Polymer brushes, charged surface-grafted

The collapse of a polymer gel in response to a change in environment can be scaled down to the single chain level. A layer of polymer chains grafted to a surface forms a polymer brush, for which the collapse transition can be nicely observed using neutron reflectivity. A pore lined with a responsive polymer brush will form a selective valve for example if the grafted polymer is a weak polybase, in aqueous acidic conditions the brush will be charged and will expand to close the pore, while in basic conditions the brush will be neutral. This principle has been used to create a selective membrane, which shows greatly reduced permeability in acidic conditions. 

Neutral [2, 58-60] and charged polymer brushes [2, 63, 64] with high molecular masses and high grafting densities of the surface-bound macromolecules have been established. While molecular weights of the surface-attached polymer chains of more than 106 g mol-1 could be realized, the distances of the surface-attached chains were in some cases less than 3 nm. 

We can visualize that when our hair is rubbed with a plastic plate, strands of hair stand up from the scalp due to electrostatic repulsion among them. Similarly, when charged functional groups, such as diethylamino groups, are introduced onto the graft chains, the polymer chains extend from the pore surface due to their mutual repulsion. This extended polymer brush conformation provides the protein with three-dimensional binding sites. The multilayer binding of various proteins onto the ion-... 

C3Ms suppress adsorption of various proteins to an extent which is dependent on surface chemistry, protein type, etc. [62, 171-174]. A promising strategy towards denser brushes with improved antifouling characteristics has been introduced by de Vos et al. [175]. Herein, ionic-neutral copolymers are adsorbed onto a surface grafted with polymers of opposite charge. 

Brzozowska et al. [18] reported on the stability of the polymer brushes formed by adsorption of ionomer complexes on hydrophilic and hydrophobic surfaces. The ionomer complexes or micelles consisted of oppositely charged polyelectrolyte blocks (poly(acrylic acid) and poly(N-methyl-2-vinyl pyri-dinium iodide)), and a neutral block (poly(vinyl alcohol)) or neutral grafts (poly(ethylene oxide)). The results showed that adsorbed micellar layers were relatively weakly attached to hydrophobic surfaces and much stronger... 

Shusharina N. R, and Linse R, Oppositely charged polyelectrolytes grafted onto planar surface mean-field lattice theory , Eur Phys J E, 2001 6 147-155. Houbenov N., Minko S., and Stamm M., Mixed polyelectrolyte brush from oppositely charged polymers for switching of surface charge and composition in aqueous environment . Macromolecules, 2003 36(16) 5897-5901. 

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