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. Unlike the conventional way for blending BCP with homopolymer, 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, by taking advantage of degradable character of the PLLA, nanoporous gyroid SiO2 can be fabricated using hydrolyzed PS–PLLA blends as a template for sol–gel reaction followed by removal of the PS matrix.