Study of the formation of structures in solutions of chitosan – polyvinyl alcohol polymer blends

The aim of this work was the investigation of the formation of structures in solutions of individual polymers, as well as their blends with each other in buffer solvents with different values of pH. In this study we used a sample of chitosan (degree of deacetylation ~ 84 %, M = 130,000), which is a polycation when dissolved, and polyvinyl alcohol (r = 1.25 g/cm3, M = 5000). Buffer systems based on acetic acid and sodium acetate with pH = 3.8, 4.25, and 4.75 were used as solvents. Viscosimetry was used to determine the intrinsic viscosity, the degree of structuring, and the Huggins constant. The Kriegbaum method was used to determine the nature of the aggregates formed by the blend of the studied polymers. In the course of the research, it was shown that an increase in the pH of the acetate buffer used as a solvent was accompanied by a compression of the macromolecular coil (a decrease in intrinsic viscosity values), a deterioration in the quality of thesolvent (an increase in Huggins constant values), and an increase in the degree of polymer aggregation in a solution for chitosan polyelectrolyte. At the same time for a solution of polyvinyl alcohol the pH of the buffer practically did not affect the nature of the polymer-solvent interaction. It has been proved that polymer blends are characterized by an increase in aggregation processes and a decrease in the thermodynamic quality of the solvent in comparison with solutions of individual polymers. The size of the “combined” macromolecular coil, characterized by the intrinsic viscosity value for the polymer blend, which can be both above (buffer solvent with pH = 3.80) and below (buffer solvent with pH = 4.25 and 4.75) additivevalues, changed depending on the type of formed polymer-polymer aggregates (homo- or hetero-). It was established that the type of aggregates (homo- or hetero-) formed in solutions of polymer blends was determined not only by the thermodynamic quality of the used solvents, but also by the concentration of the polymers in the initial solutions

PROPERTIES OF DILUTE SOLUTIONS OF COPOLYMERS OF GLYCIDYLMETHACRYLATE AND METHYLPHEOPHORBIDE «a» IN DIMETHYLFORMAMIDE

The study of the rheological properties of polymers, and also the establishment of quantitative dependencies, along with the problem of the relationship of molecular characteristics with the synthesis conditions, is an important scientific and practical task. The solution of this problem gives to predict the behavior of polymers, to develop and find the optimal modes and parameters of obtaining materials with predetermined properties. For a research of chemical interaction between macromolecules in solutions, the dilute solutions rheology of copolymers of glycidylmethacrylate and methylphaeophorbide “a” in dimethylformamide was studied. The study of dilute solutions of the corresponding copolymers was carried out by viscometric method in the temperature range of 20-35 ºC. Copolymers of glycidylmethacrylate and methylphaeophorbide “a” of different composition were obtained by radical copolymerization in solution. The synthesized copolymers are characterized by molecular-weight characteristics determined by gel-permeation chromatography. It is established that the solutions of the copolymers correspond to the systems with the lower critical temperature of dissolution. The belonging of the studied solutions to the systems with the lower critical dissolution temperature is confirmed by the dependence of the Huggins constant on the temperature. From the obtained results it follows that the ball of the macromolecule shrinks with increasing temperature. The influence of solution temperature, molecular weight and composition of copolymers on their interaction with the solvent, expressed quantitatively through the parameters of the characteristic viscosity, the Huggins constant, the mean-square distance between the ends of macromolecular chains, is shown. The mean-square distance between the ends of the chains of polymer in the solution was estimated by the equation of Flory-Fox. It is shown that for the studied copolymers the specific index decreases with increasing temperature. It was determined that the introduction of the porphyrin fragment into the structure of the polymer macromolecule retains the character of the interaction of the macromolecular tangle with the solvent.

Viscometric Study of PC / PEG blends in THF solvent and Gamma-Rays Effect on the Viscosity of PC

In this research the intermolecular interaction between polycarbonate (PC) and polyethyleneglycol (PEG) in tetrahydrofuran (THF) solvent was studied, at 25˚C using a dilute solution viscometry method (DSV). The reduced viscosity and intrinsic viscosity and viscosity interaction parameter (b) were experimentally measured, we also discuss the compatility of a polymer mixture in terms of , and the effect of gamma-rays on the reduced viscosity and intrinsic viscosity and Huggins constant of (PC). The results show that the relation between and C is liner within C=(0.9-2)g/dl, and viscometric constant KH decreases with irradiation time while increases with Tirr. http://dx.doi.org/10.25130/tjps.24.2019.055

Cryostructuring of Polymeric Systems. 49. Unexpected “Kosmotropic-Like” Impact of Organic Chaotropes on Freeze–Thaw-Induced Gelation of PVA in DMSO

Urea (URE) and guanidine hydrochloride (GHC) possessing strong chaotropic properties in aqueous media were added to DMSO solutions of poly(vinyl alcohol) (PVA) to be gelled via freeze–thaw processing. Unexpectedly, it turned out that in the case of the PVA cryotropic gel formation in DMSO medium, the URE and GHC additives caused the opposite effects to those observed in water, i.e., the formation of the PVA cryogels (PVACGs) was strengthened rather than inhibited. Our studies of this phenomenon showed that such “kosmotropic-like” effects were more pronounced for the PVACGs that were formed in DMSO in the presence of URE additives, with the effects being concentration-dependent. The additives also caused significant changes in the macroporous morphology of the cryogels; the commonly observed trend was a decrease in the structural regularity of the additive-containing samples compared to the additive-free gel sample. The viscosity measurements revealed consistent changes in the intrinsic viscosity, Huggins constant, and the excess activation heat of the viscosity caused by the additives. The results obtained evidently point to the urea-induced decrease in the solvation ability of DMSO with respect to PVA. As a result, this effect can be the key factor that is responsible for strengthening the structure formation upon the freeze–thaw gelation of this polymer in DMSO additionally containing additives such as urea, which is capable of competing with PVA for the solvent.

