Hydrolysis-Induced Self-Assembly of High-χ–Low-N Bottlebrush Copolymers

Densely grafted bottlebrush statistical copolymers (BSCPs) and bottlebrush block copolymers (BBCPs) were synthesized with polystyrene (PS) and poly(solketal methacrylate) (PSM) side chains grafted to a polynorbornene backbone. The PSM chains could be hydrolyzed into poly(glycerol monomethacrylate) (PGM), significantly increasing the segmental interaction parameter (χ). Self-assembly of the polymers was studied with small-angle X-ray scattering before and after hydrolysis. The well-known rapid self-assembly of BBCPs by thermal annealing was retarded after hydrolysis, due to a large χ between the segments of the brushes. Utilizing the well-ordered lamellar morphology before hydrolysis, we developed a solid-state hydrolysis method to achieve high-χ BBCPs with long-range order. Analysis of the Porod scattering invariant showed that for high-χ BBCPs, the density of each phase deviated from the density of linear homopolymer melts due to multiple restrictions placed on the configuration of the brushes.