Abstract
By use of the Menshutkin reaction a variety of polyviologens has been synthesised containing bromide, tosylate or mesylate counter-ions and varying methylene units. Owing to the ionic character of these main-chain polymers, these polyviologens are also known as ionene polymers. Additionally, this ionic character conveys a wide range of properties including the ability to undergo redox reactions and display liquid crystalline behaviour. The redox behaviour of these polymers can be followed easily by a colour change in the polyviologen. It was this reasoning, and the susceptibility of polyviologens to atmospheric water, that first led to the introduction of these polymers into a silica sol-gel network to produce 'durable' sol-gel redox sensors. The sol-gel process was found to be a convenient and versatile route to produce inorganic networks using the acid-catalysed hydrolysis and condensation of silicon alkoxide precursors. Synthetic methods were developed to optimise the incorporation of various polyviologens into a silica network. A variety of analytical techniques was employed to characterise the polyviologens and the corresponding sol-gel hybrids. Results from SAXS, IR and surface analysis provide strong evidence that the polyviologens have an effect on the structure of the inorganic component. Rare surface fractal behaviour was observed and the pore geometry was found to go from smooth and cylindrical to ink-bottle in shape for some of the hybrid systems. An hypothesis is forwarded suggesting that the presence and concentration of polyviologen, electrostatic interactions between N+ and silanol groups, and hydrophobic hydration may all play an important role in determining the structure of the silica network.