The Properties of Weak Solutions of N-Vinylpyrrolidone and Methyl Methacrylate Copolymers in Dimethylformamide

The rheology of solutions of N-vinylpyrrolidone and methyl methacrylate copolymers in dimethylformamide in the temperature range 20–35°C was studied. The influence of temperature and of the molecular weight and composition of the copolymers on their interaction with the solvent was shown, expressed quantitatively in terms of intrinsic viscosity, the Huggins constant, and the mean square distance between the ends of the macromolecular chains.

Synthesis of star hydrophobically-modified acrylamide copolymers and its some properties in brine

Star copolymers of acrylamide (AM) and N,N-dimethyl-Nvinylnonadecan- 1- aminium chloride (C18DMAAC) were synthesized by photopolymerization in water. Some properties of these star hydrophobically modified acrylamide copolymers (SHMPAM) with different C18DMAAC contents and the linear hydrophobically modified acrylamide copolymers (LHMPAM) in brine were characterized. The increase in C18DMAAC content resulted in decreased intrinsic viscosity and increased Huggins constant for SHMPAM. Similar results were observed for LHMPAM. With similar intrinsic viscosity and C18DMAAC content, the Huggins constant of SHMPAM was much higher than that of LHMPAM, which might be due to the fact that SHMPAM had much stronger intramolecular interaction in dilute polymer solutions. In semi-dilute solutions, the apparent viscosity of SHMPAM was increased with increasing C18DMAAC content, which was similar to that of LHMPAM. However SHMPAM exhibited higher apparent viscosity than LHMPAM because it had more arms and thus had more chances to form three-dimensional networks in semi-dilute solutions. In the flowinduced scission experiment, SHMPAM exhibited superior shear stability in comparison with LHMPAM. When the extensional shear rate was ≈ 40000 s-1, the reduction ratios of the apparent viscosities of the four SHMPAMs after the scission were about 80%. In contrast, when the extensional shear rate was ≈20000 s-1, the reduction ratio of the apparent viscosity of LHMPAM-0.40 had already reached around 80%.

Solution Properties of Cationic Polyacrylamide Modified with Fluorinated Methacrylate

Cationic polyacrylamides modified with fluorinated methacrylate (FPAM) were prepared with acrylamide, dodecafluoroheptyl methacrylate (DFM) and methacryloxyethyl trimethylammonium chloride by free radical micellar copolymerization. The solution properties of FPAM were investigated. The results show that there are strong hydrophobic associations in the FPAM aqueous solution. The intrinsic viscosity decreases and Huggins constant increases with the increase of DFM content. The apparent viscosity of FPAM solution increases with increasing the FPAM concentration both in water and salt solution. There are maximum values of the apparent viscosity of FPAM with addition of sodium chloride, CTAB and sodium dodecyl sulfate (SDS), respectively. Additionally, the FPAM has higher surface activity in salt solution than in water.

Synthesis and solution behaviors of star hydrophobically modified acrylamide copolymers

Star copolymers of acrylamide and N,N-dimethyl-N-vinyl­nonadecan-1-aminium chloride (C18DMAAC) were synthesized by photopolymerization in water. Solution behaviors of these star hydrophobically modified acrylamide copolymers (SHMPAMs) with different C18DMAAC contents and the linear hydrophobically modified acrylamide copolymers (LHMPAMs) were characterized. The increase in C18DMAAC content resulted in decreased intrinsic viscosity and increased the Huggins constant for SHMPAMs. Similar results were observed for LHMPAMs. With similar intrinsic viscosity and C18DMAAC content, the Huggins constant of SHMPAMs was much higher than that of LHMPAMs, which could be due to the fact that SHMPAMs had much stronger intramolecular interaction in dilute polymer solutions. In semi-dilute solutions, the apparent viscosity of SHMPAMs was increased with increasing C18DMAAC content, which was similar to that of LHMPAMs. However, SHMPAMs exhibited higher apparent viscosity than LHMPAMs because it had more arms and thus had more chances to form three-dimensional networks in semi-dilute solutions. In the flow-induced scission experiment, SHMPAMs exhibited superior shear stability in comparison with LHMPAMs. When the strain rate was ≈40,000 s-1, the reduction ratios of the apparent viscosities of the four SHMPAMs after the scission were approximately 80%. By contrast, when the strain rate was ≈20,000 s-1, the reduction ratio of the apparent viscosity of LHMPAM-0.40 had already reached around 80%.

Cellulose Acetate Sulfate as a Lyotropic Liquid Crystalline Polyelectrolyte: Synthesis, Properties, and Application

The optimal conditions of cellulose acetate sulfate (CAS) homogeneous synthesis with the yield of 94–98 wt.% have been determined. CAS was confirmed to have an even distribution of functional groups along the polymer chain. The polymer was characterized by an exceptionally high water solubility (up to 70 wt.%). The isothermal diagrams of its solubility in water-alcohol media have been obtained. CAS aqueous solutions stability, electrolytic, thermal, and viscous properties have been defined. The main hydrodynamic characteristics such as intrinsic viscosity, Huggins constant, and crossover concentration have been evaluated. The parameters of polymer chain thermodynamic rigidity have been calculated. The formation of liquid crystalline structures in concentrated CAS solutions has been confirmed. CAS was recommended to be used as a binder for the medicinal forms of activated carbon and carbon sorbent for water treatment, hydrophilic ointment foundation.