Trialkyl cellulose

The dependence of the clearing temperature of trialkyl cellulose on the side-group... 

Figure 24. Dependence of side-group length N on L-and for thermotropic cellulose derivatives trialkyl cellulose , cellulose trialkonates A, trialkylesters of CMC (no mesophase) (adapted from [3]).

Figure 25. Clearing temperature of trialkyl cellulose as a function of carbon number of the side group. Prediction solid curve (adapted from [3]).

On the other hand, literature data show [16] that different cellulose derivatives which form liquid crystalline solutions in organic solvents may also form cholesteric thermotropic phases in the absence of a solvent—with spontaneous molecular orientation and cholesteric reflection, such as 2-acetoxypropyl cellulose, 2-hydroxypropyl cellulose, the trifluoroacetate ester of hydroxypropyl cellulose, the propanoate ester of hydroxypropyl cellulose, the benzoate ester of hydroxypropyl cellulose, 2-ethoxypropyl cellulose, acetoacetoxypropyl cellulose, trifluoroacetoxypropyl cellulose, the phenylac-etate and 3-phenylpropionate of hydroxypropyl cellulose, phenylacetoxy, 4-methoxy-phenylacetoxy, p-tolylacetoxy cellulose, trimethylsilyl cellulose, trialkyl cellulose, cellulose trialkanoate, the trialkyl ester of (tri-o-carboxymethyl) cellulose, 6-o-a-(l-methylnaphthalene)-2,3-o-pentyl cellulose, etc. Moreover, the suspensions of cellulose crystallites spontaneously form the chiral nematic phase. The formation of mesophase suspension of cellulose crystalHtes varies from one type of cellulose to another, being influenced, in the formation of the chiral nematic phase, by the mineral acid selected... 

This class of ceUulose derivatives has attracted the attention of investigators because of their specific properti, primarily tl ir increased hydrophobicity. There is, however, a seriom dmwback, tyjrical rf most silicon-containing cellulose esters prepared by the action of trialkyl-chlorosilanes, namely, the low stability of tl C-O-Si bond to hydrolysis. One way of overcoming this difficulty is to increase the length of the organosilicon radical. 

Figure 24. Dependence of side-group length N on T and for thermotropic cellulose derivatives trialkyl...

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