The amino acid esters of hydroxypropyl cellulose (HPC) [R', = H (2a), CH3 (2b), CH2CH(CH3)2 (2c), CH2CONH2 (2d), CH2CH2CONH2 (2c), CH2CH2CH2CH2 NHOCOC(CH3)3 (2f)] were synthesized in good yield by the reaction of t-butoxycarbonyl (t-Boc)-protected amino acids with hydroxy groups of HPC (1; molar substitution (MS), 4.61). The amino acid functionalities displaying varied chemical nature, shape, and bulk were utilized and the bulk of the substituent on the a-carbon of amino acids was elucidated to be of vital significance for the observed degree of incorporation (DSESt,). The H-1 NMR spectra and elemental analysis were employed to determine the degree of incorporation of amino acid moiety (DSEst) and almost complete substitution of the hydroxy protons was revealed for 2a, 2b, and 2f. The presence of the peaks characteristic of the carbonyl group in the FTIR spectra furnished further evidence for the successful esterification of HPC. The starting as well as the resulting polymers (1 and 2a-f) were soluble in polar organic solvents; however, the esterification of 1 with bulky organic moieties resulted in an increased hydrophobicity as all of the amino acid-functionalized polymers (2a-f) were insoluble in water. The onset temperatures of weight loss of 2a-f were 175-230 degrees C, indicating fair thermal stability. The amino acid functionalization led to the enhanced polymer chain stiffness, and the glass transition temperatures of the derivatized polymers were 30-40 degrees C higher than that of 1 (T-g 3.9 degrees C cf. T-g of 2a-f, 35.1-43.3 degrees C). (C) 2008 Wiley Periodicals, Inc.