A tricontinuous $(10,3)c$ network phase is documented in a poly(cyclohexylethylene-$b$-ethylethylene-$b$-ethylene) triblock copolymer melt based on small-angle x-ray scattering. Application of shear transforms the self-assembled soft material into a single crystal $(10,3)d$ network while preserving the short-range threefold connector geometry. Long-range topological restructuring reduces the space group symmetry, from $Fddd$ to $Pnna$, maintaining orthorhombic lattice symmetry. Both phases are stable to long time annealing, indicative of nearly degenerate free energies and prohibitive kinetic barriers.

• Received 19 March 2004

DOI:https://doi.org/10.1103/PhysRevLett.93.087802