SINGLE CRYSTAL ENGINEERING OF LINEAR TRI-BLOCK COPOLYMERS:CRYSTALLIZATION AND POLYMER BRUSHES

Single crystals of poly(methyl methacrylate)-b-polystyrene-b-poly(L-lactic acid) (PMMA-b-PS-b-PLLA) triblock copolymers with different compositions have been grown in dilute solution and utilized as ideal models for the study of structures and morphologies of tethered PS-PMMA diblock copolymer chains. With control of tethering density and tethering density distribution, the diblock copolymers are found to form switchable characteristic morphologies in selective solvent treatments. A novel “onion”-like structure has been observed for the first time due to the controllable and uniform tethering density. This switching behavior has been confirmed by surface enhanced Raman spectroscopic experiments. Two series of triblock copolymers with a crystalline block in the middle, polystyrene-b-poly(ethylene oxide)-b-poly(butene oxide) (PS-b-PEO-b-PBO) and polystyrene-b-poly(ethylene oxide)-b-poly(dimethyl siloxane) (PS-b-PEO-b-PDMS) have been synthesized. Scrolled single crystals have been found which were favored with increased tethering density. The scrolling direction was found to be along the (120) plane of the PEO single lamellar crystal. Based on the curvature of scrolling, strain energy can be calculated which corresponds to the unbalanced near surface stresses caused by tethered chains on opposite folding surfaces under a mechanic equilibrium.