Template porogen

Template porogen toluene/ benzene ethylbenzene/ toluene... 

Template Porogen Polym. techn, n Mip (mg) sample (mL) Cone. range " Recovery (%)... 

Fig. 21.5. Tetrahydrofuran imprinted polyurethane layer of 300 nm with embedded phthalide indicator shows a reasonable sensor effect with tetrahydrofuran - no effect occurs with ammonia vapour. Other solvents as template/porogen shift the sensitivity of the MIPs towards the analyte (former template) to be.

Fig. 6-10. Influence of the number of basic interaction sites of the template versus the separation factor measured in chromatography for the corresponding racemate. The templates were imprinted using MAA as functional monomer by thermochemical initiation at 60/90/120 °C (24 h at each temperature) and using acetonitrile as porogen. (From Sellergren et al. [15].)...

Other microporous materials have been synthesized using the porogen polyethylene glycol in polyethylene oxide-urethane gels [27]. Micropores were formed in the gel, and it was found that the diffusion of larger species, vitamin B12, was enhanced relatively more than that of a smaller species, proxyphylline. This result is in qualitative agreement with that found for electrophoretic transport by RiU et al. [322] discussed earher, where the mobility of larger species was preferentially enhanced in the templated media. 

Molecular imprinted polymers MIPs exhibit predetermined enan-tioselectivity for a specific chiral molecnle, which is nsed as the chiral template dnring the imprinting process. Most MIPs are obtained by copolymerization from a mixture consisting of a fnnctional mono-nnsatn-rated (vinylic, acrylic, methacrylic) monomer, a di- or tri-nnsatnrated cross-linker (vinylic, acrylic, methacrylic), a chiral template (print molecnle) and a porogenic solvent to create a three-dimensional network. When removing the print molecnle, chiral cavities are released within the polymer network. The MIP will memorize the steric and functional binding featnres of the template molecnle. Therefore, inclusion of the enantiomers into the asymmetric cavities of this network can be assumed as... 

Another possible way of overcoming the limitations posed by the presence of water in the suspension polymerisation process is to substitute the continuous water phase with alternative solvents that could still act as dispersing medium for the monomer mixture but better preserve noncovalent interactions in the template-monomer assembly. For example, liquid fluorocarbons are chemically inert and do not affect interactions which are used in noncovalent imprinting. Use of such solvents for the preparation of MIP microbeads has been demonstrated already in 1996 by Mayes and Mosbach [16,17]. A range of MIPs were prepared using Boc-l-phenylalanin as the template, MAA as the functional monomer and different kinds and amounts of crosslinkers and porogenic solvents. The resulting MIP microbeads... 

The in situ polymerisation consists of filling a capillary or a column with the prepolymerisation mixture containing the template, the functional monomer, the crosslinker, the initiator and the porogenic solvent (Fig. 11). Then the column is heated or submitted to UV radiation for polymerisation. In the in situ thermally initiated polymerisation process, the tube with the pre-polymerisation mixture is submerged in a controlled-temperature water bath, whereas for in situ photoinitiated polymerisation, a UV-transparent capillary or column is needed. The resulting continuous rod of polymer is washed with an appropriate solvent to remove the template and the excess of monomer. 

The performance of the molecularly imprinted monolith in terms of molecular recognition and flow-through properties depends on several factors, especially the density and the porosity of the polymer. In order to obtain a monolith with high selectivity and high permeability, some preparation conditions must be optimised, in particular the composition of the prepolymerisation mixture including the amount of template, the type and amount of functional monomer, crosslinker, porogenic solvent and the initiator, and the polymerisation conditions such as initiation process and polymerisation time. 

Fig. 3 Top Photograph of silicon cantilevers used as depositing tool during deposition on a glass slide [53], Bottom Fluorescence microscope images of microdot matrices of the nonimprinted control polymer (left), positive control with the copolymerized template (middle), and imprinted polymer (right) synthesized with DMSO-diglyme-1% PVAc as the porogen (a) directly after deposition, (b) after washing and elution of the template, and (c) after reincubation in a solution of 30 pM fluorescein. Reprinted with permission from [53], Copyright (2007) American Chemical Society...

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