Polymers in water and

In the previous sections, we described the overall features of the heat-induced phase transition of neutral polymers in water and placed the phenomenon within the context of the general understanding of the temperature dependence of polymer solutions. We emphasised one of the characteristic features of thermally responsive polymers in water, namely their increased hydropho-bicity at elevated temperature, which can, in turn, cause coagulation and macroscopic phase separation. We noted also, that in order to circumvent this macroscopic event, polymer chemists have devised a number of routes to enhance the colloidal stability of neutral globules at elevated temperature by adjusting the properties of the particle-water interface. 

Mix polyvinyl alcohol polymers in water and completely dissolve while mixing with mechanical stirrer and adjust temperature to dissolve all polyvinyl alcohol (PVA) until the solution is clear, then reduce to temperature to 20-25°C... 

The variation of the reduced viscosity values with the neutralization degree is lower when the quaternization degree is higher. The titration curves show a plateau whose width diminishes by increasing the quaternization degree. A similar plateau is also present in the titration curves of the unquatemized polymer in water, and in this case corresponds to the precipitation range (Fig. 6). 

Table 15. Heat of mixing of proton-donating polymers and proton-accepting polymers in water and in organic solvents...

Mecerreyes et al. [91] used ionic liquid-supported HRP in water to conduct enzyme-catalyzed free radical polymerization. In this reaction procedure, the HRP was immobilized in BMIM NTf2 by simple dissolution. This was then added to an aqueous solution of aniline, dodecylbenzenesulfonic acid (DBSA) and H202 at pH 4.3. Under these conditions, polymerization occurred immediately (as evidenced by the green color of the solution), but yield was low due to precipitation and association of polyaniline at the surface of the ionic liquid. To overcome this problem, a less hydrophobic ionic liquid, BMIM PF6 was used. In this case, the solution separated into two liquid phases after 0.5 hours one contained the polymer in water and the other was ionic liquid-immobilized HRP. The IL-HRP could be recycled and polymerization successfully repeated up to five times. The resulting polymer had similar electric conductivity properties to conventionally prepared polymer. A schematic of this process is presented in Figure 13.10. 

DRAG REDUCTION IN TURBULENT FLOW. Dilute solutions of polymers in water or other solvents sometimes give the peculiar effect of a reduction in drag in turbulent flow. The phenomenon was first noted by Toms and has prompted many theoretical studies and some practical applications. As shown in Fig. 5.11, the friction factor can be significantly below the normal value for turbulent flow with only a few parts per million of polymer in water, and at 50 to 100 ppm, the drag reduction may be as much as 70 percent. Similar effects have been shown for some polymers in organic solvents. 

Only in recent years has the use of water as an infrared solvent become fairly routine in the biochemical laboratory. However, Coblentz (1905) had used water as an infrared solvent as early as 1905, and Gore et al. (1949) had studied aqueous solutions of several amino acids in 1949. Blout has published many infrared spectra of biochemical polymers in water and D2O solution, examples of which can be found in Blout and Lenormant (1953) and Blout (1957). Figure 3.9 (Blout, 1957) shows absorption spectra of water and D2O (with and without compensation) of 0.025 mm thickness in the region 4000-600 cm It can be seen that D2O transmits where water absorbs and vice versa, thus making the combination of these solvents useful for examining aqueous solutions. The O—H deformation modes of water are present between 1700 and 1600 cm" and the O—D deformation of D2O lies at 12(X) cm" Except for these regions the spectra show better than 40% transmittance and satisfactory compensation is readily obtained in a double-beam spectrometer. The optimum concentration of a solute is from 5 to 20 %. Two percent solutions have been used (Blout, 1957) and even lower concentrations are possible with a suitable solute, for example, 0.45 % phenol in water (Parker and Kirschenbaum, 1959). 

Bjorklund, R., S. Andersson, S. Allenmark, and 1. Lundstrom. 1985. Electrochromic effects of conducting polymers in water and acetonitrile. Mol Cryst Liq Cryst 121 263-270. 

Figure 29 Plots of /1//3 for pyrene as a function of DTAC concentration in the absence of polymer in water and 0.1 M NaCl, and in the presence of polyacrylate, unmodified (PA) or modified with 1% or 3% C12 groups, or 1% Cig groups. (From Ref. 90.)...

Dependence of the equilibrium degree of swelling on the composition of copolymers has been given in Tables 1-4. The solubility parameters J are estimated from swelling measurements. Swelling of uncrosslinkid polymers in water and swelling of cross-linked polymer in water are listed in Table 5. 

Investigations have been carried out, both from theoretical and experimental point of view, on a series of panz-substituted poly-L-phenylalanines [55-57]. Woody calculated the CD spectra of poly-p-amino-phenylalanine by assuming the same geometries and using the same methods as for various helical poly-L-tyrosines [55]. Comparison between computed CD curves and experimental data presently available [56] points strongly toward the RA conformation for the deprotonated polymer in water and excludes the three other... 

The most outstanding among the recendy proposed poly-NHC-based catalytic systems for this reaction was reported by the group of Karimi and Akhavan in 2009—2011 and consisted in differendy functionalized organometaUic polymers of paUadium(II) with the Janus-type ligand 17. The different functionalization induenced the dispersion of the polymers in water and, consequently, their catalytic efficiency in this solvent. The catalytic activity of these systems was very high, and in best cases, it allowed the... 

Emulsion and suspension polymerization methods are heterogeneous polymerization techniques in which the polymerization oeeurs in the monomer-swollen latexes or monomer droplets dispersed in a eontinuous water phase. Therefore, they provide effective ways to achieve nanoeomposites based on water-insoluble polymers and LDHs in aqueous system by separately dispersing hydrophilic LDHs and hydrophobic polymers in water and mieelles, respectively, which can be tightly combined by the action of the emulsifier as well. Many advantages are inherent in these methods ... 

Physical properties. All colourless. Formaldehyde, HCHO, is a gas, and only its aqueous solution, which has a characteristic pungent odour, is considered metaformaldehyde or trioxymethylene , (CH20)3, is a solid polymer, insoluble in water and ethanol. 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

It should be possible to form linear noncross-linked polymers of melamine—formaldehyde or phenol—formaldehyde by reaction of one mole of the patent with one mole of formaldehyde, but this is generally not the case. The melamine crystal itself is very insoluble in water and only becomes soluble as the formaldehyde molecules add on. If much less than 1.5 moles of formaldehyde pet mole of melamine ate used, the aqueous resin solution is very unstable. 

Properties. Hydroxypropylcellulose [9004-64-2] (HPC) is a thermoplastic, nonionic cellulose ether that is soluble in water and in many organic solvents. HPC combines organic solvent solubiUty, thermoplasticity, and surface activity with the aqueous thickening and stabilising properties characteristic of other water-soluble ceUulosic polymers described herein. Like the methylceUuloses, HPC exhibits a low critical solution temperature in water. 

Sodium poly(a-L-glutamate). It was washed with acetone, dried, dissolved in water and ppted with isopropanol at 5°. Impurities and low molecular weight fractions were removed by dialysis of the aqueous solution for 50h, followed by ultrafiltration through a filter impermeable to polymers of molecular weights greater the 10. The polymer was recovered by freeze-drying. [Mori et al. J Chem Soc, Faraday Trans I 2583 1978.]... 

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