Water-soluble copolymers. V. Compositional determination of random copolymers of acrylamide with sulfonated comonomers by infrared spectroscopy and C13 nuclear magnetic resonance

Compositional analyses of random copolymers of acrylamide with sodium-2-sulfoethyl methacrylate and with sodium-2-acrylamido-2-methylpropane sulfonate have been performed utilizing elemental analysis, infrared spectroscopy, and C¹³ NMR. A mathematical method involving nitrogen to sulfur ratios has been developed to eliminate errors which often arise from associated water in hydrophilic copolymers. The ratios of infrared absorbances at 1043 cm^?1 and 1664 cm^?1 were used to determine the composition of AM—NaAMPS copolymers; likewise, absorbance ratios at 1040 cm^?1 and 3200 cm^?1 were utilized for determination of the AM—NaSEM copolymer composition. Carbon-13 NMR spectra of the copolymers were also obtained, and characteristic peaks were utilized to quantitate copolyer composition. The results obtained by elemental analyses, infrared spectroscopic studies, and NMR were in excellent agreement. These techniques are of great value for determining composition of hygroscopic copolymers which can crosslink or form strong intramolecular hydrogen bonds, often precluding further characterization.     

pH‐responsive polyzwitterions: A comparative study of acrylamide‐based polyampholyte terpolymers and polybetaine copolymers

A comparative study of pH‐responsive polyzwitterions (PZs) with polyampholyte or polybetaine architectures was conducted with well‐defined model polymer systems. Low‐charge‐density PZs, including ampholytic terpolymers composed of acrylamide (AM), sodium 3‐acrylamido‐3‐methylbutanoate, and (3‐acrylamidopropyl)trimethylammonium chloride and carboxybetaine copolymers composed of AM and 3‐(3‐acrylamidopropyldimethylammonio)propionate, were prepared via free‐radical polymerization in 0.5M NaCl to yield ter‐ and copolymers with random termonomer and comonomer distributions. Sodium formate was used as a chain‐transfer agent during the polymerizations to eliminate the effects of the monomer feed composition on the degree of polymerization (DP) and to suppress gel effects and broadening of the molecular weight distributions. The polymer compositions were determined via ¹³C‐NMR spectroscopy, and the residual counterion content was determined via elemental analysis for Na⁺ and Cl^?. The molecular weights (MWs) and polydispersity indices (PDIs) were determined via size exclusion chromatography/multi‐angle laser light scattering (SEC–MALLS); the polymer MWs ranged from 1.4 to 1.5 × 10⁶ g/mol, corresponding to DPs of 1.6–1.9 × 10⁴ repeat units, with all the polymers exhibiting PDIs less than or equal to 2.1. The intrinsic viscosities determined from SEC–MALLS data and the Flory–Fox relationship agreed with the intrinsic viscosities determined via low‐shear dilute‐solution viscometry. Data from the SEC–MALLS analysis were used to analyze the radius of gyration/molecular weight (R_g–M) relationships and the Mark–Houwink–Sakurada intrinsic viscosity/molecular weight ([η]–M) relationships for the PZs. The R_g–M and [η]–M relationships and viscometric data revealed that under size exclusion chromatography conditions, the poly[acrylamide‐co‐3‐(3‐acrylamidopropyldimethylammonio)propionate] betaine copolymers had more open, random‐coil conformations and greater polymer–solvent interactions than the ampholytic poly[acrylamide‐co‐sodium 3‐acrylamido‐3‐methylbutanoate‐co‐(3‐acrylamidopropyl)trimethylammonium chloride] terpolymers. The pH‐ and salt‐responsive dilute‐solution viscosity behavior of the PZs was examined to assess the effects of the polymer structure and composition on the solution properties. The polyampholyte terpolymers had greater solution viscosities and more pronounced stimuli‐responsiveness than the polybetaine copolymers because of their stronger intramolecular interactions and increased chain stiffness. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 24–39, 2004     

Water‐soluble polymers. LXXXIII. Correlation of experimentally determined drag reduction efficiency and extensional viscosity of high molecular weight polymers in dilute aqueous solution

