Spectroscopic Ellipsometry and Fluorescence Study of Thermochromism in an Ultrathin Poly(diacetylene) Film:  Reversibility and Transition Kinetics

Abstract

We have investigated the thermochromic transition of an ultrathin poly(diacetylene) film. The Langmuir film is composed of three layers of polymerized 10, 12-pentacosadiynoic acid [CHJCHJ#====C===(CHJ~COOH] (poly-PCDA) organized into crystalline domains on a silicon substrate. Spectroscopic ellipsometry and fluorescence intensity measurements are obtained with in-situ temperature control. Poly-PCDA films exhibit a reversible thermal transition between the initial blue form and an intermediate "purple" form that exists only at elevated temperature" (between 303 -333 K), followed by an irreversible transition to the red form after annealing above 320 K. We propose that the purple form is thermally distorted blue poly-PCDA, and may represent a transitional configuration in the irreversible conversion to red. This hypothesis is supported by the appearance of unique features in the absorption spectra for each form as derived from the ellipsometry measurements. Significant fluorescence emission occurs only with the red form, and is reduced at elevated temperatures while the absorption remains unchanged. Reduced emission is likely related to thermal fluctuations of the hydrocarbon side chains. Time-resolved fluorescence measurements of the irreversible transition have been performed. Using a first-order kinetic analysis of these measurements we deduce an energy barrier of 17.6M. 1 kcal mo~*between the blue and red forms.

The “Precursor Approach” to Patterned Fluorescence Images in Polymer Films

“…Polydiacetylenes are nonfluorescent in the ''blue phase'' and fluorescent in the ''red phase''. [133][134][135] Recently, Kim and coworkers reported a new strategy for constructing patterned color and fluorescence images that takes advantage of these properties of polymer films comprised of polydiacetylene supramolecular systems. [136] The diacetylene monomer and the procedures used for the generation of both color and fluorescence patterns in the polymer film are shown in Figure 14 and 15.…”

Colorimetric response of azobenzene-terminated polydiacetylene vesicles under thermal and photic stimuli

“…Although tremendous efforts have been made [13][14][15][16][17][18][19][20][21][22][23], the exact mechanism of the blue-tored color transition is still not clearly understood. Recent studies suggest that the release of mechanical strain, developed on the side chains during polymerization, is the main reason for the color transition [2,21].…”

Effect of phospholipid insertion on arrayed polydiacetylene biosensors

“…Diacetylene lipids, such as 10,12-pentacosadiynoic acid (PCDA), can undergo polymerization via a 1,4-addition reaction upon UV light to form ene-yne alternating polymer chains, producing liposome-like vesicles. The vesicles show a bichromic property from blue to red upon external perturbations, such as heat, pH, and mechanical stresses, providing a cheap and convenient sensor [1][2][3]. Using the property, PDA-based sensors have been developed to detect biological samples, including influenza virus, cholera toxin, Escherichia coli, oligonucleotides, antibodies, antigens, and lipopolysaccharides [4][5][6][7][8][9][10][11][12][13].…”

“…Using the property, PDA-based sensors have been developed to detect biological samples, including influenza virus, cholera toxin, Escherichia coli, oligonucleotides, antibodies, antigens, and lipopolysaccharides [4][5][6][7][8][9][10][11][12][13]. The colorimetric change causes vesicles to turn fluorescent [3,14,15]. Micro-patterned PDA vesicles can be fluorescence-based sensor chips for external stimulation [16][17][18][19], or as a biochip for high-throughput detection of low-volume analytes [20].…”