Search Results (4)

Marine algae are a valuable source of polysaccharides. However, the information available on sulfated polysaccharides from microalgae is limited. Navicula sp. is a microalga present in the Sea of Cortez, of which little is known regarding their polysaccharides’ properties. This study investigated the physicochemical and microstructural characteristics of Navicula sp. sulfated polysaccharide (NSP). The Fourier transform infrared spectrum of NSP showed distinctive bands (1225 and 820 cm⁻¹, assigned to S–O and C–O–S stretching, respectively), confirming the molecular identity. NSP registered molecular weight, intrinsic viscosity, a radius of gyration, and a hydrodynamic radius of 1650 kDa, 197 mL/g, 61 nm, and 36 nm, respectively. The zeta potential, electrophoretic mobility, conductivity, and diffusion coefficient of the molecule were −5.8 mV, −0.45 µm cm/s V, 0.70 mS/cm, and 2.9 × 10⁻⁹ cm²/s, respectively. The characteristic ratio and persistence length calculated for NSP were 4.2 and 1.3 nm, suggesting a nonstiff polysaccharide chain conformation. The Mark–Houwink–Sakurada α and K constants were 0.5 and 1.67 × 10⁻¹, respectively, indicating a molecular random coil structure. NSP scanning electron microscopy revealed a rough and porous surface. Knowing these polysaccharides’ physicochemical and microstructural characteristics can be the starting point for elucidating their structure–function relationship as a valuable tool in advanced biomaterial design. Full article

The effect of partial acid hydrolysis on the physical and chemical properties of galactomannan, arabinoxylan, and xyloglucan was investigated. Polysaccharides were treated at 50 °C with hydrochloric acid for 3–48 h. Portions of isopropanol (i-PrOH) were added sequentially to the hydrolyzates, resulting in fractions that were collected by centrifugation. As expected, a significant reduction of weight-average molecular weight (M_w) was observed with increasing hydrolysis time. Fractional precipitation was successfully applied to collect at least one polymer fraction with dispersity (Đ) close to one for each polysaccharide. The monosaccharide composition analysis showed that the partial hydrolysis usually lowered the relative amount of side chains, with the exception of galactomannan, where the composition remained largely unaffected. Estimation of the polymer conformation in solution, through evaluation of the Mark-Houwink parameter coefficient (α), confirmed that acid hydrolysis influenced the polysaccharides’ conformation. It was demonstrated that acid treatment in dilute solution followed by fractional isopropanol precipitation is a method, extendible to a variety of polysaccharides, to obtain materials of decreased molecular weight and low dispersity with slightly altered overall composition and conformation. Full article

The interrelation of experimental rotational and translational hydrodynamic friction data as a basis for the study of macromolecules in solution represents a useful attempt for the verification of hydrodynamic information. Such interrelation originates from the basic development of colloid and macromolecular science and has proven to be a powerful tool for the study of naturally- and synthetically-based, i.e., artificial, macromolecules. In this tutorial review, we introduce this very basic concept with a brief historical background, the governing physical principles, and guidelines for anyone making use of it. This is because very often data to determine such an interrelation are available and it only takes a set of simple equations for it to be established. We exemplify this with data collected over recent years, focused primarily on water-based macromolecular systems and with relevance for pharmaceutical applications. We conclude with future incentives and opportunities for verifying an advanced design and tailored properties of natural/synthetic macromolecular materials in a dispersed or dissolved manner, i.e., in solution. Particular importance for the here outlined concept emanates from the situation that the classical scaling relationships of Kuhn–Mark–Houwink–Sakurada, most frequently applied in macromolecular science, are fulfilled, once the hydrodynamic invariant and/or sedimentation parameter are established. However, the hydrodynamic invariant and sedimentation parameter concept do not require a series of molar masses for their establishment and can help in the verification of a sound estimation of molar mass values of macromolecules. Full article

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. Full article