Polymer brushes can readily modify interfacial properties such as anti-fouling, frictional and wetting properties. Grafting polymer brushes from surfaces is commonly achieved by using Atom Transfer Radical Polymerisation (ATRP), for which a key step is to pre-initiate (i.e. functionalise) the surface with halogen groups, often via a covalently bound silane initiator. A promising alternative route to surface initiation is to utilise a polyelectrolyte molecule to anchor the initiation groups to the surface, achieved by a simple dip-coating technique.1,2
In this work we have designed and synthesised a novel two dimensional (2D) polyelectrolyte ‘mat’ initiator molecule with its networked structure bearing both cationic and halogen groups. The advantage of this approach lies in the tunability of the ratio of anchoring to initiation sites, via the degree of branching and crosslinking in the polymer mat architecture and its overall molecular weight to tailor both the polymer mat size and activity. This facilitates direct influence over the surface anchorage of polymer brushes subsequently grown and the brush grafting density.
Using these novel 2D mat initiators, we have grafted a number of different polymer brushes from both mica and silica, containing monomers of amino acid, 2-(dimethylamino)ethyl methacrylate and polyethylene glycol. Our AFM, ellipsometry and X-ray reflectivity results indicate that the grafted polymer brushes possess high surface coverage and low surface roughness on the nanometre scale. We suggest that this 2D mat initiator provides a novel and versatile route to grafting a variety of polymers to essentially all surfaces, useful both for polymer brush applications and academic research.
Literature:
1) M. Chen, et al., Science, 2009, 323, 1698-1701.
2) M. Chen, et al., ChemPhysChem, 2007, 8, 1303–1306.
tim.snow@bristol.ac.uk
