Relationships Between Average Molecular Mass and Intrinsic viscosity of Three Typical Polyanhydrides

Aim To study the relationships between average molecular mass and intrinsic viscosity of polyanhydrides. Methods With chloroform as solvent and petroleum ether as the precipitating agent polyanhydride was separated into a series of grades with different average molecular mass. The absolute average molecular mass (M) and intrinsic viscosity ([]) of every grade were measured. Results and Conclusion The relationships between [] and M of three typical polyanhydrides were obtained from bi-logarithm coordinate plotting of [] versus M.

STUDIES ON RELATION BETWEEN INTRINSIC VISCOSITY OF POLYELECTROLYTES IN SOLUTIONS USED FOR LAYER-BY-LAYER SELFASSEMBLY AND THEIR CORRESPONDING ADSORPTION AMOUNTS IN THE RESULTANT MULTILAYER MEMBRANES

The adsorption amount of poly(styrene sulfonate) and poly(dimethyldiallyl ammonium chloride) (PSS/PDDA) self-assembled multilayer membranes in designed dipping solvents were measured by UV-Vis-spectroscopy and quartz crystal microbalance (QCM). Intrinsic viscosities of PSS and PDDA in corresponding dipping solvents were determined by an Ubbelohde viscometer. It is found that the adsorption amount of PSS/PDDA self-assembled multilayer membranes built up in different dipping solutions, added salt concentration, pH of solution and solvent quality, respectively changed oppositely with the corresponding intrinsic viscosity of PSS and PDDA in dipping solvents. A negative relation between the adsorption amount and intrinsic viscosity was revealed, and explained in term of the concept of excluded volume of polymer molecule in dilute solutions.

Intrinsic viscosity of polymer solutions: fresh ideas to an old problem

Intrinsic viscosity is one of the most fundamental properties of dilute polymer solutions; its study forms an integral part of the cornerstone of the modern macromolecular theory. However, a general theory applicable to any chain architectures and solvent conditions has remained elusive, due to the formidable challenges in the theoretical treatment of the long-range, many-body and accumulative hydrodynamic effects. Recently, Lijia An and coworkers at the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, has developed a new approach that largely overcomes these challenges. Their new theory provides a simple and unified theoretical framework for describing the intrinsic viscosity of polymers with arbitrary architectures under any solvent conditions and forms the theoretical basis for inferring the polymer chain structure from intrinsic viscosity measurements. Comparisons with existing experimental data yield extensive, quantitative agreement.

Introduction of a Reliable Method for Determination of Intrinsic Viscosity for Any Polymer with High Precision

Intrinsic viscosities for a given polyelectrolyte in salt free and low-salt solvents reported in literatures are normally not comparable, because of inadequate valuation procedures. This article describes a theoretically justified reliable method, which is free of any model assumptions： The so called Wolf plot （logarithm of the relative viscosity as a function of polymer concentration） enables the unequivocal determination of intrinsic viscosities for all kinds of macromolecules, irrespective of whether they are chain molecules of different architecture or globular polymers, whether they are charged or uncharged. The validation of the method was examined by evaluation of the viscosities of a polyelectrolyte, some uncharged polymers of different architectures, uncharged polymer blends, and some literature data.

VISCOSITY BEHAVIOR OF LACQUER POLYSACCHARIDE IN AQUEOUS SOLUTION

The dependence of measured viscosity on NaCl concentration (0.1 to 3.0M), pH (range of 2—13) and cadoxen composition w_(cad) (from 2% to 100%) for the lacquer polysaccharide in NaCl/cadoxen/H_2O mixture containing HCl or without were obtained. All the viscosity exponents γ in the Mark-Houwink equations under three different solvent condition arc close to 0.5. The w_(cad) dependence of reduced viscosity ηsp/c confirms the single strand chain of the polysaccharide. As the γ values close to 0.5 and values of unperturbed dimension <S^2>_θ/M and [η] much smaller than those for usual linear polymers, these facts suggest that the polysaccharide chains in the aqueous solutions should be dense random coil owing to the highly branched structure.

