Tethered polymer chains on single crystal surfaces.

摘要

Tethered polymer chains have drawn significant research attention over the last few decades because of their unique properties for various applications. The tethering density of the chains determines the state of the chains as well as the resulting properties, as shown by various theoretical and experimental work. Through the use of single crystals of crystalline-amorphous diblock copolymers, it is possible to study tethered polymer chains as the amorphous block is attached covalently to the crystal surface. This system provides the best control of tethering density and molecular weight as compared to previous methods. Previous work on PS-b-PEO and PS- b-PLLA found the reduced tethering density value for the transition into the interacting regime ( s&d5; *) to be independent of molecular weight and solvent quality. Other factors that were not addressed were adsorption and chain stiffness. The role of chain adsorption using miscible polymers, namely PMMA-b-PLLA, and chain stiffness, with PEO-b-PCL where PEO is the amorphous block, has been determined. In order to determine the chain conformation and size of the PMMA adsorbed on the PLLA surface, Monte Carlo simulations were performed. Adsorption of the chain was found to increase s&d5; *, and the collapsed state in poor solvent led to a lower s&d5; * when compared to the PS system. Also, the PEO tethers provided a unique opportunity to study the crystallizability of tethered polymer chains.