Addition of Poor Solvents

PCeiBM as-cast PV devices with 0% (soiid iine), 0.33% (dashed iine), 0.67% (dotted iine), 1.6% (dashed-dotted iine), 3.2% (short dashed iine), and 6.3% (soiid iine) nitrobenzene added into the CB soivent. Offset from the other spectra is the as-cast PV device from the o-xyiene 

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Stage 2. Strong attraction between all monomeric units is switched on and a homopolymer globule (parent conformation) is formed (Fig. la). Of course, when we are speaking about real experiments, by switching on the attraction we should understand the jump of temperature, addition of poor solvent, etc. 

Purely aromatic ketones generally do not give satisfactory results pinacols and resinous products often predominate. The reduction of ketonic compounds of high molecular weight and very slight solubility is facilitated by the addition of a solvent, such as ethanol, acetic acid or dioxan, which is miscible with aqueous hydrochloric acid. With some carbonyl compounds, notably keto acids, poor yields are obtained even in the presence of ethanol, etc., and the difficulty has been ascribed to the formation of insoluble polymolecular reduction products, which coat the surface of the zinc. The adffition of a hydrocarbon solvent, such as toluene, is beneficial because it keeps most of the material out of contact with the zinc and the reduction occurs in the aqueous layer at such high dilution that polymolecular reactions are largdy inhibited (see Section IV,143). 

The course of addition reactions of ROH-XeF2 to alkenes has been elucidated using norbomene, 2-methylpent-2-ene and hex-l-ene as model substrates. It turned out that the alkoxyxenon fluoride intermediates (ROXeF) can react either as oxygen electrophiles (initially adding alkoxy substituent) or as apparent fluorine electrophiles (initially adding fluorine), depending on the reaction conditions. Simple addition of poorly nucleophilic alcohols to norbomene was also observed in certain instances. Selectivity between the various reaction pathways (simple fluorination, alkoxyfluorina-tion, or alcohol addition) proved to be sensitive to various reactions conditions, especially solvent, temperature, and catalyst.27... 

For the enantiomeric separation of propanolol, MIP monoliths have been rendered porous by the addition of isooctane in toluene at 2%. The poor solvent content is a crucial parameter for controlling the porosity of the MIP monolith, a higher concentration of poor solvent leading to a more porous but also more fragile material. Actually, a combination of these two techniques, where the selection of the poor solvent and the timing of polymerisation is optimised, can also be employed for the preparation of preformed imprinted monoliths [166, 167],... 

In table 3 the desorption capacities of each experiment are presented. It can be seen that the desorption capacity (ratio between the desorbed and filled nimesulide) increases with increasing solubility of nimesulide in C02. Due to the high affinity of the activated carbon surface to nimesulide the desorption capacity itself is very poor (max. value 38%). Since higher desorption capacity are related to higher solubilities, the addition of co-solvents to C02, as proposed by Macnaughton et al. [9], can increase the solubility and therewith the desorption capacity. 

The results for the removal of PAHs from the 5 surface substrates are summarized in Table 16. In general, the 23 PAHs listed in the table averaged removal rates around 90% from the smooth surfaces and over 80% for the porous cast magnesium surface. In contrast, supercritical fluid extraction studies using CO2 for the removal of PAHs from soils for environmental applications have shown relatively poor removal efficiencies for many of the compounds listed in the table often requiring the addition of secondary solvents to the C02. However, it appears that from the results on the removal of the PAHs shown in Table 16, surface contamination is... 

In addition to the formation of coordination spherical nanoparticles, the self-assembly of coordination chains and helices can also lead to the formation of crystalline nanoparticles with different shapes. Overall, these nanocrystals can be obtained following two different strategies. The first one involves the use of specific synthetic methodologies (e.g., use of poor solvent, hydrothermal... 

The collapse consists in a strong decrease of the gel volume (by a factor of several tens or hundreds) in response to a small change in the enviroirmental conditions such as temperature, pH, various additives (thermodynamically poor solvent, surfactant, linear polymer), light, electric field, and magnetic field. 

A large number of materials have poor solubilities in water and often pose a problem in the formulation of pharmaceutical products. Addition of another solvent, in which these materials are more readily soluble, will increase the concentration of the materials in the solution. This additional solvent is known as a cosolvent and common examples include glycerin, sorbitol, propylene glycol, and polyethylene glycols. The proportion of cosolvent required varies from system to system. 

Solvent retention within the polymer matrix, as discussed in Chapter 3 for P(ANi), or alternatively, retention of solvent "affinity sites", are important factors sometimes ignored by many workers. Thus, for instance, several poly (diphenyl amine) derivatives, when electropolymerized in acetonitrile or PC, will electrochemically cycle well only in the solvent of electropolymerization [36, 74, 67, 75]. Solvents may also be too nucleophilic besides its high solvation capability for even doped CPs, dimethyl formamide (DMF) is also a poor electropolymerization solvent due to high nucleophilicity if this is reduced with addition of protic solvents, electropolymerizations are observed [43]. Table 5-2 cited above has [43] summarized electropolymerization data for P(Py) in various solvents. 

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