High-Pressure Dynamic Light Scattering of Poly(ethylene-co-1-butene) in Ethane, Propane, Butane, and Pentane at 130 °C and Kilobar Pressures

Cononsolvency of the responsive polymer poly(N-isopropylacrylamide) in water/methanol mixtures: a dynamic light scattering study of the effect of pressure on the collective dynamics

The collective dynamics of 25 wt% poly(N-isopropylacrylamide) (PNIPAM) solutions in water or an 80:20 v/v water/methanol mixture are investigated in the one-phase region in dependence on pressure and temperature using dynamic light scattering. Throughout, two dynamic modes are observed, the fast one corresponding to the relaxation of the chain segments within the polymer blobs and the slow one to the relaxation of the blobs. A pressure scan in the one-phase region on an aqueous solution at 34.0 °C, i.e., slightly below the maximum of the coexistence line, reveals that the dynamic correlation length of the fast mode increases when the left and the right branch of the coexistence line are approached. Thus, the chains are rather swollen far away from the coexistence line, but contracted near the phase transition. Temperature scans of solutions in neat H2O or in H2O/CD3OD at 0.1, 130, and 200 MPa reveal that the dynamic correlation length of the fast mode shows critical behavior. However, the critical exponents are significantly larger than the value predicted by mean-field theory for the static correlation length, ν = 0.5, and the exponent is significantly larger for the solution in the H2O/CD3OD mixture than in neat H2O.

Pressure assisted stabilization of biocatalysts at elevated temperatures: characterization by dynamic light scattering

The effect of pressure, at elevated temperatures, is reported on the activity and stability of a thermophilic endo-β-glucanase from the filamentous fungus Talaromyces emersonii. The production of reduced sugars after treatment at different temperatures and pressures is used as a measure of the activity and stability of the enzyme. The activity of the enzyme is maintained to higher temperatures with increasing pressure. For example, the relative activity of endo-β-glucanase decreases to 30% after 4 h at 75°C and 1 bar, whereas it is preserved at 100% after 6 h at 75°C and 230 bar. High-pressure dynamic light scattering is used to characterize the hydrodynamic radius of the enzyme as a function of pressure, temperature, and time. At higher temperature the hydrodynamic radius increases with time, whereas increasing pressure suppresses this effect. Changes in the hydrodynamic radius are correlated with the activity measurements obtained at elevated pressures, since the changes in the hydrodynamic radius indicate structural changes of the enzyme, which cause the deactivation.