Carboxyl Chemical modification

PS has apolar characteristics and, thus, it is difficult to form a bond with metzils or polar materials. The adhesion capability of saturated polyhydrocarbons are dependent on the basis of polar properties of polymers [25]. Mitsu-aki and Masyasu [26] investigated the chemical modification of PS for anchoring of the carboxyl group to PS macromolecules with maleic anhydride (MA) in the presence of radiczil catalysis at 90-150°C. These authors... 

Hydroformylation of nitrile rubber is another chemical modification that can incorporate a reactive aldehyde group into the diene part and further open up new synthetic routes to the formation of novel nitrile elastomers with a saturated backbone containing carboxyl or hydroxyl functionalities. 

Applications of peroxide formation are underrepresented in chiral synthetic chemistry, most likely owing to the limited stability of such intermediates. Lipoxygenases, as prototype biocatalysts for such reactions, display rather limited substrate specificity. However, interesting functionalizations at allylic positions of unsaturated fatty acids can be realized in high regio- and stereoselectivity, when the enzymatic oxidation is coupled to a chemical or enzymatic reduction process. While early work focused on derivatives of arachidonic acid chemical modifications to the carboxylate moiety are possible, provided that a sufficiently hydrophilic functionality remained. By means of this strategy, chiral diendiols are accessible after hydroperoxide reduction (Scheme 9.12) [103,104]. 

In a concurrently published report [160] Crooks and coworkers reported similar MUA-SAMs modified by covalent linking of hyperbranched macromolecules. These films containing a high density of surface carboxylic acid groups could selectively bind metal ions or undergo chemical modification. 

Ami, P.C., Gray, J.D. and Scougall, R.K. (1961a). Chemical modification of wood. 1. Use of trifluoroacetic acid in the esterification of wood by carboxylic acids. Journal of Applied Chemistry, 11, 157-163. 

Chemical modification of surface residues of HRP is one method which may offer some improvement in thermal or long-term stability of the enzyme. The -amino groups of the six surface Lys residues can be modified by reaction with carboxylic anhydrides and picryl sulfonic acid (296). In this example the number of sites modified was found to be more significant than the chemical nature of the modification, at least as a criterion for improved stability. Other methods explored include the use of bifunctional crosslinking reagents to couple surface sites on the enzyme (297). Future developments are likely to be concerned with the selection of site-directed mutants of HRP C that show enhanced thermal stability. Dramatic increases in thermal stability of up to 190-fold have been reported recently for mutants of Coprinus cinereus peroxidase (CIP) generated using a directed evolution approach (298). 

Chemical modification takes place and carboxyl, hydroxyl and carbonyl groups are produced on the fiber surface. 

Ozonization of lignin forms derivatives of muconic acid that have the unique chemical structure of conjugated double bonds with two carboxyl groups. These derivatives have great potential for chemical modification. The ozonized lignin of white birch was soluble in epoxy resin at 120°C, and the free carboxyl groups were found to react with epoxide. This paper discusses developmental work on the preparation of pre-reacted ozonized lignin/epoxy resins the dynamic mechanical properties of cured resins and preliminary results of the application of these resins as wood adhesives. 

Chemically there arc important differences. There are no side chains and unlike wool the number of amino and carboxylic groups differs there is an excess of carboxylic groups. The numbers of amino groups can be changed by chemical modification, c.g.. in deep dyeing nylon, but for the most part nylon fibers can be considered lo have a limited number of sites, which can differ from one chemical type to another. 

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