The extensional viscosity for aqueous solutions of high molecular weight poly(acrylamide) copolymers and poly(ethylene oxide) homopolymers was measured using a laboratory‐designed screen extensional rheometer. A Bingham model was developed to estimate the average local polymer coil extensional viscosity (η_coil). A strong correlation was found between the measured η_coil values and the polymer extensional viscosity predicted by a bead‐spring model. The dilute aqueous solution drag reduction was measured with a rotating disk instrument under conditions minimizing the effects of shear degradation. Extensional viscosity and drag reduction measurements were performed in deionized water and in 0.514M sodium chloride. The relative drag reduction efficiency values (Δ) in both solvents were found to strongly correlate with measured η_coil values. This is the first report of the accurate prediction of drag reduction behavior for a wide range of polymer types in various solvents from the independently measured molecular parameters η_coil and [η]C. The often‐used relative drag reduction efficiency expressed as the product of [η]C and Δ can now be replaced by the absolute drag reduction efficiency [η]Cη_coil. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1222–1231, 2001     

Solution behavior of two novel anionic polyacrylamide copolymers hydrophobically modified with n‐benzyl‐n‐octylacrylamide

Two novel hydrophobically modified anionic polyacrylamides (HM‐PAMs), p(AM/NaA/NaAMC₁₂S/BOAM) and p(AM/NaA/OP‐10‐AC/BOAM) have been prepared by an aqueous micellar copolymerization technique from acrylamide, sodium acrylate (NaA), sodium 2‐(acrylamido)dodecane‐1‐sulfonate (NaAMC₁₂S), octylphenol polyoxyethylene acrylate (OP‐10‐AC), and small amounts of N‐benzyl‐N‐octylacrylamide, respectively, with the objective of investigating the copolymers' rheological behaviors and surface activities under various conditions such as polymer concentration, shear rate, temperature, and salinity. As expected, the copolymers exhibit improved thickening properties due to intermolecular hydrophobic associations as the solution viscosity of the copolymers increases sharply with increasing polymer concentration. A decrease in viscosity is observed with increasing temperature, and the solution viscosity of the copolymers decreases with increasing NaCl concentration. Furthermore, the block copolymers exhibit high air–liquid surface activities as the surface tensions (STs) decrease with increasing polymer concentration. This behavior is yet another evidence of polymolecular micelles formation of the copolymers in aqueous solution, and thus the high tendency to adsorb at an interface. The ST exhibited by the copolymers was found to be relatively insensitive to the concentration of salt (NaCl). Scanning electron micrographs showed large aggregates in solutions, which is formed by the association from the hydrophobic groups of the polymers. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Influence of added salt on dynamic viscoelasticity of carboxymethylcellulose aqueous systems

Using three series of sodium carboxymethylcellulose (NaCMC) in the range of the degree of substitution (the average number of carboxymethyl groups/glucose unit) from 0.5 to 1.3, weight-average molecular weight M_w was determined by light scattering in solution of triethylenediamine cadmium hydroxide (cadoxene). It was found that the relation between M_w and the limiting viscosity number [η] in 0.1 N sodium chloride (NaCl) aqueous solution can be represented by Staudinger's equation. Dynamic viscoelasticity of aqueous disperse systems of NaCMC with various added salts was measured by means of a cone-and-plate rheometer. If the concentration of added salt is less than the concentration at which polymer begins to salt out, frequency dependence curves of the dynamic modulus, which is measured at various salt concentrations, can be superposed into a master curve by horizontal shift only. The shift factor depends on the salt concentration and the kind of salt.     

A novel twin-tailed hydrophobically associating copolymer: synthesis, characterization and solution properties

Novel twin-tailed hydrophobically associating copolymers (DDSPAM) were prepared by micellar copolymerization of acrylamide (AM) and sodium vinylsulfonate with N,N-didecyl-N-methyl-N-(4-vinylbenzyl)ammonium chloride in an aqueous solution. The structure and composition of DDSPAM were characterized by ¹H-NMR and elemental analysis. While the molecular weights of the copolymers were obtained via static light scattering, the hydrodynamic radius of aggregates was investigated using dynamic light scattering. The critical micellar concentration cmc and γ _cmc values of DDSPAM were measured using fluorescence and later correlated with the values obtained from surface tension measurements. In addition, the viscosity stability studies of DDSPAM and hydrolyzed polyacrylamide (HPAM) revealed that DDSPAM, with twin tails of hydrophobic groups, exhibited better salt tolerance as well as temperature resistance compared to HPAM.     

