title: Orientational order in cylinder-forming block copolymer thin films.
abstract: Shear can impart a high degree of orientational order to supported block copolymer thin films containing one or more layers of cylindrical microdomains, leading to a striped pattern with a period of tens of nanometers extending over macroscopic (centimeter-squared) areas. Though the as-deposited films have a polygrain structure, after shearing at sufficiently high stresses the only defects which remain are isolated dislocations, and the orientational order can be quite high (nematic or twofold orientational order parameter >0.99, as measured by tapping-mode atomic force microscopy). The effect of isolated dislocations on orientational order is adequately captured by an isotropic elastic continuum model of the structure surrounding the dislocation, producing a linear decrease of order parameter with dislocation density. Even at zero dislocation density, however, the order parameter does not quite reach unity, due to small-amplitude undulations of the cylinders about their axes which persist in the transverse direction over several cylinder periods.
authors.affiliation: Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Marencic
authors.forename: Paul M
authors.initials: PM
authors.lastname: Chaikin
authors.forename: Richard A
authors.initials: RA
authors.lastname: Register
mesh_terms: D004548:Elasticity; D018625:Microscopy, Atomic Force; D011108:Polymers / Q000737:chemistry*
chemical_list: D011108:Polymers