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45769-SE
Block Copolymers as Nanoscale Materials, at the ACS National Meeting, September 2006, San Francisco, CA
Block Copolymers as Nanoscale Materials
Block copolymers (BCPs) are comprised of two chemically dissimilar polymer chains that are covalently linked together at one end. Due to the connectivity of the two chains, phase separation is limited to the dimensions commensurate with the copolymer chain, ~5-20 nanometers in size. The self-assembly of BCPs into ordered arrays of nanoscopic elements and the ability to chemically manipulate the constituent blocks of the BCPs have opened numerous applications in the rapidly growing area of nanotechnology. These materials can be used as nanomembranes; scaffolds for the fabrication of nanowires; templates for the preparation of high density nanodot arrays; and for the fabrication of 1D, 2D and 3D photonic crystals. The versatility of block copolymers can be appreciated when one considers that the chemistry of the individual blocks can be tailored to perform a specific function, for example, chemical reactivity, biological activity, conductivity or degradability. The diversity in synthetic strategies in preparing block copolymers opens a plethora of applications where block copolymers can be used.
This “Block Copolymers as Nanoscale Materials” symposium, co-organized by Prof. Thomas Russell from University of Massachusetts at Amherst and Prof. Christopher Li from Drexel University, provided a forum that highlighted the latest advances in the development and applications of BCPs. A total of 71 papers were presented in this exciting 4-day symposium, with focuses on novel synthesis, thin films, self-assembly in solution and bulk, hybrid materials, liquid crystalline and semi-crystalline systems, and nanoporous scaffolds and templates.
A total of 18 international renowned speakers presented their most recent research in the field of BCP as nano scale materials. Prof. Glenn Fredrickson presented a talk on “Field-Theoretic Simulations of Block Copolymer Thin Films: Defects and Confinement”, within which he discussed field-based computer simulations of block copolymer thin films. Prof. Rachel Segalman discussed “Self-Assembly of Weakly Segregated Rod-Coil Block Copolymers”. In her talk, Prof. Segalman discussed a model rod-coil system, poly(alkoxyphenylene vinylene-b-isoprene) (PPV-b-PI) where shielding of the rod block with a dense coat of short alkoxy sidechains resulted in accessible order-disorder and liquid crystalline clearing temperatures. Prof. Marc Hillmyer discussed “Nanoporous Plastics from ABC Triblocks” which included the recent results on the preparation and applications of functional nanoporous polymers formed by etching one of the components (C) of an ABC triblock terpolymers leaving behind a matrix material (A) and a functional group containing polymer (B) that “coats” the nanopores. Prof. Craig Hawker presented “Improving the Manufacturability and Structural Control of Block Copolymer Lithography”. He discussed the use of thermal and photochemical crosslinking strategies to improve the formation and patterning of neutralization layers. Prof. Nitash Balsara discussed “Ion-Containing Block Copolymer Nanostructures” with regard to the properties of nanostructured BCPs wherein one of the blocks is compatible with ionic moieties.
On the international speaker side, Prof. Gerrit ten Brinke presented a talk on “Hydrogen-Bonded Side-Chain Diblock Copolymers: Self-Assembly and Functionality”. Hierarchically ordered materials by self-assembly of hydrogen-bonded side-chain diblock copolymers was reviewed. Non-mesogenic side chains were attached to one of the blocks of a suitable BCP and self-assembly at two different length scales led to characteristic structure-within-structure morphologies. The concept has been used to prepare materials with functional properties such as photonic bandgap and directional dependent conductivity, as well as for nanoporous membranes and nanorods to be used e.g. as templates. Prof. Jin Kon Kim discussed issues related to “Nano-structured Materials prepared by Block Copolymer Thin Films for Photovoltaic Cells and Virus Filtration”. A novel route of using BCP to fabricate photovoltaic cells and virus filtration was discussed. Prof. Thomas Thurn-Albrecht presented “Formation and Reorganization of Block Copolymer Microphase Structures in External Fields”. He gave an overview about different approaches to use external fields as a means to orient block copolymer microphase structures, i.e. electric and magnetic fields, interfacial interactions as well as a static mechanic load. By comparing microphase separation with crystallization, the nature of the phase transition which is responsible for structure formation was discussed. Prof. Rong-Ming Ho presented “Nanohelical Phase in Chiral Block Copolymers”. He discussed a variety of self-assembled nanohelices in chiral block copolymers recently observed by applying internal and external stimuli (i.e., crystallization and shearing). The amorphous nanohelices in bulk are able to transfer into crystalline nanohelices and crystalline cylinders by crystallization, and amorphous cylinders by shearing. The crystallization-induced cylinders were found thermally reversible, and able to revert to original nanohelices upon remelting and annealing. This unique phase behavior thus creates a possible way for manipulating tunable nanohelical structures in practical applications.
Overall, the symposium successfully provided a platform for scientist as well as students to discuss the most recent advanced in block copolymers as nano scale materials. The symposium was extremely successful. This grant was used to partially support 6 invited speakers travel to San Francisco and present their work. This funding support from PRF is greatly appreciated.
