Capillary Viscometry Research Articles

BIOPHARMACEUTICAL STUDY OF BINARY POLOXAMER SYSTEMS AS IN SITU DRUG DELIVERY SYSTEMS POLOXAMER POLYCOMPLEXES: THE STUDY

Objective: The article presents the results of studying the parameters of in situ systems based on poloxamers. Methods: Natural, synthetic and semi-synthetic polymers were considered as additional gel-forming agents. The above-mentioned agents were cellulose derivatives, as well as rare-cross-linked acrylic polymers, alginic acid salts, and xanthan gum. The gelation temperature was visually recorded during the gradual heating. Mucoadhesion was determined by measuring the separation force of the sample from the mucosal model using pig stomach mucin. The concentration of gel formation was determined using an Ostwald capillary viscometer. Results: During the experiment, 20 samples based on poloxamer 407 18% were examined with the addition of excipients in concentrations of 0.5-2.0%. It was found that the introduction of additional gel-forming agents has a positive effect on the mucoadhesive properties of poloxamer 407. To increase the temperature of gelation of the binary mixture, it is necessary to take into account the own concentration of gelation of the introduced additional polymer, which was confirmed by capillary viscometry. Also, additional viscometric studies revealed the reasons for the absence of a thermoreversible effect in the composition of a poloxamer with xanthan gum and confirmed its use as an excipient in the thermoreversible matrix of poloxamer 407 is impractical. Composition with the best-investigated biopharmaceutical properties-the composition with HEC in a concentration of 0.5% Conclusion: The obtained results can be explained by the fact that when the concentration of additional polymer was exceeded, binary mixtures showed a decrease in the gel formation temperature up to a complete loss of the ability to temperature-dependent sol-gel transition. The choice of an additional gel-forming agent to improve the properties of the system should be based on some specific properties that affect the thermoreversible properties of the system.

Influence of doping additive on thermophysical and rheological properties of halogen-free polymer composition for cable insulation and sheaths

Introduction. The demand for halogen-free fire-resistant compositions for the manufacture of fire-retardant wires and cables is constantly growing. Problem. Therefore, the creation and further processing of these materials is an urgent problem. Goal. The aim of the article is to study the effect of the doping additive on the thermophysical and rheological properties of halogen-free compositions for power cables with voltage 1 kV with the determination of both the temperatures of phase and structural transformations of polymer compositions. Methodology. Experiments investigating the phase transformations were carried out with the help device of thermogravimetric analysis and differential scanning calorimetry TGA/DSC 1/1100 SF of METTLER TOLEDO company. Rheological studies of polymeric materials were conducted by using the method of capillary viscosimetry in the device IIRT–AM. Results. The influence of the doping additive on the formation of the supramolecular structure of the filled polymer compositions for cable products was determined, that resulted in the temperature increase of the decomposition beginning by 11 °С and the end of decomposition by 7 °С. Originality. The effect of a doping additive on reducing the effective melt viscosity of a polymer composition from 6·104 to 1·104 Pa·s with increasing shear rate has been shown for the first time. The shear rate of the polymer composition containing the doping additive increases from 0.5 to 20 s–1 with increasing shear stress. Practical value. The research results provide an opportunity to reasonably approach the development of effective technological processes for the manufacture of the insulation and sheaths of power cables from halogen-free polymer compositions.

Synthesis and gelation properties of HPMC-g-poly(AM/AA/APEG2400) quaternary copolymer

