Cellulose methyl-, polymerization degree

Vo and Zugenmaier (105) determined the pitch of cellulose tricarbanilate (CTC, D.P. = 100) in 2-pentanone and methyl ethyl ketone (MEK) and ethyl cellulose (EC) in glacial acetic acid as a function of temperature, concentration, solvent, and degree of polymerization. The pitch of the helicoidal structure of CTC/MEK and CTC/2-pentanone is right-handed but EC in glacial acetic acid is left-handed. This is the first report that the substituent will influence the sense of the cholesteric superhelicoidal structure. 

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. 

The reaction is done at a pFl of 9-11. There the hydrolysis of the product chitin is much suppressed. The degree of polymerization of synthetic chitin is some 10-20 depending on the reaction conditions (50). Peracetyloxazolines can be obtained from peracetyl saccharides (51). A facile preparation method of chitin cellulose composite films has been described (52). Hereby ionic liquids are used, l-aUyl-3-methylimidazolium bromide and l-butyl-3-methyl-imidazoUum chloride. The former liquid dissolves chitin and the latter Uquid dissolves cellulose. 

Although certain cellulose esters, such as the ammonium salt of phospho-rylated cotton and cellulose phosphate [9015-14-9], are flame-resistant, the attachment of most currently used durable polymeric flame retardants for cotton is through ether linkage to the cellulose at a relatively low degree of substitution (DS). Nondurable flame retardants based on liquid-or vapor-phase applications of boric acid [10043-35-3] or methyl borate [121-43-7] are used in treatment of cotton batting for upholstery, bedding, and automotive cushions (112-114). Cotton carpet materials will pass the U.S. Consumer Product Safety Commission (CPSC) federal flammability test for carpets (16 CFR1630) when cross-hnked with polycarboxylic acids such as 1,2,3,4-butanetetracarboxylic acid or citric acid with sodium phosphate, sodium hypophosphite, sodium bicarbonate, or sodium carbonate catalysis (115). 

Methylcellulose is a water-soluble cellulose derivative in which approximately 26-33% of the hydroxyl groups are in the form of the methyl ether. The different methylcellu-loses show varying degrees of substitution (between 1.4-2.0) and MW (10,000-220,000 Da) [27]. The solubility, as well as other polymer properties, depends on how uniform the methoxyl groups are distributed along the polymeric chain. In matrix tablets, methylcellulose is normally used in combination with HPMC. 

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