Universality in structure and elasticity of polymer-nanoparticle gels.

We propose a combination of polymer field theory and off-lattice computer simulations to study polymer-bridged gelation in polymer-nanoparticle mixtures. We use this method to study the structure of gels formed in attractive polymer-colloid systems. Our results indicate that such gels exhibit a universal structure with a fractal dimension d(f) approximately 2.5 characteristic of random percolation. By mapping to an affine-network model, the enhancement in elastic moduli is predicted to follow a critical exponent nu(eta) approximately 1.8 characteristic of the resistor network percolation. We analyze selected experimental results to suggest the existence of a universality class corresponding to our results.