TOPICAL chemical modifications

Treatments with Chemicals or Resins. Resin treatments are divided into topical or chemical modifications of the fiber itself. Most chemical treatments of synthetic fibers are topical because of the inert character of the fiber itself and the general resistance of the fiber to penetration by reagents. By contrast, ceUulosics and wool possess chemical functionality that makes them reactive with reagents containing groups designed for such purchases. Natural fibers also provide a better substrate for nonreactive topical treatments because they permit better penetration of the reagents. 

Chemical modification of polymers (J.) still remains a field of continuously increasing importance in macromolecular chemistry. In spite of its high diversification, it may be divided into 2 distinct but complementary main research lines a) the fundamental study of the chemical reactivity of macromolecular chains b) the synthesis of new homopolymers and copolymers, and the functionalization of linear or crosslinked polymers. Some of these facets have been reviewed in the last years (2-6), and the purpose of this presentation is to illustrate a number of characteristic topics both from fundamental and applied points of view, through some literature data and through our own studies on nucleophilic substitution of polymethylmethacrylate (PMMA). 

A promising approach to this topic is the development of biocompatible solid phase attachment systems for macrocycles that allow on-bead enzymatic and chemical modification [4]. While making use of recent developments in polymeric support for resins, we endeavored in constructing a new linker system, which allows easy attachment of macrocycles to the solid phase, simple organic or enzymatic reactions, and cleavage from solid support under mild conditions [98]. 

Only syntheses which involve the formation of new glycosidic linkages will be considered in this article. This restriction excludes many interesting examples of copolymerization in which only one of the monomers is a carbohydrate (or carbohydrate derivative), the polymerization of carbohydrate derivatives which contain a polymerizable group4 (such as acrylate), and the polymerization of sugar lactones.1 Many of these topics have already been discussed in reviews.1-8 Also outside the scope of this article is the chemical modification of naturally occurring polysaccharides thus, we have excluded the industrially important process of dextrini-zation,10 except as it may pertain to acid condensation processes. The radiation-catalyzed polymerization and modification of carbohydrate poly-... 

The content of this book reviews the latest developments in the characterization and chemical modification of silica surfaces. No attempt has been made to survey exhaustively the literature of any topic. The material has been collected from recent publications and own research work in this field. Also, recent disclosures of research activities in the former USSR are documented in detail in the text. 

In the present section we comment further on the chemical modifications of these materials when the R group is chosen for the preparation of micro-and mesoporous silicas. From a general point of view, the control of the porosity of silica via organic molecular templating is an attractive topic connected to molecular recognition, catalysis, chemical sensing and selective adsorption, etc. Many attempts have been made to control the pore size distribution in sol-gel derived silica30,196. 

The work was supported by Research Grant CA 16861 and Research Career Development Award CA 00462 to CFM from the National Cancer Institute, NIH, and by a Veterans Administration Research Grant to DAG. We thank R. E. Feeney for his advice on chemical modifications and numerous other topics. 

This is well illustrated by efforts in developing topically effective carbonic anhydrase inhibitors such as dorzolamide through significant alternations in chemical structure. Other efforts have been based on simple chemical modifications, i.e. a prodrug approach. 

Contact dermatitis was often observed when penicillin was used in topical formulations and still continues to be described in cases of occupational exposure to beta-lactams (218,219). The underlying mechanism is thought to involve chemical modification of antigen-presenting cells in the epidermis, leading to sensitization of drug-specific T cells (220,221). 

Application of photoinitiators is one of the most efficient methods for achieving fast polymerization or controlled chemical modification of polymers. The use of photo-initiators is common in many valuable industrial applications,174 1134 1505 such as photolithography and UV curing (Special Topic 6.27). 

Sabrine Alila, is associate professor at the Department of Chemistry of the University of Sfax (FSS). Her research topic is concerned with surface chemical modification of cellulose fibres in order to enhance their absorption capacity toward dissolved organic pollutants, including pesticides and herbicides. 

We previously described chemical modification approaches that have been used to derivatize HA (36). This section focuses on recent literature reports on conjugation of active moieties to HA. Several earlier articles dealing with this topic have been published elsewhere (37-42). 

The remarks on chemical modification of (1— 4)-glucans are restricted to aspects that are of interest for the main topic of fliis article, namely, the analysis of the substitution patterns of this class of compounds. For more details, the reader is referred to the respective literature. 

One effect of these chemical modifications is that DE-175 is intrinsically more active against pest insect species than spinosad. For example, in a laboratory bioassay of topical toxicity to beet armyworm Spodoptera exigua) larvae, DE-175 is 48X more active than spinosad (Table 29.3.3). Similar results are observed in a bioassay of ingestion activity, where DE-175 is 58 x more active on beet army-worm than spinosad. Improved potency of DE-175 is also observed against other lepidopterous insects, though to a lesser degree (Table 29.3.3). 

Thus, in the S N-amination reactions an oxidant may take part not only in aromatization of the intermediate chemical modification of nucleophile, substrate, and intermediates. This opens up new horizons for obtaining compounds, which are otherwise not easily accessible. In this regard, the one-pot synthesis of compounds 55 and 63, in which six new bonds are subsequently formed, appears to be a good example of the most complex currently known 5 -heterocyclizations (for review on this topic, see [34]). 

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