CLAY CATALYZED SYNTHESIS OF BIO-DEGRADABLE POLY(GLYCOLIC ACID)

Glycolic acid was polymerized under vacuum in the presence and absence of nano sized clay.The added clay catalyzed the condensation polymerization which can be confirmed by recording FTIR spectroscopy and intrinsic viscosity (Ⅳ)values.The relative intensity of C=O/CH is increased while increasing the amount of clay.DSC showed the appearance of multiple endotherms of poly(glycolic acid).TGA showed the percentage weight residue remain above 750℃for polymer-nano composite system was 21% and hence proved the fl...

Stannous oxalate as a novel catalyst for the synthesis of polytrimethylene terephthalate

Stannous oxalate was prepared efficiently and characterized by XRD and FT-IR. It exhibited higher catalytic activity and had profitable effect than tetrabutyl titanate and stannous octoate for the synthesis of polytrimethylene terephthalate （PTT） via esterification-route. Over this catalyst, the degree of esterification of pure terephthalic acid was up to 94.4% at 260 ℃ after 1.5 h,while the intrinsic viscosity and content of terminal carboxyl groups of the corresponding PTT polyester, polymerized at 260 ℃,60 Pa for 2 h, was 0.8950 dL/g and 15 mol/t, respectively. Stannous oxalate was a promising catalyst for the synthesis of PTT polyester.

VISCOMETRIC INVESTIGATIONS OF POLYVINYLPYRROLIDONE IN MIXED SOLVENTS AND WITH VARYING TEMPERATURE

The viscosity behavior of polyvinylpyrrolidone(PVP)has been determined at 25℃ in mixed solvents comprising water/dimethylformamide(DMF)and water/methanol(MeOH).Analysis of the data has considered the PVP as being both host and guest polymer in solution.The intrinsic viscosity of PVP in DMF is higher than in water and in MeOH,but also increases in a mixed solvent with high water content because of the effect of polymer-solvent interactions.It was also found that the intrinsic viscosity of PVP at finite concentration,[η_(pvp)]_c decreases with an increase in the concentration of PVP in solution.The viscosity behavior of PVP in a mixed solvent is affected by the concentration-dependent intermolecular excluded volume effect,which can be quantitatively expressed by the parameter,b_Y,which reflects the shrinkage of PVP chain coils,resulting in a decrease of[η_(pvp)]_c.The effect of temperature on the viscosity behavior of PVP in MeOH shows that the interaction parameter increases up to a maximum value,and then decreases after a certain temperature.

Mechanochemical degradation of potato starch paste under ultrasonic irradiation

In the paper, changes in the molecular weight, the intrinsic viscosity and the polydispersity (molecular mass distribution) of treated potato starch paste were studied under different ultrasonic conditions which include irradiation time, ultrasonic intensity, potato starch paste concentration, and distance from probe tip on the degradation of potato starch paste. Intrinsic viscosity of potato starch paste was determined following the ASTM (American Society for Testing and Materials) standard practice for dilute solution viscosity of polymers. Molecular mass and polydispersity of potato starch paste were measured on GPC (Gel Permeation Chromatography). The results showed that the average molecular mass and the intrinsic viscosity of starch strongly depended on irradiation time. Degradation increased with prolonged ultrasonic irradiation time, and the increase of ultrasonic intensity could accelerate the degradation, resulting in a faster degradation rate, a lower limiting value and a higher degradation extent. Starch samples were degraded faster in dilute solutions than in concentrated solutions. The molecular mass and the intrinsic viscosity of starch increased with the increase of distance from probe tip. Our results also showed that the polydispersity decreased with ultrasonic irradiation under all ultrasonic conditions. Ultrasonic degradation of potato starch paste occured based on the mechanism of molecular relaxation of starch paste. In the initial stage, ultrasonic degradation of potato starch paste was a random process, and the molecular mass distribution was broad. After that, ultrasonic degradation of potato starch paste changed to a nonrandom process, and the molecular mass distribution became narrower. Finally, molecular mass distribution tended toward a saturation value.

