Ian Malcolm Shirley

Polyurea-encapsulated palladium(ii) acetate: a robust and recyclable catalyst for use in conventional and supercritical mediaElectronic supplementary information (ESI) available: representative experimental procedures. See http://www.rsc.org/suppdata/cc/b2/b200677b/

Palladium(II) acetate microencapsulated in polyurea (MC-[Pd]) is an economical and versatile heterogeneous catalyst for a range of phosphine-free cross-coupling reactions in both conventional solvents and supercritical carbon dioxide (scCO2); the catalyst can be recovered by a simple filtration and recycled up to four times.

Encapsulation of palladium in polyurea microcapsules

An interfacial polymerisation approach is adopted to encapsulate palladium(II) acetate and palladium nanoparticles in polyurea microcapsules for use in catalysis.

Synthesis of poly(2-hydroxypropyl methacrylate) latex particles via aqueous dispersion polymerization

Poly(2-hydroxypropyl methacrylate) latexes were prepared by aqueous dispersion polymerization at 60 °C using poly(-vinylpyrrolidone) [PNVP] as a steric stabilizer. The mean latex diameter can be controlled over a wide range by varying the synthesis parameters (initiator type, stabilizer concentration, addition of co-surfactant or comonomer), and narrow size distributions were observed in most cases. These sterically-stabilized latex particles were characterized by electron microscopy, dynamic light scattering, Malvern Mastersizer and FT-IR spectroscopy. The presence of the PNVP stabilizer at the surface of the latex particles was confirmed by X-ray photoelectron spectroscopy and the stabilizer content was assessed by H NMR spectroscopy and nitrogen microanalyses. Colloidally stable surfactant-stabilized poly(2-hydroxypropyl methacrylate) latexes could also be prepared in the absence of any PNVP stabilizer. Since 2-hydroxypropyl methacrylate contains a small amount of dimethacrylate impurity, these latexes are actually lightly cross-linked; their degree of swelling in DO, d-methanol and d-pyridine was investigated using dynamic light scattering and H NMR spectroscopy. Finally, three ionic water-soluble comonomers were successfully copolymerized with 2-hydroxypropyl methacrylate under aqueous dispersion conditions, as judged by aqueous electrophoresis studies.

Delivery of biological performance via micro-encapsulation formulation chemistry†

Lambda-cyhalothrin micro-capsules have been prepared by a novel in situ procedure. Manipulation of the chemistry has led to slow- and fast-release formulations. The latter has a biological performance comparable to commercial lambda-cyhalothrin emulsifiable concentrates, but exhibits a significantly improved toxicological profile over EC, WP and WG formulations. Micro-encapsulation technology satisfies many of the drivers towards the safer use of pesticides.

Model-based computer-aided design for controlled release of pesticides

In the field of controlled release technology for pesticides or active ingredients (AI), models that can predict its delivery during application are important for purposes of design and marketing of the pesticide product. Appropriate models for the controlled release of pesticides, if available, can be used to study and analyze some of the important issues related to the design/application of the pesticide. This paper highlights the needs for predictive models and proposes the use of a computer aided modelling framework through which a collection of reliable and predictive constitutive (property) models can be combined with various types of release models. Use of a group-contribution based property model for one of the constitutive variables (AI solubility in polymers) and a free-volume theory based model for another (diffusion coefficient), has been proposed and the corresponding extended models have been developed and implemented into a computer-aided system. The total model consisting of the property models embedded into the release models are then employed to study the release of different combinations of AIs and polymer-based microcapsules.

Clouding of aqueous solutions of difunctional tapered-statistical copolymers of ethylene oxide and 1,2-butylene oxide

Abstract Eight statistical copolymers were prepared by anionic copolymerisation of ethylene oxide and 1,2-butylene oxide initiated by diethylene glycol. The difference in reactivity ratios of the two monomers ensured that the composition of the copolymers tapered from high E content (E denotes an oxyethylene unit) at the centre of a chain to high B content (B denotes an oxybutylene unit) at the chain ends, giving the copolymers the character of a triblock copolymer, type BEB. For comparison two true triblock (type BEB) copolymers were prepared by sequential anionic copolymerisation. Cloud point curves of aqueous solutions of the soluble copolymers were determined. These showed interesting features attributable to association, in particular sharp transitions at the points (concentration and temperature) at which the solutions attained their critical condition for micellisation. This explanation was verified by examining solutions below the cloud point by dynamic light scattering and noting the presence of micelles in appropriate cases. The range of copolymers available allowed the effects of overall composition and chain length to be explored, as well as the difference in behaviours resulting from the tapered-statistical and block copolymer architectures.

