SynopsisA 1:l hydrogen-bonded complex was formed between acrylic acid (AA) or methacrylic acid (MA) and the pyridine group of poly(4-vinylpyridine) (P4VP) in dilute solutions. A shift of infrared absorption of the hydrogen-bonded acid 0-H to a lower energy direction and an upfield shift of acid proton in the NMR were observed when the monomers were added with pyridine. The equilibrium constants of the 1:l complexation with P4VP measured by using a semipermeable membrane were 0.58 and 0.26 for AA and MA, respectively, at 25'C in methanol. The bromometrically measured initial rate of radical polymerization showed only a slight enhancement in the presence of P4VP, the rate being maximum at the 4VP unitmonomer mole ratio of 0.25 and 0.5 for AA and MA, respectively, in dilute methanol solution at 60°C.
EXPERIMENTAL MaterialsReagent-grade chemicals were used. AA (Tokyo Kasei), MA (Fluka), and 4-vinylpyridine (4VP) (Fluka) were fractionally distilled before use. 2,2'-Azobisisobutyronitrile (AIBN) (British Drug House) was recrystallized from
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