Fluctuations in symmetric diblock copolymers: Testing theories old and new

Jian Qin, David C. Morse

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Computer simulations are used to study composition fluctuations in disordered diblock copolymer melts over a range of values of the chain length N, and test several theories for the structure factor S(q). Specifically, we test the random-phase approximation (RPA), which is based on a self-consistent field treatment of fluctuations, the Fredrickson-Helfand theory, which was designed to describe fluctuations near the order-disorder transition, and the relatively new renormalized one-loop (ROL) theory. The results confirm claims that the RPA is exact in the limit N→ and that the ROL theory yields the dominant corrections to the RPA within a systematic expansion in powers of N -1 /2, and show that the ROL theory is much more accurate than either older theory.

Original languageEnglish (US)
Article number238301
JournalPhysical review letters
Issue number23
StatePublished - Jun 6 2012


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