Correlation of Composition and DP of Some ThreeComponent Phenolic Block Copolymers with Their Titration Curves in Nonaqueous Media

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Abstract
Some three-component phenolic block copolymers have been prepared from the following three monomeric units: p-amino-phenol, p-chlorophenol, and p-creso1. Homopolymerization of these monomers has been done with formaldehyde in the presence of acid catalyst. The homopolymer samples were then condensed together with stoichiometric quantities of formaldehyde and acid catalyst. Several samples of the copolymers were also prepared by changing the composition of the feed during homopolymerization. Composition, DP, and the average number of a particular monomeric uhit in a block of a copolymer chain has been deduced from electrometric titration curves of the copolymers in nonaqueous media. Simultaneous copolymerization of three different monomer species may give rise to a copolymer whose composition will depend on the relative reactivity of the monomers. In normal copolymerization the different monomers alternate in the chain either in a more or less regular or in a completely random manner. Some preliminary investigations on a few three-component random phenolic copolymers revealed that composition, DP, and dissociation behavior of such systems could be evaluated by electrometric titration techniques in nonaqueous media [1]. Since three-component copolymers as such are quite complex, it was therefore considered of interest to see whether such simple techniques could be used for getting information about these copolymers prepared under various conditions. Keeping this fact in view, block copolymers involving the following three monomeric units have been prepared: p-aminophenol (PAP), p-chlorophenol (PClP), and p-cresol (PC). Block copolymers have been prepared by combining the homopolymer chains of the three monomers with the aid of functional groups and formaldehyde. The feed composition of the homopolymers has also been varied to change the size of the blocks. The characteristic feature of these three-component copolymers is the presence of a phenolic OH group in each of its repeating units and the presence of -NH2 and Cl groups as structural substi-tuents in some of the repeating units. One can thus deduce the composition of the copolymers from the quantitative estimation of C1 and -NHz groups. An attempt has been made in this paper to correlate composition, DP, size of some of the blocks in the copolymer chains, intramolecular hydrogen bonding, etc. with the features of electro-metric titration curves of the copolymers in nonaqueous media.