Properties solutions

Solutions of poly(p-benzamide) of quite low concentration (2-3%) were 

Rate of Dissolution. Section 14.2.1 dealt with the thermodynamic equilibrium between the solvent and substance to be dissolved the mixing time was disregarded. Dissolution proceeds, however, at a finite rate which depends on the specific surface area of the substance to be dissolved, its degree of crystallisation, its rate of diffusion into the solvent, and on the temperature. Often a substance is considered to be sparingly soluble if its rate of dissolution is low. This assumption is, however, incorrect [14.63]. 

A) Hexane-nitrobenzene B) Triethylamine-water C) Nicotine-water 

Systems with a lower critical dissolution temperature include  

Systems with an upper and lower critical dissolution temperature include nicotine-water (60 and 218 C, Fig. 4C). 

The miscibilities of various solvents with water are given in Table 16. 

The fiber morphology has been shown to be dependent on process parameters, namely solution properties (system parameters), process conditions (operational parameters), and ambient conditions [1,2], 

Solution properties are those such as molecular weight, molecular weight distribution, and architecture of the polymer, and properties such as viscosity, conductivity, dielectric constant, and surface tension. The polymer solution must have a concentration high 

It has been found that some morphological characteristics, such as fibre diameter and uniformity of the electrospun polymer fibres, are dependent on many processing parameters, which may be divided into three groups (a) solution properties (b) processing conditions and (c) ambient conditions. Each parameter affects the morphology of the electrospun fibres. 

Solution parameters such as viscosity, polymer concentration, molecular mass of the polymer, electrical conductivity, elasticity and surface tension exert important effects on the morphology of the polymer and on its solution characteristics. 

At room temperature, PEEK is insoluble in all common solvents and dissolves only in some concentrated acids such as sulfuric. 

The use of molecular mechanics as an aid in the interpretation of spectroscopic data is outlined in more detail in Chapter 10. One of the most rapidly developing applications of molecular mechanics is the use of the structures to aid in the analysis of multi-dimensional NMR spectra [217, 291, 292]. This is particularly pertinent to the study of metal-macromolecule interactions, where the spectroscopic data often has too low an observation/variable ratio to allow an unequivocal determination of the structure. Therefore, an additional source of structural information is needed. The number of studies involving metal ions has increased rapidly in recent years, and examples are discussed in Chapters 10 and 13. 

In general, you usually have the choice of more than one method to generate supersaturation. You should evaluate the system equipment available, solubility versus temperature of the material, and the production rate required before choosing one of the methods we discussed. 

The density of the solution is often needed for mass balance, flow rate, and product yield calculations. Density is also needed to convert from concentration units based on solution volume to units of concentration based on mass or moles of the solution. Density is defined as the mass per unit volume and is commonly reported in g/cm, however, other units such as pounds mass (Ibm)/ft and kg/m are often used. When dealing with solutions, density refers to a homogeneous solution (not including any crystal present). Specific volume is the volume per unit mass and is equal to 1/p. 

Densities are a function of temperature and must be reported at a specific temperature. A method for reporting densities uses a ratio known as the specific gravity. Specific gravity is the ratio of the density of the substance of interest to that of a reference 

If density data is not available for the solution of interest, the density can be estimated by using the density of the pure solvent and pure solid solute at the temperature of interest and assuming the volumes are additive 

Density can be measured in the laboratory in a number of different ways depending on the need for accuracy and the number of measurements required. Solution density can be easily estimated with reasonable accuracy by weighing a known volume of solution. Very precise instruments for the measurement of density that work employing a vibrating quartz element in a tube are sold by the Mettler Company (Hightstown, New Jersey). The period of vibration of the element is proportional to the density of the material placed in the tube. With careful calibration and temperature control the accuracy of these instruments ranges from 1 x 10 to 1 X 10 g/cm. It is possible to use these instruments for on-line solution density measurement of fluid in a crystallizer (Rush 1991). 