Studies on the polyblends of poly(vinyl chloride) with various methacrylate copolymers,melt rheological properties. II

Studies have been made on the melt rheological properties of poly(vinyl chloride) (PVC) with copolymers of methyl methacrylate (MMA) and methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), and 2-ethyl hexyl acrylate (EHA) at a blending ratio of 80:20. Effect of blend composition on shear stress–shear rate, melt viscosity, melt elasticity, and extrudate distortion have been studied. A significant decrease in the melt viscosity is observed on incorporation of low T_g, acrylate copolymers such as those with BA and EHA, thereby reducing the processing temperature. First normal stress and die swell ratio also decreases with an increase in the side chains of acrylate copolymer. PVC blended with P(MMA-co-BA) and P(MMA-co-EHA) is sensitive to both temperature and shear stress.     

Water‐soluble copolymers from functionalized monomers (sodium o‐ and p‐methacryloylaminophenylarsonate): Synthesis and characterization

Copolymers of sodium o‐methacryloylaminophenylarsonate (o‐MAPHA‐Na) 1 and p‐methacrylolylaminophenylarsonate (p‐MAPHA‐Na) 2 with sodium acrylate (AA‐Na) 3 , sodium methacrylate (AM‐Na) 4 and acrylamide (AAD) 5 were prepared by free radical polymerization in aqueous media at 70°C using potassium persulfate (K₂S₂O₈) as the initiator. The total monomer concentration was carried out at 0.5M and the feed ratio ( M₁ : M₂ ) was varied from 10 : 90 to 90 : 10 mol%. The kinetic study was carried out by dilatometric method. The copolymer compositions were calculated by arsenic content in the copolymers. The As content (ppm) was determined by atomic absorption spectrometry (AAS). The reactivity ratios (r₁, r₂) were estimated by the Kelen‐Tüdös linearization method as well as error‐in‐variables method using the computer program RREVM®. In all cases, r₁ < 1 and r₂ > 1, indicating a tendency to form random copolymers. The values suggest that the copolymers contain a larger proportion of comonomer (i.e., AA‐Na, AM‐Na, or AAD). Weight‐average molar masses (M _w) of copolymers were determined by multi‐angle light scattering. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Solution and interfacial behavior of hydrophobically modified water-soluble block copolymers of acrylamide and N-phenethylacrylamide

Hydrophobically modified water-soluble block copolymers were prepared by aqueous micellar copolymerization of acrylamide and small amounts (2 and 3 mol %) of a hydrophobe (N-phenethylacrylamide) that is characterized by a long spacer that places the aromatic ring far away from the backbone, with the objective of investigating the copolymers' rheological behavior and surface and interfacial activities under various conditions such as polymer concentration, shear rate, temperature, and salinity. As expected, the block copolymers exhibit improved thickening properties attributed to intermolecular hydrophobic associations as the solution viscosity of the copolymers increases sharply with increasing polymer concentration. Additional evidence for intermolecular association is provided by the effect of NaCl, the presence of which substantially enhances the viscosity. An almost shear rate–independent viscosity (Newtonian plateau) is also exhibited at high shear rate and a typical non-Newtonian shear thinning behavior appears at low shear rates and high temperatures. Furthermore, the block copolymers exhibit high air–liquid surface and liquid–liquid interfacial activities as the surface and interfacial tensions decrease with increasing polymer concentration, indicating strong adsorption of the copolymer at the interface. The surface and interfacial tensions exhibited by the copolymers were found to be relatively insensitive to the concentration of salt (NaCl). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 467–476, 2001     

Temperature and salt-induced micellization of some block copolymers in aqueous solution

