Macro- and microphase separation in multifunctional supramolecular polymer networks

We present a field-based model for the phase separation and gelation of a binary melt of multifunctional monomeric units that can reversibly bond to form copolymer networks. The mean-field phase separation behavior of several model networks with heterogeneous bonding is calculated via the random phase approximation (RPA). By this technique, the spinodal phase boundary (stability limit of the homogeneous disordered phase) is obtained by a combination of analytical and numerical methods. It is demonstrated that higher functionality and more favorable bonding energy suppresses macroscopic phase separation due to greater connectivity between unlike species. Gelation occurs with sufficiently high connectivity of tri- or higher functional monomeric units and microphase separation of the copolymer network can occur either preceding or after the gel point. Eutectic-like behavior of the spinodal is seen in highly connected networks due to excess loosely connected material in systems having nonstoichiometric ratios...