Bulletin of the American Physical Society
2006 Ohio Section of the APS Fall Meeting
Friday–Saturday, October 13–14, 2006; Orrville, Ohio
Session D1: Polymer Thin Films |
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Chair: Sasa Dordevic, The University of Akron Room: Wayne College A107 |
Saturday, October 14, 2006 9:30AM - 9:42AM |
D1.00001: Surface and Interface Structure of Diblock Copolymer Brushes Gokce Ugur, Bulent Akgun, William J. Brittain, Mark D. Foster, Xuefa Li, Jin Wang Internal and surface structure of polystyrene-$b$-polyacrylate diblock copolymer brushes have been studied using grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM). Polystyrene-$b$-polyacrylate and polyacrylate-$b$-polystyrene brushes were synthesized using atom transfer radical polymerization. Poly(methyl acrylate) (PMA) or poly($n$-butyl acrylate) (P$n$BA) was used as the acrylate block. Each asymmetric as-deposited diblock brush with a sufficiently large $\chi $N value shows an internal lateral structure with a spacing comparable to the thickness of the PMA layer. After a brush is treated with a selective solvent which is a good or theta solvent for the bottom block and poor solvent for the top block, Bragg rods appear in the GISAXS pattern. The lateral spacing corresponding to the Bragg rods is on the order of the total thickness of the brush. This lateral correlation is also detected by power spectral density analysis of AFM images made using tapping mode. The Bragg rods disappear upon heating to 80 $^{\circ}$C. [Preview Abstract] |
Saturday, October 14, 2006 9:42AM - 9:54AM |
D1.00002: Determination of the Internal Structure of Plasma Polymerized Films via X-ray Reflectometry Holley Wickwire, Dan Dreyer, Mark Foster Passive filters for photonics can be made using multilayer polymer films deposited using Plasmas Enhanced Chemical Vapor Deposition. In this process, gaseous monomer is fragmented into reactive radical species by interaction with plasma. These radicals react with one another as they deposit on a substrate from a flowing stream of carrier gas, forming a complex cross-linked structure. The objective of this work is to determine the internal structure of the plasma polymerized films and the manner in which cross-link density and equilibrium degree of swelling vary with plasma power, monomer feed location inside the reactor, deposition time, and substrate size. X-ray reflectometry measurements provide information on the thickness, roughness, and scattering length density of films as deposited. The overall degree of swelling of a film in a good solvent vapor and the kinetics of swelling can be determined also with X-ray reflectometry, for films that are tens of nanometers in thickness. The overall cross-link density, which is an important structure characteristic, can be inferred from the degree of swelling. [Preview Abstract] |
Saturday, October 14, 2006 9:54AM - 10:06AM |
D1.00003: Internal Structure of Ultrathin Diblock Copolymer Brushes Bulent Akgun, William J. Brittain, Mark D. Foster, Charles F. Majkrzak, Xuefa Li, Jin Wang Diblock copolymer brushes (DCBs) have garnered enormous interest in recent years due to their stimuli-responsive behavior. Although the synthesis of DCBs has been widely studied, the internal brush structure of these films is still not clear. We have resolved the internal structure of ultrathin DCBs using neutron reflectivity and grazing incidence small-angle X-ray scattering (GISAXS). DCBs of deuterated polystyrene (dPS) and poly(methyl acrylate) (PMA) with dPS adjacent to the substrate (d-PS-b-PMA) or with PMA adjacent to the substrate (PMA-b-dPS) and having different thicknesses were synthesized using atom transfer radical polymerization. It was found that internal brush structure depends strongly on the block sequence and the value of XN. For the thinnest films a model of two layers with an interfacial region of finite width provides a good description of the data. For dPS-b-PMA films that are thicker and of sufficiently asymmetric composition, a third layer must be included. The necessity of including a third layer is consistent with the presence of a lateral ordering of some type in the center of the brush, as evidenced by correlation peaks in the GISAXS data. The interface width is found to be smaller for PMA-b-dPS than for dPS-b-PMA brushes. [Preview Abstract] |
Saturday, October 14, 2006 10:06AM - 10:18AM |
D1.00004: Structure of Copolymer Films Created by Plasma Enhanced Chemical Vapor Deposition (PECVD) Someshwara Peri, Hyeonjae Kim, Mark Foster The structures of substrate/layer and layer/air interfaces in copolymer films made using plasma enhanced chemical vapor deposition (PECVD) have been probed for the first time using x-ray reflectivity (XR). Both XR and atomic force microscopy (AFM) measurements revealed extremely smooth surfaces for copolymer films made from comonomers benzene and octafluorocylcobutane (B-OFCB) and from comonomers hexamethyldisiloxane and octafluorocylcobutane (HMDS-OFCB). The surface roughnesses range from 2.5 to 9.5 {\AA} for both B-OFCB and HMDS-OFCB films. HMDS-OFCB copolymer films and B-OFCB copolymer films deposited on Si substrates are characterized by a uniform scattering length density throughout the film thickness. The XR measurements also reveal that one can tune the refractive index by varying the monomer feed ratio in the copolymer films. [Preview Abstract] |
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