Valorization of arabinoxylans from Linum usitatissimum (flaxseed) and galactomannans from Leucaena leucocephala (subabul) to develop hybrid hydrogels: Rheological, morphological and thermal characterization

Abstract

The present investigation was aimed at preparing hydrogels from galactomannans extracted from the defatted seeds of Leucaena leucocephala (subabul) (SGM) and κ-carrageenan (кC) in an aqueous phase (pH 6.8) using KCl as ionic crosslinker. The dynamic moduli (G’ and G”) and Power law parameters (n’ and n”) of the hydrogels were optimized through full factorial design (CCD). The optimized hydrogel was prepared with SGM (6.5% w/v) and кC (1% w/v) in the presence of KCl (0.63% w/v) (GA1). A hybrid hydrogel using a combination of SGM and crude arabinoxylan from flaxseed (FX) was also optimized similarly as GA1. The optimized hybrid hydrogel was composed of FX (1% w/w), SGM (5.5% w/v), and кC (1.32% w/v) crosslinked with 0.25% w/v KCl (GAX). GAX showed higher dynamic moduli (G’-2871 Pa, G”-1711 Pa) than GA1 (G’-2589 Pa and G”-1399 Pa) due to the formation of stable interpenetrating polymer network between the hydrogel components. The structural (NMR (1H), FTIR), morphological (SEM), rheological as well as thermal studies confirmed superior characteristics of GAX than GA1. This was also evident from high gel strength (2019 N) and increased firmness (1231 N.s) of GAX. GAX also exhibited 389% water uptake ratio (q) at neutral pH and 45 ℃, and did not show any syneresis for 72 h at 4 ℃. The synergistic amalgamation of a galactomannan from a forest resource and an arabinoxylan from flaxseed processing byproduct not only valorizes them but also enables the development of a self-stable hydrogel that can find far reaching applications in various industrial sectors.