We present a novel type of "rod-coil" graft copolymer containing a polyphenylene backbone linked with poly(ethylene oxide) (PEO) side chains. Such graft copolymers manifest unprecedented temperature-dependent one-dimensional (1D) and two-dimensional (2D) self-assembly in solution. At 20 degrees C, which is higher than the crystallization temperature (T-c) of the PEO chains, the achiral graft copolymers self-organize into nanoribbons that twist into similar to 30 mu m ultralong helices with controlled pitch depending on the grafting ratio of the PEO chains. At 10 degrees C, which is lower than the T-c, quadrangular multilayer sheets of over 10 mu m in lateral size are obtained. To our knowledge, this work presents the first example of controlled self-assembly of graft polymers into 1D helix and 2D sheet superstructures.