To improve the stability of the polymers applied to profile control in high-temperature and high-salinity reservoirs, a water-soluble graft-copolymer HPMC-g-poly(AM/AA/APEG2400) was synthesized from hydroxypropylmethylcellulose (HPMC), acrylamide (AM), acrylic acid (AA), and allyl polyoxyethylene ether (APEG2400) via free-radical copolymerization using potassium persulfate (KPS) as the initiator. The molecular weight (Mw) of HPMC-g-poly(AM/AA/APEG2400) was controlled by the addition of the chain-transfer agent, sodium formate (SF), to the polymerization medium and was measured by capillary viscometry. Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), proton nuclear magnetic resonance (1H NMR), and scanning electron microscopy (SEM) were performed to characterize the graft-copolymer. The rheological properties of the graft-copolymer were investigated at different salinities and temperatures. The graft-copolymer solution showed better salt resistance, temperature tolerance, and long-term thermal stability than partially hydrolyzed polyacrylamide (HPAM). In addition, hydrogels were prepared using the graft-copolymer with varying Mw (346 × 104–1319 × 104), a crosslinker (hexamethylenetetramine–resorcinol, (HMTA–RC)), and additives (citric acid, (CA), and ammonium phosphate monobasic, (MAP)), and the hydrogels exhibited adequate strength and tunable gelation time. The hydrogels prepared using the graft-copolymer with high Mw possessed excellent long-term stabilities with negligible syneresis at 45 °C after 130 d, for the same conditions, the syneresis of conventional hydrogels prepared by HPAM reached approximately 90%.

Inter-laboratory analysis of cereal beta-glucan extracts of nutritional importance: An evaluation of different methods for determining weight-average molecular weight and molecular weight distribution

In an interlaboratory study we compare different methods to determine the weight-average molecular weight (Mw) and molecular weight distribution of six cereal beta-glucan isolates of nutritional importance. Size-exclusion chromatography (SEC) with multi-angle light scattering (MALS), capillary viscometry, sedimentation velocity analytical ultracentrifugation and one asymmetric flow field-flow fractionation (AF4)-MALS method all yielded similar Mw values for mostly individual chains of dissolved beta-glucan molecules. SEC with post-column calcofluor detection underestimated the Mw of beta-glucan >500 × 103 g/mol. The beta-glucan molecules analysed by these methods were primarily in a random coil conformation as evidenced from individual Mark-Houwink-Kuhn-Sakurada (MHKS) scaling coefficients between 0.5 and 0.6 and Wales-Van Holde ratios between 1.4 and 1.7. In contrast, a second AF4-MALS method yielded much larger Mw values for these same samples indicating the presence and detection of beta-glucan aggregates. Storage of the six beta-glucan solutions in the dark at 4 °C for 4 years revealed them to be stable. This suggests an absence of storage-induced irreversible aggregation phenomena or chain-scission. Shear forces in SEC and the viscometer capillary and hydrostatic pressure in analytical ultracentrifugation probably led to the reversable dissociation of beta-glucan aggregates into molecularly dissolved species. Thus, all these methods yield true weight-average molecular weight values not biased by the presence of aggregates as was the case in one of the AF4 based methods employed.

Interaction of surfactants with poloxamers 338 and its effect on some properties of cream base

The aim. Study of the interaction of surfactants with poloxamer 338 (P338) and the effect of P338 on the properties of cream bases.
 Materials and methods. Solutions of the surfactants and P338 as well as cream bases were under study. The average hydrodynamic diameter (Dh) and zeta potential (ζ‑potential) were determined by the light scattering intensity and electrophoretic mobility of micelles. The electron paramagnetic resonance (EPR) spectra of spin probes in micelles, solvents and bases were obtained; the type of spectrum, isotropic constant (AN), rotational correlation times (τ) and anisotropy parameter (ε) were determined. Liquids and cream bases were studied by capillary and rotational viscometry; the flow behaviour and yield stress (t0), dynamic and apparent viscosity (η) as well as the hysteresis (thixotropic) area (AH) were determined. The microstructure of the bases was examined by optical microscopy. The strength of adhesion (Sm) was assessed by the pull-off test, and the absorption of water was studied by dialysis.
 Results. Under the impact of P338 the hydrodynamic diameters of micelles formed by cationic, anionic and nonionic surfactants decreased as well as the absolute values of their ζ‑potential became lower, but the microviscosity of the micelle nuclei increased. There was also a change in the structure of the aggregates of surfactant with fatty alcohols; EPR spectra, which were superpositions characteristic for the lateral phase separation, converted into triplets that indicated the uniform distribution of lipophilic probes in the surfactant phase. When the content of P338 increased to 17 %, the rheological parameters of the bases increased drastically, the flow behaviour and the microstructure changed. The bases had the consistency of cream within temperature range from 25 °C to 70 °C and completely restored their apparent viscosity, which had decreased under shear stress. P338 enhances the adhesive properties of the bases. Due to their microstructure, cream bases have a lower ability to absorb water compared to a solution and gel containing 17 % and 20 % P338, respectively.
 Conclusions. The structure of surfactant micelles and aggregates of surfactants with fatty alcohols changed under impact of P338 due to the interaction of surfactants with P338. As a result of this interaction, at a sufficiently high concentration of P338, the microstructure and flow behaviour of bases changed, their rheological parameters, which remain high at temperatures from 25 °C to 70 °C, increased significantly, and water absorption parameters decreased. The bases with P338 were more adhesive

