Porogen imprinting effects

Yoshizako, K. Hosoya, K. Iwakoshi, Y. Kimata, K. Tanaka, N. Porogen imprinting effects. Anal. Chem. 1998, 70, 386-389. 

Low-weight organic molecules, such as volatile organic compounds (VOCs) [25], e.g. hydrocarbons without functionalities or anaesthetics, can be used as print molecules for non-covalent MIPs. If the print molecule is a suitable organic solvent, the print molecule itself is the porogen during the polymerisation process. Enhanced imprinting effects are promoted by n-n interactions between aromatic moieties in monomers and analytes, such as polycyclic aromatic hydrocarbons (PAHs) or aromatic VOCs (xylene or toluene, for example). 

Fig. 21.13. QCM responses to coatings polymerised from different porogens (acting as print molecules) with/without embedded calix[6]arene in brackets. The sensor response of 70 nm layers to 500 ppm of xylene isomers is shown. Compared to the layer polymerised in chloroform, the pronounced imprint effect for xylene can be seen. o-Xylene has the lowest volatility of the xylene isomers and therefore is equally detected in all layers.

There are two processes by which the bulk imprinted polymers are formed covalent imprinting and noncovalent imprinting. In the former, the template molecule is first covalently functionalized with the monomer, and then copolymerized with the pure monomer. After that the covalent bond is broken and the template molecule is removed by extraction. In order to facilitate the extraction step, a so-called porogenic solvent is used. It effectively swells the polymer matrix. 

Another in situ preparation of molecularly imprinted columns employs dispersion polymerisation, whereby agglomerated polymer particles are obtained [16]. The procedure is similar to the rod preparation a mixture of the chemicals for the polymer preparation, such as a template, a functional monomer, a cross-linker, a porogen and an initiator is put in a column and heated to effect polymerisation. This method also requires polar solvents, such as cyclohexanol-dodecanol and isopropanol-water, to obtain aggregated polymer particles of well-defined micro-sises. A crucial difference with the rod preparation lies in the volume of the porogen used larger volumes of porogens are used in dispersion polymerisation. 

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.

Omeprazole The optimized imprinted polymer was prepared in chloroform as a porogen. 4-vinylpyridine and ethylene glycol dimethacrylate were selected as a functional monomer and a crosslinker, respectively. (Because of the instability of OMP under polymerization conditions and the inability of the molecule to form effective interactions with monomers, pantoprazole (PANTO) was used as a dummy template for the imprinting process.) For OMP controlled release [223]... 

M. Esfandyari-Manesh, M. Javanbakht, F. Atyabi, A. Badiei and R. Dinarvand, Effect of Porogenic Solvent on the Morphology, Recognition and Release Properties of Carbamazepine-Molecularly Imprinted Polymer Nanospheres, J. Appl. Polym. Sci., 121... 

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