Spectroscopic study of the modification of cellulose with polyethylenimines

Abstract

ABSTRACT:The reaction of cellulose with polyethylenimines (PEIs) was studied using diffuse reflectance ultraviolet-visible (UV-vis) spectroscopy, diffuse reflectance FTIR spectroscopy, and standard colorimetry. PEIs were applied from aqueous solutions at the natural pH (pH ϳ 11) and at pH ϭ 6. The obtained materials were exposed to different thermal treatments in air. Celluloses treated at pH ϭ 11 suffer the reversible formation of amine bicarbonate salts. This reaction was not observed in celluloses treated at pH ϭ 6 because of the protonation of the amine groups. In all treated celluloses, the PEI amine groups reacted with cellulose carbonyl groups at moderate temperatures to form Schiff bases, which were responsible for the yellowing of the material. At higher temperatures other oxidation products were detected in the UV-vis and infrared spectra.

Study of the effects of the reaction conditions on the modification of clays with polyelectrolytes and silanes

“…This result may be explained as a result of the protonation of the amino groups. When the modification is conducted at acid pH, using HCl, most of the amino groups are protonated and the medium intensity band at 1600 cm À1 , characteristic of the free -NH 2 groups, is substituted by a weak absorption at 1512 cm À1 , corresponding to the protonated groups [22]. …”

Doubly crosslinked poly(vinyl amine) microgels: hydrogels of covalently inter-linked cationic microgel particles

“…38 In the case of GMA, the formation of imine groups by reaction of C]O groups with primary amines is possible. 39 The FTIR spectrum for DX PVAM (Fig. S4, ESI †) was similar to that for SX PVAM-GMA (Fig.…”

Modification of electrospun, ultra-thin cellulose fibres by means of polycarboxylic acid–based cross-linking agents

“…This observation can be explained by the fact that the amino-containing units are more inclined to decompose and thus form compounds which decrease the WI values. 44 -46…”