Membranes composite imprinted

Fig. 17 Summary of composite imprinted membrane preparation methods...

Molecularly imprinted composite membranes have been developed based on the functionalisation of a commercial membrane with an MIP in order to improve the mechanical stability of the imprinted polymer phase, similarly to the preparation of MIP composite beads, discussed in Sect. 2.2.2. 

A few studies have reported the embedding of an MIP film between two membranes as a strategy for the construction of composite membranes. For example, a metal ion-selective membrane composed of a Zn(II)-imprinted film between two layers of a porous support material was reported [253]. The imprinted membrane was prepared by surface water-in-oil emulsion polymerisation of divinylbenzene as polymer matrix with 1,12-dodecanediol-0,0 -diphenylphosphonic acid as functional host molecule for Zn(II) binding in the presence of acrylonitrile-butadiene rubber as reinforcing material and L-glutamic acid dioleylester ribitol as emulsion stabiliser. By using the acrylonitrile-butadiene rubber in the polymer matrix and the porous support PTFE, an improvement of the flexibility and the mechanical strength has been obtained for this membrane. 

This technique has also been employed for the preparation of a catalytic imprinted membrane by coating a cellulose membrane with a polymer incorporating particles imprinted with the transition-state analogue of a dehydrofluorination reaction [264]. The application of such an MIP composite membrane as the recognition element in an optical sensor has been reported for digitoxin analysis in serum samples by embedding digitoxin-MIP particles in polyvinyl chloride film in presence of plasticizer by the dry inversion process [265],... 

Kochkodan, V., W. Weigel, and M. Ulbricht (2002). Molecularly imprinted composite membranes for selective binding of desmetryn from aqueous solutions. Desalination, 149 323-328. 

A wide variety of polymeric membranes with different barrier properties is already available, many of them in various formats and with various dedicated specifications. The ongoing development in the field is very dynamic and focused on further increasing barrier selectivities (if possible at maximum transmembrane fluxes) and/ or improving membrane stability in order to broaden the applicability. This tailoring of membrane performance is done via various routes controlled macro-molecular synthesis (with a focus on functional polymeric architectures), development of advanced polymer blends or mixed-matrix materials, preparation of novel composite membranes and selective surface modification are the most important trends. Advanced functional polymer membranes such as stimuli-responsive [54] or molecularly imprinted polymer (MIP) membranes [55] are examples of the development of another dimension in that field. On that basis, it is expected that polymeric membranes will play a major role in process intensification in many different fields. 

Molecularly imprinted membranes can be prepared either as thick films or as composites in the pores of base-membranes. In composite membranes, the selective properties of the imprinted material are combined with the properties of the base-membrane. Membranes can also be prepared by phase inversion polymerization. The selective nature of MIPs makes it possible to prepare membranes with selective permeability [113, 114],... 

An ultrathin-film composite membrane selective for theophylline has been reported [48]. The theophylline-imprinted polymer was prepared inside pores of a microporous alumina support membrane with a thickness of 500 nm and a pore size of 20 nm, in which pores of the membrane were filled by the polymerization solution containing the template theophylline, methacrylic acid, and ethylene glycol dimethacrylate, and the membrane was illuminated with UV light for 1 h, followed by immersion in methanol containing 10 %(v/v) acetic acid to remove the template and any excess monomer. Because the membrane is extremely thin, the flux rate is high, being at least two orders of mag-... 

Suedee, R., Bodhibukkana, C., Tangthong, N., Amnuaikit, C., Kaewnopparat, S., Srichana, T. (2008]. Development of a reservoir-type transdermal enantioselective-controlled delivery system for racemic propranolol using a molecularly imprinted polymer composite membrane, /. Control. Release. 129,170-178. 

Ulbricht, M. Belter, M. Langenhangen, U. Schneider, F. Weigel, W. Novel molecularly imprinted polymer (MIP) composite membranes via controlled surface and pore functionalizations. Desalination 2002, 149, 293-295. 

Thin-film MIP composite membranes (cf. Scheme lb), imprinted for theophyUin and caffein, had been prepared by Hong et al. [99], using photo-copolymerization of a MAA/EDMA mixture on top of an asymmetric 20 nm pore size alumina membrane. Additional gas permeation studies suggested that the membranes were defect ( pinhole ) free. 

Pore-filling MIP composite membranes had been first prepared by Dzgoev and Haupt [100]. They casted the reaction mixture into the pores of a symmetric microfiltration membrane from polypropylene (cutoff pore size 0.2 pm) and performed a cross -linking copolymerization of a functional polyacrylate for imprinting protected tyrosine. Hattori et al. [101] had used a commercial cellulosic dialysis membrane (Cuprophan) as matrix and applied a two-step grafting procedure by, (i) activation of the cellulose by reaction with 3-methacryloxypropyl trimethoxysilane from toluene in order to introduce polymerizable groups into the outer surface layer, (ii) UV-initiation of an in situ copolymerization of a typical reaction mixture (MAA/EDMA, AIBN) for imprinting theophylline. 

Lehmann, M. Brunner, H. Tovar, G. Enantioselective separations a new approach using molecularly imprinted nanoparticle composite membranes. Desalination2002,149,315 321. 

Nickel, A.M.L. Seker, F. Ziemer, B.P. Ellis, A.B. Imprinted poly (acrylic acid) films on cadmium selenide. A composite sensor structure that couples selective amine binding with semiconductor substrate photoluminescence. Chem. Mater. 2001, 13, 1391-1397. Sallacan, N. Zayats, M. Bourenko, T. Kharitonov, A.B. Willner, I. Imprinting of nucleotide and monosaccharide recognition sites in acrylamidephenylboronic acid-acrylamide copolymer membranes associated with electronic transducers. Anal. Chem. 2002, 74, 702 712. 

Hong, J.M. Anderson, P.E. Qian, J. Martin, C.R. Selectively-permeable ultrathin film composite membranes based on molecularly imprinted pol mers. Chem. Mater. 1998, 10, 1029-1033. 

C. Bodhibukkana, S.T. Kaewnopparat, N. Tangthong, P. Bouking, G.P.R. Martin, Suedee bacterially-derived composite membranes of cellulose cuid molecularly imprinted polymer for use as a transdermal enantioselective controlled-release system of racemic propranolol, /. Controlled Release, 113,43-56,2006. 

Atomic force microscopy is finding more use in examination of membranes, but artifacts must be addressed, as was done by Bowen and Doneva [197], who noted changes in pore size and structure and used Fast Fourier Transform (FFT) filtering to show the true pore shape. Samples for AFM were prepared by attaching them to steel disks with double sided tape. These same authors used AFM to characterize ultrafiltration membranes [198, 199] and characterized the pore dimensions and quantified the interaction or adhesion of cellulose with two polymeric UF membranes. Atomic force microscopy was also used to characterize molecularly imprinted composite polyethersulfone membranes for quantification of the pore size and surface roughness [200]. 

---