Amphiphilic block copolymers have been used to assemble extended polymer bilayers and polymersomes that mimic cellular membranes. These biomimetic structures are typically composed of block copolymers with molecular weights much larger than lipids and/or with high glass transition temperatures, leading to polymer membranes that lack the hallmark fluidity of biological membranes. This fluidity is key for a range of applications, from controlled drug release to polymer membrane-based diagnostics. Here, we show that a low molecular weight poly(butadiene)-<i>block</i>-poly(acrylic acid) (pBd-pAA) can self-assemble into supported polymer bilayers that exhibit environment-dependent fluidity. Micelles of the pBd-pAA form bilayers on pristine hydrophilic glass. We characterize the fluidity of these pBd-pAA membranes doped with a small percentage of fluorescently labeled lipid using fluorescence recovery after photobleaching (FRAP) and compare this fluidity to a prototypical lipid membrane of 1 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). pBd-pAA bilayers were found to exhibit diffusion coefficients of about 10 µm^2/s in buffered aqueous solutions both above and below the pKa of poly(acrylic acid). These diffusion coefficients are more than five times greater than for DOPC membranes. The surface hydrophobicity can be tuned to toggle between pBd-pAA monolayer and bilayer formation. I will also report our investigation of the pH dependence of pBd-pAA membrane fluidity and thickness.

Self-assembly of short-chain polyelectrolyte block copolymers into fluid biomimetic membranes

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.