A Facile Method to Fabricate Double Gyroid as A Polymer Template for Nanohybrids

Here, we suggest a facile method to acquire double gyroid (DG) phase from the self-assembly of chiral block copolymers (BCPs*), polystyrene-$b$-poly(L-lactide) (PS-PLLA). A wide region for the formation of DG can be found in the phase diagram of the BCPs*, suggesting that helical phase (H*) from the self-assembly of BCPs* can serve as a stepping stone for the formation of the DG due to an easy path for order-order transition from two-dimensional to three-dimensional (network) structure. Moreover, the order-order transition from metastable H* to stable DG can be expedited by blending the PS-PLLA with compatible entity. Moreover, PS-PLLA blends are prepared by using styrene oligomer (S) to fine-tune the morphologies of the blends at which the molecular weight ratio of the S and compatible PS block ($r)$ is less than 0.1. Owing to the use of the low-molecular-weight oligomer, the increase of BCP chain mobility in the blends significantly reduces the transformation time for the order-order transition from H* to DG. Consequently, nanoporous gyroid SiO$_{\mathrm{2}}$ can be fabricated using hydrolyzed PS-PLLA blends as a template for sol-gel reaction followed by removal of the PS matrix.