Polymer Synthesis and Microreactors
Our research lies at the borderline between disciplines. In the past, we investigated electroluminescent polymers for application in organic light-emitting diodes, shape-memory polymers and polymeric supramolecular receptors capable of binding biologically interesting ions. In previous years, we have looked at the effect nanoparticle fillers have on the mechanical properties of polymers, the chemistry in microreactors and methods for determining important physicochemical properties of pharmaceutical drugs.
1. Polymer–Filler Nanocomposites
Polymer nanocomposites based on sub-micrometer fillers with high surface-to-volume ratios are currently studied intensively in both academia and industry. A variety of silica nanoparticles are commercially available and their high surface-to-volume ratio makes them compatible with many polymer matrices. In collaboration with Dr V. Arrighi, we have synthesised various polymer–filler nanocomposites where the polymer is grafted from the surface of nanoparticles using techniques such as atom-transfer radical polymerisations (ATRP). Recent results show that covalent attachment of polymer chains to silica nanoparticles is particularly effective in improving the thermal and dynamic mechanical properties of the composite at elevated temperatures.
Figure 1. Procedure for grafting a polymer from the surface of a silica nanoparticle.
2. Chemistry in Microreactors
Microreactors allow chemical reactions to be optimised on a small scale, with improved safety, excellent temperature control, and accelerated reaction times using high reagent concentrations or superheated solvents. Promising results can be achieved even with a simple microreactor assembly consisting of syringes, ordinary laboratory tubing, a mixing unit, and syringe pumps.
Figure 2. Comparison of an organic synthesis carried out in a conventional glass vessel versus a microreactor.
3. Permeability Measurements as a Model for Drug Absorption in the Body
In collaboration with , we are measuring important physicochemical properties for pharmaceutical drugs, such as pKa and partition coeffient log P using standard lab equipment and Excel spreadsheets. More recently, we have looked at dissolution rates and permeabilities of active pharmaceutical ingredients. These are two important parameters in modern drug development that make it possible to predict, if not simulate, the absorption of a pharmaceutical drug in the body. For this, we have developed a semi-automatic method to determine drug permeability across a lipid-coated membrane based on a diffusion cell, a syringe/peristaltic pump and a UV flow cell.Dr. N. M. Howarth
Figure 3. Set-up for measuring the permeability of a drug across a lipid-coated membrane using a diffusion cell, a pump and a UV flow cell.