Filamentous networks in phase-separating two-dimensional gelsO. Peleg1, M. Kröger2, I. Hecht1 and Y. Rabin1
1 Department of Physics, BarIlan University - Ramat-Gan 52900, Israel
2 Polymer Physics, ETH Zurich, Department of Materials - CH-8093 Zürich, Switzerland
received 20 October 2006; accepted in final form 19 January 2007; published March 2007
published online 22 February 2007
We introduce a toy model that contains the basic features of microphase separation in polymer gels: a stretched elastic network of Lennard-Jones particles, studied in two dimensions. When temperature is lowered below some value T*, attraction between particles dominates over both thermal motion and elastic forces, and the network separates into dense domains of filaments connected by three-fold vertices, surrounded by low-density domains in which the network is homogeneously stretched. The length of the filaments decreases and the number of domains increases with decreasing temperature. The system exhibits hysteresis characteristic of first-order phase transitions: pre-formed filaments thin upon heating and eventually melt at a temperature T** (> T*). Although details may vary, the above general features are independent of network topology (square or hexagonal), system size, distribution of spring constants, and perturbations of initial conditions.
82.70.Gg - Gels and sols.
64.70.Kb - Solid-solid transitions.
68.55.Ac - Nucleation and growth: microscopic aspect.
© Europhysics Letters Association 2007