Correction of MHS Viscosimetric Constants upon Numerical Simulation of Temperature Induced Degradation Kinetic of Chitosan Solutions

Abstract

Abstract:The Mark-Houwink-Sakurada (MHS) equation allows for estimation of rheological properties, if the molecular weight is known along with good understanding of the polymer conformation. The intrinsic viscosity of a polymer solution is related to the polymer molecular weight according to the MHS equation, where the value of the constants is related to the specific solvent and its concentration. However, MHS constants do not account for other characteristics of the polymeric solutions, i.e., Deacetilation Degree (DD) when the solute is chitosan. In this paper, the degradation of chitosan in different acidic environments by thermal treatment is addressed. In particular, two different solutions are investigated (used as solvent acetic or hydrochloric acid) with different concentrations used for the preparation of chitosan solutions. The samples were treated at different temperatures (4, 30, and 80˝C) and time points (3, 6 and 24 h). Rheological, Gel Permeation Chromatography (GPC), Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analyses (TGA) were performed in order to assess the degradation rate of the polymer backbones. Measured values of molecular weight have been integrated in the simulation of the batch degradation of chitosan solutions for evaluating MHS coefficients to be compared with their corresponding experimental values. Evaluating the relationship between the different parameters used in the preparation of chitosan solutions (e.g., temperature, time, acid type and concentration), and their contribution to the degradation of chitosan backbone, it is important to have a mathematical frame that could account for phenomena involved in polymer degradation that go beyond the solvent-solute combination. Therefore, the goal of the present work is to propose an integration of MHS coefficients for chitosan solutions that contemplate a deacetylation degree for chitosan systems or a more general substitution degree for polymers in which viscosity depends not only on molecular weight and solvent combinations.

A rigid spirocyclic diol from fructose-based 5-hydroxymethylfurfural: synthesis, life-cycle assessment, and polymerization for renewable polyesters and poly(urethane-urea)s

“…For the polyesters with higher S-content (PHST-10, PHST-16 and PHST-19), the a parameter was slightly below 0.5 (0.44-0.48), indicating that these polymers attained compact spherical conformations in chloroform. 82 This observation was consistent with the presence of branching in these polymers. Compared with hyperbranched polymers with a ∼0.16-0.40, 83 the PHST samples had a values closer to 0.5, which qualitatively suggested that they had a lower degree of branching compared with hyperbranched polymers.…”

Chitosan: A Natural Biopolymer with a Wide and Varied Range of Applications

“…Molecular weight [21,22] Gel permeation chromatography [23][24][25] From a chemical viewpoint, chitin is a poly(β-(1-4)-N-acetyl-d-glucosamine) with β(1→4) linkages [1], and it is considered to have a cellulose-like structure, where the hydroxyl group in the C2 position has been replaced by an acetamido group (Figure 1). Depending on the orientation of polysaccharide chains, chitin displays three polymorphs, denoted as α, β and γ [3].…”

“…Deacetylation degree [12,13] Elemental analysis [14] Fourier transform infrared (FTIR) [15][16][17][18] Nuclear magnetic resonance (NMR) [19,20] Viscosimetry Molecular weight [21,22] Gel permeation chromatography [23][24][25] Molecules 2020, 25…”

“…An efficient pervaporation membrane should be characterized by a good mechanical durability, chemical resistance, high selectivity and high permeate rates [181]. Molecules 2020, 25 Taking into account these considerations, chitosan is a hydrophilic material under acid conditions, which can react, through its hydroxyl and amine groups, with several functional groups, such as epoxy groups. The hydrophilic groups can play a key role in the preferential H2O sorption and diffusion through the chitosan membrane.…”

Chitosan, Chitosan Derivatives and their Biomedical Applications

“…Deacetylation degree (DD) Potentiometric titration [27,28] Elemental analysis [29] Fourier transform infrared (FTIR) [30][31][32][33] Nuclear magnetic resonance (NMR) [34][35][36] Molecular weight (MW) Viscometry [37,38] Gel permeation chromatography (GPC) [37,39,40] Biological Activities and Application of Marine Polysaccharidesglutaric acid. The cross-linking of chitosan with glutaraldehyde and sulfosuccinic acid has been used to generate membranes with a good proton conductivity, which makes them useful in fuel cells [44].…”