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 (DSEt), 2.69). 1H NMR spectra and elemental analysis were employed to determine the degree of esterification (DSEst) of the resulting polymers. The presence of the peak characteristic of the CO 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.