David John Duncalf

Formation and enhanced biocidal activity of water-dispersable organic nanoparticles

Water-insoluble organic compounds are often used in aqueous environments in various pharmaceutical and consumer products. To overcome insolubility, the particles are dispersed in a medium during product formation, but large particles that are formed may affect product performance and safety. Many techniques have been used to produce nanodispersions-dispersions with nanometre-scale dimensions-that have properties similar to solutions. However, making nanodispersions requires complex processing, and it is difficult to achieve stability over long periods. Here we report a generic method for producing organic nanoparticles with a combination of modified emulsion-templating and freeze-drying. The dry powder composites formed using this method are highly porous, stable and form nanodispersions upon simple addition of water. Aqueous nanodispersions of Triclosan (a commercial antimicrobial agent) produced with this approach show greater activity than organic/aqueous solutions of Triclosan.

Investigation of the Experimental Factors Affecting the Trithiocarbonate-Mediated RAFT Polymerization of Methyl Acrylate

The reversible addition–fragmentation chain transfer polymerization of acrylates, using methyl acrylate (MA) as a monomer model, mediated by a trithiocarbonate was tested under several conditions where the experimental parameters were systematically altered. The most significant parameter in controlling the rate and control of the polymerization was found to be the ratio of chain transfer agent (CTA) to initiator. Decreasing this ratio increased the rate of polymerization and had little noticeable effect on the control over molecular weight distribution. A ratio of CTA to initiator of unity was shown to give the best compromise between rate and control of the polymerization. Targeted degrees of polymerization (equivalent to ratios of monomer to CTA) had negligible effect on the rate of polymerization and polydispersity index (PDI). Performing the polymerization in the presence of solvent (up to 41.2% (w/w) in toluene) had no negative effect on the rate of polymerization. Indeed, marginally higher conversions and lower PDIs than for bulk polymerization were achieved for similar reaction times. A higher amount of toluene (66.6% (w/w)) induced a lower rate of polymerization, but the evolution of molecular weight and PDI were unaffected. Polymerizations performed in the presence of toluene, N,N′-dimethylformamide, and methyl ethyl ketone showed that solvent polarity and aromaticity had no observable effect on the rate of polymerization and over the control of molecular weight distribution. The optimum conditions for the polymerization of MA, mediated by 2-ethylthiocarbonylsulfanyl-propionic acid ethyl ester at 50°C were found to be [CTA]/[AIBN] = 1/1 and ~40% solvent (w/w).