Micka et al. [169] were the first who simulated a multichain HPE system. They studied regular copolymers with alternating neutral and charged monomers (with a charge fraction of / = 1/3) in a poor solvent in the presence of monovalent counterions. The paper by Micka et al. [169] nicely demonstrated that the necklace microstructures exhibit a variety of conformational transitions as a function of polymer concentration. The end-to-end distance was found to be a nonmonotonic function of concentration and showed a strong minimum in the semidilute regime. 

It is often difficult to compare the various mannan-type polysaccharides with regard to their molecular weight, because of the different analytical techniques used. Nevertheless, the Mw values reported for the GM and GGM isolated from woody tissues are rather low (1600 to 64000g/mol) [197-199, 216,219,221] in comparison to those of the water-extractable galactoman- 

In the linear konjac mannan, the degree of acetylation profoundly affects the solubility and flow properties of this hydrocolloid. The acetyl substitution prevents self-association of the mannan chains, but following deacetylation chain interactions become more energetically favorable [230]. 

6FDA-PFMB could be quickly dissolved in many common organic solvents at ambient temperature, including tetrahydrofuran (THF), methyl ethyl ketone 

The recently reported value of q = 13 nm for a soluble aromatic polyimide containing entirely 77-catenations - exemplifies the differences that symmetry makes in terms of the persistence length. We did not obtain the persistence 

All solubilities were determined at room temperature and are presented in Table 8. The soluble lities are reported in accordance with U.S.P.(XXu ed.) definitions.(5) 

The negative logarithm of the proton dissociation constant for atenolol was determined as pK = =9.6.(7) a 

The dipole moment of atenolol was determined in propionic acid solutions, at 2o°C, using a Dipol-meter DM ol (Wiss.-Techn. V/erksl atten, D 812 Weil-heim). The value found was 5.71-o.2o D.(5) 

The atenolol molecule contains an asymmetric carbon atom. The commercial product, however, is a racemic mixture and its resolution has not been reported so far. 

Aromatic polyimide films that are spin-coated or solution-cast with thicknesses under 15 pm exhibit structural anisotropy in the condensed state. This anisotropy is associated with the tendency of the chains to align parallel to the 

Fourier transform infrared spectroscopy (FTIR) was also used to study the anisotropic structure of polyimide films. This work was based on the fact that there are characteristic absorptions associated with in-plane and out-of-plane vibrations of some functional groups, such as the carbonyl doublet absorption bands at 1700-1800 cm The origin of this doublet has been attributed to the in-phase (symmetrical stretching) and out-of-phase (asymmetrical stretching) coupled 

PBO is soluble in some strong acids such as PPA, methanesulfonic acid (MSA), chlorosulfonic acid, and trifluoroacetic acid [59] via backbone protonation, which weakens intermolecular interaction and reduces chain stiffness [60, 61]. The Mark-Houwink equation of PBO in MSA at 308°C is given by [49]  

The Mark-Houwink exponent of 1.8 indicates the high polymer chain rigidity. The persistence length of cis-PBO in MSA reported about 20-30 nm [62] and 50 nm ], whereas the theoretical persistence calculated in the range of 22-65 nm [64-66]. By comparison, the persistence length of flexible polymers such as PE is much shorter (1 nm or less). 

The self-assembly of arborescent PS-gro -PEO copolymers spread as monolayers at the air/ water interface was recently investigated (Njikang et al., 2008a). AFM imaging was used to examine the influence of molecular structure and composition on the characteristics of the 

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The concentration at which micellization commences is called the critical micelle concentration, erne. Any experimental teclmique sensitive to a solution property modified by micellization or sensitive to some probe (molecule or ion) property modified by micellization is generally adequate to quantitatively estimate the onset of micellization. The detennination of erne is usually done by plotting the experimentally measured property or response as a hmction of the logarithm of the surfactant concentration. The intersection of asymptotes fitted to the experimental data or as a breakpoint in the experimental data denotes the erne. A partial listing of experimental... 

Fleischman S H and C L Brooks III 1987. Thermodynamics of Aqueous Solvation - Solution Properties of. Mcohols and Alkanes. Journal of Chemical Physics 87 3029-3037. 

