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.
Organic solar cells typically employ only two organic semiconductors: a p-type Donor and a n-type Acceptor. Due to the intrinsic narrow absorption width of organic Donors, the binary solar cells exhibit a noticeably poor light-harvesting capability, which limits their highest efficiency achieved today to ~ 10 %. Ternary solar cells that mix two or more Donors of different absorption features, on the other hand, enjoy both an increased light absorption width, and an easy fabrication process associated with their simple structures. However, their fundamental working principles are still under investigation.
In a Perspective, published in the Journal of Physical Chemistry Letters, investigators in the You Group offer their insights on the major governing mechanisms in these intriguing ternary solar cells. Through careful analyses of exemplary cases, they summarize the advantages and limitations of the three major mechanisms: charge transfer, energy transfer, and parallel-linkage. Further, they identify a few worthy future directions for these ternary solar cells. For example, incorporating singlet fission or upconversion materials into the energy transfer dominant ternary solar cells can theoretically breach the S-Q limit of single junction solar cells. This Perspective assures researchers working in this area that the feedback loop between fundamental understanding of mechanisms and materials selection will accelerate the efficiency improvement of these ternary solar cells.
Published in Macromolecules, Jason Rochette in the Ashby Group describes how the synthesis of a library of poly(ester urethane)s (PEUs) containing pendant photoresponsive moieties afforded through the incorporation of one of two novel bifunctional monomers resulted in degradable materials with a range of tunable thermal and mechanical properties.
Examination of these materials under physiological conditions displayed tunable degradation with rates faster than PCL-based materials, and initial biocompatibility studies exhibited negligible cytotoxicity for HeLa cells based on results of ATP assay. The ability to tune thermal properties also allowed specific polymer compositions to boast transition temperatures within a range of applicable temperature for thermal shape memory.
Self-Healing of Unentangled Polymer Networks with Reversible Bonds. Evgeny B. Stukalin, Li-Heng Cai, N. Arun Kumar, Ludwik Leibler, and Michael Rubinstein. Macromolecules, 2013, 46 (18), pp 7525–7541.
Nonflammable Perfluoropolyether-Based Electrolytes for Lithium Batteries. Dominica H. C. Wong, Jacob L. Thelen, Yanbao Fu, Didier Devaux, Ashish A. Pandya, Vincent S. Battaglia, Nitash P. Balsara, and Joseph M. DeSimone. PNAS, Online: DOI10.1073/pnas.1314615111.
Synthetically Encoding 10 nm Morphology in Silicon Nanowires. Joseph D. Christesen, Christopher W. Pinion, Erik M. Grumstrup, John M. Papanikolas, and James F. Cahoon. Nano Lett., 2013, 13 (12), pp 6281–6286.
Nanoparticle Drug Loading as a Design Parameter to Improve Docetaxel Pharmacokinetics and Efficacy. Kevin S. Chu, Allison N. Schorzman, Mathew C. Finniss, Charles J. Bowerman, Lei Peng, James C. Luft, Andrew J. Madden, Andrew Z. Wang, William C. Zamboni, Joseph M. DeSimone. Biomaterials, Volume 34, Issue 33, November 2013, Pages 8424–8429.
RNA Replicon Delivery via Lipid-Complexed PRINT Protein Particles. Jing Xu, J. Christopher Luft, Xianwen Yi, Shaomin Tian, Gary Owens, Jin Wang, Ashley Johnson, Peter Berglund, Jonathan Smith, Mary E. Napier, and Joseph M. DeSimone. Mol. Pharmaceutics, 2013, 10 (9), pp 3366–3374.
Real Function of Semiconducting Polymer in GaAs/Polymer Planar Heterojunction Solar Cells. Liang Yan and Wei You. ACS Nano, 2013, 7 (8), pp 6619–6626.
Near-Infrared Activation of Semi-Crystalline Shape Memory Polymer Nanocomposites. Duy M. Le, Michael A. Tycon, Christopher J. Fecko, Valerie S. Ashby. JAPS, Online, 27 JUL, 2013, DOI: 10.1002/app.39604.
Identifying Champion Nanostructures for Solar Water-Splitting. Scott C. Warren, Kislon Voïtchovsky, Hen Dotan, Celine M. Leroy, Maurin Cornuz, Francesco Stellacci, Cécile Hébert, Avner Rothschild & Michael Grätzel. Nature Materials (2013) doi:10.1038/nmat3684.
Scalable Manufacture of Built-to-Order Nanomedicine: Spray-Assisted Layer-by-Layer Functionalization of PRINT Nanoparticles. Stephen W. Morton, Kevin P. Herlihy, Kevin E. Shopsowitz, Zhou J. Deng, Kevin S. Chu, Charles J. Bowerman, Joseph M. DeSimone, Paula T. Hammond. Advanced Materials, online, July 1, 2013. DOI: 10.1002/adma.201302025.
Perfect Mixing of Immiscible Macromolecules at Fluid Interfaces. Sergei S. Sheiko, Jing Zhou, Jamie Arnold, Dorota Neugebauer, Krzysztof Matyjaszewski, Constantinos Tsitsilianis, Vladimir V. Tsukruk, Jan-Michael Y. Carrillo, Andrey V. Dobrynin & Michael Rubinstein . Nature Materials (2013) doi:10.1038/nmat3651.