Synthesis and characterization of a trifunctional aminoamide cellulose derivative

As part of an effort to synthesize a dendronized cellulose, we have synthesized a trifunctional aminoamide derivative, which is the first generation of a dendron substituent. We anticipate that a dendronized cellulose would have applications in complexing metals and could be employed as an adjuvant for drugs. The trifunctional aminoamide substituent was introduced by coupling di-tert-butyl 4-[2-(tert-butoxycarbonyl)ethyl]-4-aminoheptanedicarboxylate, BA, directly to a (carboxymethyl)cellulose (CMC) backbone and converting the tert-butyl ester peripheral groups to aminoamide substituents by use of N,N-dimethyl-1,3-propanediamine. Confirmation of the proposed chemical structure of the intermediates as well as the water-soluble aminoamide derivative (CMCBADMPDA) was obtained by Fourier transform infrared (FT-IR) and NMR spectroscopy. The degree of substitution (DS) was determined to be 0.40 +/- 0.01 by thermogravimetric analysis. Typical weight average molecular weight (M(w)), molecular weight distribution (MWD), and molecular size of the dendronized polymers were found to be 97,000, 1.7, and 17.4 nm for derivatives of a CMC with corresponding M(w), MWD, and root-mean-square radius (RMS) of 230 000, 3.2, and 24 nm. A differential refractive index (dn/dc) for the aminoamide derivative measured in aqueous 0.40 N ammonium acetate-0.01 N NaOH was found to be 0.1473. The intrinsic viscosity of the dendronized cellulose decreased significantly when compared with that of CMC, that is, 0.40 dL/g relative to 5.60 dL/g. The hydrophobicity of the CMCBADMPDA microenvironment in aqueous solution was probed by evaluating the relative fluorescence intensities of the I(373)/I(384) pyrene bands; a slightly more hydrophobic environment was observed.