Block copolymer synthesis by controlled/living radical polymerisation in heterogeneous systems

Nanostructured soft materials open up new opportunities in material design and application, and block copolymer self-assembly is one particularly powerful phenomenon that can be exploited for their synthesis. The advent of controlled/living radical polymerisation (CLRP) has greatly simplified block copolymer synthesis, and versatility towards monomer types and polymer architectures across the different forms of CLRP has vastly expanded the range of functional materials accessible. CLRP-controlled synthesis of block copolymers has been applied in heterogeneous systems, motivated by the numerous process advantages and the position of emulsion polymerisation at the forefront of industrial latex synthesis. In addition to the inherent environmental advantages of heterogeneous routes, the incidence of block copolymer self-assembly within dispersed particles during polymerisation leads to novel nanostructured materials that offer enticing prospects for entirely new applications of block copolymers. Here, we review the range of block copolymers prepared by heterogeneous CLRP techniques, evaluate the methods applied to maximise purity of the products, and summarise the unique nanoscale morphologies resulting from in situ self-assembly, before discussing future opportunities within the field

Mild synthesis of poly(HEMA)-networks as well-defined nanoparticles in supercritical carbon dioxide

Free-radical dispersion polymerisation of 2-hydroxyethyl methacrylate was carried out in supercritical carbon dioxide (scCO2) in the presence of stabilisers based on polyethylene oxide (PEO) and poly(heptadecafluorodecyl acrylate) (PFDA). Different architectures of copolymers (random, palm-tree and diblock) were tested for their surface tension, cloud point and as a stabilising agent. The diblock architecture was found to be the best candidate resulting in poly(HEMA) spherical particles with a size of 316 nm. Furthermore, the effect of the CO2-phobic block (PEO) in the diblock architecture was investigated by using three different chain lengths (1000, 2000, 5000 g mol−1). By optimizing the stabiliser composition and structure, mild reaction conditions have been identified allowing us to obtain well-defined spherical cross-linked poly(HEMA) particles with a mean diameter of unprecedented low size (216 nm) at a temperature as low as 35 °C

Green process for green materials: viable low-temperature lipase-catalysed synthesis of renewable telechelics in supercritical CO2

We present a novel near ambient temperature approach to telechelic renewable polyesters by exploiting the unique properties of supercritical CO2 (scCO2). Bio-based commercially available monomers have been polymerised and functional telechelic materials with targeted molecular weight were prepared by end-capping the chains with molecules containing reactive moieties in a one-pot reaction. The use of scCO2 as a reaction medium facilitates the effective use of Candida Antarctica Lipase B (CaLB) as a catalyst at a temperature as low as 35 °C, hence avoiding side reactions, maintaining the end-capper functionality and preserving the enzyme activity. The functionalised polymer products have been characterised by 1H-NMR, MALDI-TOF, GPC and DSC in order to carefully assess their structural and thermal properties. We demonstrate that telechelic materials can be produced enzymatically at mild temperatures, in a solvent-free system and using renewably sourced monomers without pre-modification, by exploiting the unique properties of scCO2. The macromolecules we prepare are ideal green precursors that can be further reacted to prepare useful bio-derived films and coatings

One-pot synthesis of micron-sized polybetaine particles: innovative use of supercritical carbon dioxide

Polybetaines exhibit unique properties combining anti-polyelectrolyte and low protein fouling behaviour, as well as biocompatibility. To date, the synthesis of polybetaine particles >50 nm has proved to be extremely challenging with standard emulsion and dispersion techniques being unsuccessful. Here we present the first reported synthesis of micron-sized, discrete cross-linked polybetaine particles, using polymerisation in scCO2 with methanol as a co-solvent. Discrete particles are produced only when the methanol is efficiently removed in situ using scCO2 extraction. A relatively high crosslinking agent initial concentration (10 wt%) was found to result in the most well defined particles, and particle integrity reduced as the crosslinking agent initial concentration was decreased. A monomer loading of between 3.0 × 10−2 mol L−1 and 1.8 × 10−1 mol L−1 resulted in discrete micron sized particles, with significant agglomoration occuring as the monomer loading was increased further. A spherical morphology and extremely low size dispersity was observed by SEM analysis for the optimised particles. The particles were readily re-dispersed in aqueous solution and light scattering measurements confirmed their low size dispersity

Controlled polymerisation and purification of branched poly(lactic acid) surfactants in supercritical carbon dioxide

Product degradability, sustainability and low-toxicity are driving demand for the synthesis of biobased polymers and surfactants. Here we report the synthesis of novel surface active polymers using cyclic esters (D,L-lactide) and temperature sensitive polyols (D-sorbitol) as renewable building blocks. We highlight the modification of chain length and degree of branching to provide a route to tailoring the properties and application performance of these new compounds. High processing temperatures (≥180 °C) and harsh post-reaction treatments are often needed to remove residual monomer and catalysts and these can become barriers to creating materials based on renewable resources. Here we exploit supercritical carbon dioxide (scCO2) as a green solvent to overcome these challenges; significantly reducing reaction temperatures, targeting controlled molecular weights with narrow dispersities and reducing sideproduct formation. Additionally in the same pot, we can use supercritical extraction to purify the compounds and to efficiently remove unreacted reagents, which could be recovered and recycled. We believe that our approach to the production and purification of these novel branched poly(lactides) is a significant step towards the development of the next generation of biopolymers and green surfactants, combining both the use of bio-sourced raw materials and the potential to use sustainable, low energy processes and techniques

The Experiences of Specialist Nurses Working Within the Uro-oncology Multidisciplinary Team in the United Kingdom.

PURPOSE: United Kingdom prostate cancer nursing care is provided by a variety of urology and uro-oncology nurses. The experience of working in multidisciplinary teams (MDT) was investigated in a national study. DESIGN: The study consisted of a national survey with descriptive statistics and thematic analysis. METHODS: A secondary analysis of a data subset from a UK whole population survey was undertaken (n = 285) of the specialist nursing workforce and the services they provide. Data were collected on the experience of working in the MDT. RESULTS: Forty-five percent of the respondents felt that they worked in a functional MDT, 12% felt that they worked in a dysfunctional MDT, and 3.5% found the MDT meeting intimidating. Furthermore, 34% of the nurses felt that they could constructively challenge all members of the MDT in meetings. Themes emerging from open-ended questions were lack of interest in nonmedical concerns by other team members, ability to constructively challenge decisions or views within the meeting, and little opportunity for patients' wishes to be expressed. CONCLUSIONS: Despite expertise and experience, nurses had a variable, often negative, experience of the MDT. It is necessary to ensure that all participants can contribute and are heard and valued. More emphasis should be given to patients' nonmedical needs

Within Thy Heart: Composure Amy Beach

This presentation serves as a learning guide for a singer and teacher for Amy Beachs\u27 Withing Thy Heart. This guide is a step-by-step guide to help the student learn notes, rhythms, and text, as well as includes an accompaniment track for the singer\u27s use

Enhanced spontaneous raman scattering and gas composition analysis using a photonic crystal fiber

Spontaneous gas-phase Raman scattering using a hollow-core photonic bandgap fiber (HC-PBF) for both the gas cell and the Stokes light collector is reported. It was predicted that the HC-PBF configuration would yield several hundred times signal enhancement in Stokes power over a traditional free-space configuration because of increased interaction lengths and large collection angles. Predictions were verified by using nitrogen Stokes signals. The utility of this system was demonstrated by measuring the Raman signals as functions of concentration for major species in natural gas. This allowed photomultiplier-based measurements of natural gas species in relatively short integration times, measurements that were previously difficult with other systems. © 2008 Optical Society of America