In situ study of dynamic conformational transitions of a water-soluble poly(3-hexylthiophene) derivative by surfactant complexation.
Transitions in the backbone conformation of polythiophenes (PTs) in organic solvents, measurable spectroscopically, have been widely observed to influence thin-film morphology; however, such conformational transitions of water-soluble PT derivatives, with respect to their intramolecular versus intermolecular origin, remain largely obscure. Here, we report on dynamic conformational transitions of poly(3-potassium hexanoate thiophene) in aqueous cetyltrimethylammonium bromide investigated by means of Fourier transform infrared spectroscopy, differential scanning calorimetry, polarizing optical microscopy, and ultraviolet-visible absorption and fluorescence spectroscopy. As-prepared complexes exist as stable hydrogels. Upon dilution, a significant time-dependent chromism occurs spontaneously. A coil-to-rod conformational transition is identified in this mechanism. Study into the corresponding kinetics demonstrates an inverse first-order rate law. It is found that the conformational transition is thermally reversible and concentration-independent. The critical transition temperature is largely dependent on the surfactant architecture. A theoretical model is presented to explain this new phenomenon and the mechanisms behind its influence on the optoelectronic properties.
Department of Chemistry and Biochemistry, California Polytechnic State University, San Luis Obispo, California 93407, USA.
Cameron D
CD
Danesh
Nathan S
NS
Starkweather
Shanju
S
Zhang
D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry*; D007700:Kinetics; D008968:Molecular Conformation; D012995:Solubility; D013501:Surface-Active Agents / Q000737:chemistry*; D013816:Thermodynamics; D013876:Thiophenes / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
D002593:Cetrimonium Compounds; D013501:Surface-Active Agents; D013876:Thiophenes; C507295:poly(3-hexylthiophene); D014867:Water; D000077286:Cetrimonium