Synthesis, Characterization, and Gas Permeation Properties

Conclusions
Table 3. Thermal Properties of Polymers 1 and 2a–f
polymer T0 a (°C) Tg b (°C)
1 311 3.9
2a 222 35.1
2b 180 43.3
2c 230 36.9
2d 212 42.0
2e 184 39.5
2f 175 43.2
149
Chapter5
a T0: Onset temperature of weight loss. Determined from TGA measurement in air.
b Tg: Glass transition temperature. Determined by DSC analysis under nitrogen.
The present study is concerned with the synthesis of a series of t-Boc protected
amino acid esters of hydroxypropyl cellulose (2a: DSEst, 3.0; 2b: DSEst, 3.0; 2c: DSEst,
1.1; 2d: DSEst, 1.0; 2e: DSEst, 1.7; and 2f: DSEst, 3.0) delineating an approach to
transform the hydrophobicity and thermal characteristics of an organosoluble
cellulosic. The use of EDC·HCl as a condensating agent in the presence of DMAP
has been demonstrated to accomplish a facile mode of amino acid esterification of 1
without any polymer chain cleavage in the course of the reaction. The bulk of the
substituent on the α-carbon of the amino acid pendants was revealed to be the most
significant parameter effecting the extent of substitution of the hydroxy protons of
hydroxypropyl cellulose (1: MS, 4.61). The complete incorporation of amino acid
functionalities (DSEst ≈ 3.0) was observed for t-Boc protected glycine, alanine, and
lysine groups as evidenced by the 1 H NMR and confirmed by elemental analysis.
The derivatized polymers displayed good solubility in common organic solvents and
were insoluble in water. Good thermal stability was revealed and initiation of weight
loss was elucidated to ensue from for the degradation of t-butyl moieties around
175–230 °C under air. The amino acid functionalization of HPC accompanied a