Chemical modification to produce

An important polymer modification reaction is the grafting to or from a polymer backbone by some chemical method to produce a branched structure Q). The characterization of the products of these reactions is often somewhat less well defined than block copolymers (2) due to the complexity of the mixture of products formed. It is therefore useful to prepare and characterize more well defined branched systems as models for the less well defined copolymers. The macromonomer method (3 ) allows for the preparation of more well defined copolymers than previously available. 

Chemical modification of both the primary and secondary hydroxyl substituents has been used to further improve their toxicity, water solubility, and biodegradability. Since the hydroxyl groups differ in chemical reactivity, chemical modification typically produces thousands of regio- and stereoisomers resulting in a substantially less crystalline molecule. The amorphous character of chemically modified cyclodextrins has beneficial effects on aqueous solubility and toxicity. Variation of the degree of substitution provides a means for optimizing physical and chemical parameters of the molecules in specific applications. 

Cellulose, the most abundant renewable agricultural raw material, is transformed into multifarious products affecting every phase of our daily life. The presence of active hydroxyl groups in cellulose has been utilized in a variety of chemical reactions to produce commercially important cellulose derivatives, such as cellulose ethers and cellulose esters. Although the practical purpose of cellulose derivatization is by and large to improve various properties of the original cellulose, these cellulose derivatives are often not competitive with most of the petrochemically derived synthetic polymers. In order to provide a better market position for cellulose derivatives, there is little doubt that further chemical modification is required. Grafting of vinyl monomers onto cellulose and... 

Cmde lecithin contains a number of functional groups that can be successfully hydrolyzed, hydrogenated, hydroxylated, ethoxylated, halogenated, sulfonated, acylated, succinylated, ozonized, and phosphorylated, to name just a few possibilities (1). The only chemically modified food-grade products produced in significant commercial quantities at the present time are the ones obtained by hydroxylation, acetylation, and enzymatic hydrolysis (58). Hydroxylated or acylated lecithins represent chemical modifications to improve the functionality in water-based systems. 

The use of the chlorate and sugar or nitrobenzene mixtures for purposes of political assassination and sabotage as in partisan mixtures, and their modifications to produce delayed reaction mixtures such as Molotov Cocktails are described by Stettbacher. He attributes the death of Tsar Alexander II of Russia in 1881 and the Irish baggage explosions in London in 1938 to bombs containing such ingredients. The author also quotes in this book articles by himself about chemical ignition... 

Once graphene had been prepared and isolated it was realised that it could act as a template for chemical modification to other two-dimensional nanocrystals. There are a number of ways in which it can be modified although it has proved difficult to produce stoichiometric derivatives. One way in which people have tried to produce stable... 

Metallophthalocyanine polymers offer good stability in thermal, chemical, hydrolytic and photochemical environments. The reversible redox property and cycle stability of phthalocyanine compounds and their polymers make them useful as active components in sensors, switches, diodes, memory devices, NLO materials, etc. different types of phthalocyanine polymers are available and they are amenable to chemical modifications to suit the devices requirements. It is possible to exercise chemical control of the properties of the phthalocyanine polymers as well as functionalize other conducting polymers with the characteristics of phthalocyanines. Hence phthalocyanine polymers have become potential candidates for producing useful and viable materials for electronic, optoelectronic and molecular electronic applications. 

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