The active and critical contribution of the HEA monomer and polymer to the self-assembly of GMO was evident through modifications in the composition-temperature phase behavior of the GMO/water system. The photo-induced polymerization of HEA inside the nanoconfined domains led to a reorganization of the water channel network. This is evident from transforming the Pn3mtype cubic structure to an Im3m-type cubic structure in bulk and thin films. The Im3m structure in the GMO/poly-HEA/water system was stable over a wide temperature range. The larger polymer molecules within the structural network appear to act as a backbone, reducing the degrees of freedom in this system and stabilizing the structure. Additionally, GISAXS demonstrated the structural orientation of bicontinuous cubic phases on silicon-wafer surfaces and their reorientation accompanying polymerization-triggered phase transitions.