Rheological properties of dispersed-filled polymer composite materials based on polyethylene containing glass microbeads

This article presents the results of a study of the effect of the filler content on the rheological properties of polymer composite materials based on high density polyethylene containing glass microbeads. The flow curves of the compositions were obtained by the method of capillary viscosimetry. Simple mathematical models have been constructed that allow estimating the viscosity of the compositions’ melts based on a given filler content.

Effect of heat treatment on conformational and structural properties of sugar beet pectin

The effect of heat treatment on conformational and structural properties of sugar beet pectin (SBP) was investigated using Ubbelohde capillary viscometry and Fourier Transform Infrared (FT-IR) spectroscopy. Intrinsic viscosity, [η], was estimated from the Rao plot for the Fedors-Rao equation, indicating degradation of SBP by heat treatment. The temperature T dependence of [η] for both SBPs in an aqueous solution was studied from T = 30–60°C. The value of [η] was found to decrease with increasing temperature for all samples. This result indicated that the hydrodynamic volume of SBP becomes smaller with increasing T, which could be attributed to an increase in hydrophobic interaction and decreased softening of chain stiffness with increasing temperature. Compositional change due to heat treatment was investigated using FT-IR over the region 4000–400 cm−1, suggesting degradation behavior due to the heat treatment of SBP, which was in agreement with the capillary viscometry results.

Scale-Up of Biosynthesis Process of Bacterial Nanocellulose.

Bacterial nanocellulose (BNC) is a unique product of microbiological synthesis, having a lot of applications among which the most important is biomedicine. Objective complexities in scaling up the biosynthesis of BNC are associated with the nature of microbial producers for which BNC is not the target metabolite, therefore biosynthesis lasts long, with the BNC yield being small. Thus, the BNC scale-up problem has not yet been overcome. Here we performed biosynthesis of three scaled sheets of BNC (each having a surface area of 29,400 cm2, a container volume of 441 L, and a nutrient medium volume of 260 L and characterized them. The static biosynthesis of BNC in a semisynthetic nutrient medium was scaled up using the Medusomyces gisevii Sa-12 symbiotic culture. The experiment was run in duplicate. The BNC pellicle was removed once from the nutrient medium in the first experiment and twice in the second experiment, in which case the inoculum and glucose were not additionally added to the medium. The resultant BNC sheets were characterized by scanning electron microscopy, capillary viscosimetry, infrared spectroscopy, thermomechanical and thermogravimetric analyses. When the nutrient medium was scaled up from 0.1 to 260 L, the elastic modulus of BNC samples increased tenfold and the degree of polymerization 2.5-fold. Besides, we demonstrated that scaled BNC sheets could be removed at least twice from one volume of the nutrient medium, with the yield and quality of BNC remaining the same. Consequently, the world’s largest BNC sheets 210 cm long and 140 cm wide, having a surface area of 29,400 cm2 each (weighing 16.24 to 17.04 kg), have been obtained in which an adult with burns or vast wounds can easily be wrapped. The resultant sheets exhibit a typical architecture of cellulosic fibers that form a spatial 3D structure which refers to individual and extremely important characteristics of BNC. Here we thus demonstrated the scale-up of biosynthesis of BNC with improved properties, and this result was achieved by using the symbiotic culture.