A NEW TYPE LOW SHEAR RATE VISCOMETER FOR HIGH MOLECULAR WEIGHT POLYMER

In this paper, the effects of shear rate on the intrinsic viscosity measurement of partially Hydrolysed Polyacrylamide (HPAM) in salt solution were studied with homemade multibulb viscometer and low shear rate rheometer. The critical shear rate of HPAM in salt solution for high molecular weight HPAM was determined. A low shear rate capillary viscometer was designed in which the [eta] approached to value at zero shear rate can be obtained for HPAM -salt system. The effect of molecular weight on shear rate dependence of viscosity was also studied.

EFFECT OF THE COMPOSITION OF m-CRESOL/H_2O SOLVENT ON HYDRODYNAMIC PROPERTIES OF NYLON 6

The intrinsic viscosity [η], Huggins constant （Ku）, [η]0, α^3 and flow activation energy values of nylon 6 have been measured in wateηm-cresol （0/100-20/80） systems at different temperatures （20-60℃）. It has been found that the intrinsic viscosity, [η]0 and α^3 increase with the increase in water contents in m-cresol up to 15% and then decrease. They increase with the increase in temperature irrespective of solvent composition. It has been noted that the percent increase of α^3 is the highest at 60℃ and the lowest at 20℃ for a particular solvent system. The intrinsic viscosity data obey Arrhenius equation over the considered conditions. The activation energy and the KH values decrease very sharply with the addition of water, giving a minimum value at 15% of water and then increase slowly. The variation of all the parameters has been explained in terms of variation in thermodynamic quality of solvent with the addition of water to m-cresol and change in temperature, resulting in the change of conformational and orientational properties of polymer molecules. This change of solvent quality also results in variation of selective sorption of solvent over the polymer, such as hydrogen bonding, etc.

SOLVENT QUALITY AND SOLUTION BEHAVIOR OF NYLON 12

The refractive index increment, dynamic and static laser light scattering, intrinsic viscosity [η] and Huggins constant （KH） of nylon 12 have been measured in m-cresol and sulphuric acid/water system at 10-60℃. The intrinsic viscosity, Rn, Rg, A2, and （〈 S 〉2）^1/2 （calculated from viscosity data） and ＂a＂ values of nylon 12 are found to be higher in m-cresol than in sulphuric acid. All these parameters decrease with the increase in water contents in sulphuric acid. The refractive index increment, KH and activation energy show an opposite trend to that of [η]. The intrinsic viscosity, RH, Rg, A2, and （〈 S 〉2）^1/2 have maximum values around 30-40℃ in sulphuric acid/water system, whereas in m-cresol they fall at about 20℃. It has been concluded that the variation in size, interaction parameter （second virial coefficient）, [η] and KH of the polymer solutions with the alteration in solvent composition and temperature are the out come of change in thermodynamic quality of solvents, selective adsorption, hydrogen bonding and conformational transitions. It has also been concluded that the increase in temperature first enhances the quality of the solvent, encourages hydrogen bonding and specific adsorption, and then deteriorates, bringing conformational transitions in the polymer molecules. However, the addition of water to sulphuric acid continuously deteriorates the solvent quality. This characteristic of the solvent system brings conformational changes in the polymer especially at low temperatures.

