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). H-1 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 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 degrees C and 3a - c (312 - 320 degrees C) in air were slightly higher than 294 degrees C, indicating that the thermal stability was retained upon dendron functionalization. Free-standing membranes of I and 2a - c were fabricated, and 2a - c exhibited enhanced permselectivity for He/N-2, H-2/N-2, CO2/N-2, and CO2/CH4 gas pairs as compared to 1.