Micellization of three commercial samples of ethylene oxide (EO)-propylene oxide (PO) (PEO-PPO-PEO) triblock copolymers (pluronics) P65 (EO₂₅PO₃₀EO₂₅, mw PPO=1750, %PEO=50), P85 (EO₂₅PO₄₀EO₂₅, mw PPO=2250, %PEO=50), and F88 (EO₁₀₂PO₄₀EO₁₀₂, mw PPO=2250, %PEO=80) in aqueous sodium chloride solution (0–3 M) was examined by cloud point, surface tension, dye spectral change, fluorescence, and viscosity measurements over a temperature range of 25–50°C. Salt-induced micellization and micelle growth were observed. The presence of sodium chloride enhanced hydrophobicity in the PPO moiety and reduced hydrophilicity of PEO moieties, favoring micellization at relatively lower concentrations than in water at ambient temperature. The effect of salt on micellization is similar to that of increasing temperature. The critical micelle concentrations (CMC) and critical micelle temperatures showed a marked decrease in the presence of added salt. CMC obtained by different methods were in good agreement.     

The phase transition and shear modulus of ionic N-isopropylacrylamide gels in concentrated salt solutions

The swelling and mechanical properties of thermally sensitive N-isopropylacrylamide (NIPA) hydrogels containing 0–35 mM sodium acrylate comonomer have been investigated at room temperature. The swelling medium is an aqueous solution with an NaCl concentration varying from 0 to 3.0M. As the NaCl concentration increases, the ionic NIPA gels shrink. In a dilute sodium chloride solution with NaCl less than 0.1M, the conformational change of the gels is a simple process of osmotic deswelling. As the sodium chloride concentration increases above 0.8M, the gels undergo a shrinkage phase transition. Corresponding to the shrinking of the gels, the shear modulus of the gels gradually increases at the transition point. It is found that the phase transition significantly affects the turbidity of the NIPA gels. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1851–1856, 1997     

Viscoelastic properties of poly(ethylene-co-styrene) copolymers

The viscoelastic properties of narrowly distributed linear poly(ethylene-co-styrene) copolymers with different mole fractions of styrene (x_S = 0–20.5 mol %) and molecular weights (M_w = 64–214 kg/mol) were analyzed in the molten state at different temperatures by means of oscillatory rheometry. Analyzing the thermorheological properties of the polymers, we found that the time temperature superposition principle is fulfilled. The corresponding shift factors follow up to 16.5 mol % of styrene units the Arrhenius behavior of neat polyethylene. For a styrene content of about 20 mol %, the polymers no longer crystallize and a transition from Arrhenius to WLF behavior of pure polystyrene was observed. The zero shear viscosity, η₀, of the polymers was derived from the mastercurves. The determination of the plateau modulus by the well-known tan δ-min criterion is not possible due to the beginning crystallization in the corresponding temperature range. An approximate calculation of this value is based on the characteristic relaxation time λ_x = 1/ω_x, corresponding to the crossover of G′ and G′. Indeed, the characteristic modulus G_px calculated as η₀/λ_x is a good approximation for the plateau modulus G_p. The viscosity–molecular weight and relaxation time–molecular weight scaling relations were established for three copolymers with different molecular weights and nearly the same styrene content. For both material parameters, the scaling exponent is around 3.4, confirming the linear architecture of the investigated polymers. The mixing rules describing the change of such material parameters like zero shear viscosity or plateau modulus independent of styrene content are of logarithmic linear character using the weight fraction of styrene units instead of the mole fraction. The relations found allow the prediction of melt state properties for polymers with arbitrary styrene content. In the future, when catalysts with sufficient activity for the synthesis of high styrene content copolymers are available, these predictions will have to be checked. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:209–215, 1997     

Water-soluble copolymers: 22. Copolymers of acrylamide with 2-acrylamido-2-methylpropanedimethylammonium chloride: Aqueous solution properties of a polycation

The viscometric, turbidimetric and potentiometric properties of copolymers of acrylamide (AM) with 2-acrylamido-2-methylpropanedimethylammonium chloride (AMPDAC) were studied in aqueous solutions. The AMPDAC polymers exhibit poor salt tolerance and large, negative viscosity/temperature coefficients. Furthermore, the polymers were found to be sensitive to changes in pH. The AMPDAC polymers undergo phase separation in the presence of dianions as a function of temperature and AMPDAC composition.     

