Comblike Complexes of Poly(itaconic acid) and Poly(mono methyl itaconate) and Alkyltrimethylamonium Cationic Surfactants

Preparation and thermal stability of carboxymethyl starch/quaternary ammonium salts complexes

“…3, only the signals corresponding to the surfactant fragment could be clearly appreciated when the spectra were taken in DMSO-d 6 at room temperature. This difficulty to perform NMR analysis from starch derivates has been previously reported when the product is not subjected to an additional chemical treatment, and may be attributed to a restricted mobility of the starch backbone, as well as to the conformation of the complex in solution, orienting their hydrophobic moieties towards the solvent; similar results have been published for systems such as poly(itaconic acid)/QAS or poly(methyl monoitaconate)/QAS (Báez, Jiménez, Laredo, García, Martínez, & López-Carrasquero, 2007). In spite of this limitation, the combined analysis of the 13 C NMR spectra together with DEPT 135 allowed us to confirm the presence of the alkyl chain within the starch molecule, as it is indicated in the spectrum, where the signals were assigned to the different carbons of the complex.…”

“…Therefore, we took a sample of the system in which the highest DS* was obtained, CMS 0.30 /C 18 TAB (1:1), and it was investigated by differential scanning calorimetry and wide angle X-ray diffraction. Previous studies on the crystallization of polyelectrolyte/QAS ionic complexes have shown that the alkyl chains of the surfactants are able to crystallize when they reach a minimum length, which changes depending on the system that is being investigated (Báez, Jiménez, Laredo, García, Martínez, & López-Carrasquero, 2007;López-Carrasquero et al, 2006); nevertheless, their transitions appear at temperatures that are markedly depressed compared with the free surfactant. The DSC heating scans obtained for CMS 0.30 /C 18 TAB (1:1) and C 18 TAB as reference (results not shown here) demonstrated that complexes with shorter alkyl chains did not show any crystallization under the conditions explored.…”