Many challenging problems in the modern science and technology are related to preparation, properties, and utilization of novel functional materials. The polymer chemistry and the chemical microelectronics programs represent parts of the multidisciplinary effort in this field. The many-pronged approach includes: synthesis and molecular characterization of well-defined block and graft copolymers; preparation of new engineering thermoplastics and liquid crystalline materials; synthesis, modification and processing of polymers in super-critical carbon dioxide; chemical design of hybrid polymers for catalysis and photoredox activity, polymers for microelectronics applications including 193 nm and 157 nm photoresists and low-k dielectrics, and defined microstructures.
Chemical microelectronics is focused on preparation of organic and inorganic electronic materials; microscopic patterning of thin films using novel techniques, plasma, ion beam, laser beam, etc.; kinetics of etching and film formation; characterization of mechanical, electronic, and optical properties; spatially resolved chemical analysis of surfaces, interfaces, and thin films and microstructures. A broad variety of expertise includes visualization and probing of submicrometer surface structures by scanning probe microscopy, characterization of polymer dynamics by NMR techniques and light scattering, measurement of molecular conductivity, and analytical as well as computational and numerical methods in polymers.
Assistant Professor Scott Warren, a joint faculty member with the Department of Chemistry and the Applied Physical Sciences Department here at UNC, is one of the co-authors of an article, published in Angewandte Chemie, describing how single crystals of a cyclodextrin-based metal-organic framework, MOF, infused with an ionic electrolyte and flanked by silver electrodes act as memristors. The article is highlighted in ChemistryWorld, where the invention is referred to as "Computer Memory Made From Sugar Cube."
Tony Kenyon, an electronic engineer at University College London, says the sugar-cube memory-performance would not be compatible with existing complementary metal oxide semiconductor, CMOS, technology, the staple of modern computing. But he also points out that other applications could be very interesting. The authors comment that commercial RRAMs have faster read and write times, but state they believe they can make this type of memory cheaper and most definitely greener. The researchers are thinking along the lines of "biodegradable memory."
Self-healing polymeric materials are systems that after damage can revert to their original state with full or partial recovery of mechanical strength. Using scaling theory, researchers in the Rubinstein Group, as published in Macromolecules, studied a simple model of autonomic self-healing of unentangled polymer networks. In this model one of the two end monomers of each polymer chain is fixed in space mimicking dangling chains attachment to a polymer network, while the sticky monomer at the other end of each chain can form pairwise reversible bond with the sticky end of another chain. The group studied the reaction kinetics of reversible bonds in this simple model and analyzed the different stages in the self-repair process.
The team observed the slowest formation of bridges for self-adhesion after bringing into contact two bare surfaces with equilibrium, very low, density of open stickers in comparison with self-healing. The primary role of anomalous diffusion in material self-repair for short waiting times is established, while at long waiting times the recovery of bonds across fractured interface is due to hopping diffusion of stickers between different bonded partners. Acceleration in bridge formation for self-healing compared to self-adhesion is due to excess nonequilibrium concentration of open stickers. Full recovery of reversible bonds across fractured interface, formation of bridges, occurs after appreciably longer time than the equilibration time of the concentration of reversible bonds in the bulk.
The Role of Temperature in Forming Sol–Gel Biocomposites Containing Polydopamine. Jason Christopher Dyke, Huamin Hu, Dong Joon Lee, Ching-Chang Ko, and Wei You. J. Mater. Chem. B, 2014,2, 7704-7711.
Lubrication by Polyelectrolyte Brushes. Ekaterina B. Zhulina and Michael Rubinstein. Macromolecules, 2014, 47 (16), pp 5825–5838.
Shapeshifting: Reversible Shape Memory in Semicrystalline Elastomers. Jing Zhou, Sara A. Turner, Sarah M. Brosnan, Qiaoxi Li, Jan-Michael Y. Carrillo, Dmytro Nykypanchuk, Oleg Gang, Valerie S. Ashby, Andrey V. Dobrynin, and Sergei S. Sheiko. Nature Methods 11, 959–965 (2014).
Waveguide Scattering Microscopy for Dark-Field Imaging and Spectroscopy of Photonic Nanostructures. David J. Hill , Christopher W. Pinion , Joseph D. Christesen , and James F. Cahoon. ACS Photonics, 2014, 1 (8), pp 725–731.
Switchable Micropatterned Surface Topographies Mediated by Reversible Shape Memory. Sara A. Turner, Jing Zhou, Sergei S. Sheiko, and Valerie Sheares Ashby. ACS Appl. Mater. Interfaces, 2014, 6 (11), pp 8017–8021.
Particle Replication in Nonwetting Templates Nanoparticles with Tumor Selective Alkyl Silyl Ether Docetaxel Prodrug Reduces Toxicity. Kevin S. Chu, Mathew C. Finniss, Allison N. Schorzman, Jennifer L. Kuijer, J. Christopher Luft, Charles J. Bowerman, Mary E. Napier, Zishan A. Haroon, William C. Zamboni. Nano Lett., 2014, 14 (3), pp 1472–1476.
Controlling Molecular Weight of a High Efficiency Donor-Acceptor Conjugated Polymer and Understanding Its Significant Impact on Photovoltaic Properties. Wentao Li, Liqiang Yang, John R. Tumbleston, Liang Yan, Harald Ade, and Wei You. Adv. Mat., First published online, 14 MAR 2014, DOI: 10.1002/adma.201305251.
The Influence of Molecular Orientation on Organic Bulk Heterojunction Solar Cells. John R. Tumbleston, Brian A. Collins, Eliot Gann, Wei Ma and Harald Ade, Liqiang Yang, Andrew C. Stuart and Wei You. Nature Photonics (2014) doi:10.1038/nphoton.2014.55.
Copolymerization of Metal Nanoparticles: A Route to Colloidal Plasmonic Copolymers. Kun Liu, Ariella Lukach, Kouta Sugikawa, Siyon Chung, Jemma Vickery, Heloise Therien-Aubin, Bai Yang, Michael Rubinstein, and Eugenia Kumacheva. Angewandte Chemie International Edition, Volume 53, Issue 10, pages 2648–2653, March 3, 2014.
Storage of Electrical Information in Metalâ€“Organic-Framework Memristors. Seok Min Yoon, Scott C. Warren, and Bartosz A. Grzybowski. Article first published online: 14 MAR 2014, DOI: 10.1002/anie.201309642.