Viscometric behavior of disulfonated poly(arylene ether sulfone) random copolymers used as proton exchange membranes

tert-Butylphenyl-terminated disulfonated poly(arylene ether sulfone) random copolymers with a sulfonation degree of 35 mol% (BPS35) and controlled molecular weights (M_n), 20-50 kg mol⁻¹, were successfully prepared by direct copolymerization of the two activated halides, 4,4′-dichlorodiphenyl sulfone (DCDPS) and 3,3′-disulfonate-4,4′-dichlorodiphenyl sulfone (SDCDPS) with 4,4′-biphenol and the endcapper, 4-tert-butylphenol. Dilute viscosity measurements of the BPS35 random copolymers were successfully conducted in NMP containing various concentrations of LiBr from 0.01 to 0.2 M and mostly at 0.05 M according to the measured theory. The effects of salt concentration and molecular weights of the copolymers on the viscometric behavior were studied and compared with published data for sulfonated polystyrene. The charge density parameter (ξ) for the BPS35 copolymers was determined to be smaller than 1, suggesting that no counterion condensation occurs. Studies of the effect of ionic strength (I) on the intrinsic viscosities ([η]) under theta condition were obtained by plotting [η] vs. I^−1/2 and extrapolating to infinite ionic strength. For salt-free BPS35 solutions, the viscometric behavior was shown to fit well with the Liberti-Stivala equation, providing a way to determining intrinsic viscosity when the copolymer charge is fully screened. Intrinsic viscosity and molecular weight characterization of BPS35 copolymers by SEC and static light scattering are also presented. The results are very useful for characterizing polymeric electrolyte membrane (PEM) for fuel cells, reverse osmosis and ionic transducer membranes.     

Swelling and rheology of saponified starch–g–polyacrylonitrile copolymers. Effect of starch granule pretreatment and grafted chain length

A series of well-characterized starch–g–polyacrylonitrile (PAN) graft copolymers was prepared from corn starch which had been heated in water at temperatures up to 94°C to vary the extent of starch granule swelling and disruption. Graft polymerization onto gelatinized starch gave less frequent grafting of higher molecular weight PAN than comparable graft polymerizations onto ungelatinized starch. A graft copolymer was also prepared from gelatinized starch under high dilution conditions to give lower molecular weight grafted PAN and more frequent grafting. Graft copolymers were then saponified with sodium hydroxide to convert nitrile substituents to a mixture of carboxamide and sodium carboxylate. Saponified graft copolymers were only partially water soluble and consisted largely of highly swollen, insoluble gel, which was separated from solubles for the study of physical properties. Saponification mixtures were also dried to yield highly absorbent polymer films. With the exception of the graft copolymer prepared under high dilution conditions, the physical properties of saponified graft copolymers depended on whether or not the granules of starch were gelatinized before graft polymerization. Compared with saponified graft copolymers derived from ungelatinized starch, those prepared from gelatinized starch gave films that absorbed larger amounts of aqueous fluids. Also, the gel fractions from these saponified gelatinized polymers exhibited higher water swelling, lower shear modulus, and a lower reduced viscosity function (η/cQ). The saponified graft copolymer prepared from gelatinized starch under high dilution conditions more closely resembled those prepared from ungelatinized starch, suggesting that molecular weight of grafted PAN and the grafting frequency rather than starch granule pretreatment might be the most important factor which influences properties.     

Mark–Houwink equation and GPC calibration for linear short-chain branched polyolefines,including polypropylene and ethylene–propylene copolymers

The reduction in molecular dimensions due to the presence of short side chains in otherwise linear polyolefins can very simply by calculated by assuming that the configuration of the main chain is not influenced by the side chains. This enables us to express the intrinsic viscosity–molar mass relationship as a function of the mass fraction of side chains (S): [η] = (1 ? S)^α+1K_PEM_ν^α and, with use of the universal calibration principle, to convert the GPC calibration for purely linear polymers samples into the calibration for short-chain branched polymers: M^* = (1 ? S)M. Experimental data from literature on short-chain branched poly-ethylenes, and our own data on ethylene–propylene copolymers are used to verify the above assumption. It appears that the experimentally found relations between [η], M_w and M^*_w (GPC) within the usual accuracy justify this approach.     

