Chemistry in block copolymer nanocontainers : self-assembly, container properties and confined enzymatic reactions

Abstract

The research described in this Thesis is centered around the utilization of block copolymer (BCP) vesicles formed by the self-organization of amphiphilic block copolymers in solvents as nanocontainers to encapsulate enzymes and substrates, and the investigation of the influence of the container’s dimensions on the catalytic activity of the enzymes. In the Thesis, the phase behavior of PS-b-PAA in solution is described. The effect of preparation conditions on the size and morphology of the BCP aggregates is addressed in detail. The stiffness of the membranes of PS-b-PAA vesicles is assessed using an AFM based nano-indentation method. The relation between the rigidity and the thickness of the membranes was elucidated. The enzymatic reactions in nanocontainers and the confinement effect on the catalytic activity of different enzymes were subsequently investigated using two different enzyme-substrate systems. The kinetic parameters for the enzymatic reactions were obtained for the unrestricted reaction in solution as well as for the reaction confined to the interior of polymeric vesicles with different sizes, and the dependence of the rate constants of the reaction on the size of the containers was studied. The morphology and size of PS-b-PAA aggregates prepared at different temperatures were studied. The existence of a phase transition from vesicles to micelles as a result of temperature change was confirmed. A change in temperature was then utilized as an external stimulus to trigger the release and encapsulation of enzyme and substrates, initiating their reaction.