Hydrogen bonding stabilizes some protein molecules in helical forms, and disulfide cross-links stabilize some protein molecules in globular forms. We shall consider helical structures in Sec. 1.11 and shall learn more about ellipsoidal globular proteins in the chapters concerned with the solution properties of polymers, especially Chap. 9. Both secondary and tertiary levels of structure are also influenced by the distribution of polar and nonpolar amino acid molecules relative to the aqueous environment of the protein molecules. Nonpolar amino acids are designated in Table 1.3. 

We start with contact problems for plates. The contact problems with nonpenetration conditions can be viewed as a specific type of crack problem. On the other hand, the analysis of solution properties when the contact occurs is useful in the sequel. 

Our aim is to analyze the solution properties of the variational inequality describing the equilibrium state of the elastic plate. The plate is assumed to have a vertical crack and, simultaneously, to contact with a rigid punch. 

The solutions properties related to the case where the thickness of the plate tends to zero. 

The crack shape is defined by the function -ip. This function is assumed to be fixed. It is noteworthy that the problems of choice of the so-called extreme crack shapes were considered in (Khludnev, 1994 Khludnev, Sokolowski, 1997). We also address this problem in Sections 2.4 and 4.9. The solution regularity for biharmonic variational inequalities was analysed in (Frehse, 1973 Caffarelli et ah, 1979 Schild, 1984). The last paper also contains the results on the solution smoothness in the case of thin obstacles. As for general solution properties for the equilibrium problem of the plates having cracks, one may refer to (Morozov, 1984). Referring to this book, the boundary conditions imposed on crack faces have the equality type. In this case there is no interaction between the crack faces. 

Solution Properties. Typically, if a polymer is soluble ia a solvent, it is soluble ia all proportions. As solvent evaporates from the solution, no phase separation or precipitation occurs. The solution viscosity iacreases continually until a coherent film is formed. The film is held together by molecular entanglements and secondary bonding forces. The solubiUty of the acrylate polymers is affected by the nature of the side group. Polymers that contain short side chaias are relatively polar and are soluble ia polar solvents such as ketones, esters, or ether alcohols. As the side chaia iacreases ia length the polymers are less polar and dissolve ia relatively nonpolar solvents, such as aromatic or aUphatic hydrocarbons. 

P. W. AHen, Technique of Polymers Characterisation, Butterworths, London, 1959 Dilute Solution Properties of Acrylic andMethacylic Polymers, SP-160, Rohm and Haas Co., Philadelphia, Pa. 

Gums are used in industry because their aqueous solutions or dispersions possess suspending and stabilising properties. In addition, gums may produce gels or act as emulsifiers, adhesives, flocculants, binders, film formers, lubricants, or friction reducers, depending on the shape and chemical nature of the particular gum (2). Considerable research has been carried out to relate the stmeture and shape (conformation) of some gums to their solution properties (3,4). 

Solution Properties. Lignin in wood behaves as an insoluble, three-dimensional network. Isolated lignins (milled wood, kraft, or organosolv lignins) exhibit maximum solubiUty in solvents having a Hildebrand s solubiUty parameter, 5, of 20.5 — 22.5(J/cm ) (10 — ll(cal/cm ) > and A// in excess of 0.14 micrometer where A]1 is the infrared shift in the O—D bond when the solvents are mixed with CH OD. Solvents meeting these requirements include dioxane, acetone, methyl ceUosolve, pyridine, and dimethyl sulfoxide. 

K. Gekko, ia D. A. Brant, ed.. Solution Properties ofPoljsaccharides ACS Symposium Series 150, American Chemical Society, Washington, D.C., 1981, pp. 415-438. 

Orthophosphate salts are generally prepared by the partial or total neutralization of orthophosphoric acid. Phase equiUbrium diagrams are particularly usehil in identifying conditions for the preparation of particular phosphate salts. The solution properties of orthophosphate salts of monovalent cations are distincdy different from those of the polyvalent cations, the latter exhibiting incongment solubiUty in most cases. The commercial phosphates include alkah metal, alkaline-earth, heavy metal, mixed metal, and ammonium salts of phosphoric acid. Sodium phosphates are the most important, followed by calcium, ammonium, and potassium salts. 

