TY  - JOUR
AU  - Pohlmeier, A.
AU  - Haber-Pohlmeier, S.
TI  - Ionization of short polymethacrylic acid: titration, DLS and model calculations
JO  - Journal of colloid and interface science
VL  - 273
SN  - 0021-9797
CY  - Amsterdam [u.a.]
PB  - Elsevier
M1  - PreJuSER-38456
SP  - 369 - 380
PY  - 2004
N1  - Record converted from VDB: 12.11.2012
AB  - In this work the charging of polymethacrylic acid in excess electrolyte solution is investigated experimentally by titration and dynamic light scattering. The results are analyzed by a penetrable sphere model, which employs the Poisson-Boltzmann equation for the description of electrostatic interactions and takes into account specific binding of H+ and Na+. The evaluation of the DLS data yields two relaxation modes. The slow mode is present only at finite degrees of charging and is therefore caused by collective diffusion. The fast mode, which corresponds to diffusion coefficients in the range from (1.1 to 1.5) x 10(-10) m2 s(-1), is present over the whole pH range. This reflects the diffusional dynamics of the polyion itself and allows the calculation of hydrodynamic radii for equivalent spheres (RH). These increase from 1.5 nm at pH 2.14 up to 1.8 nm for a degree of deprotonation alpha=0.47 at pH 5.86. With a further increase of pH the radii slightly decrease to 1.6 nm. Setting the radius of the penetrable sphere equal to RH, we can successfully model the overall charging curve with logK0H=4.85 and logK0Na=-0.6. This means that weak complexes of the type COO---Na are formed, which reduce the effective charge inside the polyelectrolyte coil.
KW  - J (WoSType)
LB  - PUB:(DE-HGF)16
C6  - pmid:15082370
UR  - <Go to ISI:>//WOS:000220999000005
DO  - DOI:10.1016/j.jcis.2004.02.047
UR  - https://juser.fz-juelich.de/record/38456
ER  -