An ESR spin label study of the dynamics of a zwitterionic polymer, a polyelectrolyte, poly(methacrylic acid) and poly(acrylic acid) in aqueous solution

✍ Scribed by Thomas A. Wielema; Jan B.F.N. Engberts

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 324 KB
• Volume: 24
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(88)90028-6

✦ Synopsis

The ESR spectra of a spin-labelled 9:1 copolymer of 1-(2-sulphoethyl)-4-vinylpyridinium betaine and 4-vinylpyridine hydrochloride (a zwitterionic polymer) and spin-labelled poly(4-vinylpyridine) hydrochloride (a polyelectrolyte) have been measured in water as a function of the NaC1 concentration. It was found that the molecular tumbling of the spin label (as revealed by the effective rotational correlation time %) was affected by the salt only to a minor extent, despite large variations in the intrinsic viscosity. The ESR spectrum of spin-labelled poly(methacrylic acid) exhibited large changes as a function of the degree of ionization (ct). At low ~t, two distinct ESR spectra were observed showing large differences in z c. The "slow motion" spectrum is assigned to the spin label attached to those parts of the polymer chain which are involved in the formation of hydrophobic microdomains. As anticipated, this type of ESR spectrum disappears at higher ct values where the polymer resides solely in the expanded coil. In accord with this interpretation, spin-labelled poly(acrylic acid) shows only the "fast motion" ESR spectrum irrespective of the value of ~t.