Highly Branched Polymers

Active members: Prof Stephen RimmerDr Thomas Swift, Dr Richard Hoskins
Past members: David Pownall, Dr Prodip Sarker, Dr Richard Plenderleith, Dr James LapworthDr Louise GilmoreRichard England, Stephen Carter,

The use of a branching reversible-addition fragmentation transfer agent we have developed over several years a new technology platform based on a unique branching architecture of polymer design. Initial investigations into PNIPAM branching and temperature/collapse have led to a range of applications and uses, with research still ongoing with grants from the Wellcome Trust, Smith and Nephew and the MRC currently underway.  Additionally whilst the majority of the work has used temperature sensitive polymer PNIPAM other systems are being studied for their comparative properties.

Highlights:
1. S. Carter, B. Hunt and S. Rimmer, Macromolecules, 2005, 38, 4595-4603 – In which Steve Carter et al. discuss the role of a branching CTA as a method to produce highly branched PNIPAM polymers.
2. S. Carter, S. Rimmer, A. Sturdy and M. Webb, Macromolecular Bioscience, 2005, 5, 373-378 – These branched structures are shown to collapse at sub-ambient temperatures and with imidazole modified chain ends can be used to purify proteins.
3. S. Carter, S. Rimmer, R. Rutkaite, L. Swanson, J. P. A. Fairclough, A. Sturdy and M. Webb, Biomacromolecules, 2006, 7, 1124-1130 – Further investigation into the role these polymers can play in protein purification and used to detect a histidine tagged breast cancer susceptibility protein.
4. S. Rimmer, S. Carter, R. Rutkaite, J. W. Haycock and L. Swanson, Soft Matter, 2007, 3, 971-973 –  The role of end groups is discussed in the collapse of the polymer chains.
5. S. Hopkins, S. Carter, L. Swanson, S. MacNeil and S. Rimmer, Journal of Materials Chemistry, 2007, 17, 4022-4027 – Hyperbranched imidizole ended fluorophore containing PNIPAM polymers are only taken into fibroblasts depending on their conformational state.
6. S. R. Carter, R. M. England, B. J. Hunt and S. Rimmer, Macromolecular Bioscience, 2007, 7, 975-986 – The synthesis of linear PNIPAM polymers with comonomer VBC, which can be converted into an equivilent RAFT agent. This leads to graft rather than highly branched structures.
7. S. Hopkins, S. R. Carter, J. W. Haycock, N. J. Fullwood, S. MacNeil and S. Rimmer, Soft Matter, 2009, 5, 4928-4937 – GRGDS is attached to polymer chain ends and the collapsed form of the polymer extrudes the peptides allowing for reversible temperature sensitive cell binding.
8. J. Shepherd, P. Sarker, K. Swindells, I. Douglas, S. MacNeil, L. Swanson and S. Rimmer, Journal of the American Chemical Society, 2010, 132, 1736-1737 – Vancomycin is attached to polymer chain ends and the lower critical solution temperature is triggered by bacteria binding. First demonstration of a bacteria-triggered stimuli responsive polymer using this technology.
9. R. M. England and S. Rimmer, Polymer Chemistry, 2010, 1, 1533-1544 –  A review of branched polymer design, in which a comparison of this methodology and others can be gleaned.
10. P. Sarker, J. Shepherd, K. Swindells, I. Douglas, S. MacNeil, L. Swanson and S. Rimmer, Biomacromolecules, 2011, 12, 1-5 – Polymyxin end groups are shown to bind to gram negative bacteria, and specificity between this and vancomycin is shown.
11. J. Shepherd, P. Sarker, S. Rimmer, L. Swanson, S. MacNeil and I. Douglas, Biomaterials, 2011, 32, 258-267 –  Both polymyxin and vancomycin versions of polymers are attached to a hydrogel membrane. This solid surface is shown to deplete bacteria in a tissue engineered wound.
12. J. W. Lapworth, P. V. Hatton and S. Rimmer, RSC Advances, 2013, 3, 18107-18114 – Trihistidine endgroups added to polymer particles shown to fundamentally alter viscometric behaviour.
13.  L. Platt, L. Kelly and S. Rimmer, Journal of Materials Chemistry B, 2014, 2, 494-501 – P-AMPS synthesized by use of a branching raft agent was loaded into emulsion droplets and different architectures were compared for their effects on controlled release of growth factors.
14. P. Sarker, K. Swindells, C. W. I. Douglas, S. MacNeil, S. Rimmer and L. Swanson, Soft Matter, 2014, 10, 5824-5835 – FRET investigation of the mode of binding between polymer and bacteria, demonstrating further collapse of the polymer.
15. R. Plenderleith, T. Swift and S. Rimmer, RSC Advances, 2014, 4, 50932-50937 – A paper which explores the collapse of these branched systems using calorimetry and the fluorescence of a nile red, suggesting the existence of a previously unknown core-shell structure.