Chemical structure and polymer properties of wheat and cabbage lignins – Valuable biopolymers for biomedical applications

This article presents the features of macromolecular structure of lignins of wheat and cabbage, as well as the relations of lignin structure with practically important properties. The methods of sedimentation-diffusion analysis and capillary viscometry were used to study the hydrodynamic properties of macromolecules in solutions and to reveal the features of topological structure. Molecular mass of the fractions, radii of macromolecules and hydrodynamic invariants were determined. The analysis of the scaling dependences within the framework of Mark-Kuhn-Houwink equation was performed. The molecular hydrodynamic methods showed that wheat lignin is a linear polymer, whereas cabbage lignin is a chaotically weakly branched polymer. These lignins had a high adsorption capacity for various mycotoxins, including mycotoxin T-2. The influence of conformational properties and topology of macromolecules on the mycotoxin T-2 adsorption-desorption characteristics was established. A significant content of phenolic hydroxyl groups provides the high antioxidant activity of cabbage and wheat lignins. Natural lignins from food crops have a significant biomedical potential for creation of new multifunctional drugs with a wide spectrum of activity.

Comparing flow characteristics of viscoelastic liquids in long and short capillaries (entrance effects)

This study is devoted to the analysis of the physical meaning of the difference in the results of the viscosity measurements obtained by using the two-capillary method—carrying on the same flow rate through two circular parallel capillaries of different lengths but the same diameter. Furthermore, there is the other approach for using short capillaries for determination of a value, known as “elongational viscosity,” based on the concept of domination extension at the convergent flow along the inlet of a capillary. The theory of this method dates back to the publication of Cogswell. However, it was shown that this approach is inadequate for polymeric liquids that demonstrate time-dependence effects. In this study, we present experimental data for melts of two polyethylenes of different molecular weights and their mixtures. The data of capillary viscometry are accompanied by measuring their viscoelastic properties. The obtained data showed that the two-capillary method cannot give a chance to estimate “elongational viscosity” for elastic liquids. The difference between the losses in flow through long and short capillaries is treated in the terms of “end correction,” which is determined by the Weissenberg number. Hence, elasticity is the main physical parameter responsible for additional losses in the flow through a short capillary.

Formation of microfibrillar structure of polypropylene/copolyamide blends in the presence of nanoparticles of metal oxides

The influence of nanoparticles made of ifferent metals oxides (ZnO, Al2O3, TiO2, and ZnO/Al2O3) on the in situ formation of microfibrils by the components of a dispersed phase was studied in a thermodynamically incompatible blend of polypropylene/copolyamide (PP/CPA). The viscosity of the melts was determined by capillary viscometry method. Elastic properties were evaluated by the degree of extrudate swelling. The morphology of the compositions was studied by optical polarization microscopy. The method of image analysis was used to quantify the structural characteristics of the blends. It was established that the introduction of 1.0 wt.% of nanoparticles of the studied oxides made from different metals allows tuning the microstructure of the melt of the PP/CPA blend, which is realized in the course of extrusion. More perfect morphology is formed in nanofilled systems: the average diameter of PP microfibrils decreases and their mass fraction increases. The modifying effect of oxide nanoparticles is manifested due to their influence on interfacial phenomena and rheological properties of nanofilled PP melt. The viscosity of the PP melts increases and their elasticity decreases in the presence of nanoparticles of the studied metal oxides. The values of the ratio of the viscoelastic characteristics of the dispersed phase and the matrix in nanofilled systems depend on the nature of oxide and indirectly correlate with the microstructure of the extrudate. As these ratios approach unity, the diameter of PP microfibrils decreases and their share increases. The efficiency of the studied oxides to improve the microfibrillar structure increases in the following series: ZnO, Al2O3, TiO2, ZnO/Al2O3. The obtained results demonstrate the possibility to create the microfiber textile and filter materials with improved consumer characteristics by adjusting the phase morphology of the blends.

