Towards Functional Nanopores Using Polymers

Licentiate thesis, 2016

In nature there are several examples of nanometer sized gateways able to control the passage of molecules and other substances with remarkable precision. This has inspired research in trying to create nanoscale openings which resemble such gateways. To gain functionalities similar to what is available in nature it is necessary to functionalize such mimics with soft materials. One candidate for such functionalization is polymers, as these posses a lot of the characteristics desirable to mimic biological systems. This thesis is focused on how polymers behave at interfaces and how polymer surfaces can be prepared and characterized. Different approaches to functionalize surfaces with two kinds of polymers is described: poly(ethylene glycol), which e.g. can be used to reduce non-specific adsorption of serum by up to 97 %, and poly(N-isopropylacrylamide) which can be used to create thermoresponsive surfaces with tunable thickness. The approaches involve "grafting to", when polymers are attached to a surface using material specific end-groups, and "grafting from" where a radical polymerization scheme is used to grow the polymer directly from the surface. The formed brushes are characterized using different methods, such as surface plasmon resonance and quartz crystal microbalance with dissipation, and the basis of these methods are presented. In particular new ways to use surface plasmon resonance for height determination is utilized and discussed. The protocols described in this thesis is intended for implementation with plasmonic nanostructures, in particular nanopores, to create different kinds of passive and active nanoscale gates with uses in bioseparation and biosensing