Backbone structures polymer synthesis

In mammalian cells, glucose is the most abundant carbohydrate energy source. It is metabolized in all cells as a glycolytic fuel and is stored in liver and muscle as the polymer glycogen. But certain cells have the enzymes to catalyze the synthesis of glucose under certain conditions. The requirements are (1) the availability of specific carbon skeletons (carbon backbone structures of various types), (2) energy, in the form of ATP, necessary to accomplish the sequence of reactions, and (3) the enzymes to catalyze reactions of the sequence. 

A variety of CEs with tailorable physico-chemical and thermo-mechanical properties have been synthesized by appropriate selection of the precursor phenol [39,40]. The physical characteristics like melting point and processing window, dielectric characteristics, environmental stability, and thermo-mechanical characteristics largely depend on the backbone structure. Several cyanate ester systems bearing elements such as P, S, F, Br, etc. have been reported [39-41,45-47]. Mainly three approaches can be seen. While dicyanate esters are based on simple diphenols, cyanate telechelics are derived from phenol telechelic polymers whose basic properties are dictated by the backbone structure. The terminal cyanate groups serve as crosslinking sites. The polycyanate esters are obtained by cyanation of polyhydric polymers which, in turn, are synthesized by suitable synthesis protocols. Thus, in addition to the bisphenol-based CEs, other types like cyanate esters of novolacs [37,48], polystyrene [49], resorcinol [36], tert-butyl, and cyano substituted phenols [50], poly cyanate esters with hydrophobic cycloaliphatic backbone [51], and allyl-functionalized cyanate esters [52] have been reported. 

The methodology of solid phase peptide synthesis (SPPS) [65, 66] has been credited with the award of 1984 Nobel Prize in chemistry [67] to its inventor, Bruce R. Merrifield of the Rockefeller University. At the heart of the SPPS lies an insoluble polymer support or gel , which renders the synthetic peptide intermediates insoluble, and hence readily separable from excess reagents and by-products. In addition to peptide synthesis, beaded polymer gels are also being studied for a number of other synthetic and catalytic reactions [2]. Ideally, the polymer support should be chemically inert and not interfere with the chemistry under investigation. The provision of chemical inertiKss presents no difficulty, but the backbone structure of the polymer may profoundly influence the course of the reaction on the polymer support. This topic has attracted considerable interest, particularly in relation to the properties of polystyrene (nonpolar, hydrophobic), polydimethylacrylamide (polar, hydrophilic), and copoIy(styrene-dimethylaciylamide) (polar-nonpolar, amphiphilic) (see later). 

Synthesis of highly crowded graft copolymers with graft frequencies of up to 50% of the total monomeric units in approximately alternate positions on the polymer backbone (structure 24). 

The direct introduction of peroxide groups into the backbone of polymers, such as poly(methyl methacrylate), has been used to produce macro-molecular initiators for the synthesis of block copolymers for example, poly(methyl methacrylate- -acrylonitrile) and poly(methyl methacrylate-Z -styrene). Ozonization can also be used, with careful control of the degree of ozonolysis, to introduce epoxy ring structures into natural rubber ... 

Several synthetic strategies have been developed to prepare phosphonated aromatic polymers, where the acid groups are attached either directly " or via spacers to an aromatic backbone. " These polymers can be prepared either by post-phosphonation of prepolymers via, e.g. transition metal catalyzed Michaelis-Arbuzov reactions and lithiation chemistiy, or by direct polymerization of phosphonated monomers via polycondensation. Both synthetic strategies then require hydrolysis of the esters to obtain the free acid. The former strategy requires the formation of C-P bonds in the polymer structure, and the latter necessitates the synthesis and purification of suitable monomers. 

The elastic modulus is controlled by the polymer network structure and synthesis conditions. The number of cross-links added per mole of main monomer helps define the molecular mass between cross-links. The molecular mass of the backbone polymer chain (obtained if no cross-linker was used) affects the effectiveness of the cross-links in forming a fiilly connected network with no soluble fraction and minimum content of dangling chains. The polymer volume fraction during cross-linking t>2<> defines the extent of entanglement of the network chains, and therefore influences the elastic modulus. 

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