Phenyl-modified matrices

Figure 40.12 Thermal bleaching kinetics of the photochromic molecules (a) in phenyl-modified matrices (SiO-Ph) and (b) in samples SiO-R7o%, where R is iBu, Ph, and Me.

Figure 40.9 Schematic representation of the pore structure in the phenyl-modified silica matrix (SiO-Ph).

This reaction has been modified extensively to proceed under different conditions. For example, it has been performed in liquid crystalline matrixes, sg in zeolite,in supercritical C02, on a silica gel surface, or in the presence of cyclo-dextrin. In addition, this reaction has been catalyzed by photoacid. Moreover, this reaction has been extended to various substrates other than the regular phenyl (or aryl) esters as described earlier. 

Among the various methods, grafting of long-chain polymers and small molecules are the most common. Alkenyl succinic anhydride (ASA), phenyl isocyanate, and isopropenyl-a,a -dimethylbenzyl isocyanate were used to modify the surface of CHNCs. The surface modification of CHNCs with these compounds increased the filler-matrix interactions in nanocomposites. ... 

Gopalan Nair et ehemieally modified the chitin whiskers by using different coupling agents, namely phenyl isocyanate (PI), alkenyl succinic anhydride (ASA) and 3-isopropenyl-R, R -dimethylbenzyl isocyanate (TMI). These various chemieal treatments on chitin whiskers improve the adhesion between the chemically modified ehitin whiskers and the NR matrix. However, the mechanical performances of these NR composites markedly decrease after chemical modification. This is due to the partial or total destruction of the three-dimensional network of ehitin whiskers, which is assumed for the unmodified composites. 

Wood as a form of natural plant fiber is a composite material in which the cellulose fibers as reinforcing elements are embedded in the lignin matrix. It is used as fuel or as a construction material, for packaging, artworks, and paper. Lignins are aromatic amorphous oligomers of di- and trisubstituted phenyl propane units obtained from the wood as by-products of the pulp and paper industries by solvent extraction. Lignin can be used after fractionation as fillers or as antioxidants and can be modified by esterification [105,106],... 

Reversed-phase extractions are used to enrich nonpolar compounds from a polar sample matrix. The extraction is based on interactions between carbon-hydrogen bonds from the compound and the sorbent. These hydrophobic interactions are shown in Figure 9.1a, and have been discussed in Section 3.5.2. Most organic compounds contain carbon-hydrogen-rich groups and will, therefore, be retained. Exceptions are ionized compounds or compounds with relatively many polar functional groups. Silica-based materials modified with C2, C4, C8, C18, cyclohexyl, phenyl, and cyano groups are examples of reversed-phase sorbents (see Table 9.3 for their structures). 

High-pressure in situ ETIR and polymer matrix techniques were used to study the rhodium-catalyzed hydroformylation of 1-octene, 1-butene, propene, and ethene using Rh(acac)(CO)2 or Rh(acac)(CO)(PPh3) in a polyethylene matrix as the catalyst precursor. The acyl rhodium intermediates, RC(=0)Rh(C0)4 and RC(=0)Rh (CO)3(PPh3), were observed. It was found that the acyl rhodium tetracarbonyl intermediates easily react with ethene to form acyl rhodium tricarbonyl species RC(=0)Rh(C0)3(C2H4) [61]. Deuterioformylation of l-phenyl-l-(n-pyridyl)-ethenes in the presence of a phosphane-modified Rh4(CO)i2 as catalyst precursor was carried out at 100 bar of CO D2 = 1 1 and 80 °C at partial substrate conversion. On basis ofa direct NMR analysis of the crude reaction mixture, it was concluded that the branched alkyl rhodium intermediate is almost exclusively formed [62]. 

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