INTERACTION OF POLYVINYLPYRROLIDONE WITH METAL CHLORIDE AQUEOUS SOLUTIONS

Interactions of polyvinylpyrrolidone (PVP) with metal chlorides (MgCl 2 , CaCl 2 , KCl and BaCl 2 ) have been investigated by viscometric and spectrophotometric techniques in aqueous solutions. Intrinsic viscosity [η] of (PVP) has shown a discontinuity with varying concentration of metal chlorides. The decreasing order of effectiveness of cation is K 1+ > Ca 2+ > Mg 2+ > Ba 2+ for poly(vinylpyrrolidone) solution. Changes in the absorption spectra of the cosolutes were observed in the presence of PVP in the lower limit of the UV-visible region i.e. 200-210 nm. These changes were attributed to interaction of PVP molecules with the cosolute molecules. As the concentration of the cosolute increased, a red shift in the peaks was observed, indicating an increase in interaction between PVP and cosolutes.

ITSTUDIES ON THE EFFECT OF UREA ON THE COMPATIBILITY OF PMMA/PVC MIXTURES IN DMF BY A DILUTE- SOLUTION VISCOMETRY METHOD

The interaction between poly(methymethacrylate) (PMMA) and poly(vinyl chloride) (PVC) has been studied indilute urea solutions of dimethylformamide (DMF) at 28℃ using a dilute solution viscometry method. The results show thatthe polymer mixtures are compatible in DMF solution in the absence of urea. The influence of urea addition on the degree ofcompatibility of the polymer mixtures has been studied in terms of the compatibility parameters (△b_m and △[η]_m). It wasfound that the compatibility of the polymer mixtures is decreased with increasing urea addition, passing through a minimumat 0.5 M urea.

Solution Properties of Soy Protein in DMSO/Urea Solvent System

Solution properties of 7S globulins (7S), 11S globulins (11S) and soy protein isolates (SPI) in dimethylsulfoxide (DMSO)/urea solvent system were studied by intrinsic viscosity and particle size distributions. The results showed that the existence of urea was the main reason for the denaturation and solubility of soy protein in the system, and the effects were more obvious with increasing of urea concentration in solutions. Suitably dissolution temperature and time contributed to the solubility of soy proteins.

Sulfur polymerization strategy based on the intrinsic properties of polymers for advanced binder-free and high-sulfur-content Li–S batteries

Lithium-sulfur(Li-S)batteries are the promising next-generation secondary energy storage systems,because of their advantages of high energy density and environmental friendliness.Among numerous cathode materials,organosulfur polymer materials have received extensive attentions because of their controllable structure and uniform sulfur distribution.However,the sulfur content of most organosulfur polymer cathodes is limited(S content<60%)due to the addition of large amounts of conductive agents and binders,which adversely affects the energy density of Li-S batteries.Herein,a hyperbranched sulfur-rich polymer based on modified polyethyleneimine(Ath-PEI)named carbon nanotubeentangled poly(allyl-terminated hyperbranched ethyleneimine-random-sulfur)(CNT/Ath-PEI@S)was prepared by sulfur polymerization and used as a Li-S battery cathode.The high intrinsic viscosity of Ath-PEI provided considerable adhesion and avoided the addition of PVDF binder,thereby increasing the sulfur content of cathodes to 75%.Moreover,considering the uniform distribution of elemental sulfur by the polymer,the utilization of sulfur was successfully improved,thus improving the rate capability and discharge capacity of the battery.The binder-free,sulfur-rich polymer cathode exhibited ultra-high initial discharge capacity(1520.7 mAh g^(−1) at 0.1 C),and high rate capability(804 mAh g^(−1) at 2.0 C).And cell-level calculations show that the electrode exhibits an initial capacity of 942.3 mAh g^(−1) electrode,which is much higher than those of conventional sulfur-polymer electrodes reported in the literature.

