Chemical synthesis, polymers substitution

Polymer films may also be synthesized by direct chemical routesT 101. These chemical synthesis routes generally involve some form of electrophilic substitution using Grignard reagents or other modified precursors. The purity and electrical properties of the films produced from the chemical route are generally poorer than... 

One of the best examples of the utility of enzymatic synthesis in catalyzing reactions that cannot be accomplished by any other route is the synthesis of substituted oxazolidine diesters. The oxazolidine ring is extremely water sensitive, the oxazolidine rapidly reverting back to the alkanolamine and aldehyde in the presence of water. Bis-oxazolidines have been used as hardeners for polymer coatings but the diester based on the hydroxyethyl oxazolidine and adipic acid cannot be synthesized directly with chemical catalysis because of the rapid rate of reaction of the oxazolidine ring with either the water from the esterification or the alcohol from transesterification. ... 

Chemically functionalized polymers have also been used in polymer-assisted solution-phase synthesis to perform reaction-quenching functions. These polymers often are used in operations that substitute for traditional liquid-phase extractions in classical synthesis. 

Direct chemical synthesis of polymers to probe these mechanisms has shown that there are cases where the. shift of optical absorption may be interpreted by the coexistence of two phases, while also cases exist of a continuous change in the optical absorption, with no isobestic point evident. This can be correlated to the local substitution pattern, where some of the patterns, giving a two-phase behaviour, show a co-operative aspect of the transition. 

P. Soudan, H. A. Ho, L. Breau and D. Belanger, Chemical synthesis and electrochemical properties of poly(cyano-substituted-diheteroarenethylene) as conducting polymers for electrochemical supercapacitors, J. Elec-trochem. Soc., 148, A775-A782 (2001). 

Leclerc [125] has shown that poly(2-methyl aniline) has properties similar to that of polyaniline. Dao et al. [127] have carried out extensive investigations on chemical and electrochemical polymerization of substituted polyanilines. These authors report that chemical synthesis yields a polymer having a higher molecular weight. Some of their results are given in Table 12.13. Their study further shows that there is no polymer film on an electrode surface in the presence of the following substitutions ... 

Two approaches currently seem open. The first is directed toward conjugated polymers. Here substituted systems may hold potential. Cyclopol3nnerization is a viable method of synthesis of substituted polyacetylenes. Likewise, chemical modification of polyacetylene itself may have potential. The preparation of polyacetylenes by elimination reactions from precursor polymers needs more attention. The second approach is toward non-conju-gated polymers containing aromatic functionalities little work has been done in this area. Much creative chemistry remains to be explored and it will most likely involve new monomers and polymers. ... 

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