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

The assembly of rod-like particles due to weak attractive interactions is an important problem in both understanding the properties several soft biological materials as in designing colloidal gels with tailored properties at extremely low solid contents. Understanding 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, as 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 total interaction potential can be tailored independently 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 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 balance between the attractive and repulsive contributions and the volume fraction.