Neil L. Campbell

Controlled release from modified amino acid hydrogels governed by molecular size or network dynamics

Hydrogels can be prepared using the commercially available Fmoc-phenylalanine or Fmoc-tyrosine as the gelator. Gelation is triggered by careful adjustment of the pH of the solution using glucono-delta-lactone (GdL). Model dyes have been entrapped in the hydrogels, and the release of the dyes from the hydrogels has been monitored. The release ratios indicate that the systems are under Fickian diffusion control. A range of dyes with different radii of gyration diffuse from the Fmoc-phenylalanine hydrogels with similar diffusion coefficients, implying that the network is not specifically retaining even relatively large (5 nm) dyes. On the other hand, the larger dyes are restricted in their diffusion from Fmoc-tyrosine hydrogels. These results correlate with the rheological measurements for the hydrogels, where those formed from Fmoc-tyrosine were shown to have significantly higher storage moduli than those formed from Fmoc-phenylalanine. In addition, the frequency-dependent behavior of the hydrogels demonstrates that Fmoc-tyrosine shows the classic response of a strong gel with a storage modulus that is nearly independent of frequency. However, for Fmoc-phenylalanine, the frequency dependence of moduli is very strong and very similar to that displayed by a transient network, where the interconnections between junction zones in the network are highly flexible and able to withstand large deformations.

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.

Scalable Synthesis for Porous Organic Cages

Abstract We describe an improved synthesis for a [4 + 6] imine-linked cage, which was shown recently to exhibit microporosity in the crystalline state and which can be converted by recrystallization to produce either porous or nonporous polymorphs. The original methodology for the synthesis of this molecule resulted in poor yields (approximately 35%). Here, we demonstrate that the cage can be prepared in almost 100% yields and can be isolated with high chemical purity.

The Application of Automation to Significantly Accelerate Polymer Latex Research

Polymer latexes are essential components in a wide range of commercial products and formulations such as, paints, cosmetics, coatings, biotechnology, and functionalized supports. Many difficulties are intrinsic to the implementation of polymer latex research, particularly in the purification of the final latex dispersions and the control and reproducibility of particle size, therefore making high-throughput research in this area especially challenging. In this article, we demonstrate how the investigation of the influential synthesis factors on polymer latex materials properties can be swiftly and reproducibly achieved by the combinational use of experimental design, automated synthesis, and a newly developed high-throughput purification process. Through the implementation of flexible automated platforms, a significant increase in the throughput of this previously manual process was achieved. Reaction models were used to examine the synergistic and antagonistic effects of the latex synthesis parameters, thereby allowing the controlled synthesis of fully characterized libraries of surface–functional polymer latexes to be rapidly produced and screened for a wide range of applications.