Acid, carboxylic water-polymer functional group

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. 

M. Yoshikawa, T. Yukoshi, K. Sanui, N. Ogata, Selective separation of water-ethanol mixture through synthetic polymer membranes having carboxylic acid as a functional group, J. Polym. Sci. Part A Polym. Chem. 24 (1986) 1585-1597. 

Monomers can be joined by means of two principal methods to form polymers, and these methods are used as the broad basis for classification of synthetic polymers. The first of these, condensation, or step-growth polymerization, involves the use of functional group reactions such as esterification or amide formation to form polymers. When each of the molecules involved has only one functional group then the reaction between a carboxylic acid and an alcohol gives an ester (Eq. 20.3). In this equilibrium reaction water removal will help drive the reaction to the right. 

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