Assessment of the Use of Low Molecular Weight Diblock Copolymers for the Formation of Stable, Tunable Droplet Interface Bilayers

This thesis presents the use of diblock copolymers, poly(butadiene)-b-poly(ethylene oxide) (PB_m PEO_n) and poly(isoprene)-b-poly(ethylene oxide) (PI_mPEO_n), as amphiphilic molecular building blocks for the formation of synthetic polymer bilayer membranes using the droplet interface bilayer (DIB) technique. The DIB technique makes use of the self-assembly of amphiphilic macromolecules along oil-water droplet interfaces that can then be physically connected for the construction of liquid supported macromolecular bilayers at the droplet interface. These bilayer membranes are capable of hosting both naturally occurring and synthetic protein channels. This technique has been used to form synthetic bilayer membranes using various combinations of macromolecules. Much success has been had with a variety of lipids as the primary surfactant in the formation of DIBs, but questions remain regarding the use of diblock copolymers as the building blocks of DIBs.

A diblock copolymer is a combination of two separate polymer blocks, in this case a hydrophobic block (polybutadiene) and a hydrophilic block (polyethylene oxide). Block copolymers (BCPs) exhibit a high level of tunability, with previous studies showing the possibility of varying the types of polymers used in either block, the chain length of either block and effective bilayer thickness, and/or terminal functional groups of the blocks, effectively changing the BCP’s functionality. BCP structures have been shown to have a higher stability and greater longevity than lipid structures due to their higher molecular weight. BCPs could allow for a new dimension of customization at the interface with a greater potential for testing a variety of applications.

Previous attempts at using BCPs in the formation of DIBs were successful in forming bilayers with applied voltage, but the interfaces proved to be too thick for the successful incorporation of protein channels. The goals of this study are to show that a BCP with a lower molecular weight, PB₁₂PEO₈ or PI₁₇PEO₁₇, can successfully form a DIB, and then to quantify the effects of BCP presence in DIBs. With BCP bilayer DIBs realized, a wealth of potential applications could arise, ranging from drug delivery and protein characterization to neural networks and biomimetic computation.