Catalyst templated polymeric

New templated polymer support materials have been developed for use as re versed-phase packing materials. Pore size and particle size have not usually been precisely controlled by conventional suspension polymerization. A templated polymerization is used to obtain controllable pore size and particle-size distribution. In this technique, hydrophilic monomers and divinylbenzene are formulated and filled into pores in templated silica material, at room temperature. After polymerization, the templated silica material is removed by base hydrolysis. The surface of the polymer may be modified in various ways to obtain the desired functionality. The particles are useful in chromatography, adsorption, and ion exchange and as polymeric supports of catalysts (39,40). 

This simple scheme can help us to understand unusual selectivity and high efficiency of such template reactions. The specific character of the enzyme effectiveness towards a particular substrate becomes obvious. The effect of macromolecular template on the reaction rate and particularly on its selectivity suggests that this type of reaction can be regarded as a catalyzed reaction. The template plays a role of a polymeric catalyst. On the other hand, the template polymerization is a particular case of a more general... 

Pegylated hematin was developed as an effective biomimetic catalyst for polymerization of various anihnes [56]. PEG modified hematin, a biomimetic catalyst, was used in the synthesis of PEDOT and PPYR at the presence of SPS template [57]. The polymerization was carried out in an aqueous solution at pH 1.0. The polymers were electrochemically active. Conductivity was measured as 10 S/cm for PEDOT and 10 S/cm for PPYR. The conductivity was substantially improved by the copolymerization of PEDOT and PPYR and was found to be in the range of O.l-l.O S/cm. 

Thin fQm of molecularly imprinted polymer can be prepared on a SPR chip, and the specific binding activity can be monitored as a change in angle for tight reflected from the chip. However the preparation of molecularly imprinted polymer on the chip requires often a careful control of polymer composition. The most common method involves the free radical polymerization with the use of a photo-initiator, and this process can lead to changes of template structure in the case of proteins their denaturation occurs. Other preparation procedures of molecularly imprinted polymers for SPR are atom transfer radical polymerization and polymer grafting method these methods provide a better control of the film physical characteristics, but require a suitable catalyst for polymerization. 

Since the coordination almost certainly involves the transition metal atom, there is a resemblance here to anionic polymerization. The coordination is an important aspect of the present picture, since it is this feature which allows the catalyst to serve as a template for stereoregulation. 

Borovik et al. [70] prepared a highly crosslinked polymeric porous material containing Co-salen units 38 (Figme 13) by template copolymerization method. The authors reported that as the cross-linking degree increases from 5 % to 50 %, the catalyst become more efficient in terms of reactivity, possibly due to the improved proximity of metal centers that work in cooperation. Unfortunately low enantioselectivity for the product epoxide was observed (<42 % ee) while the ee for concomitantly produced diol did not go above 86%. Reusability of the catalyst containing 50 mol% template showed consistent activity and enantioselectivity for three consecutive recycle experiments. 

Our research group has developed a multicatalyst system around an encapsulated amine catalyst (Kobaslija and McQuade 2006) that promotes nitroaUcene synthesis. Like the Royer catalysts, these microcapsules are based on a PEI shell. Unlike that system, however, templating is accomplished with a methanol in cyclohexane ( oil-in-oil ) emulsion in an interfacial polymerization, with the PEI cross-linked... 

Investigation of template poly condensation kinetics has only been studied within a very narrow scope. Polymerization of dimethyl tartrate with hexamethylene diamine was found to be enhanced by using as a template poly(vinyl pyrrolidone), poly(2-vinyl pyridine), or polysaccharides and poly(vinyl alcohol), poly(4-vinyl pyridine). In this case, the template can be treated as a catalyst. No information exists on the influence of the template on the order of reaction. The increase in molecular weight of the polymerization product by the template can be induced by a shift of equilibrium or by an increase in the reaction rate. A similar increase in the reaction rate was observed when poly(4-vi-nyl pyridine) was used in the synthesis of poly(terephtalamides) activated by triphenyl phosphite.The authors suggested that a high molecular weight template was involved in the increase of the local concentration of the substrate (terephthalic acid) by adsorption and activation via N-phosphonium salt of poly(4- vinyl pyridine). 

A second, equally powerful means to prepare such materials relies on traditional inorganic polymerization tools, most notably sol-gel polymerization.24 25 A number of excellent reviews have appeared on this subject as well.5,12,17 In sol-gel processing, the functional monomer [i.e., an organoalkoxysilane such as 3-aminopropyltrimethox-ysilane (APTMS)] is combined with the cross-linking agent [i.e., a tetrafunctional alkoxysilane such as tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS)], a catalyst (such as hydrochloric acid or ammonia), and the template molecule. The resultant sol can be left to gel to form a monolith, which can then be dried, sieved, and extensively washed to remove the template. Alternatively, the sol can be spin coated, dip coated, or electrodeposited on a surface to yield a thin film, which can be subsequently washed with a solvent to remove the template and yield the imprinted cavities. 

A similar concept was used in the development of artificial chymotrypsin mimics [54]. The esterase-site was modeled by using the phosphonate template 75 as a stable transition state analogue (Scheme 13.19). The catalytic triad of the active site of chymotrypsin - that is, serine, histidine and aspartic acid (carboxy-late anion) - was mimicked by imidazole, phenolic hydroxy and carboxyl groups, respectively. The catalytically active MIP catalyst 76 was prepared using free radical polymerization, in the presence of the phosphonate template 75, methacrylic acid, ethylene glycol dimethacrylate and AIBN. The template removal conditions had a decisive influence on the efficiency of the polymer-mediated catalysis, and best results were obtained with aqueous Na2CC>3. 

Enantioselective hydrolysis of p-nitrophenyl-N-(benzylocycarbonyl)-L-leucinate compared to its D-isomer could also be performed with a MIP catalyst built up with a racemic template [55]. In that case, the enantiodiscrimination is insured by the presence of r-His monomer during the polymerization process, performed under finely tuned conditions. The random distribution of quaternary trimethyl-ammonium groups through the polymer framework makes this MIP very soluble in water. The MIP-catalyzed ester hydrolysis was performed in a mixture of... 

---