Post-functionalization approach

Functional moieties for click reaction can either be incorporated in the polymer chain directly with the monomer, by quenching or via post-functionalization approaches. If the functional moiety is introduced with the monomer or the quencher, one has to consider the cross-reactivities between the metathesis catalyst and the functional moiety. In this case, the specific functional group can either be introduced by using protective groups, for example, complexing alkyne with Co2(CO)g, di-cobalt octacarbonyl or has to be introduced after the actual polymerization reaction. Post-functionalization approaches thereby often... 

Monomers with unprotected alkyne groups in the side chain cannot be polymerized without side reactions, as the alkylidene catalyst will engage in a competing alkyne metathesis. This side reaction can be avoided by using monomers with alkyne groups either complexed with di-cobalt octacarbonyl 1 or TMS-protected 2 (Scheme 9.3a,b) [14, 35, 36]. Alkyne incorporation at the chain end was achieved in a post-functionalization approach, reacting hydroxyl-terminated polynorbornene (PNBE) 5 with propargylic acid 6 (Scheme 9.3c) [37]. 

Recently, Diels-Alder reaction between maleimide-containing NLO chro-mophores and pendant anthracenyl moieties of the polymer chain has been used in the context of post-functionalization approach [69], This is particularly interesting in view of the mild reaction conditions, quantitative yield and absence of ionic species and catalyst. 

The post-HF approaches that have been pursued have typically taken two forms. One is based on the variational principle in which the lowest energy of the system can be obtained by varying parameters of an assumed functional form [6, 9]. The other approach is perturbation theory, which in its early development, was based on using the solutions of a known system to obtain the energy of a system that did not differ much from the known system. 

There are opportunities for using on-farm and post-farm approaches for manipulating milk fat to improve its attractiveness as an ingredient in functional foods (Baer et al., 2001 Hillbrick and Augustin, 2002). The emergence of the functional foods (i.e., foods that provide benefits beyond normal nutrition) and the accumulating evidence that some fats, minor lipids and fat-soluble products can have important roles in nutrition and the prevention of disease (Parodi, 2003, 2004 see Chapter 17) has opened opportunities for milk fat and its components in the growing market for functional foods. 

The original paper concerning SOS-DFPT [28] contains a description of the theory and a wide range of applications to different types of systems. In this Chapter we will include the most illustrative material. Here we will present the comparison between Zero-order and Loc.l approximations, and experimental data discuss the influence of the choice of the exchange-correlational functional on the results of the chemical shift calculations and compare our SOS-DFPT results with the results of HF and post-HF approaches for cyclic organic compounds and for the ozone molecule. 

Another approach to tuning the optical properties and improving the emission of PT derivatives in the solid state was proposed by Holdcroft and co-workers [60], They used post-functionalization of P3HT (9f) by an electrophilic substitution reaction (to afford polymers 34) followed by Pd-catalyzed coupling (Suzuki, Stille or Heck reactions) to afford polymers 35 (Scheme 19.5) [61], In this case, functionalization with bulky aryl substituents (35) hindered the interchain interactions and allowed a substantial increase in d>PL in the films from 1.6 % to 13-22 %. 

The synthesis and use of immobilized iridium pincer complexes on solid supports for the transfer dehydrogenation of alkanes have also been examined [131]. Three approaches are reported (i) the post-functionalization of a Mer-rifield resin by incorporating the pincer complex (ii) the covalent bonding of the catalyst to silica via a pendant alkoxysilane linker and (iii) the adsorption of the catalyst onto y-alumina via the interaction of the phenolate group on the para-position of the pincer ligand with the Lewis-acidic sites on the alumina. The last approach showed the best activity, affording thermally robust, recyclable, and active supported ( PCP)Ir (Ir-2) and ( POCOP)Ir (Ir-13) catalysts. 

The attachment of a functional unit to the polymer chain can be done before polymerization of the monomer but also in a post-polymerization functionalization approach by preparing activated polymers with monomers such as 14 [49-53]. The NBE derivative containing isoxazolino anchor group 15, which... 

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