HYDROGEN BONDS OF POLY(N-ALKYL METHACRYLATE)-CO-(METHACRYLIC ACID)'S IN DILUTE SOLUTIONS

The nature of the association of poly[(n-alkyl methacrylate)-co-(methacrylic acid)]’s (poly(RMA-co-MAA)’s) in dilute chloroform solutions was investigated by Fourier transform infrared (FT-IR) spectroscopy and the solution viscosity. The proportions (Pfree) of free carboxyls increased with the length of the alkyl groups in RMA’s and with the decreasing MAA composition. From the relationships between Pfree and the effective concentration (Ceff) of carboxyls attached to the polymer chain, it was shown that the major substituent effects of the alkyl groups on the hydrogen bonds in the copolymers are the extension of the polymer chain and the steric effect on the association between carboxyls and ester groups. Also, from the features of the shrinkage of the polymer chains accompanied with the intrachain association of carboxyls it was suggested that the hydrogen bonds in the copolymers are formed chiefly between neighboring sites along the chain.