Publications - 1989
Previous year | Overview | Next year
The diffusion of benzene in high silica zeolite ZSM 5 studied by PFGNMR and QUENS
Mark Morgan, Terence Cosgrove and Robert Richardson
School of Chemistry, University of Bristol, Bristol, UK
Colloids Surf. (1989), 36(2), 209-19
Abstract
The diffusion of C6H6 in high silica zeolite ZSM5 has been studied at various coverages by pulsed field gradient NMR (PFGNMR) and quasi-elastic neutron scattering (QUENS). The PFGNMR technique has probed inter- and intra-cryst. diffusion over the millisecond timescale giving intra coeffs. of the order 10-10 m2 s-1 and inter coeffs. in the range from 10-7 to 10-9 m2 s-1 with increasing coverage. This suggests a 'viscous' liq.-like environment inside the zeolite but rather faster diffusion between crystallites. QUENS has probed intra-cryst. diffusion on the nanosecond timescale giving results in the range 10-10 to 10-9 m2 s-1 at high coverages. A jump activation energy for this process of 5.0 ± 0.4 kJ mol-1 has been estd. over the temp. range of 213 to 343 K.
The determination of the structure of block copolymers at interfaces using small-angle neutron scattering
T. Cosgrove, T.L. Crowley, L.M. Mallagh, K. Ryan and J.R.P. Webster
School of Chemistry, University of Bristol, Bristol, UK
Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) (1989), 30(1), 370-1
Abstract
Small-angle neutron scattering was used to det. the vol. fraction profiles of polyoxyethylene, ethylene oxide-propylene oxide block copolymer, and vinyl alc.-vinyl acetate copolymer adsorbed on polystyrene latex from water. The results were compared with vol. fraction profiles obtained by the self-consistent mean-field theory of Scheutjens and Fleer and Monte Carlo simulations. The collapse of an adsorbed layer was obsd. as the solvency worsened, leading to flocculation of the dispersion.
Previous year | Overview | Next year
