Thermodynamic Study of Colorimetric Transitions in Polydiacetylene Vesicles Induced by the Solvent Effect

Abstract

We report the synthesis of 10,12-pentacosadyinoic acid (PCDA) and PCDA + cholesterol (CHO) + sphingomyelin (SPH) vesicles dispersed in water and the determination of their colorimetric response induced by small amount of organic solvents. In the absence of solvent, PCDA and PCDA/CHO/SPH vesicles showed an intense blue color. The addition of CHCl(3), CH(2)Cl(2), and CCl(4) caused a colorimetric transition (CT) in both structures with the following efficiency: CHCl(3) > CH(2)Cl(2) ≅ CCl(4). However, CH(3)OH did not cause a blue-to-red transition. By microcalorimetric technique we also determined, for the first time, the enthalpy change associated with the CT process and the energy of interaction between solvent molecules and vesicle self-assembly. We observed that the chloride solvents induced a colorimetric transition, but the thermodynamic mechanism was different for each of them. CT induced by CHCl(3) was enthalpically driven, while that caused by CH(2)Cl(2) or CCl(4) was entropically driven.

Polydiacetylene Vesicles for Detecting Surfactants: Understanding the Driven Forces of Polydiacetylene-Surfactant Interaction

“…As we demonstrated, the enthalpy changes associated with the PDA colorimetric transition are a result of conformational changes associated with the rotation of the functional group around the carbon-carbon bond present in polydiacetylene chains [12,22].…”

“…The PDA and PDA/CHO/SPH vesicles were prepared as described elsewhere [12,[23][24][25]. Briefly, to obtain PDA vesicles, the PDA monomer (10,12-pentacosadiynoic acid, 97% w/w, Sigma ® ) was dissolved in CHCl 3 (98% w/w, Sigma ® ), which was removed by a stream of N 2 gas to promote the formation of a PDA film on the glass surface.…”

“…These results show that there is a higher hydrophobic contribution for the PDA-CTAB interaction than for PDA/ CHO/SPH interaction. The entropic contribution could be ascribed to two processes: i) the releasing of water molecules solvating the surfactant molecules and the hydrophilic surface of the vesicles, increasing the translational entropy of the system and ii) the conformational change associated with PDA molecules, which transform from a linear chain to a coil structure, increasing the conformational entropy of the vesicle [12], and/or twist out of planarity during the colorimetric transition, but still largely linear.…”

“…As is well known, polydiacetylene vesicle building by self-organized diacetylene monomers and then polymerized by UV light could be used as nanosensors due to its molecules undergo spectrophotometric transitions in J ournal of Food Chemistry & Nanotechnology response to different stimuli, such as temperature change [4][5][6], pH [5,7,8], mechanical stress [9,10], solvents [5,11,12], and interaction with other molecules, such as surfactants [13][14][15][16][17][18][19].…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 21, 2010) and the discipline

“…Colorimetry and calorimetry have occasionally been combined to enhance understanding of solvatochromic systems, e.g. [102].…”