Title
Supramolecular assembly of thermoresponsive steroidal surfactant with oppositely charged thermoresponsive block copolymer
Author
Maria Chiara di Gregorio, Marta Gubitosi, Leana Travaglini, Nicolae Viorel Pavel, Aida Jover, Francisco Meijide, Jose Vezquez Tato, Simona Sennato, Karin Schillen, Francesco Tranchini, Serena De Santis, Giancarlo Masci, Luciano Galantini
Year
2016
Journal
Physical Chemistry Chemical Physics
Abstract
Supramolecular rearrangements are crucial in determining the response of stimuli sensitive soft matter systems such as those formed by mixtures of oppositely charged amphiphiles. Here mixtures of this kind were prepared by mixing the cationic block copolymer pAMPTMA30-b-pNIPAAM120 and an anionic surfactant obtained by modification of the bile salt sodium cholate. As pure components, the two compounds presented a thermoresponsive self-assembly around 30-35 °C; a micelle formation in the case of the copolymer and a transition from fiber to tubes in the case of the bile salt derivative. When both were present in the same solution they associated into mixed aggregates that showed complex thermoresponsive features. At room temperature, the core of the aggregate was comprised of a supramolecular twisted ribbon of the bile salt derivative. The block copolymers were anchored on the surface of this ribbon through electrostatic interactions between their charged blocks and the oppositely charged heads of the bile salt molecules. The whole structure was stabilized by a corona of the uncharged blocks that protruded into the surrounding solvent. By increasing the temperature to 30-34 °C the mixed aggregates transformed into rods with smooth edges that associated into bundles and clusters, which in turn induced clouding of the solution. Circular dichroism allowed us to follow a progressive rearrangements of the supramolecular organization within the complex, occurring in the range of temperature of 20-70 °C.
Instrument
J-715
Keywords
Circular dichroism, Polymers, Aggregation, Thermal stability, Materials