Spacer groups silyl

A typical experimental apparatus for studying photorefractivity in liquid crystals is illustrated in Fig. 2. Two coherent laser beams from an Ar+ laser are crossed in the sample, with a total of 5 mW of p-polarized output at 514 nm. The beams are unfocused and have a 1/e diameter of 2.5 mm. The liquid crystal composite is sandwiched between two ITO coated glass slides that are coated with octadecyl-silyl groups to induce the liquid crystal director to align perpendicular to the face of the glass slides, that is, homeotropic alignment [43], The cell thickness is determined by a Teflon spacer that is 12 to 100 p,m thick. A small electric field... 

Usually, it is different to make a clear distinction between linker and spacer. The linker is the minimum part of the resin required for the functional cleavage (for silyl linkers it is the silyl group, for trityl linkers it is the triphenylmethyl moiety, and for the triazene linker it is the 1-aryltriazenyl group, etc.). The spacer is, therefore, the part between the linker and the resin as depicted in Figure 6.1.1. 

Klabunde and Ittel reported the use of nickel complexes containing the phosphorus—oxygen chelating ligands to homo- and copolymerize ethylene with a variety of functional olefins.Negative results were obtained with both vinyl acetate and methyl methacrylate, but copolymers could be obtained if monomers with at least two methylene spacers between the olefin and polar group, lihe functionalities successfully tolerated include ester, trimethyl-silyl-protected acids, ketones, fluoro groups, and 2° amides. 

The intramolecular photocyclodimerization of anthracenes and aryl-substituted alkenes having silyl groups via excimer intermediates has been reported by several groups. In these photoreactions, the silyl groups either activate alkenyl or aryl groups or act as a spacer. In some cases, two alkenyl groups are temporarily connected by a silyl... 

Figure 20 Scheme showing the imprinting of Wheterocycles using silyl ether 33 (Ref. 27) and silyl ester 34 (Ref. 29) templates. The dimethyl silyl groups acts as a sacrificial spacer. 

An approach taken to overcome these deficiencies is the use of the so-called sacrificial spacers [29]. In this method the intermediate species used during the pre-polymerization of the MIP to link the monomers and the template is chosen so that it is eliminated—or in other words sacrificed—during the removal of the template. This way not only is the template attached to the monomer, the chances of steric influences of the residual moe-ities during the future rebindings with the target species are also avoided. Instances of the common sacrificial intermediate species are spacers with carbonyl groups [59-70] or the less frequent instances of salicylate (2-hydroxybenzoate) [60,71], dimethyl silyl group of silyl ethers [72] and silyl esters [73]. 

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