Synthesis, Characterization, and Gas Permeation Properties

143
Chapter5
as shown in Scheme 1, and the results are summarized in Table 1. The amino acid
esters (2a–f) were characterized by 1 H NMR and IR spectroscopy and elemental
analysis. Each anhydroglucose unit (AGU) in HPC (1) possesses one anomeric
proton and each hydroxypropyl group contributes three methyl protons thus its molar
substitution (MS) could be calculated as (ICH3/3)/ IH1, where ICH3 (at 1.04 ppm,
indicated as ‘a’ in Figure 1) and IH1 (at 4.41 ppm, indicated as ‘b’ in Figure 1) are the
peak intensities of the methyl protons and anomeric proton, respectively. The 1 H
NMR spectral data of amino acid esters of HPC (2a–f) were recorded to determine the
degree of incorporation of aminoalkanoyl substituents (DSEst) by making an estimation
of the peak intensity ratios of the terminal methyl protons of hydroxypropyl group (at
≈ 1.04–1.17 ppm, indicated as ‘a’ in Figure 1) and those of t-Boc moieties of the
amino acid pendants (at ≈1.4 ppm, indicated as ‘b’ in Figure 1). The 1 H NMR spectra
of the starting (1) as well as derivatized polymers (2c–e) are shown in Figure 1 and
complete substitution of three hydroxy protons was revealed for the t-Boc-protected
Figure 1. 1 H NMR spectra of polymers 1 and 2c–e.
Labels: a, terminal methyl protons of hydroxypropyl cellulose; b, anomeric
proton of hydroxypropyl cellulose; c, terminal methyl protons derived from the
hydroxypropyl cellulose; d, terminal methyl protons of the t-butoxycarbonyl
moiety.