A Review of Wood Polymer Composites Rheology and Its Implications for Processing.

Despite the fact that wood polymer composites are interesting materials for many different reasons, they are quite difficult to shape through standard polymer processing techniques, such as extrusion or injection molding. Rheological characterization can be very helpful for understanding the role played by the many variables that are involved in manufacturing and to achieve a good quality final product through an optimized mix of formulation and processing parameters. The main methods that have been used for the rheological characterization of these materials are capillary and parallel plate rheometry. Both are very useful: rotational rheometry is particularly convenient to investigate the compounding phase and obtain structural information on the material, while capillary viscometry is well suited to understand final manufacturing. The results available in the literature at the moment are indeed very interesting and are mostly aimed at investigating the influence of the material formulation, the additives in particular, on the structural, mechanical, and morphological properties of the composite: despite a good number of papers, though, it is difficult to draw general conclusions, as many issues are still debated. The purpose of this article was to overview the state of the art and to highlight the issues that deserve further investigation.

Hydrodynamic Compatibility of Hyaluronic Acid and Tamarind Seed Polysaccharide as Ocular Mucin Supplements.

Hyaluronic acid (HA) has been commonly used in eyedrop formulations due to its viscous lubricating properties even at low concentration, acting as a supplement for ocular mucin (principally MUC5AC) which diminishes with aging in a condition known as Keratoconjunctivitis sicca or “dry eye”. A difficulty has been its short residence time on ocular surfaces due to ocular clearance mechanisms which remove the polysaccharide almost immediately. To prolong its retention time, tamarind seed gum polysaccharide (TSP) is mixed as a helper biopolymer with HA. Here we look at the hydrodynamic characteristics of HA and TSP (weight average molar mass Mw and viscosity ) and then explore the compatibility of these polymers, including the possibility of potentially harmful aggregation effects. The research is based on a novel combination of three methods: sedimentation velocity in the analytical ultracentrifuge (SV-AUC), size-exclusion chromatography coupled to multiangle light scattering (SEC-MALS) and capillary viscometry. HA and TSP were found to have ) kg/mol and ) kg/mol respectively, and and ml/g, respectively. The structure of HA ranges from a rodlike molecule at lower molar masses changing to a random coil for Mw > 800 kg/mol, based on the Mark–Houwink–Kuhn–Sakurada (MHKS) coefficient. TSP, by contrast, is a random coil across the range of molar masses. For the mixed HA-TSP systems, SEC-MALS indicates a weak interaction. However, sedimentation coefficient (s) distributions obtained from SV-AUC measurements together with intrinsic viscosity demonstrated no evidence of any significant aggregation phenomenon, reassuring in terms of eye-drop formulation technology involving these substances.

Pullulan derivative with cationic and hydrophobic moieties as an appropriate macromolecule in the synthesis of nanoparticles for drug delivery

A new amphiphilic pullulan derivative (DBAP-PO) was obtained by grafting tertiary butyl amine and octanoyl groups on the pullulan backbone as cationic and hydrophobic moieties, respectively. The structural characteristics of the modified polymer were investigated by FT-IR and 1H and 13C NMR spectroscopy.The self-association ability in aqueous solution of DBAP-PO was studied by viscosity and fluorescence methods. The intrinsic viscosity of the polymer was determined by Wolf model. The critical aggregation concentration (CAC) value of 0.028 g/dL, determined by fluorescence measurements in the presence of pyrene, was confirmed by capillary viscosimetry and dynamic laser scattering (DLS). Dialysis method was used to demonstrate the capacity of the pullulan derivative to form spherical nanoparticles (d ~ 200 nm) loaded with model drug, sodium diclofenac (DF) (74% entrapment efficiency). The DF release was sustained and pH-dependent. In vitro cytotoxicity as well as morphological studies conducted on the human skin fibroblasts showed that DBAP-PO/DF nanoparticles do not exhibit cytotoxic effects at the pharmacologically relevant concentration of DF, maintaining the typical morphology of the cells.

