Interpolymer complexation of a polymer brush

Licentiate thesis, 2020

Controllable macromolecular gating between nanoscopic compartments is of high interest for single molecule studies of biological macromolecules. By definition, a good macromolecular gate should completely stop biomolecules, such as proteins, from crossing between compartments in its closed state while letting them pass in its open state. Polymer brushes of poly(ethylene glycol) have been proven excellent barriers for proteins in previous work, but are limited in terms of stimuli-responsive behaviour needed for macromolecular gating. In this thesis work, the pH reversible interpolymer complexation between a poly(ethylene glycol) brush and poly(methacrylic acid) was investigated as a potential macromolecular gating mechanism. Conclusions were based on the evaluation of the resulting surface complex using three surface sensitive characterisation techniques. Upon complexing at low pH, the polymer layer was found to adopt a shrunken state with significant behavioural changes, while completely reversing back to its initial state after a neutral pH had been introduced. This pH reversible interaction show great promise as a pH controlled macromolecular gating mechanism and calls for further studies with suitable nanostructures. To this end, the fabrication and properties of a new solid-state nanopore device is also presented, together with the direction needed for future work towards a new macromolecular gating system.