Dynamics Simulation on the Associative Properties of Amphiphilic Functional Monomer Modified Polyacrylamide Copolymers

A kind of amphiphilic functional monomer was selected to modify polyacrylamide （PAM） or partially hydrolyzed polyacrylamide （HPAM）. The relative properties of the modified polyacrylamide （HM-PAM） and modified partially hydrolyzed polyacrylamide （HM-HPAM） such as radius of gyration （Rg）, hydrodynamic radius （RH）, and radial distribution functions （RDFs） have been studied to find the intrinsic relation between the microstructure of the polymer chain and the intrinsic viscosities with changing the amotmt of modified monomers from 1% to 4%. The simulation results show that, compared to HPAM, HM-HPAM has a better performance in increasing viscosity when the percentage of modified monomers is 2% and has a stronger salt tolerance when the modified monomers is 4%. Furthermore, a complex hydrogen bonding network was revealed with the analysis of radial distribution functions （RDFs） and the pair correlation function was used to investigate the diffusivity of Na^＋ and carbon atoms in the COO^- group.

Metal alginates for polyphenol delivery systems: Studies on crosslinking ions and easy-to-use patches for release of protective flavonoids in skin

Incorporation of bioactive natural compounds like polyphenols is an attractive approach for enhanced functionalities of biomaterials.In particular flavonoids have important pharmacological activities,and controlled release systems may be instrumental to realize the full potential of these phytochemicals.Alginate presents interesting attributes for dermal and other biomaterial applications,and studies were carried here to support the development of polyphenol-loaded alginate systems.Studies of capillary viscosity indicated that ionic medium is an effective strategy to modulate the polyelectrolyte effect and viscosity properties of alginates.On gelation,considerable differences were observed between alginate gels produced with Ca^2+,Ba^2+,Cu^2+,Fe^2+,Fe^3+and Zn^2+as crosslinkers,especially concerning shrinkage and morphological regularity.Stability assays with different polyphenols in the presence of alginate-gelling cations pointed to the choice of calcium,barium and zinc as safer crosslinkers.Alginate-based films loaded with epicatechin were prepared and the kinetics of release of the flavonoid investigated.The results with calcium,barium and zinc alginate matrices indicated that the release dynamics is dependent on film thicknesses,but also on the crosslinking metal used.On these grounds,an alginate-based system of convenient use was devised,so that flavonoids can be easily loaded at simple point-of-care conditions before dermal application.This epicatechin-loaded patch was tested on an ex-vivo skin model and demonstrated capacity to deliver therapeutically relevant concentrations on skin surface.Moreover,the flavonoid released was not modified and retained full antioxidant bioactivity.The alginate-based system proposed offers a multifunctional approach for flavonoid controllable delivery and protection of skin injured or under risk.

RHEOLOGICAL PROPERTIES OF WHEAT GLIADINS IN AQUEOUS PROPANOL

Rheological properties of wheat gliadins in 50% （V/F） aqueous propanol were carried out as a function of gliadin concentration c and temperature. The solutions at 20 g L-1 to 200 g L-1 behave as Newtonian fluids with an flow activation energy of 23.5-27.3 kJ mol-1. Intrinsic viscosity [η] and Huggins constant kH are determined according to Huggins plot at c 〈 120 g L-1. The results reveal that gliadins are not spherical shaped and the molecular size tends to increase with temperature due to improved solvation.

Hydrophobically modified polyelectrolytes I. Dilute solution properties of fluorocarbon-containing poly (acrylic acid)

Dilute solution viscosity of fluorocarbon-containing hydrophobically modified poly (acrylic add) was measured in aqueous solutions of various NaCl concentrations. The intrinsic viscosity ([η]) and Huggins coefficient (kH) were evaluated using Huggins equations. It is found that, at low Nacl concentration, the modified polymers exhibit values of intrinsic viscosity ([η]) and Huggins coefficient (kH) similar to those of unmodified polymers. For both of the modified and unmodified polymers, the intrinsic viscosity decreases with increase of NaCl concentration, while the Huggins coefficient increases upon addition of NaCl. But the variation of [η] and kH is more significant for the modified polymers, which reflects the enhanced intra- and intermolecular hydrophobic association at higher Nacl concentration.