Polymers templating

Molecularly imprinted polymers (MIPs) can be prepared according to a number of approaches that are different in the way the template is linked to the functional monomer and subsequently to the polymeric binding sites (Fig. 6-1). Thus, the template can be linked and subsequently recognized by virtually any combination of cleavable covalent bonds, metal ion co-ordination or noncovalent bonds. The first example of molecular imprinting of organic network polymers introduced by Wulff was based on a covalent attachment strategy i.e. covalent monomer-template, covalent polymer-template [12]. 

To control the formation of nanoparticles with desired size, composition, structure, dispersion, and stability, a multifunction nanoagent is used. The active metals (Pd and Pt) react with the functional groups of the nanoagent, i.e., a pol5mier template. The polymer template determines the size, monodisperity, composition, and morphology of the particles (which is somewhat reminiscent of the reversed micelles technique mentioned above). 

Figure 19 illustrates key steps of the FI2O2 formation at the nanostructured catalyst surface. An important feature is the imprintment and maintenance of the (11 0) crystal surface through the polymer template because the specific row of metal atoms favours the formation of hydrogen peroxide while minimizing byproducts such as water. 

The scope of this chapter is to review such bio-controlled syntheses of metallic and oxide nanopartides using biological molecular and macromolecular templates. The possible use of polymer templates to organize pre-formed nanopartides has been... 

Goltner, C. G Henke, S. Weissenberger, M. C. Antonietti, M. 1998. Mesoporous silica from lyotropic liquid crystal polymer templates. Angew. Chem. Int. Ed. 37 613-616. 

From this equation, it is clear that concentration of the solvent, S, influences a number of sites on the template which are occupied by the monomer, M. As the result of monomer units association with the template, the orientation of the substrate takes place and some special type of structure can be created. The structures, in which the monomer is aligned in a regular manner on the polymer template, were described by Chapiro in the case of polymerization of acrylic acid and acrylonitrile and details are described below. The ordered structure increases concentration of monomer at the reaction site, affects distances between pre-oriented monomer molecules, and changes a steric hindrance. This change in structure leads to the change in the kinetics of the polymerization reaction and it is responsible for stereo-control of the propagation step. 

Donor-acceptor interaction between monomer and polymer template offers an elegant methods of replication degree of polymerization. Similar system was described for copolymerization of vinylpyridine with p-chlorostyrene in the presence of poly(maleic anhydride) used as template. " ... 

Template Polymers. Template effects in chelating polymers constitute an interesting development in the field of metal containing polymers. The Template effects are interpreted by the fact that the small molecule is templating a pattern in the macromolecule which can be recognized by the same molecule in a subsequent process. The idea is to prepare a polymer from the metal-chelated monomer, to remove the metal ion, and then to measure the selectivity of the prepared polymer for the metal ion of the template [36]. Typical examples of template systems are 4-vinyl-4 -methylbipyridine (Neckers [36]) and 1-vinyl-imidazole (Tsuchida [37]). These are polymerized in presence of divinylbenzene [36] and appropriate metal salts (Co2+, Cu2+, Ni2+, Zn2+). The template metal ions are removed by acid leaching and the polymer subsequently used for metal ion absorption studies (Fig. 16). 

A novel approach to polymer-template mesoporous molecular sieves... 

Figure la Nitrogen isotherm of a polymer templated material at 77 K (sample 5) 10 100 1000... 

Figure lb Pore size distribution of a polymer templated material calculated from the isotherm in figure la (BJHoes)-... 

Figure 2 SEM of polymer templated material of an average particle diameter of 200 nm...

The typical procedure (42) involved mixing 4 g of nonionic triblock copolymer L123 (BASF), 20 g of water, and 80 g of 2M HC1. To this solution, 8 g of tetraethylorthosilicate was added at room temperature. The mixture was then stirred at room temperature for 24 h. The solid product was recovered by filtration. The polymer template was removed by calcination at 500°C for 5 h. 

Li, C.M. "Silk polymer templates in biomineralization", Ph.D. Thesis, Tufts University (2005). 

Ding, J. H., and Gin, D. L., Catalytic Pd nanoparticles synthesized using a lyotropic liquid crystal polymer template, Chem. Mater. 12,22 (2000). 

The polymer-templated OMSs such as SBA-1545 possess pores about 8-12 nm, which are more spacious and can be decorated with more complex ligands. The SBA-15 sample studied exhibited ordered mesopores about 10 nm, and irregular micropores in the mesopore walls as shown in Figure 1. Initially chloropropyl-SBA-15 material was obtained and subsequently grafted with 2,5-dimercapto-l,3,4-thiadiazole ligand16 (OMM-3 material in Figure 1). These... 

Expanding the synthesis tool box beyond surfactant self-assembly 2.6.1 Block co-polymers templates... 

In addition to recent advances in block co-polymer templating of periodic mesoporous silica and silica colloidal crystal templating of periodic mesopo-rous polymers [79], SAMs have been used for polymer patterning [80]. Mixtures of two strongly incompatible polymers, a polystyrene (PS)-polyvinylpyridine (PVP) blend, were found to phase separate when placed on a... 

Johnston P, Fleam MYW, Saito K (2010) Solid-state photoreversible polymerization of n-alkyl-linked bis-thymines using non-covalent polymer-templating. Aust J Chem 63 631-639... 

Templates should be removed from the composites to yield porous structures. Polymer templates can be removed by calcination, by dissolution with appropriate solvents, or by photo degradation, while silicas are eliminated by dissolution in aqueous HF or NaOH solution. 

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