Water-soluble cellulose ether molecular weight

Surface tensions of 2% aqueous solutions of commercially used water-soluble cellulose ethers were determined for comparative purposes in the author s laboratory (Table 10). Five derivatives were selected, each with two different molecular weights (nominal viscosity grades). 

Several polymers were found to fit all or most of the above criteria and were used to prepare the carrier films. Many polymers have been used for this purpose, viz., ethyl cellulose, poly(y-benzyl glutamate), poly(vinyl acetate), cellulose acetate phthalate, and the copolymer of methyl vinyl ether with maleic anhydride. In addition to the base polymers, plasticizers were often needed to impart a suitable degree of flexibility. Plasticizers, which are found to be compatible with polymeric materials include, acetylated monoglycerides, esters of phthalic acid such as dibutyl tartarate, etc. An excipient was usually incorporated into the matrix of the carrier films. The excipients used were water-soluble materials, which are capable of creating channels in the polymer matrix and facilitate diffusion of the drug. PEGs of different molecular weights were used for this purpose. 

Examples of aqueous coating solutions include water-soluble low molecular weight cellulose ethers, emulsion polymerization latexes of polymethacrylates, and dispersions of water-insoluble polymers such as ethyl-cellulose in the form of pseudolatex. These solvent-free coating solutions provide a range of different coatings... 

A majority of commercial applications of aqueous developable ceramic compositions use acid-containing polymer binders and dilute aqueous base as a development solution. However, a totally aqueous development system can be formulated with the use of water-soluble polymer binders [22]. Ogawa proposes the use of nonionic water-soluble polymers, such as the cellulose ethers methyl cellulose, hydroxy methyl cellulose, hydroxy ethyl cellulose, and hydroxy propyl cellulose, as the polymeric binder. Molecular weights in the range of 30,000 to 1,(X)0,(X)0 are preferred in these compositions. When... 

Hydroxypropylcellulose is a non-ionic, water-soluble, polyhydroxypropy I cellulose ether that is commercially available in a wide range of molecular weights (50000-1,250,000 g mol ). It is widely used in the pharmaceutical industry as a binder for tablets, in film coatings and as a controlled release matrix (255). 

The simple carbohydrates are rich in hydroxyl groups and are consequently very soluble in water but insoluble in ether. High molecular weight carbohydrates (CdHioO.-,)/, such as starches and cellulose, are insoluble in w atcr as well as in ether. The insolubility of most starches in cold water is controlled also by the physical structure of the starch granules. In hot water, the external membranes of the cells are broken and a colloidal starch solution results. 

MC, HPC and HPMC, nonionic cellulose ethers, are commercially available in powder or granular form, and in varying molecular weights and DS. They are insoluble in hot water but are soluble in cold water and organic solvents (solubilitacion of MC in organic solvents depends of the degree of substitution, under 2.6 DS is partially soluble and upper 2.6 DS is complete soluble). 

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