Experiments and Simulations of Complex Sugar-Based Coil-Brush Block Polymer Nanoassemblies in Aqueous Solution

M Dong and MG Wessels and JY Lee and L Su and H Wang and RA Letteri and Y Song and YN Lin and YC Chen and RC Li and DJ Pochan and A Jayaraman and KL Wooley, ACS NANO, 13, 5147-5162 (2019).

DOI: 10.1021/acsnano.8b08811

In this work, we investigated the fundamental molecular parameters that guide the supramolecular assembly of glucose-based amphiphilic coil- brush block polymers in aqueous solution and elucidated architecture morphology relationships through experimental and simulation tools. Well-defined coil-brush polymers were synthesized through ring-opening polymerizations (ROP) of glucose carbonates to afford norbornenyl- functionalized poly(glucose carbonate) (NB-PGC) macromonomers, followed by sequential ring-opening metathesis polymerizations (ROMP) of norbornene N-hydroxysuccinimidyl (NHS) esters and the NB-PGC macromonomers. Variation of the macromonomer length and grafting through ROMP conditions allowed for a series of coil-brush polymers to be synthesized with differences in the brush and coil dimensions, independently, where the side chain graft length and brush backbone were used to tune the brush, and the coil-block length was used to vary the coil. Hydrolysis of the NHS moieties gave the amphiphilic coil-brush polymers, where the hydrophilic hydrophobic ratios were dependent on the brush and coil relative dimensions. Experimental assembly in solution was studied and found to yield a variety of structurally dependent nanostructures. Simulations were conducted on the solution assembly of coil-brush polymers, where the polymers were represented by a coarse- grained model and the solvent was represented implicitly. There is qualitative agreement in the phase diagrams obtained from simulations and experiments, in terms of the morphologies of the assembled nanoscopic structures achieved as a function of coil-brush design parameters (e.g., brush and coil lengths, composition). The simulations further showed the chain conformations adopted by the coil-brush polymers and the packing within these assembled nanoscopic structures. This work enables the predictive design of nanostructures from this glucose-based coil-brush polymer platform while providing a fundamental understanding of interactions within solution assembly of complex polymer building blocks.

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