Structures Ethylcellulose Polymer

Fig. 1 Chemical structures of the polymers commonly used for preparation of beads poly (styrene-co-maleic acid) (=PS-MA) poly(methyl methacrylate-co-methacrylic acid) (=PMMA-MA) poly(acrylonitrile-co-acrylic acid) (=PAN-AA) polyvinylchloride (=PVC) polysulfone (=PSulf) ethylcellulose (=EC) cellulose acetate (=CAc) polyacrylamide (=PAAm) poly(sty-rene-Wocfc-vinylpyrrolidone) (=PS-PVP) and Organically modified silica (=Ormosil). PS-MA is commercially available as an anhydride and negative charges on the bead surface are generated during preparation of the beads...

The introduction of the relatively small methyl group into the cellulosic structure is not sufficient to render methylcellulose fusible without decomposition and the polymer cannot be melt processed. However, the disruption of the cellulosic structure is sufficient to make methylcellulose soluble. The solubility characteristics of methylcellulose are similar to those of ethylcellulose. The following solvents are effective at the degrees of substitution indicated aqueous alkali (0.1—0.6), cold water (1.3—2.4), oxygenated solvents (2.4-2.7) and hydrocarbons (2.6—2.8). As indicated previously only products with degrees of... 

Most work has been concentrated on the formation, structure and properties of ternary systems composed of one cellulose derivative and mixed solvents or other polymer blended solutions. Thus, the liquid crystal properties of ethylcellulose/acrylic acid, ethylcellulose/dichloroacetic acid and ethylcellulose/glacial acetic acid solutions were studied, observing the mesophase behavior when their concentrations exceeded 0.6, 0.3, and 0.35 g/ml, respectively, at room temperature [143]. Also,... 

Ethylcellulose is an ethyl ether of cellulose, prepared by ethylation of the alkali cellulose, whose most important property is to be insoluble in water. Different ethylcelluloses are commercially available varying both the ethoxyl content (45.0-49.5%) (Ethocel , by Dow Chemical Company) and viscosity values (10-100 cP). As a general rule, viscosity increases as the molecular weight (MW) of polymer increases. The lower viscosity grades of this polymer are more compressible and compactible, leading to harder tablets and, consequently, to lower drug dissolution rates [14-16], This increase in com-pactibility has been explained based on the fact that the polymers with lower MW show a less ordered structure [14]. 

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