Formation of Diverse Ordered Structures in ABC Triblock Terpolymer Templated Macroporous Silicas

The macroporous silica synthesis system with the ABC triblock terpolymer poly­(ethylene oxide)-<i>block</i>-polystyrene-<i>block</i>-poly­(<i>tert</i>-butyl acrylate) (denoted as OSA) as template and tetraethyl orthosilicate as silica source under acidic conditions in a mixture solvent of tetrahydrofuran and H₂O has been investigated, and two synthesis–field phase diagrams are plotted. Eight different structures varied from normal-phase (oil in water) cage-type (<i>n</i>-C), normal-phase 2D hexagonal (<i>n</i>-H), and lamellar (L) to unique inverse-phase (water in oil) hyperbolic-surface (<i>i</i>-HS) structures, including the shifted double-diamond (<i>i</i>-SDD), single-gyroid (<i>i</i>-SG), and shifted double-primitive (<i>i</i>-SDP), inverse-phase 2D hexagonal (<i>i</i>-H) and inverse-phase micellar (<i>i</i>-M) structures, have been formed by varying the degree of polymerization of the hydrophobic blocks in OSA. From the two-component phase diagram, it can be concluded that the macroporous structures formation is affected by the packing parameter <i>p</i> and the segregation product (χ<i>N</i>) of the hydrophilic and hydrophobic blocks. With an increase in <i>p</i>, the structures <i>n</i>-C and <i>n</i>-H were found in the range of low χ<i>N</i>, whereas the structures <i>i</i>-HS, <i>i</i>-H, and <i>i</i>-M were found in the range of higher χ<i>N</i>, while L is in between. In the three-component phase diagram, different volume fraction ratios (VFR) of the hydrophobic/hydrophilic block (S/O, A/O) and those of hydrophobic/hydrophobic block (S/A) in this co-assembly system divided the resultant ordered structures in various regions. The <i>n</i>-C, <i>n</i>-H, and L structures were found in low VFRs of S/O and A/O; <i>i</i>-H and <i>i</i>-M structures were formed in high VFRs of S/O and A/O. The formations of the <i>i</i>-HS structures including <i>i</i>-SDD, <i>i</i>-SDP, and <i>i</i>-SG are depending on low VFRs regions of S/O and S/A with similar packing parameter