Trimethylolpropane trimethacrylate TRIM

Fig. 21. Molecular imprinting of (R)-propranolol using methacrylic acid (MAA) as the functional monomer and trimethylolpropane trimethacrylate (TRIM) as the crosslinking monomer. (Reprinted with permission from [126], Copyright 1998 Elsevier). The enantiose-lectivity of a given polymer is predetermined by the configuration of the ligand, R-propranolol present during its preparation. Since the imprinted enantiomer possesses a higher affinity for the polymer, the separation is obtained with a predictable elution order of the enantiomers...

Figure 15.1 Examples of common cioss-liiikers used in the preparation of molecular imprinted polymers ethylene glycol dimethylcrylate (EGDMA) divinyl benzene (DVB), trimethylolpropane trimethacrylate (TRIM), VA -methylenebisacrylamide (MBA), and V,0-bismethacryloyl ethanolamine (NOBE).

Glad M, Reinholdsson P, Mosbach K. Molecularly imprinted composite polymers based on trimethylolpropane trimethacrylate (TRIM) particles for efficient enantiomeric separations. React Polym 1995 25 47-54. 

MIP films, applied to a QCM transducer, have been employed for chiral recognition of the R- and 5-propranolol enantiomers [107]. MIP films were prepared for that purpose by surface grafted photo-radical polymerization. First, a monolayer of 11-mercaptoundecanoic acid was self-assembled on a gold electrode of the quartz resonator. Then, a 2,2 -azobis(2-amidinopropane) hydrochloride initiator (AAPH), was attached to this monolayer. Subsequently, this surface-modified resonator was immersed in an ACN solution containing the MAA functional monomer, enantiomer template and trimethylolpropane trimethacrylate (TRIM) cross-linker. Next, the solution was irradiated with UV light for photopolymerization. The resulting MIP-coated resonator was used for enantioselective determination of the propranolol enantiomers under the batch [107] conditions and the FIA [107] conditions with an aqueous-ACN mixed solvent solution as the carrier. The MIP-QCM chemosensor was enantioselective to 5-propranolol at concentrations exceeding 0.38 mM [107]. 

Mosbach and co-workers developed a method to prepare molecularly imprinted polymers by precipitation polymerization [24]. They started from a dilute, homogenous solution of the monomer methacrylic acid (MAA) and the crosslinker trimethylolpropane trimethacrylate (TRIM) or ethylene glycol dimethacrylate (EGDMA). The polymer formed in the presence of the template molecule 17/1-estradiol, theophylline, or caffeine contained a high proportion of discrete spheres of diameter less than a micron. Because the effect of coalescence becomes predominant with higher solid content of the reaction mixture, this approach is limited to solid contents of typically <2 wt%. 

The template, the functional monomers and the cross-linking monomers are dissolved in a non-polar solvent. The functional monomers and the template form complexes and the strength of these are reflected in the selectivity of the imprinted polymer. The choice of functional monomer is based on the template structure. Functional monomers are chosen for their ability to interact non-covalently with the template molecule. The most frequently used functional monomer so far is methacrylic acid (MAA). Also vinylpyridines have been frequently used. As cross-linking monomers, ethyleneglycol dimethacrylate (EDMA) or trimethylolpropane trimethacrylate (TRIM) are widely used. Several other types of functional and cross-linking monomers have been used in molecular imprinting experiments using the non-covalent approach. The choice of monomers is of course important to the... 

In situ preparation of imprinted polymer films on a QCM was performed using S-propranolol as the template [4]. A pre-polymerization mixture containing MAA, trimethylolpropane trimethacrylate (TRIM, a crosslinker), the template and acetonitrile (porogen) was poured on the electrode of the QCM and immediately covered by glass and polymerized by UV irradiation. A low amount of the crosslinker (about 40 % of total monomers) was used to prepare more flexible polymer, allowing the polymer to be stably adhered on the electrode. The sensor showed enantioselective response with a selectivity factor of 5, and the detectability of S-propranolol was 50 iM in acetonitrile. 

Figure 5 Selection of common cross-linkers used in molecular imprinting protocols. Both ethyleneglycol dimethacrylate (EDMA) and divinylbenzene (DVB) are very common crosslinkers in molecular imprinting. Other acrylate-based cross-linking monomers conunonly used include the branched cross-linker trimethylolpropane trimethacrylate (TRIM)-[24]. Among the water-soluble cross-linkers, there are phenylene-diacrylamide, V,V-methylene diacrylamide [22], and Z w-acryloylpiperazine [92], which have been used in aqueous systems for the imprinting of, e.g., enzymes.

UV transparent fused-silica capillaries (50,75, or 100-pm i.d., 375-pm o.d.) (TSU075 Polymicro Technologies, Pheonix, AZ) were used.Trimethylolpropane trimethacrylate (TRIM) was purchased from Aldrich. AIBN and ( S)-propranolol hydrochloride were obtained from Sigma. The (5)-propranolol hydrochloride was changed into its free-base form (1) through extraction in a solution of ethyl acetate and saturated NaHCOs. Following this treatment, the free-base was washed once with water, dried and stored at -20°C until use. 

The dispersed phase was injected through a 35 pm hole drilled in the acetate sheet. The formulation for the MIP synthesis, containing the template [(J, S)-propranolol], the monomer (methacrylic acid, MAA), the crosslinker (trimethylolpropane trimethacrylate, TRIM), the photoinitiator (2,2-dimethoxy-2-phenylacetophenone, DMPAP) and a porogenic solvent (acetonitrile), was emulsified at the T-junction with a mineral oil (heavy white) and then photopolymerized by UV irradiation in the spiral-like channel. The resulting MIP particles were compared with those obtained with a conventional batch process. The continuous microsystem-assisted process led to near-monodisperse particles (CV <2%), whereas the conventional process gave particles having a broad range of sizes (CV >10%). The same conclusion holds for... 

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