the mixed films, the πÀA isotherms were generally shifted to lower mean molecular areas as compared to the pure individual components, which is indicative of deviations from ideal mixing behavior.…”

Facile method to detect oligonucleotides with functionalized polydiacetylene vesicles

“…This is possible through the formation of an alternating conjugated ene-yne backbone as a result of UV-initiated topochemical polymerization of diacetylenes. The highly conjugated and visibly blue polymer can be converted into red and less conjugated form by several external stimuli, such as temperature [23][24][25], solvent [26], pH [27], and external stress [28,29]. As previously reported [11], the stress of polydiacetylene vesicles and the force imposed onto the polydiacetylenic structures play a crucial role in the color change of polydiacetylene vesicles for biological recognition.…”

Total Alignment of Calcite at Acidic Polydiacetylene Films: Cooperativity at the Organic-Inorganic Interface

“…The color changes observed upon calcite mineralization suggest that while the p-PDA may be preorganized into the 30" tilted structures, further reorganization of p-PDA occurs, most likely to optimize the specific stereochemistry of the carboxyl group. Color changes in polydiacetylenes have been shown experimentally (28) and theoretically (29) to be coupled to sidechain conformation and can be induced by high temperature (30,31), mechanical stress (32), or specific viral binding (19). To ascertain the role of side-chain reorganization with respect to calcite nucleation, we did an in situ analysis (33) by Fourier transform infrared spectroscopy.…”