Université de Fribourg

A new instrument for time-resolved static and dynamic light-scattering experiments in turbid media

Moitzi, Christian ; Vavrin, Ronny ; Bhat, Suresh Kumar ; Stradner, Anna ; Schurtenberger, Peter

In: Journal of Colloid and Interface Science, 2009, vol. 336, no. 2, p. 565-574

We present a new 3D cross-correlation instrument that not only allows for static and dynamic scattering experiments with turbid samples but measures at four angles simultaneously. It thus extends the application of cross-correlation light scattering to time-resolved studies where we can, for example, efficiently investigate the temporal evolution of aggregating or phase separating turbid...

Université de Fribourg

Deswelling microgel particles using hydrostatic pressure

Lietor-Santos, Juan-Jose ; Sierra-Martin, Benjamin ; Vavrin, Ronny ; Hu, Zhibing ; Gasser, Urs ; Fernandez-Nieves, Alberto

In: Macromolecules, 2009, vol. 42, no. 16, p. 6225–6230

We report on the use of hydrostatic pressure, P, to deswell thermosensitive poly(N-isopropylacrylamide) (pNIPAM) microgels and show that it can affect the polymer−solvent mixing as much as temperature, which is the traditional variable used to deswell pNIPAM particles. Interestingly, the microgel volume changes more gradually with pressure than it does with temperature. By comparing the...

Université de Fribourg

Time-resolved investigation of aggregation and sol-gel transition in colloidal suspensions

Vavrin, Ronny ; Schurtenberger, Peter (Dir.)

Thèse de doctorat : Université de Fribourg, 2005 ; Nr. 1497.

In this work we present a study of the aggregation and sol-gel transition of colloidal suspensions using a wide range of experimental techniques, where some of them were modified or developed especially for this purpose. Covering all relevant time and length scales, we investigate in the first part of this work a model system which undergoes a sol-gel transition in the hope to gain further...