Chemical synthesis, polymers soluble

M. Zagorska and B. Krische, Chemical synthesis and characterization of soluble poly(4,4 -dialkyl-2,2 -bithiophenes), Polymer, 31 1379-1383, 1990. 

Chemical synthesis assisted by soluble polymers originally developed as an alternative to solid phase synthesis is now undergoing a second period of expansion. Just like in the early days, the desire to combine the advantages of solution chemistry with those of reactions on a solid phase has triggered this development. Soluble polymers can provide this and have therefore be-... 

Linear polystyrene can be functionalized by various methods . The functional group capacity in these polymers diould not be too high otherwise, steric complications may arise. Poly(ethylene ycol) has been found to be most suitable for liquid-phase synthesis. This linear polyether and the block copolymers with functional groups at defined distances are chemically stable and soluble in a large number of solvents including water and can be precipitated selectively. Partially hydrolyzed poly(vinylpyrrolidone) and its copolymers with vinyl acetate were successfully applied in peptide synthesis. Poly(acrylic acid), poly(vinyl alcdiol), and poly-(ethylenimine) are less suitable for the sequential type synthesis because of the... 

Structural analysis of linear polymers molecularly dissolved in a suitable solvent using and solution phase NMR spectroscopy is long established [87-89]. Not surprisingly therefore when a linear soluble polymer is used as a support in solid phase synthesis and solution phase NMR spectroscopy can be a powerful tool in following the chemical synthesis on the support [90]. Figure 15.3.58, for example, shows a series of H NMR spectra of dissolved linear polymer samples taken at various stages in the solid phase synthesis of oligoethers on soluble polystyrene [91]. The various chemical steps Fig. 15.3.59 are clearly demonstrated. 

Although most metal-containing polythiophenes have been synthesized by electropolymerization on an electrode surface, there are many reasons to chemically synthesize these polymers. Chemical synthesis may allow isolation of soluble polymers, enabling complete solution characterization (GPC, light scattering, NMR, etc.) and facilitating conductivity studies. Moreover, it can enable improved thin-film preparation and film deposition onto nonconducting substrates. Finally, monomers that are unsuitable for electropolymerization may be polymerized by chemical methods. 

Cellulose is the most abundant polysaccharide on Earth, with several thousand D-glucose units in a polymer chain (Figure 21.6). It is the main structural component of the cell wall of green plants. Cotton contains almost 90% of cellulose, whereas wood and dried hemp contain 50% and 45%, respectively. The first cellulose-based thermoplastic polymer was manufactured in 1870 and the first chemical synthesis was done by Kobayashi and Shoda in 1992 [130]. Solubility of cellulose in water depends on its chain length and it is degradable by enzymatic reaction [131]. Cellulose is easy to machine to form various shapes such as textiles, microsphere, sponges, and membranes. 

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