Crosslinked hydroxypropyl cellulose films retaining cholesteric liquid crystalline order: Part III Tensile creep behaviour in vacuo

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The crosslinked and uncrosslinked hydroxypropyl cellulose solid films retaining the cholesteric liquid crystalline order were cast from the liquid crystalline solutions in methanol. The tensile creep behaviour of the films was determined and the deformability of the films and the size of the liquid crystalline domains in the films were discussed. There was a great difference in the creep behaviour between the crosslinked and uncrosslinked films; both kinds of the films exhibited a linear increase in strain with time, however, only the crosslinked films exhibited a constant region of strain after a given time. The constant strain depended on the crosslinking conditions: The strain decreased with increasing crosslinking agent concentration. The Eyring activation volume (V) could be evaluated. V for the crosslinked films was smaller than that for the uncrosslinked films; V decreased exponentially with increasing crosslinking agent concentration. Our data suggested that the inter-domain crosslinking occurred more or less. There was a critical stress where V changed; V in the lower stress region was greater than that in the higher stress region.

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