Poly solution viscosity

Concentration and Molecular Weight Effects. The viscosity of aqueous solutions of poly(ethylene oxide) depends on the concentration of the polymer solute, the molecular weight, the solution temperature, concentration of dissolved inorganic salts, and the shear rate. Viscosity increases with concentration and this dependence becomes more pronounced with increasing molecular weight. This combined effect is shown in Figure 3, in which solution viscosity is presented as a function of concentration for various molecular weight polymers. 

Fig. 8. Effect of shear on aqueous solution viscosities of poly (ethylene oxide) resins (a) 1.0 wt % solution, (b) 5.0 wt % solution (10). Each curve...

When equal amounts of solutions of poly(ethylene oxide) and poly(acryhc acid) ate mixed, a precipitate, which appears to be an association product of the two polymers, forms immediately. This association reaction is influenced by hydrogen-ion concentration. Below ca pH 4, the complex precipitates from solution. Above ca pH 12, precipitation also occurs, but probably only poly(ethylene oxide) precipitates. If solution viscosity is used as an indication of the degree of association, it appears that association becomes mote pronounced as the pH is reduced toward a lower limit of about four. The highest yield of insoluble complex usually occurs at an equimolar ratio of ether and carboxyl groups. Studies of the poly(ethylene oxide)—poly(methacryhc acid) complexes indicate a stoichiometric ratio of three monomeric units of ethylene oxide for each methacrylic acid unit. 

Of the three worldwide manufacturers of poly(ethylene oxide) resins. Union Carbide Corp. offers the broadest range of products. The primary quaUty control measure for these resins is the concentrated aqueous solution viscosity, which is related to molecular weight. Specifications for Polyox are summarized in Table 4. Additional product specifications frequendy include moisture content, particle size distribution, and residual catalyst by-product level. 

Aqueous Solution Viscosity. A special solution preparation method is used for one type of measurement of aqueous solution viscosity (96). The appropriate amount of poly(ethylene oxide) resin is dispersed in 125 mL of anhydrous isopropyl alcohol by vigorous stirring. Because the resin is insoluble in anhydrous isopropyl alcohol, a slurry forms and the alcohol wets the resin particles. An appropriate amount of water is added and stirring is slowed to about 100 rpm to avoid shear degradation of the polymer. In Table 4, the nominal resin concentration reported is based on the amount of water present and ignores the isopropyl alcohol. 

SolubiHty parameters of 19.3, 16.2, and 16.2 (f /cm ) (7.9 (cal/cm ) ) have been determined for polyoxetane, po1y(3,3-dimethyl oxetane), and poly(3,3-diethyloxetane), respectively, by measuring solution viscosities (302). Heat capacities have been determined for POX and compared to those of other polyethers and polyethylene (303,304). The thermal decomposition behavior of poly[3,3-bis(ethoxymethyl)oxetane] has been examined (305). 

Polymer Solvent. Sulfolane is a solvent for a variety of polymers, including polyacrylonitrile (PAN), poly(vinyhdene cyanide), poly(vinyl chloride) (PVC), poly(vinyl fluoride), and polysulfones (124—129). Sulfolane solutions of PAN, poly(vinyhdene cyanide), and PVC have been patented for fiber-spinning processes, in which the relatively low solution viscosity, good thermal stabiUty, and comparatively low solvent toxicity of sulfolane are advantageous. Powdered perfluorocarbon copolymers bearing sulfo or carboxy groups have been prepared by precipitation from sulfolane solution with toluene at temperatures below 300°C. Particle sizes of 0.5—100 p.m result. 

Membrane stmcture is a function of the materials used (polymer composition, molecular weight distribution, solvent system, etc) and the mode of preparation (solution viscosity, evaporation time, humidity, etc). Commonly used polymers include cellulose acetates, polyamides, polysulfones, dynels (vinyl chloride-acrylonitrile copolymers) and poly(vinyhdene fluoride). 

Poly(vinyl alcohol) can be recovered from the desizing Hquid by means of commercial ultrafiltration equipment. Recovery rates and effluent losses ate inversely proportional to the PVA solution viscosity and independent of the degree of hydrolysis. 

Adhesives for paper tubes, paperboard, cormgated paperboard, and laminated fiber board are made from dispersions of clays suspended with fully hydrolyzed poly(vinyl alcohol). Addition of boric acid improves wet tack and reduces penetration into porous surfaces (312,313). The tackified grades have higher solution viscosity than unmodified PVA and must be maintained at pH 4.6—4.9 for optimum wet adhesion. 

The main polymers used as thickeners are modified celluloses and poly(acrylic acid). Several different modified celluloses are available, including methyl-, hydroxypropyl methyl-, and sodium carboxymethyl-cellulose and their properties vary according to the number and distribution of the substituents and according to relative molar mass of the parent cellulose. Hence a range of materials is available, some of which dissolve more readily than others, and which provide a wide spread of possible solution viscosities. Poly(acrylic acid) is also used as a thickener, and is also available in a range of relative molar masses which give rise to give solutions of different viscosities. 

