Polystyrene/polyglycidol copolymers and particles synthesis and properties - does the shape matter?

Amphiphilic block copolymers (BCPs), their assemblies into polymer micelles, nano- and microparticles and higher order structures of the type of colloidal crystals found numerous applications in various areas of science and industry; such as polymer blends, surfactant systems for emulsion stabilization, antibacterial and protein antifouling coatings, polymer membranes, nanoreactors with embedded enzymes, electrochemical sensors, polymer solar cells, drug and other biactive compounds carriers, tissue engineering materials, and many others. For all aforementioned applications are needed BCPs with adequately tailored properties. Control of BCPs` and nanoparticles’ properties was usually achieved by designing appropriate chemical structures of copolymer blocks. We presumed that some control could be assured by changing copolymer architecture and shape of nano and microparticles. For our studies we selected copolymers with hydrophobic polystyrene and hydrophilic polyglycidol blocks. Particles were obtained either by synthesis of block copolymers and their subsequent self-assembly into polymeric micelles, with diameters about 20 nm, larger aggregates (among them colloidal crystals) with diameters in nano- and micrometer range or by polymerization induced self-assembly (PISA) during dispersion copolymerization of styrene and α-tert-butoxy-ω-vinylbenzyl-polyglycidol yielding particles with polyglycidol enriched shells and diameters ranging from 60 to 830 nm. Synthesized copolymers had polystyrene-b-polyglycidol and polystyrene-b-(polyglycidol-g-polyglycidol) structure, i.e. in the second copolymer type the polyglycidol block had a “bottle-brush” architecture. The degree of polymerization of the polystyrene block was constant and equal 29, the degree of polymerization the polyglycidol blocks was varied from 14 to 136. It should be noted that critical micelle concentration (CMC) for copolymers with “bottle-brush” polyglycidol was about ten times higher than in the case of linear ones. The microspheres obtained by th PISA-type process were converted into microspheroids. It was found that the microspheres self-assembled forming hexagonal-like packed colloidal crystals, whereas microspheroids self-assembled into structures resembling nematic liquid-crystalline domains. Optical properties (angle-resolved reflection spectra) of these assemblies were investigated.

Acknowledgment: This work was financially supported by the National Science Centre

(Poland) Grants UMO-2018/29/B/ST4/02178 and UMO-2018/29/B/ST8/01721