The Formation of Ordered Polymer Structures at Interfaces

Abstract

Nano-meter sized ordered structures emerge naturally in thin copolymer films. Control of this order and in particular the orientation of copolymer mesophases is possible, for example by modifying substrate interactions. Near neutral surfaces lamellae forming diblock copolymers are forced into a perpendicular order. Using the results of Monte Carlo simulations, it can be shown that this effect is guided by the kinetic pathway the system takes during the microphase ordering process. Microphase separation is prone to defect structures, which inhibit long-range order required for potential applications in nano-technology. A better understanding of the dynamics of the healing-out of defects is necessary to allow us to develop procedures which can lead to long-range ordered copolymer films. As an example, aspects of this dynamic in cylinder-forming copolymers are discussed. Besides microphase separation, polymer crystallization presents another possibility for the creation of soft-ordered systems. It is shown how crystallization in diblock copolymers influences the microphase morphology in thin films and eventually leads to highly ordered surface patterns, which may be guided by external constraints such as three-phase contact lines. Crystallization of polymer monolayers results in growth patterns, which are controlled by temperature and polymer architecture. We present a generic lattice model where the crystallization behavior of thin polymer films is linked to the interplay between internal chain order and growth. Using this model we show that anisotropy of the substrate leads to oriented dendritic growth patterns with order on multiple length scales.