Developing a tool box for post-polymerisation modification of conjugated polymers

An interesting potential application of conjugated polymers is their use as materials for optically amplified chemical and biological fluorescent sensors. The unique backbone of CPs, in which there is extensive delocalization of the pi-electrons, enhances the electronic coupling between chain segments, thereby allowing excited states to interact with analytes within a larger sample volume, compared to traditional small-molecule counterparts. Such attributes allow for a significant enhancement of the sensing effect. In order to act as biological sensors, water solubility is a prerequisite for CPs. Existing approaches to developing water soluble CPs have generally focused upon attaching side-chains to the polymer backbone with ionic functionality (for example ammonium, carboxylate) or highly polar functionalities like oligoethylene. Polymers with ionic functionality are formally polyelectrolytes, and the sensing mechanism in such materials has to date, relied on non-specific Coulombic interactions, especially for probe molecules like DNA. Such non-specific binding is highly undesirable, since it can increase background noise or false-positive readings. Alternative approaches rely on the synthesis of water soluble conjugated polymers containing specific binding groups (for example biotin) to improve selectivity. However to date, the synthesis of such polymers has been time-consuming and laborious, since often the binding groups are very sensitive to the conditions usually required for conjugated polymer synthesis, requiring extensive optimization of both reaction conditions and polymer synthesis conditions. In this project we will develop an alternative approach to incorporating both water solubilizing groups, and a range of binding groups by nucleophilic substitution reactions directly on the conjugated polymer backbone. . We aim to develop understanding of the optimal PEG sidechain length, and percentage inclusion to ensure water solubility. Once water solubility is optimized, we will add specific receptor to groups to the backbone, by the thiol 'click' reaction to give specific responses.

The primary beneficiaries of the proposed training programme will be the plastic electronics (PE) industry (both UK and international) and relevant disciplines within UK academia, all of which suffer from a critical need for trained postdoctoral scientists to work in the science and application of plastic electronic materials. The need to address this skills shortage and for comprehensive training in this area is evident through recent government reports specifically identifying the field and associated technologies, the TSB Enabling Technologies Strategy 2012-2015 specifically flags plastic electronics under its Materials and ESP themes. In addition, PE makes a major contribution to the Advanced Materials theme identified in Science Minister David Willet's 'eight great technologies' and further evidence is detailed in the letters of support for this proposal.

This well-identified need for such personnel is linked to the rapid growth of PE, nationally and globally. It is predicted to become critical in the next decade through the rapidly expanding organic display market, and the growth of the nascent industries of printed electronics, organic photovoltaics and lighting, with their enormous market potential. Skilled researchers are in demand both upstream by materials suppliers, and downstream by device and equipment manufacturers. Many of the companies working in PE are SMEs with a relatively narrow focus, who are therefore unable to provide the comprehensive, multidisciplinary graduate training needed to support innovation and growth. The proposed cross-disciplinary programme aims to produce post-doctoral researchers with a multidisciplinary background and a comprehensive view of the field, who are capable of carrying ideas forward to application. In addition to the companies, research institutes and universities that will employ graduates of the CDT, the programme stands to benefit those organisations (both UK and international) that will work in collaboration with the CDT either through co-supervision of projects, hosting student placements, or by collaborative research visits to the CDT.

Until now, UK research in PE, much of it sponsored by EPSRC, has been world-leading. In order to continue the excellent links between UK academic research and the PE industry, the supply of trained doctoral graduates needs to increase in response to the growth of the area. The CDT will provide long-term collaborations and a lasting structured training programme between the project partners yielding long-term, sustainable impact in research and education.

Finally, the students themselves stand to benefit from the integrated training environment, where PE focused academic learning is combined with practical skills training, exposure to latest research via invited lectures, and interactions with industrial and international collaborators via research projects. A wider pool of non-CDT students will be incorporated and similarly benefit from the training programme. External organisations and institutions will benefit by sending staff to the condensed format courses and advanced training courses that will be run by the CDT, these offered externally through continuing professional development programmes. Learning is widely transferable to other advanced functional materials, low-energy electronics and photonics, manufacturing and energy areas. In addition, the training extends beyond developing scientific knowledge and skills. The programme of generic and discipline specific transferable skills training and the supportive and stimulating postgraduate research environment is intended to offer the students a greatly enhanced postgraduate experience, and provide students with clear pathways and motivation for their future careers. Awareness and capability in relation to these will be established through the overall programme and enable the UK to maintain a supply of much needed researchers.