Synthesis and characterization of highly hydrophilic self-associating terpolymers: Rheological, thermal, and corrosion protection studies

In this study, water-soluble terpolymers containing highly hydrophilic monomers of acrylamide and maleic anhydride and highly hydrophobic monomers of styrene were synthesized (ASM) through the one-step inverse emulsion polymerization. Protonnuclear magnetic resonance (1H NMR), fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction pattern (XRD) were performed to investigate the chemical structures and structural transformations of ASM. Thermal stability and thermal decomposition steps of ASM were studied by thermogravimetric analysis (TGA). An Ubbelhode capillary viscometer and a rheological mechanical spectrometer (RMS) were employed to obtain the specific, relative, and intrinsic viscosities and rheological properties of ASM solutions at different temperatures and in the presence of different concentrations of salts. Gel permeation chromatography (GPC) test and the capillary viscometry method were utilized to obtain the molecular weight of ASM chains. The obtained results showed that the shear viscosity of ASM solutions increased by the increment of the temperature and salts’ concentration. Long-term thermal stability of the ASM solutions was assessed by an aging test in which long-lasting exposure endurance attained and the shear viscosity increased after the thermal aging due to the branching of ASM chains through ring-opening anhydride reactions. Corrosion protection properties of mild steel samples immersed in terpolymer solutions before and after aging at 150 °C were studied via the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests. Corrosion protection properties of solutions were enhanced after the thermal aging. The inhibition efficiency of ASM and thermally aged ASM (A/ASM) were obtained ~52% and ~94%, respectively.

Error amplification in capillary viscometry of power law fluids with slip

Rheological characterization through capillary viscometry of molten polymers that slip at solid walls is quite a challenging task. In fact, it is based on an indirect measurement that introduces remarkable error amplifications, mainly because of the Mooney procedure. Sometimes these are so large that unphysical results are obtained. In this paper we study these issues analytically, using a particular power law fluid as a test model. Interestingly, it is found that there is dependence on the fluid characteristics, such as the shear thinning behavior. Two software programs are provided in the Mendeley Data Repository. One quantifies the error amplification, the other one can be used by interested researchers for properly designing the testing setup (e.g. the most convenient choice for the capillary diameters). In order to use the programs, though, the material constants of the fluid that is intended to be characterized must be known at least approximately.

Physicochemical and rheological properties of aqueous Tara gum solutions

Commercial Tara gum from three sources was purified by precipitation with isopropanol and evaluated on the structural, physicochemical and rheological properties. FT–IR and NMR techniques were used to determine the molecule structure and monosaccharide composition of Tara gum. The physicochemical properties were determined by intrinsic viscosity measurement using capillary viscosimetry and the rheological properties were determined by rotational viscosimetry. The monosaccharide composition of Tara gum galactomannans showed strong influence of their origin, with a mannose/galactose (Man/Gal) ratio varying between 1.54 and 1.85. Intrinsic viscosity of Tara gum in aqueous solution was influenced by its origin and temperature, and it was well correlated to the sigmoidal model. Hydrochloric acid was found to influence intrinsic viscosity below pH 2, however, combined with temperature treatment (80 ∘C), this limit was increased to pH 4. The rheological behavior at diluted concentrations resulted in shear thickening fluid, with an exponential increase of the consistency coefficient with concentration. Apparent viscosity of semi-diluted and concentrated Tara gum aqueous solutions were modeled by the Cross equation, where zero shear viscosity was influenced by gum concentration and temperature, with different activation energies.

