Fluctuation stabilization of the <i>Fddd</i> network phase in diblock, triblock, and starblock copolymer melts
M. W. Matsen, T. M. Beardsley, James D. Willis
Abstract
The latest complex network phase to be discovered in diblock copolymer melts is the orthorhombic $F\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}d$ phase. Mean-field theory predicts it to be stable, but only at weak segregations where ordered phases are typically destroyed by thermal fluctuations. Indeed, Landau-Brazovskii theory confirmed this expectation, raising the question of how $F\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}d$ survives in experiments. However, this problem was recently resolved by accurate field-theoretic simulations, which found that $F\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}d$ is simply more resilient to fluctuations than other ordered phases. Here, the authors find that this is also true for the family of (AB)${}_{M}$ starblock copolymer architectures. This resilience may very well extend to numerous other architectures, and thus it would be prudent to keep our eyes open for $F\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}d$.