Butadiene copolymers are mainly prepared to yield mbbers (see Styrene-butadiene rubber). Many commercially significant latex paints are based on styrene—butadiene copolymers (see Coatings Paint). In latex paint the weight ratio S B is usually 60 40 with high conversion. Most of the block copolymers prepared by anionic catalysts, eg, butyUithium, are also elastomers. However, some of these block copolymers are thermoplastic mbbers, which behave like cross-linked mbbers at room temperature but show regular thermoplastic flow at elevated temperatures (45,46). Diblock (styrene—butadiene (SB)) and triblock (styrene—butadiene—styrene (SBS)) copolymers are commercially available. Typically, they are blended with PS to achieve a desirable property, eg, improved clarity/flexibiHty (see Polymerblends) (46). These block copolymers represent a class of new and interesting polymeric materials (47,48). Of particular interest are their morphologies (49—52), solution properties (53,54), and mechanical behavior (55,56). 

This definition is the means by which partial properties are calculated from solution properties. Equation 115 can now be written as equation 117 ... 

This summability equation, the counterpart of equation 116, provides for the calculation of solution properties from partial properties. Differentiation of equation 122 yields equation 123 ... 

Solubility and Solution Properties. Poly(vinyhdene chloride), like many high melting polymers, does not dissolve in most common solvents at ambient temperatures. Copolymers, particularly those of low crystallinity, are much more soluble. However, one of the outstanding characteristics of vinyUdene chloride polymers is resistance to a wide range of solvents and chemical reagents. The insolubiUty of PVDC results less from its... 

The dilute solution properties of copolymers are similar to those of the homopolymer. The intrinsic viscosity—molecular weight relationship for a VDC—AN copolymer (9 wt % AN) is [77] = 1.06 x 10 (83). The characteristic ratio is 8.8 for this copolymer. 

An extensive investigation of the dilute solution properties of several acrylate copolymers has been reported (80). The behavior is typical of flexible-backbone vinyl polymers. The length of the acrylate ester side chain has Httle effect on properties. 

Monovalent cations are compatible with CMC and have Httle effect on solution properties when added in moderate amounts. An exception is sUver ion, which precipitates CMC. Divalent cations show borderline behavior and trivalent cations form insoluble salts or gels. The effects vary with the specific cation and counterion, pH, DS, and manner in which the CMC and salt are brought into contact. High DS (0.9—1.2) CMCs are more tolerant of monovalent salts than lower DS types, and CMC in solution tolerates higher quantities of added salt than dry CMC added to a brine solution. 

Polyisobutylene is readily soluble in nonpolar Hquids. The polymer—solvent interaction parameter Xis a. good indication of solubiHty. Values of 0.5 or less for a polymer—solvent system indicate good solubiHty values above 0.5 indicate poor solubiHty. Values of X foi several solvents are shown in Table 2 (78). The solution properties of polyisobutylene, butyl mbber, and halogenated butyl mbber are very similar. Cyclohexane is an exceUent solvent, benzene a moderate solvent, and dioxane a nonsolvent for polyisobutylene polymers. 

The basis for calculation of partial properties from solution properties is provided by this equation. Moreover, the preceding equation becomes... 

Equation (4-49) is merely a special case of Eq. (4-48) however, Eq. (4-50) is a vital new relation. Known as the summahility equation, it provides for the calculation of solution properties from partial properties. Thus, a solution property apportioned according to the recipe of Eq. (4-47) may be recovered simply by adding the properties attributed to the individual species, each weighted oy its mole fraction in solution. The equations for partial molar properties are also valid for partial specific properties, in which case m replaces n and the x, are mass fractions. Equation (4-47) applied to the definitions of Eqs. (4-11) through (4-13) yields the partial-property relations ... 

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