Branched architecture of fucoidan characterized by dynamic and static light scattering

Branched architecture of fucoidans (sulfated fucose-rich polysaccharides) gained considerable interest in recent years in view of the effect of this branching on fucoidan’s biological activity. The aim of this work was to characterize the branching architecture of the pristine and hydrolyzed fucoidan macromolecules of the marine seaweed Fucus vesiculosus. We studied the influence of the duration of acidic hydrolysis on the fucoidan macromolecules. The structure-sensitive ratios of macromolecular radii, obtained by dynamic and static (SLS) light scattering, and capillary viscometry corresponded to spherical form of the macromolecules, indicating their branched architecture. The structure-sensitive ratios were analyzed with respect to the molecular weight distributions obtained by size-exclusion chromatography. The Kratky representation of the angular dependences of SLS intensity provided a spectacular evidence for the fucoidans’ branching. For the first time, the fucoidans’ branching was characterized quantitatively by fitting the scattering form factor developed for hyperbranched macromolecules. Under acidic hydrolysis, the molecular mass and size of the fucoidan macromolecules decreased, but the globular form of macromolecules remained unchanged. Upon increasing the time of the acidic hydrolysis, the ζ-potential of the fucoidans changed from − 14 to − 27 mV. The hydrolyzed fucoidans, in turn, exhibited pronounced polyelectrolyte expansion in aqueous solutions when compared with the unhydrolyzed one.

Rheological and Structural Study of Salmon Gelatin with Controlled Molecular Weight.

This study explores the molecular structuring of salmon gelatin (SG) with controlled molecular weight produced from salmon skin, and its relationship with its thermal and rheological properties. SG was produced under different pH conditions to produce samples with well-defined high (SGH), medium (SGM), and low (SGL) molecular weight. These samples were characterized in terms of their molecular weight (MW, capillary viscometry), molecular weight distribution (electrophoresis), amino acid profile, and Raman spectroscopy. These results were correlated with thermal (gelation energy) and rheological properties. SGH presented the higher MW (173 kDa) whereas SGL showed shorter gelatin polymer chains (MW < 65 kDa). Raman spectra and gelation energy suggest that amount of helical structures in gelatin is dependent on the molecular weight, which was well reflected by the higher viscosity and G′ values for SGH. Interestingly, for all the molecular weight and molecular configuration tested, SG behaved as a strong gel (tan δ < 1), despite its low viscosity and low gelation temperature (3–10 °C). Hence, the molecular structuring of SG reflected directly on the thermal and viscosity properties, but not in terms of the viscoelastic strength of gelatin produced. These results give new insights about the relationship among structural features and macromolecular properties (thermal and rheological), which is relevant to design a low viscosity biomaterial with tailored properties for specific applications.

Topological structure and antioxidant properties of macromolecules of lignin of hogweed Heracleum sosnowskyi Manden

This article presents the study of topological and chemical structure of lignin macromolecules isolated from stems of hogweed Heracleum sosnowskyi Manden. The chemical structure was characterized by 13C and 2D NMR-spectroscopy, chemical analysis and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The methods of sedimentation-diffusion analysis and capillary viscometry were used to study the hydrodynamic properties of macromolecules in solutions and to reveal the features of the topological structure. The molecular mass of the fractions, the macromolecular radii and the hydrodynamic invariants were determined. The analysis of the scaling dependences within the framework of Mark-Kuhn-Houwink equation was performed. The obtained results showed that the behavior of hogweed lignin macromolecules corresponded to high-molecular weight compounds with chaotically branched topological structure. It was determined that the hogweed lignin had high antioxidant activity comparable to that of recognized antioxidants. The sorption properties of several lignins were studied and the significant adsorption capacity to T-2 mycotoxin and naturally occurring long-lived thorium radionuclide (Th232) was determined.