Self-Assembly of Complex Functional Polymersomes

Abstract

Amphiphilic block copolymers are nanoscale building blocks that have the ability to self-assemble into a variety of morphologies in dilute solution. This Thesis focuses primarily on polymersomes, which are one of the many classes of self-assembled block copolymer nanostructures. Polymersomes are hollow membrane sacs that are not only able to encapsulate hydrophobic and/or hydrophilic molecules, but also possess exceptional chemical and physical stability, structural versatility, and surface modifiability. For the above reasons, polymersomes have in recent years emerged as a powerful tool for a wide range of applications in the fields of drug delivery and biomimicry. With that being said, the full potential of polymersomes has yet to be harnessed due to a lack of definitive methods for shape control.

The overall objective of this Thesis was to develop approaches to direct the self-assembly of block copolymer building blocks into complex yet functional polymersomes with shapes that deviate from a traditional sphere. To this end, a series of novel block copolymers with carefully incorporated supramolecular interaction motifs were synthesized and shown to be useful building blocks for the generation of spherical and non-spherical polymersomes; specifically, ones that are ellipsoidal, tubular or polyhedral shaped. The underlying mechanisms that govern the formation and shape transformation of these non-spherical polymersomes were also studied in detail.

Some of the spherical and non-spherical polymersomes prepared were subsequently used for studies in vitro to understand how variations in polymersome shape and size influence their interactions with cells. In the final section of this Thesis, a protein-polymer bioconjugate with thermoresponsive properties was synthesized and shown to reversibly self-assemble into polymersomes that synergistically exhibit properties of both protein and polymer components. The ability of these biohybrid polymersomes to selectively (co-)encapsulate drug and protein molecules within different compartments was further demonstrated to highlight their potential use as advanced drug delivery vehicles.

The findings reported in this Thesis should open up an avenue of opportunities for those who utilize polymersomes for drug delivery applications or as artificial cell and organelle scaffolds, as well as researchers interested in the fundamental aspects of polymer self-assembly and supramolecular chemistry.