TEM micrographs of an 8% hPS blend (a) n = 5; (d) n = n* = 8 sphere layers

1. Thickness-induced Phase Transition of Block Copolymer/Homopolymer Blends Edward J. Kramer, University of California-Santa Barbara, DMR 0704539 In multilayer thin films of spherical morphology block copolymers, the surface layers prefer hexagonal packing while the inner layers prefer BCC. Thin films with spherical morphology of PS-b-P2VP blends with short homopolymer polystyrene (hPS) chains have an HCP structure up a thickness n* at which there is a transition to a face centered orthorhombic structure. Using grazing incidence small angle X-ray scattering and transmission electron microscopy we show that that n* increases from 5 to 9 with increase in hPS from 0 to 12 vol%. For thicknesses just below n* the HCP and FCO structures coexist. Our self-consistent mean field simulations show that the PS segregates to the interstices in the HCP structure, thus reducing the non-uniform stretching of the PS blocks and the free energy penalty of HCP versus BCC inner layers Phase diagram showing the regions of HCP and FCO stability as well as a region of coexistence between them. TEM micrographs of an 8% hPS blend (a) n = 5; (d) n = n* = 8 sphere layers

2. Thickness-induced Phase Transition of Block Copolymer/Homopolymer Blends Edward J. Kramer (UCSB),DMR-Award #07-04539 Before his REU experience Victor Grande was a sophomore at Allan Hancock Community College, a predominately Hispanic institution in northern Santa Barbara county. He is now a rising senior in Mechanical Engineering at UCSB. Vindhya Mishra is a graduate student in ChE at UCSB, a member of the Kramer research group and the first author of a paper in preparation describing the research on the 1st slide of this highlight. During the first part of the summer, Vindhya spent a month in the group of Professor Axel Müller at the University of Bayreuth, Germany learning large scale anionic synthesis of block copolymers. Besides making her own block copolymers, Vindhya has also been carrying out SCF computer simulations of her films in collaboration with Glenn Fredrickson and his student Su-mi Hur. Please insert an image or group of images here to illustrate your broader impacts activities. If you need more space, you may reduce the adjacent textbox. Please use lettering that is clearly visible (i.e. not too small). Please include a brief figure caption. Victor Grande (center), who was an REU student in the Kramer group in summer 2008, discusses a poster explaining his research with Vindhya Mishra, who acted as one of his mentors. While Vindhya was In Europe, Victor was mentored by Adetunji Onikoyi, a 2nd ChE graduate student in the Kramer group.