as efficient electron transfer media to improve the performance of electric double-layer capacitors (EDLCs). [9] Furthermore, the blending of a self-assembled block copolymer with the carbon source (e.g., phenolic resin) is becoming more widespread. This method has the advantage of providing well-ordered mesoporous structures that can be used efficiently in various applications. [10,11] Typically, a block copolymer that forms a self-assembled structure is mixed with a carbon source to obtain various dimensional carbon structures. The blending of a commercial Pluronic-type triblock copolymer, such as poly(ethylene oxide-b-propylene oxideb-ethylene oxide), as the template is the method used most widely to prepare mesoporous materials. [12][13][14][15][16][17][18][19] Because of limitations in molecular weight and composition, it can, however, be difficult to prepare mesoporous materials having pore sizes of greater than 10 nm when using Pluronic-type triblock copolymers. Block copolymers featuring long hydrophobic segments and high molecular weight-for instance, poly(ethylene oxideb-styrene) (PEO-b-PS) [20,21] and poly(ethylene oxide-b-methyl methacrylate) (PEO-b-PMMA) [22] -are promising candidates as templates to prepare large-pore-size mesoporous carbons. For example, Zhao et al. prepared mesoporous carbons with long-range order, large surface areas (>1500 m 2 g −1 ), and large pores (≈23 nm) when using PEO 125 -b-PS 230 as the template as displayed in Scheme S1a-c in the Supporting Information. [21] With PEO 125 -b-PMMA 114 as the template, they obtained mesoporous carbons having large surface areas (>1500 m 2 g −1 ) and pores (≈10 nm) [22] when applying resol as the carbon source. Mesoporous carbons with smaller pores but thicker walls were obtained when using PEO-b-PMMA as the template, rather than PEO-b-PS, because the phenolic OH units could interact strongly with the PEO segment (interassociation equilibrium constant (K A ) = 286) [23] and weakly with the PMMA CO units (K A = 20) [24,25] through hydrogen bonding, but not with the hydrophobic PS segment. Indeed, the PS block segment would undergo complete microphase In this study, mesoporous carbons are prepared by using a resol-type phenolic resin as the carbon source and poly(ethylene oxide-b-lactic acid) (PEO-b-PLA) copolymer as the template, with a process of thermal curing, calcination, carbonization, and activation. The structures of these mesoporous carbons are strongly influenced by the self-assembled structures formed from phenolic/PEO-b-PLA blends, varying from double-gyroid, to cylinder, and finally to spherical micelle structures upon increasing the phenolic concentrations. The large pores (>20 nm) and high surface areas (>1000 m 2 g −1 ) of these activated mesoporous carbons arise because the phenolic resin interacts only with the PEO segment (i.e., not with the PLA segment) through hydrogen bonding; thus, the relative wall thickness of the phenolic matrix decreases after template removal (thereby increasing the pore size), similar to the beha...