COMBINATORIAL CHARACTERIZATION OF BLOCK COPOLYMER FILM MORPHOLOGY.Combinatorial methods have been successfully applied by researchers at NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. to observe novel morphologies and to establish fundamental kinetic relationships in the ordering properties of block copolymer copolymer: see polymer. films. Copolymers are a class of polymer materials that have large potential for commercial applications. Unique properties in melts, blends and solutions lead to their use as adhesives, emulsifying agents, thermoplastic elastomers, compatibilizers, etc. Block copolymers are an important sub-class of copolymers consisting of polymers of different chemistry that are covalently linked. A key question in block copolymers is the nature of interactions between blocks, as well as block interactions with different materials. To address this question NIST researchers exploited the ability of block copolymers to form quantized quan·tize tr.v. quan·tized, quan·tiz·ing, quan·tiz·es Physics 1. To limit the possible values of (a magnitude or quantity) to a discrete set of values by quantum mechanical rules. 2. periodic structures, such as lamellae lamellae (l  mel´ē),n the nearly parallel layers of bone tissue found in compact bone. , that directly reflect molecular parameters such as block lengths, chemical interactions between the block constituents, and interactions with an external (substrate) material in thin films. The work of the NIST researchers published in Physical Review Letters Physical Review Letters is one of the most prestigious journals in physics.[1] Since 1958, it has been published by the American Physical Society as an outgrowth of The Physical Review. and Journal of Polymers Science Polymer: Part B Polymer Physics, demonstrates that these fundamental properties can be very efficiently determined in a high-throughput manner using a combinatorial approach. This was accomplished by flow-coating multiple films having different molecular masses and gradients in film thickness. Each "library," the size of a standard microscope slide, contains as many as 1500 differentiable dif·fer·en·tia·ble adj. 1. That can be differentiated: differentiable species. 2. Mathematics Possessing a derivative. experimental conditions, including process variables of temper ature and time. Novel morphologies observed including a labyrinthine lab·y·rin·thine adj. Of, relating to, resembling, or constituting a labyrinth. labyrinthine pertaining to or emanating from a labyrinth. (or spinodal) surface patterns as well as extended smooth regions. These morphologies are related to an enthalpic vs entropic balance of interactions in block copolymers. In addition, the size of the surface patterns unexpectedly displayed an inverse relationship with molecular mass that can be attributed to the copolymer surface elasticity. |
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