Solubility structure effects

Solubility Structure Effects Pressure Effects Temperature Effects (for Aqueous Solutions)... 

Organic peroxide-aromatic tertiary amine system is a well-known organic redox system 1]. The typical examples are benzoyl peroxide(BPO)-N,N-dimethylani-line(DMA) and BPO-DMT(N,N-dimethyl-p-toluidine) systems. The binary initiation system has been used in vinyl polymerization in dental acrylic resins and composite resins [2] and in bone cement [3]. Many papers have reported the initiation reaction of these systems for several decades, but the initiation mechanism is still not unified and in controversy [4,5]. Another kind of organic redox system consists of organic hydroperoxide and an aromatic tertiary amine system such as cumene hydroperoxide(CHP)-DMT is used in anaerobic adhesives [6]. Much less attention has been paid to this redox system and its initiation mechanism. A water-soluble peroxide such as persulfate and amine systems have been used in industrial aqueous solution and emulsion polymerization [7-10], yet the initiation mechanism has not been proposed in detail until recently [5]. In order to clarify the structural effect of peroxides and amines including functional monomers containing an amino group, a polymerizable amine, on the redox-initiated polymerization of vinyl monomers and its initiation mechanism, a series of studies have been carried out in our laboratory. 

For most organic chemicals the solubility is reported at a defined temperature in distilled water. For substances which dissociate (e.g., phenols, carboxylic acids and amines) it is essential to report the pH of the determination because the extent of dissociation affects the solubility. It is common to maintain the desired pH by buffering with an appropriate electrolyte mixture. This raises the complication that the presence of electrolytes modifies the water structure and changes the solubility. The effect is usually salting-out. For example, many hydrocarbons have solubilities in seawater about 75% of their solubilities in distilled water. Care must thus be taken to interpret and use reported data properly when electrolytes are present. 

The largest solubility isotope effects are found for sparingly soluble salts. For example, lead chloride and potassium bichromate are 36% and 33.5% more soluble in H20 than D20 at 298.15 and 278.15 K, respectively. For the more soluble salts, NaCl and KC1, the values are 6.4% and 9.0%. Interestingly LiF and LiCl.aq have inverse effects of 13% and 2%, respectively. Recall that lithium salts are commonly designated as structure makers . Almost all other electrolytes are structure breakers . 

Because the entropy of formation in Hildebrand theory is ideal, this approach should be restricted to those systems in which there are no structure effects due to solute-solvent and solvent-solvent interactions. The implication of this is that the solute should be non-ionic and not have functional groups which can interact with the solvent. According to Equation (4.8), the maximum solubility occurs when the Hildebrand parameter of the solvent is equal to the Hildebrand parameter of the solute. That is, when plotting the solubility versus the Hildebrand parameter, the solubility exhibits a maximum when the solubility parameter of the solvent is equal to the solubility parameter of the solute. 

Fluorine is an essential element involved in several enzymatic reactions in various organs, it is present as a trace element in bone mineral, dentine and tooth enamel and is considered as one of the most efficient elements for the prophylaxis and treatment of dental caries. In addition to their direct effect on cell biology, fluoride ions can also modify the physico-chemical properties of materials (solubility, structure and microstructure, surface properties), resulting in indirect biological effects. The biological and physico-chemical roles of fluoride ions are the main reasons for their incorporation in biomaterials, with a pre-eminence for the biological role and often both in conjunction. This chapter focuses on fluoridated bioceramics and related materials, including cements. The specific role of fluorinated polymers and molecules will not be reviewed here. 

Absorption is necessary for the chemical to exert a systemic biological/toxic effect and involves crossing membranes. Membranes are semipermeable phospholipid/protein bilayers. The phospholipids and proteins are of variable structure, and the membrane is selectively permeable. The physicochemical characteristics of foreign molecules that are important include size/shape, lipid solubility, structure, and charge/polarity. 

Entropy is a measure of disorder. The largest negative entropy of solution in Table 3.1 is generally considered as evidence of the creation of structure (increased order) within the body of water. More recently it has been suggested that the creation of a cavity can explain the entropy decrease. Large heat capacity changes also indicate the structuring effect of the solute on the water molecules. The size of the solute molecule has a substantial effect on solubility. 

Registry of Toxic Effects of Chemicals (Sub-)Structural Alerts Statistical Analysis System Aqueous solubility Structure-Activity Relationship Self-Consistent Field Structure Data File Sex Hormone Binding Globulin Simplified Molecular Line Entry System... 

Deviation from this conventional aggregation behaviour and appearance of more complex superstructures occur, like in biological systems, when specific non-covalent interactions, chirality, and secondary structure effects come into play [11,12]. Particularly interesting are block copolymers that combine advantageous features of synthetic polymers (solubility, process-... 

The phase behaviour of biomimetic polypeptide-based copolymers in solution was described and discussed with respect to the occurrence of secondary structure effects. Evidently, incorporation of crystallisable polypeptide segments inside the core of an aggregate has impact on the curvature of the corecorona interface and promotes the formation of fibrils or vesicles or other flat superstructures. Spherical micelles are usually not observed. Copolymers with soluble polypeptide segments, on the other hand, seem to behave like conventional block copolymers. A pH-induced change of the conformation of coronal polypeptide chains only affects the size of aggregates but not their shape. The lyotropic phases of polypeptide copolymers indicate the existence of hierarchical superstructures with ordering in the length-scale of microns. 

One hydrophilic anthraquinone dye (Al) and one hydrophobic anthraquinone dye (A2) were selected to explore the effect of solubility to the UV-irradiation. From the experimental data, the hydrophilic anthraquinone dye (sulphonate anthraquinone reactive dye) has about twice the dye removal rate than hydrophobic anthraquinone dyes at high pH. Since all the anthraquinone dyes have similar chemical structures and the pH did not show any distinguish effect in dye removal for A2, it is obvious that the rate difference is mainly due to the difference of solubility. The effect of dye s solubility to the photodegradation may be interpreted by the photo-ionization mechanisms proposed by Leaver I.H. (1980). The water can carry the charged intermediates (Al only), which lower the photo-ionization energy and therefore facilitate the dye degradation. 

Structural effects are best illustrated with respect to polyesters. The vast majority of aromatic polyesters which are fusible and contain a substantial number of para links tend to be liquid crystalline in the melt. Their low solubility means that such materials are not normally found to be lyotropic. 

Since three of the major wall components are potentially water soluble, the effective removal or weakening of the cell wall must involve enzymatic hydrolysis of the long chains of / -(1 - 3)-linked glucose residues in the microfibrillar, alkali-insoluble glucan layer. In some species of yeast an additional structural wall component occurs, which has been identified as a linear -( —> 3)-glucan. 

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