Polymer Brushes
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Polymer brushes are formed when a closely spaced layer of end-grafted polymer chains on a surface is exposed to a good solvent for the polymer in question. In order to reduce the overall free energy of the system, the polymer chains stretch out (against their entropy elasticity) into the surrounding solvent, forming a brush-like structure. LSST has been active in polymer brushes for nearly a decade and a half, and more recently has been exploring the properties and applications of polymer gels, which involve crosslinked polymer chains. Polymer brushes have remarkable properties, both in their ability to reduce biofouling, and their extraordinary lubricious behavior, both in aqueous environments, and in oil. While initial forays into this field were carried out by means of grafting-to systems, we now make significant use of grafting-from approaches, including iniferter reactions and atom-transfer radical polymerization (ATRP). The major part of our effort is experimental, but we have also collaborated with the group of Prof. Martin Kröger at ETH, to carry out molecular-dynamics simulations of the behavior of polymer brushes as lubricants. Other activities with polymer brushes include the incorporation of moeities that lead to light-responsive, or “smart” behaviour, and the extension of our research activities to practical lubrication applications.
References
- external page Influence of Chain Stiffness, Grafting Density, and Normal Load on Tribological and Structural Behavior of Polymer Brushes: a Nonequilibrium Molecular Dynamics Study
Manjesh K. Singh, Patrick Ilg, Rosa Maria Espinosa-Marzal, Nicholas D. Spencer, Martin Kröger
Polymers; 2016; 8(7) pp 254 - external page The influence of surface grafting on the growth rate of polymer chains
Chengjun Kang, Rowena Crockett, and Nicholas D. Spencer
RSC Polymer Chemistry; 2016; 7(2) pp 302-309 - external page Impact of chain morphology on the lubricity of surface-grafted polysaccharides
T. Goren, N. D. Spencer and R.M. Crockett
RSC Advances; 2014; 4 pp 21497-21503 - external page Stratified Polymer Grafts: Synthesis and Characterization of Layered Brush and Gel Structures
Ang Li, Shivaprakash N. Ramakrishna, Prathima C. Nalam, Edmondo M. Benetti, and Nicholas D. Spencer
Advanced Materials Interfaces; 2014; 1(1) pp 1300007 - external page Tuning Surface Mechanical Properties by Amplified Polyelectrolyte Self-Assembly: Where Grafting-From Meets Grafting-To
Ang Li, Shivaprakash N. Ramakrishna, Tobias Schwarz, Edmondo M. Benetti and Nicholas D. Spencer
ACS Applied Materials and Interfaces; 2013; 5(11) pp 4913-4920 - external page Ultrathin, Oil-compatible, Lubricious Polymer Coatings: a Comparison of Grafting-to and Grafting-from Strategies
Robert M. Bielecki, Patricia Doll, Nicholas D. Spencer
Tribology Letters; 2013; 49(1) pp 273-280 - external page Poly(acrylamide) Films at the Solvent-Induced Glass Transition: Adhesion, Tribology, and the Influence of Crosslinking
Ang Li, Shivaprakash N. Ramakrishna, E. Stefan Kooij, Rosa M. Espinosa-Marzal, Nicholas D. Spencer
Soft Matter; 2012; 8(35) pp 9092-9100