Carboxylic acids solubilising

Positive photoresists, by contrast, are based on water-soluble novolak resins with naphthalene diazoquinone sulfonate (NDS) as the photosensi-tiser. On photolysis the NDS causes a rearrangement in the polymer to yield nitrogen gas plus an indene carboxylic acid. This latter functional group considerably increases the solubility of the polymer, hence solubilising those areas of the polymer that had been exposed to light. 

Although not part of soil, lichens, by virtue of their solubilising action on rocks, contribute to the elemental enrichment of soil. Several studies have identified lichen acids as complexing agents for the iron and aluminium of rocks (95, 96). An examination of the various structures indicates that the basic structure responsible for the chelation is the carboxylic acid group with an orthophenolic group. Grodzinskii (97) has found lichens to be intense accumulators of elements in the uranium-radium, actinouranium and thorium orders. 

The action of alkaline scouring agent is to saponify any residual oils, to neutralise carboxylic acids, to solubilise any sizing materials and to cause dispersion of naturally occuring impurities in natural fibres. Table 4.1 summerises the removal process involved during scouring. 

Poly(alkyl aryl ether) dendrimers functionalised at the periphery with carboxylic acid groups [69] or phenol groups [70] have been employed in this capacity by Ramamurthy and co-workers. After the presence of a hydrophobic microenvironment within the den-drimer core had been established via pyrene solubilisation studies, photochemical reactions were carried out to assess the viability of the dendrimers as reaction cages or phase transfer catalysts. All of the photochemical reactions studied were carried out successfully in aqueous media, on compounds normally water insoluble, with increasing cage effect observed for higher generation dendrimers. The viability of these dendrimer systems as photochemical reaction media was thus established. 

The present report describes the covalent conjugation of paclitaxel to y-carboxylic acids of poly-L-glutamic (PG) acid (CT-2103). Paclitaxel is a particularly appropriate molecule for conjugation to a polymer carrier because it is broadly active as an anti-tumour agent, yet it is difficult to deliver because it is highly hydrophobic. The commercial preparations of pacKtaxel use Cremophor and ethanol as solubilising agents. These have inherent toxicities and require slow infusions and premedications with corticosteroids and histamine receptor blockers. 

The polymer composition raises several interesting points. Hydroxy ethyl methacrylate could be replaced effectively wt./wt. by hydroxy ethyl acrylate. The hydroxyethyl acrylate reacts more readily with melamine resins than carboxylic acids. The acrylic acid is added to give water solubility when neutralised. Note that in the absence of the hydroxy monomer, more acrylic acid would be required to solubilise the polymer. The VeoVa has a softening effect on the copolymer and also contributes water resistance to the film. 

Many acrylic acid copolymers are water-soluble but unlike poly(vinyl alcohol) they are not degraded by alkali. In fact they need alkali for effective desizing as they are more soluble at alkaline pH than in neutral solutions. They are sensitive to acidic media, which should not be used. Solubilisation occurs by the formation of sodium carboxylate groups from the anionic polyacid. The polyelectrolyte formed in this way is readily soluble and shows a rapid rate of dissolution. However, the presence of electrolytes such as magnesium or calcium salts from hard water can inhibit removal [191]. 

PEEKS can be made by two general routes. In both cases the main difficulty is to keep the crystallisable polymer in solution. Formation of the carboxyl link by polyaroylation can be carried out in liquid HF by catalysts such as BF3. The reaction is also possible in solvents such as dichlorobenzene with an excess of AICI3 both to catalyse the reaction and to solubilise the polymer by complexing with the carbonyl group in the backbone. AICI3 must then be neutralized and extracted from the polymer. The waste stream contains organic compounds, aluminium salts and hydrochloric acid. 

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