Micellar Solutions of a Symmetrical Amphiphilic ABA Triblock Copolymer with a Temperature‐Responsive Shell

Abstract

We have studied the thermal behavior of an ABA triblock copolymer having short, deuterated polystyrene end‐blocks and a longer poly(N‐isopropyl acrylamide) middle block, the latter exhibiting a lower critical solution temperature. The collapse of the micelles was investigated using dynamic light scattering. Small‐angle neutron scattering with contrast matching allowed us to quantify the core‐shell structure of the micelles as well as their correlations as a function of temperature.

Deuterium Isotope Effect on Solution Behavior of Thermoresponsive Star-Shaped Poly(2-isopropyl-2-oxazoline)

“…All mentioned temperature changes are small and close to 1 C. The same variations were observed for the phase transition temperature of PNIPAM gel, [6] the cloud point of PNIPAM solutions, [13] and the transition temperature T m of linear poly(2-isopropyl-2-oxazoline)s. [3,12] However, in the case of PNIPAM systems in D 2 O solutions the temperatures under consideration are higher than those in H 2 O, whereas for linear and star poly(2-isopropyl-2-oxazolines) these changes have the opposite character, namely, T m and T max decrease during the passage from H 2 O to D 2 O. We may assume that this difference is caused by the hydrogen bond balance formed in solutions of the compared polymers.…”

“…[9][10][11][12] Similar behavior was observed for polystyrene and PNIPAM triblock copolymer. [13] The temperature at which the collapse of dissolved particles starts (phase transition temperature) was lower in the mixture D 2 O and H 2 O than in deuterated water (by about 1 C). Besides that, at the H-temperatures and in the fully collapsed globular state, the average sizes of the PNIPAM molecules in deuterated water were larger than in H 2 O.…”

Synthesis of Symmetrical Triblock Copolymers of Styrene and N‐isopropylacrylamide Using Bifunctional Bis(trithiocarbonate)s as RAFT Agents

“…DLS indicated the formation of micellar aggregates with hydrodynamic diameters of about 40 nm at ambient temperature, while heating to 32 °C produced turbid solutions, which cleared reversibly upon cooling. Concentrated solutions form thermoresponsive, micellar hydrogels 76. Further studies on the associative and thermoresponsive behavior of the polymers in water, including the formation of thermally sensitive hydrogels are under way.…”

“…They self-organize into micellar aggregates at low, and into hydrogels at high concentrations. Further studies on the associative and thermoresponsive behavior of the copolymers and of analogs bearing perdeuterated polySt blocks [76] in water are under way, including the formation of thermally sensitive hydrogels.…”

“…Concentrated solutions form thermoresponsive, micellar hydrogels. [76] Further studies on the associative and thermoresponsive behavior of the polymers in water, including the formation of thermally sensitive hydrogels are under way.…”