The phases occur in the order they do because the progression of functions $a(\lambda)$ from quadratic $\lambda^2$ (spheres) to linear $\lambda$ (cylinders) to $\lambda(2-\lambda)$ (bicontinuous) to constant (lamellae) gives progressively less volume to the “outer” chain to avoid stretching, but uses progressively less area to separate the two species at higher volume fractions of the minority species.

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However, we cannot argue as before that our simple estimate for the bicontinuous phase is a lower bound for actual bicontinuous phases, because there is no way to pack together copies of one infinitesimal wedge to produce a “micelle” that 1) fills some region of space, and 2) is bounded by some surface(s), the volume outside of which could be filled by homopolymer. Neither can we argue that this estimate is an upper bound, because we certainly cannot pack a unit cell of the region bounded by the D or G surfaces with identical copies of one infinitesimal wedge.

Bicontinuous phases are assembled from different wedges $\alpha$, with different shape factors $p_{\alpha}$ in Table \[table1\]. The shape factor roughly gauges the splay or Gaussian curvature of the surface at the top of the wedge, with $p=1$ (cylinders) corresponding to zero Gaussian curvature, 