Synthesis and physicochemical characterization of a novel ampholytic pullulan derivative with amphiphilic behavior in alkaline media

Pullulan derivative was synthesized by coupling carboxymethylpullulan (degree of substitution DS0in=0.7) and dimethylaminopropylamine (DMAPA), activated by a hydrosoluble carbodiimide N′N′-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDAC). FTIR and 13C and 1H NMR spectroscopic analyses have evidenced that the polysaccharide has been successfully modified. 1H NMR, nitrogen analysis, and conductimetric measurements allow determination of the degree of substitution in both carboxylic acid and amine functions. We have found that both functions present a similar DS of 0.35, which is characteristic of an ampholytic polymer with possible zwitterionic-type properties. Solution properties have been studied by flow field flow fractionation (F4) coupled on-line with multiangle laser light scattering (MALLS) and quasi elastic light scattering (QELS), surface tension, and viscosity measurements. The behavior has been found largely pH dependent and an amphiphilic behavior has been evidenced in alkaline media.

Graphical abstractPolyampholyte pullulan derivative (DMAP-CMP) was synthesized by coupling carboxymethylpullulan and dimethylaminopropylamine (DMAPA). As a result, the obtained derivative presents the same amount of carboxymethyl and amino functions (i.e., DS=0.35DS=0.35). Solution properties have been found largely pH dependent and an amphiphilic behavior has been evidenced in alkaline media. Surface tension (equilibrated γ  ) versus pH for DMAP-CMP in pure water. Cp=2 gL−1, T=25°C.Figure optionsDownload full-size imageDownload as PowerPoint slide