Simon, P.F.W., Muller, A.H.E., and Pakula, T. Characterization of highly branched poly(methyl methacrylate) by solution viscosity and viscoelastic spectroscopy. Macromolecules, 34, 1677, 2001. 

As an example, consider the use of PVPy as a solid poison in the study of poly(noibomene)-supported Pd-NHC complexes in Suzuki reactions of aryl chlorides and phenylboroiuc acid in DMF (23). This polymeric piecatalyst is soluble under some of the reaction conditions employed and thus it presents a different situation from the work using porous, insoluble oxide catalysts (12-13). Like past studies, addition of PVPy resulted in a reduction in reaction yield. However, the reaction solution was observed to become noticeably more viscous, and the cause of the reduced yield - catalyst poisoning vs. transport limitations on reaction kinetics - was not immediately obvious. The authors thus added a non-functionalized poly(styrene), which should only affect the reaction via non-specific physical means (e.g., increase in solution viscosity, etc.), and also observed a decrease in reaction yield. They thus demonstrated a drawback in the use of the potentially swellable PVPy with soluble (23) or swellable (20) catalysts in certain solvents. 

Certain mixtures of polymers have been shown to form complexes which exhibit substantially higher than expected solution viscosity under low shear conditions. Xanthan gum blends with guar gum (38, 39), sodium poly(styrene sulfonate) (40), polyacrylamide (41), sulfonated guar gum (38), sodium poly(vinylsulfonate) (40), hydrolyzed sodium poly(styrene sulfonate-co-maleic anhydride) (38), and poly(ethylene oxide) (41) and blends of xanthan gum and locust bean gum have exhibited substantially higher than expected solution viscosity (42, 43). 

Figure 8. Solution viscosity as a function of calcium chloride concentration for hydrolyzed poly(starch-g- (2 propenamide)) terpolymer.

Not all modified starches are suitable for removal by aqueous dissolution alone. Such modifications of natural starches are carried out to reduce solution viscosity, to improve adhesion and ostensibly to enhance aqueous solubility. Commercial brands vary [169], however, from readily soluble types to those of limited solubility. Indeed, some may be as difficult to dissolve as potato starch if they have been overdried. It is thus very important to be sure of the properties of any modified starch present. If there are any doubts about aqueous dissolution, desizing should be carried out by enzymatic or oxidative treatment. Even if the size polymer is sufficiently soluble, it is important to ensure that the washing-off range is adequate. Whilst the above comments relate to modified starches, other size polymers such as poly(vinyl acetate/alcohol) and acrylic acid copolymers vary from brand to brand with regard to ease of dissolution. 

Staudinger was probably the first to recognize this, for in 1928 he proposed that synthetic macromolecules were poly-disperse and their molecular weights would have to be expressed as average values (93). He also recognized the dependence of physical properties on molecular weight, and pursued this dependence as a measure of molecular weight determination. The result was his application of solution viscosity. 

Solution Viscosity Studies. Ths polymer solution viscosity was run on two modified polymers and the original poly(vinyl alcohol) at 30°C in DMSO solutions using a series 100 Cannon-Fenske viscometer. The observed specific viscosities and the intrinsic viscosity for each of these samples are summarized in Table III. 

The original poly(vinyl alcohol) was studied in both aqueous and DMSO solutions. Viscosity-molecular weight relationships have been reported for each of these solutions at 30°C as shown in Equations 19 and 20 (3). 

Figure 4.11 Solution viscosity of (a) telechelic UPy functional poly(dimethylsiloxane) and (b) a benzyl protected analog in chloroform at 20 °C. Reprinted from Cates (1987). Copyright 1987 American Chemical Society.

It is well established that poly(styryl)lithium is predominantly associated into dimers in hydrocarbon solutions (14,15), while it is monomeric in tetrahydrofuran (j ). Furthermore, concentrated solution viscosity measurements have shown that the equilibrium constant (K ) for the process shown in eq l [PSLi = poly(styryl)lithium] ha i value... 

The state of association of poly(dienyl)lithium compounds in hydrocarbon solutions is a matter of current controversy (15-18). Aggregation states of two (.16 and four (.15) have been reported based on light-scattering and concentrated solution viscosity measurements. The most recent concentrated solution viscosity studies ( 1 6 J 7.) > which include results of various endcapping and linking techniques, provide convincing evidence for predominantly dimeric association of poly(isoprenyl)lithium in hydrocarbon solution. The effect of tetrahydrofuran on the degree of association of poly(isoprenyl)lithium has also been examined by concentrated solution viscosity measurements (13). These results indicate that the equilibrium constant for the process shown in eq 3 [PILi = poly(isoprenyl)lithium] exhibits an equilibrium... 

The solution behavior of poly(amic acids) was until recently, probably the least understood aspect of the soluble polyimide precursor. However, the advent of sophisticated laser light scattering and size exclusion chromatography instrumentation has allowed elucidation of the solution behavior of poly(amic adds). In the early days of polyimide chemistry, when most molecular weight characterization was based on viscosity determinations, a decrease in viscosity was associated with molecular weight degradation [15, 28, 29]. Upon combination of the two monomers an increase in the viscosity to the stoichiometric equivalence point is observed, followed by a decrease in the solution viscosity as a... 

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