Colloidal Mikado: Rheology and Structure of Thermoreversible Gels of Sticky Rod-Like Particles

The assembly of rod-like particles by weak attractive inter- actions is important for the properties of several soft biological materials as well as in tailoring the properties of colloidal gels in a variety of applications. Under- standing the link between the physicochemical parameters such as size and aspect ratio, volume fraction, interparticle forces with the resulting microstructure and the rheological response remains however challenging. It is often difficult to obtain a good control over these parameters due to the lack of suitable model systems. In the present work a model rod-like fd-virus particle has been surface modified with a thermoreversible polymer poly(N-isoproplyacrlyamide). The repulsive and attractive contributions to the overall interaction potential can be varied indepen- dently by changing the ionic strength and the temperature. The effects of these changes on the strength and structure of the gel have been studied near the gel transition using a combination of rheological and scattering measurements. The results show that for these thermoreversible ’sticky’ rod systems, the variations of the structure in the gelled state are relatively weak, with the gel strength mainly being controlled by the relative magnitudes between the attractive and repulsive contributions and the volume fraction, the anisotropic nature of the electrostatic interactions seems to have a minor effect.status: accepte