High-molecular weight bottlebrushes via continuous flow photoiniferter polymerization of macromonomers

Abstract

High-molecular weight amphiphilic PEG-based bottlebrushes have been synthesized via continuous flow photoiniferter polymerization of macromonomers using trithiocarbonates as chain transfer agents. Blue LED light-mediated polymerization of macromonomers under mild conditions (22–50 °C) resulted in thermoresponsive copolymers with low dispersity and high yield. The effect of a solvent, temperature, comonomer composition and flow rate on the macromonomer conversions and solution properties of the copolymers have been investigated. The possibility of scaling the process to produce up to 54 g of pure polymer in an 8-hour day has been shown. Thermoresponsive properties of the bottlebrushes in aqueous solutions were studied by light scattering, turbidimetry and cryo-TEM. The samples synthesized in THF and toluene were compositionally homogeneous random copolymers with sharp reversible phase transitions while in DMSO, copolymers had broad thermoresponsive transitions. According to cryo-TEM, spherical unimolecular micelles at 10 °C transformed during LCST transition into tangled worm-like aggregates at 40 °C.