Properties of aqueous salt solutions of poly(vinylpyrrolidone). II. Polymer dimensions and thermodynamic quantities

The unperturbed dimensions and thermodynamic parameters of poly(vinylpyrrolidone) (PVP) have been studied in aqueous salt solutions, e.g. phosphates, mono- and dihydrogen phosphates, carbonates, sulphates of sodium and potassium. Values of K₀ ( = [η]_ΘM^-1/2, where [η]_Θ is intrinsic viscosity at the theta temperature and M is molecular weight) with M_w = 78 000 g mol^-1 were found to range from 4·63×10^-4 to 5·56×10^-4 dl g^-1, and root-mean-square end-to-end distances, 〈r²〉₀^1/2, ranging from 1·61×10^-6 to 1·68×10^-6cm were evaluated. Values of the characteristic ratio, C_n, the steric parameter, σ, and the enthalpy and the entropy of dilution parameters, χ_H and χ_S, have also been calculated, and the interaction parameter was found to be χ-0·5<-0·001 for aqueous salt solutions of PVP. ©1997 SCI     

Polyelectrolytes with various charge densities: Synthesis and characterization of diallyldimethylammonium chloride-acrylamide copolymers

The synthesis of defined polyelectrolyte models by radical copolymerization of diallyldimethylammonium chloride (DADMAC, M₁) and acrylamide (AAM, M₂) in aqueous solution is impeded by a large difference of the reactivity ratios (r₁ ? r₂) leading to a strong conversion dependence of the copolymer composition. For the synthesis of normally distributed polyelectrolytes of the same molecular weight with various charge densities, a general algorithm based on a feeded polymerization with dosage of the more reactive monomer was therefore developed. Various copolymer compositions predictable by the Mayo-Lewis equation and determined by chloride potentiometry were obtained. The sequence lengths distributions investigated by ¹³C NMR spectroscopy followed a Markov statistic of first order. The ¹³C NMR spectroscopy is shown as alternative method to gravimetry in determining reactivity ratios. The partial specific volumes and the refractive index increments of the copolymers correspond to the additivity principle. Further molecular and dynamic parameters are determined by membrane osmometry, static and dynamic light scattering, analytical ultracentrifugation, gel permeation chromatography, and viscometry. Monomodal molecular weight distributions, small polydispersities only for copolymers with high content of DADMAC are obtained at given comonomer and initiator concentration. The number-average molecular weight is almost constant for a broad copolymer composition range. R_g-M and [η]-M relations could be established for practical use at high ionic strength, despite the various chemical compositions. Some indications for a higher stiffness of copolymers with high contents of DADMAC despite the shielding of the electrostatic interactions are, however, given. At low ionic strength the electrostatic interactions prevail. Their influence with increasing charge density is stronger on the Huggins constants (intermolecular interactions) than their effect on the intrinsic viscosities (intramolecular interactions).     

Rheological properties of cotton pulp cellulose dissolved in 1‐butyl‐3‐methylimidazolium chloride solutions

Rheological properties of cotton pulp dissolved in 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl) solutions were characterized using an advanced rheometer. The complex viscosity, dynamic modulus, and shear viscosity at different temperature were studied. In the steady shear measurements, all the solutions show a shear‐thinning behavior at high shear rates. The complex viscosity as a function of frequency was fitted by extended Carreau–Yasuda model. In all cotton pulp/[Bmim]Cl solutions, the complex dynamic viscosity (η*) and steady shear viscosity (η_a) followed the Cox–Merz rule only at lower frequency. The effects of tested temperature on viscosity and viscoelastic behavior of the solutions were also investigated. The value of activation energy for the dissolution of cotton pulp in ionic liquids was 65.28 kJ/mol at the concentration of 10 wt% and was comparable with the ones for the dissolution of cellulose in NMMO. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

The effect of shear rate on the molecular weight determination of acrylamide polymers from intrinsic viscosity measurements

The rheological response of dilute solutions of high molecular weight polyacrylamides at low shear rates has been measured using a capillary viscometer that provided for a fivefold variation in shear rate at each concentration. The non-Newtonian effects were found to be significant for polyacrylamides with number-average molecular weights exceeding 10⁶. The molecular weight average–intrinsic viscosity relationship most widely used in the literature, [η] = 6.80 × 10^?4M , was found to be valid when [η] was measured at high shear rates where the polymer solutions approached Newtonian behavior. A new relationship was developed relating M _n to the intrinsic viscosity extrapolated to zero shear rate.