Abstract/Summary

The aim of this thesis was to assess the diffusive properties of functionalised and unfunctionalised nanomaterials in a variety of different media. The main goal was to gain an insight into the fundamental mechanisms underpinning nanoparticle diffusion and how the surface properties of nanoparticles alter their net movement through different environments. Initially a library of polymer-functionalised silica nanoparticles were synthesised and characterised. The polymers chosen were; poly(ethylene glycol) (PEG), poly(2-oxazolines) (POZ) and poly(n-isopropyl acrylamide) (PNIPAM). Firstly, the diffusion of different sized gold nanoparticles was assessed in concentrations of Pluronic F-127, in order to determine how the solution properties affected diffusion. It was found that as the solution undergoes a transition in response to environmental stimuli, there is an increase in diffusion coefficient; however the area they move in becomes more confined (assessed using a bespoke python script written for use with NTA). PNIPAM- and PNPOZ-silica nanoparticles were assessed for their aggregation and diffusion using DLS, NTA, and SANS. It was found that the position of a nitrogen atom in the amide group, present in both polymers, plays a key role in governing how the particles aggregate in solution, which in turn affects how they diffuse through solvents of varying polarities. POZ-silica nanoparticles were assessed for mucus penetration against a positive control of PEGylated nanoparticles. It was found that POZ-silica was effective at enhancing nanoparticle mucus penetration, and the hydrophilicity of these polymers plays a key role in determining the degree of permeation (with methylated POZ significantly more diffusive than propylated POZ). These finding provide valuable insight into some of the molecular mechanisms governing nanoparticle diffusion and how surface chemistry governs these effects.