Synthesis and Properties of Amidoimide Dendrons and Dendronized Cellulose Derivatives

Abstract

First and second generation amidoimide dendrons (G1-a-II−G1-c-II and G2-a-II−G2-c-II) having branched alkyl periphery and focal carboxyl functionality were synthesized via a convergent pathway and incorporated into ethyl cellulose. Dendronized ethyl cellulose derivatives (2a−c, 3a−c) were synthesized in good yield by the reaction of the terminal carboxyl moiety of various dendrons with residual hydroxy groups of ethyl cellulose (1; degree of substitution with ethyl group (DS Et), 2.69). 1H NMR spectra and elemental analysis were employed to determine the degree of esterification (DS Est) of the resulting polymers. The presence of the peak characteristic of the CO group in the FTIR spectra accomplished further evidence for the incorporation of dendritic moieties into ethyl cellulose. All of the derivatives (2a−c, 3a−c) were soluble in chloroform and methanol, and the solubility window narrowed in going from G1- to G2-derivatized polymers. The onset temperatures of weight loss of 2a−c (295−325 °C) and 3a−c (312−320 °C) in air were slightly higher than 294 °C, indicating that the thermal stability was retained upon dendron functionalization. Free-standing membranes of 1 and 2a−c were fabricated, and 2a−c exhibited enhanced permselectivity for He/N2, H2/N2, CO2/N2, and CO2/CH4 gas pairs as compared to 1.

Amino acid‐functionalized ethyl cellulose: Synthesis, characterization, and gas permeation properties

“…50 In our previous studies concerning the dendronization of EC, the presence of polar amide-containing dendritic wedges with bulky and spherical nonpolar periphery has been reported to lead to a considerable decrease in the T g of the polymers. 42 Similarly, the present series of polymers (1-6) is characterized by the presence of polar amino and ester linkages along with fairly bulky and spherical nonpolar periphery, probably the latter being more dominant in the determination of T g . Hence, the substitution of small hydroxy protons by bulkier aminoalkanoyl functionalities has resulted in the lowering of T g in the present series of polymeric materials.…”

“…The DS Et of EC was estimated to be 2.69, by calculating the integration ratio of methyl protons to the rest of the protons in the 1 H NMR spectrum of EC, indicating the presence of 0.31 hydroxy groups per AGU. 40,42,44,45 The 1 H NMR spectral data of amino acid esters of EC (1-6) were obtained to determine the degree of substitution by ester group, namely aminoalkanoyl substituent, (DS Est ) by making an estimation of the peak intensity ratios of the terminal methyl protons of ethyl group of EC and those of t-Boc moieties of the amino acid pendants. The DS Est of amino acid esters of EC, synthesized by using a condensation agent, was discerned to be primarily affected by the bulk of the substituent on the a-carbon of the amino acid moieties, and the residual hydroxy protons of the starting cellulosic were quantitatively substituted only in the t-Boc-protected glycine-and alanine-derivatized polymers (1 and 2: DS Est , 100%).…”

“…In polymeric membranes, the decrement of gas permeability emanating from the introduction of polar substituents due to the reduced free volume inside the polymer matrix is a wellestablished concept. 42,[51][52][53][54][55][56][57] As seen from Table 4, the substitution of small hydroxy protons of EC with relatively bulky and polar aminoalkanoyl substituents resulted in the decreased permeability coefficients for all the gases; for example, the P O 2 and P N 2 of EC are 25 and 7.8 barrers and those observed for its derivatized counterparts were 9.5-13 and 2.4-3.6 barrers, respectively. These trends in the gas permeability of amino acid-functionalized polymers can reasonably be ascribed to the presence of polar (amino and ester) groups resulting in a denser chain packing, leading to the reduced free volume inside the polymer matrix, and in turn lower gas permeability.…”

“…The hydroxy anchors of EC and the carboxy termini of amino acids provide an ample opportunity of bringing about a successful conjunction of the two biocompatible families of materials. Our previous efforts to effect the derivatization of organosoluble cellulosic polymers with a variety of substituents are quite evident of the fact that the tailoring of pendants on the cellulosic backbone results in a significant alteration of solubility, thermal, charge/discharge, and gas permeation characteristics as desired for specific applications 39–45. Hence, amino acid esterification of EC is anticipated to lead to the enhanced CO 2 separation performance, making these materials interesting candidates for gas separation membranes.…”

Synthesis and properties of amino acid esters of hydroxypropyl cellulose

“…The hydroxy anchors of HPC and the carboxy termini of amino acids provide an ample opportunity of bringing about a successful conjunction of the two biocompatible families of materials. Our previous efforts to effect the derivatization of organosoluble cellulosic polymers with a variety of substituents are quite evident of the fact that the tailoring of pendants on the cellulosic backbone results in a significant alteration of solubility characteristics as desired for specific applications 39–42. Hence, amino acid esterification of HPC is anticipated to lead to the modification of solubility and hydrophobicity of the derivatized counterparts, making these materials interesting candidates for hydrophobic drug carriers.…”