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Dr Easan Sivaniah
EPSRC Advanced Research Fellow
in Experimental Physics
Telephone: 01223 337007
E-mail: es10009 [at] cam.ac.uk
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Research Summary
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| Physics and Biophysical applications of Block copolymer |
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| A-block-B block copolymers are two polymer species that have been linearly chemically connected. The chemical linkage in the block copolymer (BCP) restricts phase separation to occur at molecular dimensions only. The resulting material can form a myriad of different architectures where one group of polymer chains is periodically spaced in a matrix of the other polymer chains. There are outstanding challenges in this field. One is to generate BCP material with large degrees of long range order. This problem resonates with examples outside of BCP systems, e.g. the intrinsic strength of a metal is much higher than its actual strength. The latter depends on heat treatment of the material as it solidifies (or on the addition of suitable additives) to reduce the number of defects in the material. Metals and ceramics and semi-conductors technologies have their own particular solutions to this problem. A practical one, i.e. one that can be adopted industrially, does not exist for block copolymers.
Our research group looks at ways to address this problem. In one approach, we look at the effects of rough surfaces on the self-assembly properties of the block copolymer. It is possible that some degree of roughness or surface imperfection is required for improving the long range perfection within the block copolymer. In another approach we use novel additives to dilute the interactions that bring about microphase separation in block copolymers. Gaining control of this is akin to gaining control of the melting point of the material; the result is we can more carefully control the 'heat treatment'. In a related project, we applying the lessons we learn about BCP self assembly for the creation of nanoporous membranes to be used in separation or sensor technology.
(Right image shows BCP defect structures from a thin film on a grating surface; image size 2 μm square)
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| Bacterial and Enzymatic Production, Characterization and Application of Bioplastics |
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| This is an exciting new research direction for our group. We are initially looking at Polyhydroxyalkanoates (PHAs), are a class of aliphatic polyesters that can be produced by microbial fermentation of agricultural resources. PHAs are accumulated as an intra-cellular energy reserve by several types of bacteria. PHAs are strong candidates to replace conventional plastics because its material properties can be fine-tuned to resemble common synthetic commodity thermoplastics (polypropylene, synthetic rubber). Moreover PHAs are completely degraded upon disposal by microorganisms or hydrolytically. Due to its high production costs, current applications of PHA materials are in niche products or high-end biomedical applications. These rely on the particular properties of PHAs such as biocompatibility and biodegradability. Our research looks at different aspect of this field including the optimization of the production of the polymer using in-vitro techniques as well the preparation of scaffolds of the material for medical implants. This work is being developed in collaboration with microbiology research groups in Cambridge, Univ. of Westminster and Tokyo Institute of Technology.
(Right image: Fluorescence microscopy highlights polyhydroxyalkanoate inclusions inside bacteria; optical image left, fluorescence image right)
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