  We have formulated a theory of self-assembly based on the notion of local
gauge invariance at the mesoscale. Local gauge invariance at the mesoscale
generates the required long- range entropic forces responsible for
self-assembly in binary systems. Our theory was applied to study the onset of
mesostructure formation above a critical temperature in estane, a diblock
copolymer. We used diagrammatic methods to transcend the Gaussian approximation
and obtain a correlation length zeta ~ (c-c*)^-gamma, where c* is the minimum
concentration below which self-assembly is impossible, c is the current
concentration, and gamma was found numerically to be close to 2/3. The
renormalized diffusion constant vanishes as the c* is approached, indicating
the occurrence of critical slowing down, while the correlation function remains
finite at the transition point.
