Complexation of sequence-ordered methacrylic acid copolymers with poly(4-vinylpyridine)

The complexation of three kinds of sequence-ordered acid (co)polymers with a base homopolymer was studied. The acid polymers used are poly(methacrylic acid) 1, alternating (1 : 1) ethylene-methacrylic acid copolymer 2, and periodic (2 : 1) ethylene-methacrylic acid copolymer 3, and the base polymer is poly(4-vinylpyridine) 4. When mixing a methanol solution of 1, 2, or 3 with that of 4 (0.1 M of each functional group), precipitate was formed immediately for all polymer pairs. All the precipitates contained carboxyl and pyridyl groups in ca. 1 : 1 molar ratio and showed IR spectra indicating the hydrogen bonding between carboxyl and pyridyl groups. When mixing dilute methanol solutions (10(-4) M) of the above polymer pairs, no precipitation was observed, but the extinction coefficient (epsilon(B)) at 255 nm of pyridyl groups in 4 was found to increase with an increasing acid polymer concentration. This is ascribed to hydrogen bonding between carboxyl and pyridyl groups in methanol. Based on the epsilon(B) variation, the order of complexation constants for acid/base polymer pairs was estimated as follows: 1/4 pair similar to 2/4 pair much greater than 3/4 pair. (C) 1996 John Wiley & Sons, Inc.