Solubility natural polymers

Solvent-Soluble Natural Polymers. The exudate of the lac insect is dissolved in alcohol to yield shellac. This solution has adhesive properties and should be reversible by treatment with the appropriate alcohol or similar solvent, although it may present problems in other performance areas (8). Solvent-soluble plant gums, especially coniferous resins (e.g., from firs or pines) can be dissolved in organic solvents and used as adhesives. Solvent solutions of some plant waxes may also have limited utility in gluing. All such glues should be reversible by treatment with solvents similar to those they were dissolved in when applied. 

Water-soluble natural polymers are the groups of polymer synthesized naturally mostly by different plants and lower forms of organism. They occupy a very important portion of the total pharmaceutical application of polymers. Some of the most frequently used polymers under this group are presented with a short description. 

For instance, water-soluble natural polymers, such as agarose and /c-carrageenan, first change their conformation from a random coil to a partially helical one. The helical parts then aggregate into network junctions (Figure 10.16(a)) [34,44,46-48]. 

Organic Flocculants. The organic flocculants are all water-soluble natural or synthetic polymers. 

Bv employing a soluble cationic polymer as the solution electrolyte polymer films can be sterical ly blocked from reducing beyond the formal zero valent form. In the zero-valent form the polymer is an ohmic conductor both in solution and dry. A model has been proposed which describes the conductivity of the polymer and in part accounts for its ohmic nature and semi conductor-1 ike temperature dependence. 

In the most succinct sense, a hydrogel is simply a hydrophilic polymeric network cross-linked in some fashion to produce an elastic structure. Thus any technique which can be used to create a cross-linked polymer can be used to produce a hydrogel. Copolymerization/cross-linking free radical polymerizations are commonly used to produce hydrogels by reacting hydrophilic monomers with multifunctional cross-linkers. Water-soluble linear polymers of both natural and synthetic origin are cross-linked to form hydrogels in a number of ways ... 

G Gustafsson, Y Cao, GM Treacy, F Klavetter, N Colaneri, and AJ Heeger, Flexible light-emitting diodes made from soluble conducting polymers, Nature, 357 477-479, 1992. 

Normally synthetic reactions for modification of these natural polymers have been conducted heterogeneously. In the absence of acceptable solvents, characterization of starting materials is difficult and reaction yields are often low due to unfavorable kinetics. Only in those cases in which the substituted products were soluble, have polymer structures been readily identifiable by instrumental analysis.. . ... 

Cross-linking is important because this is a major mechanism for retaining shape, which, in turn, influences the physical properties, such as solubility, of polymers. There are three types of cross-linking present in synthetic and natural polymer. Two of the three types are physical... 

Graft polymers were obtained by mastication of a 60/40 blend of natural rubber and chlorosulphonated polyethylene (/). From 10-55% natural rubber was obtained as side chains. Grafting presumably proceeds by transfer of chlorine atoms to the rubber radicals to give grafting sites for combination with rubber radicals. Soluble linear polymers were also obtained by mastication for 50-180 min under nitrogen for a blend 50/50 of natural rubber and a polyurethane rubber (Vulcaprene A) (/). 

Therefore, die polarity and solubility of polymer can be modified deliberately by varying the nature of the components. High aqueous solubilities of polyamides and polyurethane threaded with crown ethers or CD are intriguing, because this observation implies potential applications of the polyrotaxane concept in coatings, adhesives, and water-borne processing. The observation of the emulsification of... 

This group (sometimes called water-soluble resins) includes such chemically treated natural polymers as carboxymcthylcclluosc, mcthylccllulosc, and other cellulose esters, as well as various kinds of modified starches (esters and acetates). 

Novel, hyper-branched polyphenylenes 20 have been prepared by the selfcoupling of 3,5-dibromophenylboronic acid in the presence of Pd(PPh3)4 as shown in Scheme 25 [90,91]. (The monomer was prepared by treatment of the monolithiate of 1,3,5-triboromobenzene with trimethyl borate.) The hyper-branched polymer was found to be organic soluble, and could be converted to a water-soluble, polyphenylene derivative by treatment with butyl lithium followed by quenching with C02. The water-soluble nature of such hyper-branched polyphenylenes has made them suitable candidates for use in various applications such as unimolecular micelles. 

As the unsubstituted polysaccharides are rarely stable in solution, soluble derivatives must almost invariably be used, and a study of the unavoidable degradation accompanying the preparation of such derivatives is also essential. The use of soluble derivatives may not be entirely satisfactory as there is the possibility that linear natural polymers might aggregate in solution (compare the behavior of certain synthetic polymers, e.g., polyvinyl chloride24). A similar effect may occur in the presence of... 

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