Breakout and breakdown induced by crystallization in cylinder-forming diblock copolymers

We report dynamic Monte Carlo simulations of polymer crystallization confined softly in cylindrical microdomains of diblock copolymers. We observed both the breakout that generally raises coalescence of microdomains and the breakdown that uniquely turns cylinders into strings of single crystallites. They can be monitored by the disappearance of structure factors at the wave vector of the square root of seven with reference to the highest peak of structure factors. By comparison of two cases with and without the postgrowth crystal thickening, we found that for those tilted or perpendicular-oriented crystals in cylinders their postgrowth isothermal thickening makes the breakout, while their lateral crystal growth is responsible for the breakdown if the growth thickness goes beyond the thickness of cylinders. The results may facilitate our better understanding of the morphological control in the crystallization of cylinder-forming diblock copolymers. © 2008 American Chemical Society.