Thermotropic Behavior of Cholesterol-Linked Polysaccharides V. A. E. SHAIKH, 1 N. N. MALDAR, 1 S. V. LONIKAR, 1 C. R. RAJAN, 2 S. PONRATHNAM 2 1 Shivaji University Centre for Postgraduate Studies, Medical College old Campus, Solapur 413003, India 2 Division of Chemical Engineering, National Chemical Laboratory, Pune 411008, India Received 21 August 1997; accepted 24 March 1998 ABSTRACT: Cholesterol-linked polysaccharides were prepared by reacting monocho- lesterylsuccinate (ChMS) with cellulose acetate [AC; degree of substitution (DS) 1.00, 1.80, and 2.33], ethyl cellulose (EC; DS 2.46), starch, and hydroxyethyl starch (HES; molar substitution, 0.05– 0.07). The degree of ChMS substitution ranged from 0.27 to 1.29. The polymers were characterized by IR, NMR, DSC, and hot-stage coupled polarizing microscopy. Polymers with a higher DS of ChMS showed a thermotropic liquid crystalline behavior. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 195–201, 1998 Key words: thermotropic; polysaccharides; cholesterol; cellulosics; polarizing optical microscopy INTRODUCTION Cellulosic polymers display liquid crystalline properties. The first cellulose derivative reported to exhibit lyotropic liquid crystalline behavior was hydroxypropyl cellulose. 1 Several reviews on cellulosic liquid crystals have appeared. 2–4 Hy- droxypropyl cellulose 5 and its derivatives 6–8 have been shown to be thermotropic materials. Re- cently, mesophase formation in hydroxyethyl cel- lulose acetate 9 and fully decanoated cellulose 10 was reported. Tri-o-benzylcellulose, prepared in a homogeneous medium, with a DP w of 130 showed characteristics of a thermotropic liquid crystal. 11 In all these investigations, the substituents in- troduced onto the cellulose backbone are nonme- sogenic. Here, we report on the synthesis and mesomorphic behavior of monocholesterylsucci- nate derivatives of acetyl cellulose (AC), ethyl cellulose (EC), starch, and hydroxyethyl starch (HES). The effect of the degree of substitution (DS) on the mesomorphic behavior of a monocho- lesterylsuccinate derivative of hydroxyethyl cellu- lose forms the basis of another communication. Cholesterol is important in the field of liquid crys- tals and biological materials. Side-chain liquid crystalline polymers where cholesterol is used as mesogenic units have been reported. 12–14 It is not necessary that the mesogenic group is present at every repeating unit as is indicated by the real- ization of a mesophase in the copolymer of the cholesteryl monomer with nonmesogenic mono- mers. 14 Combined liquid crystalline polymers containing mesogenic units in both the main chain and side chains with the side chains at- tached to rigid rodlike polymer main chain are known. 15 This suggests that introducing a bulky substituent onto a semirigid backbone would not necessarily preclude mesophase formation. The intended application for the monocholesterylsuc- cinate derivatives of polysaccharide is as bile acid/ cholesterol sequestrants. Many studies describe the use of a variety of carbohydrate-derived ma- terials including hydroxypropyl methyl cellulose Correspondence to: S. V. Lonikar. Contract grant sponsor: Department of Science and Tech- nology (DST), New Delhi; contract grant number: SP/S1/G-72/ 90. Journal of Applied Polymer Science, Vol. 70, 195–201 (1998) © 1998 John Wiley & Sons, Inc. CCC 0021-8995/98/010195-07 195