A NOVEL ORIENTATION TECHNIQUE FOR SEMIRIGID POLYMERS .1. PREPARATION OF CROSS-LINKED CELLULOSE-ACETATE AND HYDROXYPROPYLCELLULOSE FILMS HAVING PERMANENT ANISOTROPY IN THE SWOLLEN STATE

It has been predicted that unusually good mechanical properties can be obtained by drying swollen networks of semi-rigid chains while they are in the deformed state, as described in several theoretical investigations [Macromolecules, 23: 5335, 5341 (1990), 24: 901 (1991)]. The present investigation involves the preparation of networks of this type from cellulose acetate (CA) and hydroxypropylcellulose (HPC), in order to test these concepts. The cross-linking required to maintain anisotropy during the drying process was obtained using formaldehyde, while the polymers were in either the anisotropic or isotropic state. Control of the cross-linking was obtained by studying the effects of the concentration of formaldehyde, temperature, and reaction time.