Hyperuniformity and density fluctuations at a rigidity transition in a model of biological tissues

Density fluctuations are suppressed up to a length scale which diverges at the putative solid–liquid transition.

The role of rigidity in controlling material failure

We investigate how material rigidity acts as a key control parameter for the failure of solids under stress. In both experiments and simulations, we demonstrate that material failure can be continuously tuned by varying the underlying rigidity of the material while holding the amount of disorder constant. As the rigidity transition is approached, failure due to the application of uniaxial stress evolves from brittle cracking to system-spanning diffuse breaking. This evolution in failure behavior can be parameterized by the width of the crack. As a system becomes more and more floppy, this crack width increases until it saturates at the system size. Thus, the spatial extent of the failure zone can be used as a direct probe for material rigidity.

Effect of cross-linking on rheological properties and a model for flexibility-rigidity transition in SBS/PBMA LIPNs

A series of latex interpenetrating polymer networks (LIPNs) with various cross-linking levels were prepared with polystyrene-polybutadiene-polystyrene (SBS) and butyl methacrylate (BMA) by emulsion polymerization. The gel content of the resultant latex particles ranged from 13.2% to 90.8%, with the amount of cross-linking agent increased. The structural, thermal and rheological properties of the latex particles were investigated by laser particle analysis, transmission electron microscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry and torque rheometry. Furthermore, in order to study the effect of gel content on the flow properties, a model is shown to predict the existence of a flexibility-rigidity transition of SBS/PBMA LIPNs as the amount of cross-linking agent increased. Torque data were interpreted in terms of shear rate, shear stress and viscosity. The relationship between gel content of SBS/PBMA LIPNs and polyvinyl chloride compositions and their effect on plasticization performance were determined, and the predictions of the model have good agreement with their flexibility-rigidity transition.