Monitoring Collapse of Uniform Cylindrical Brushes with a Thermoresponsive Corona in Water

We generated rod-like micelles of uniform length by living crystallization-driven self-assembly of a polyferrocenylsilane (PFS) block copolymer PFS26-b-POEGMA163 in a methanol-ethanol mixture and then transferred these micelles to water. The corona chains consisted of poly(oligoethyleneglycol methacrylate) that had a lower critical solution temperature (LCST) of 40.5 °C in water. We used a combination of static (SLS) and dynamic (DLS) multiangle light scattering to determine the dimensions of these cylindrical brush micelles in solution. Measurements carried out in dilute solution in water over a series of temperatures from 23 to 50 °C showed that the collapse transition was broad and continuous, both upon heating and cooling. This response is different from the collapse transition of POEGMA163 homopolymer in water, which occurs over a very narrow temperature range. Thus we show that the collapse transition of a cylindrical brush has important features in common with the collapse of a brush of thermoresponsive polymers on a planar surface.