Semisynthetic polymer

Semisynthetic polymers Semisynthetic polymers are tailored polymers. Some chemical modifications are made to natural polymers in order to obtain semisynthetic polymers. 

Starch is a polysaccharide found in many plant species. Com and potatoes are two common sources of industrial starch. The composition of starch varies somewhat in terms of the amount of branching of the polymer chains (11). Its principal use as a flocculant is in the Bayer process for extracting aluminum from bauxite ore. The digestion of bauxite in sodium hydroxide solution produces a suspension of finely divided iron minerals and siUcates, called red mud, in a highly alkaline Hquor. Starch is used to settle the red mud so that relatively pure alumina can be produced from the clarified Hquor. It has been largely replaced by acryHc acid and acrylamide-based (11,12) polymers, although a number of plants stiH add some starch in addition to synthetic polymers to reduce the level of residual suspended soHds in the Hquor. Starch [9005-25-8] can be modified with various reagents to produce semisynthetic polymers. The principal one of these is cationic starch, which is used as a retention aid in paper production as a component of a dual system (13,14) or a microparticle system (15). 

Starch is usually derivatized by the introduction of acrylic groups, prior to polymerization and manufacture into microspheres. Poly(acryl) starch microspheres, as they are referred to, are an example of a semisynthetic polymer system. Their extensive use as... 

Docetaxel -semisynthetic taxane stabilizes tubulin polymers leading to death of mitotic cells -bone marrow suppression -nausea and vomiting -mucocutaneous effects (mucositis, stomatitis, diarrhea) -hypersensitivity reactions -fluid retention syndrome -fatigue -myalgias -alopecia (universal)... 

Semisolid Dosage Forms The nature of the base (vehicle) used for the fabrication of semisolid dosage forms affects their hydrolytic stability. Increased degradation of benzylpenicillin sodium in hydrogels of various natural and semisynthetic polymers has been reported [14]. Also at pH 6 in Carbopol hydrogels, the percentage of undecomposed pilocarpine at equilibrium is a function of the apparent viscosity of the medium [15]. 

The natural polymers frequently used for the preparation of pharmaceutical gels include tragacanth, pectin, carrageenan, agar, and alginic acid, as well as semisynthetic polysaccharides such as methylcellulose, hydroxymethylcellulose, and carb-oxymethylcellulose. 

It can be expected that these semisynthetic carbohydrate polymers exert quite specific effects in the kinetics of drug release. 

POLYMERS, WATER-SOLUBLE. Any substance of high molecular weight which swells or dissolves in water at normal temperature. These fall into several groups, including natural, semisynthetic, and synthetic products. Their common property of water solubility makes them valuable for a wide variety of applications as thickeners, adhesives, coatings, fooe additives, textile sizing, etc. 

Binding enzymes to solid supports can be achieved via covalent bonds, ionic interactions, or physical adsorption, although the last two options are prone to leaching. Enzymes are easily bound to several types of synthetic polymers, such as acrylic resins, as well as biopolymers, e.g., starch, cellulose [52], or chitosan [53,54]. Degussa s Eupergit resins, for example, are used as enzyme carriers in the production of semisynthetic antibiotics and chiral pharmaceuticals [55], Typically, these copolymers contain an acrylamide/methacrylate backbone, with epoxide side groups... 

Shellac is the oldest known material that has been used as enteric coating material. However, as a natural material, it lacks a crucial quality criterion of more modern polymers (i.e., batch-to-batch reproducibility). Hence, the most commonly used polymers today are the synthetic methacrylate copolymers or semisynthetic derivatives of cellulose. The main structural element of these polymers is an acidic function (either phthalate or methacrylic acid), which is responsible for the pH-dependent dissolution. 

Kulicke, W.-M., and Nottelmann, H. (1989). Structure and swelling of some synthetic, semisynthetic, and biopolymer hydrogels. In Polymers in Aqueous Media, Glass, J. E. (Ed.), Advances in Chemistry 223, pp. 15-44. Am. Chem. Soc., Washington, DC. 

In reference to cloth or fiber, the term acetate usually means cellulose acetate, a semisynthetic polymer made by treating cellulose with acetic anhydride. Cellulose acetate is spun into yarn by dissolving it in acetone or methylene chloride and forcing the solution through spinnerets into warm air, where the solvent evaporates. 

Although these polymers were found to be suitable for drug delivery applications, in vivo studies in dogs showed that, when implanted in muscle, the polymer degraded to semisynthetic FAD monomers, which slowly cleared (6 months) from the implantation site [386]. This erucic acid-based FAD is not easily metabolized in vivo, probably due to the C-C linkage between the two fatty acids. 

Many publications, particularly from academic institutes, contain information concerning synthetic or semisynthetic polymers, which are designed to enhance... 

The classification of polymers previously described has been used in this book for the discussion of pyrolysis results. An important class of polymers that is not discussed here is that of chemically modified natural polymers (or semisynthetic polymers). Examples of such polymers are the modified celluloses (carboxymethyl cellulose, ethyl cellulose, etc ), modified starches, casein plastics (Galalith), etc. These types of compounds were discussed in the book on pyrolysis of natural organic polymers [2]. 

Rayon is a semisynthetic fiber because it is prepared from a natural polymeric starting material. The first truly synthetic polymeric fiber was nylon, developed in the 1930s by the American chemist Wallace Carothers at DuPont Company. He knew of the condensation of an amine with a carboxylic acid to form an amide linkage (see Section 7.6) and noted that, if each molecule had two amine or carboxylic acid functional groups, long-chain polymers could form. The specific starting materials upon which Carothers settled, after numerous attempts, were adipic acid and hexamethylenediamine ... 

Semisynthetic and synthetic fibers introduced from the 1920s made new demands on the ingenuity of dye-makers. The commercial value of new polymers relied entirely on the ease of coloration. Normal dyeing is accomplished in aqueous solution, often in the presence of a fixing agent, or mordant. This is ideal for cotton, silk and wool, but not for synthetic fibers such as nylon and polyester, that are plastic in nature. They require... 

CAS 9004-32-4. A semisynthetic, water-soluble polymer in which CH2COOH groups are substituted on the glucose units of the cellulose chain through an ether linkage. Mw ranges from 21,000 to 500,000. Since the reaction occurs in an alkaline medium, the product is the sodium salt of the carboxylic acid R-0-CH2COON a. 

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