Positionable Vertical Microfluidic Cell Based on Electromigration in a Theta Pipet

A microscale vertical fluidic cell system has been implemented, based on a simple theta pipet pulled to a sharp point (ca. 10-20 μm diameter for the studies herein) and positioned with a high degree of control on a surface. The dual channel arrangement allows an electric field to be generated between an electrode in each compartment of the pipet that can be used to control the electromigration of charged species between the two compartments, across a thin liquid meniscus in contact with the substrate of interest. By visualizing the interfacial region using laser scanning confocal microscopy, the adsorption of fluorescently-labeled materials on surfaces is monitored quantitatively in real time, exemplified through studies of the adsorption of anionic microparticles (1.1 μm diameter) on positively and negatively charged substrate surfaces of poly-L-lysine (PLL) and poly-L-glutamic acid (PGA), respectively, on glass. These studies highlight significant electrostatic effects on adsorption rates and also that the adsorption of these particles is dominated by the three phase meniscus/solid/air boundary. The technique is easily modified to the case of a submerged substrate, resulting in a much larger deposition area. Finite element method modeling is used to calculate local electric field strengths that are used to understand surface deposition patterns. To demonstrate the applicability of the technique to live biological substrates, the delivery of fluorescent particles directly to the surface of a single root hair cell of Zea mays is demonstrated. The mobile pipet allows deposition to be directed to specific regions of the cell, allowing discrete sites to be labeled with particles. Finally, the technique is used to study the uptake of fluorescent polymer molecules to single root hair cells, with quantitative analysis of the adsorption rates of vinyl-sulfonic acid copolymers, with varying rhodamine B content.

Synthesis of microcapsules via reactive surfactants

A statistical library of well-defined ionic and non-ionic amphiphilic block copolymers of P(MMA/HEMA)-b-PDMAEMA and PEG-b-P(MMA/HEMA) were synthesised via living radical polymerisation employing the macroinitiator technique. All the block copolymers show monomodal peaks and narrow weight distributions, indicating they were obtained in controlled manner. Those copolymers were further modified in order to prepare inisurfs and surfmers. This yielded a selection of active surfactants of desired molecular weight and low polydispersity. Soap-free miniemulsion polymerisations of butyl methacrylate were carried out using the obtained active surfactants to prepare core–shell microcapsules in which various concentrations of inert oil, hexadecane, as a model system were encapsulated. The influence of the block copolymer structure on the particle formation was studied. The core–shell nature of the particles could be confirmed using scanning electron microscopy. Up to 66% of hexadecane could be incorporated in PBMA microcapsules.

Evanescent wave cavity ring-down spectroscopy (EW-CRDS) as a probe of macromolecule adsorption kinetics at functionalized interfaces.

Evanescent wave cavity ring-down spectroscopy (EW-CRDS) has been employed to study the interfacial adsorption kinetics of coumarin-tagged macromolecules onto a range of functionalized planar surfaces. Such studies are valuable in designing polymers for complex systems where the degree of interaction between the polymer and surface needs to be tailored. Three tagged synthetic polymers with different functionalities are examined: poly(acrylic acid) (PAA), poly(3-sulfopropyl methacrylate, potassium salt) (PSPMA), and a mannose-modified glycopolymer. Adsorption transients at the silica/water interface are found to be characteristic for each polymer, and kinetics are deduced from the initial rates. The chemistry of the adsorption interfaces has been varied by, first, manipulation of silica surface chemistry via the bulk pH, followed by surfaces modified by poly(L-glutamic acid) (PGA) and cellulose, giving five chemically different surfaces. Complementary atomic force microscopy (AFM) imaging has been used for additional surface characterization of adsorbed layers and functionalized interfaces to allow adsorption rates to be interpreted more fully. Adsorption rates for PSPMA and the glycopolymer are seen to be highly surface sensitive, with significantly higher rates on cellulose-modified surfaces, whereas PAA shows a much smaller rate dependence on the nature of the adsorption surface.

Computer-aided and predictive models for design of controlled release of pesticides

Abstract In the field of pesticide controlled release technology, a computer based model that can predict the delivery of the Active Ingredient (AI) from fabricated units is important for purposes of product design and marketing. A model for the release of an AI from a microcapsule device is presented in this paper, together with a specific case study application to highlight its scope and significance. The paper also addresses the need for predictive models and proposes a computer aided modelling framework for achieving it through the development and introduction of reliable and predictive constitutive models. A group-contribution based model for one of the constitutive variables (AI solubility in polymers) is presented together with examples of application and validation.