Membranes with SP-grafted pores

Stimuli-responsive membranes are widely used for controlled drug release and delivery, flux control and cell detachment these applications are discussed in other chapters of this book. In this chapter we will focus mainly on the examples of separation of different substances using stimuli-responsive membranes rather than on the demonstration of a permeation on-off switch. One of the earliest reviews on using membranes in bioseparation was published in 1992 (Heath and Belfort, 1992). Recent works include examples where SPs contribute an additional function to the membrane (Chu et al, 2011 Koros, 2004 Tokarev and Minko, 2010 Tokarev et al., 2009). 

6 Membrane structures stimuli-responsive hydrogel membrane (a), membrane with stimuli-responsive grafted brushes (b), stimuli-responsive membrane with porous substrate (c) and responsive gates (d). Source Reproduced from Chu, Xie and Ju (2011). Stimuli-responsive membranes Smart tools for controllable mass-transfer and separation processes. Chinese Journal of Chemical Engineering, 19,891-903. Copyright (2012), with permission from Elsevier.) (Chu eta ., 2011). 

Introduction of SP provides an additional tool for the variation of the membrane structure and thus changing/controlling the membrane permeability (Fig. 13.6). The possibility of altering the membrane permeability by varying external stimuli allows the opportunity for designing novel advanced materials (Chu ef a/., 2011). 

Recently, membranes with SP nanoparticles have been introduced which operate on a slightly different principle, as illustrated in Fig. 13.7. The membranes contain an ordered array of stimuli-responsive core-shell type magnetic polystyrene latex particles. The particles change their size in response to external stimuli, acting as on-off switches or permeability valves , regulating the permeation through membrane channels. 

7 Schematic representation of the permeation mechanism through the channels of magnetic poly(styrene)-latex-pNIPAM smart nanocomposite membranes (a) off state below LOST and (b) on state above LCST. Source Reproduced with permission from Csetneki, I., Filipcsei, G. and Zrinyi, M. (2006). Smart nanocomposite polymer membranes with on/off switching control. Macromolecules, 39, 1939-1942. Copyright (2006) American Chemical Society.) (Csetneki et a ., 2006). 

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