The Max Planck Institute for Polymer Research is a scientific center in the field of polymer science located in Mainz, Germany. The institute was founded in 1983 by Erhard W. Fischer and Gerhard Wegner. Belonging to the Chemistry, Physics and Technology Section, it is one of the 80 institutes in the Max Planck Society . Wikipedia.
News Article | May 10, 2017
MEDFORD/SOMERVILLE, Mass. (May 10, 2017) - More than 400 years ago, renowned mathematician and scientist Johannes Kepler speculated about the creation of one of nature's most angelic and unique shapes: the six-sided snowflake. Although atoms would not be discovered until over two centuries later, Kepler openly pondered about the microscopic building blocks that lead to the ice crystal's hexagonal formation, including the myriad of factors behind this recurring phenomenon. Now, research led by a Tufts University chemist has answered Kepler's questions by shedding new light on this process by combining an electron backscatter with a large single crystal ice model. In a study published in the Proceedings of the National Academy of Sciences, scientists discovered that an ice crystal's flat sides are formed by a hexagon that is larger and consists of a central water molecule surrounded by six others in the same layer. Mary Jane Shultz, Ph.D., a chemistry professor in the School of Arts and Sciences at Tufts University and first author of the study, said the chair-form hexagon has three molecules in one layer and three more slightly lower in what is called a bilayer structure. The six flat sides of a snowflake grow from a hexagon formed within one layer. This larger hexagon is rotated 30 degrees relative to the chair-form hexagon. "Snowflakes grow from water vapor. Faces that release the most heat (per unit area) vaporize," said Shultz. "The face with the least heat release is the hexagonal face; next is the flat face of the larger hexagon. The flat side of the chair-form hexagon releases the most heat per area, which vaporizes itself. Thus, the snowflake hexagonal prism has flat sides that correspond to the larger hexagon." The study findings debunk previous assumptions that snowflakes grow from the flat sides of the chair-form hexagon, Shultz said. To determine how the formation occurs, researchers built a model that balances the heat released when molecules are incorporated in the solid lattice against probability of successful attachment. Combining macroscopic and molecular-level techniques allowed the team to investigate the same surface at different scales. The macroscopic probe has been used for decades to investigate ice. This technique produces the beautiful visual images of the macroscopic hexagonal shape. The molecular-level probe is more recent. While an X-ray is commonly used to show the molecular-level, Shultz and her team opted to use the electron backscatter diffraction technique, which produces orientation density plots that are more illustrative and visually compelling. "Careful sample orientation tracking enabled us to link the two images to produce the connection," she said. The research confirmed that snowflake points align with the crystallographic a axes shown as hot spots in the electron backscatter data. The significance is that the flat side of a snowflake consists of a bilayer structure. The basal face is a chair-form hexagon; the up-down alteration forms a bilayer. The flat side is a boat-form hexagon consisting of pairs of water molecules bridging pairs in the lower half of the bilayer. Flexibility and mobility of a pair is expected to result in unique reactivity of this face, including potentially catalyzing conversion of gases like CO2 and nitrogen oxides in the atmosphere. Shultz said the team is now investigating this reactivity. Additional authors of the study are Alexandra Brumberg, former undergraduate student, Department of Chemistry, Laboratory for Water and Surface Studies, Tufts University; Kevin D. Hammonds, assistant professor, Department of Civil Engineering, Montana State University, Bozeman, MT; Ian Baker, Ph.D., associate dean, Thayer School of Engineering, Dartmouth College, Hanover, NY; Ellen H.G. Backus, Ph.D., professor, Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, Mainz, Germany; Patrick J. Bisson, Ph.D., post doctoral researcher, Department of Chemistry, Laboratory for Water and Surface Studies, Tufts University; Mischa Bonn, Ph.D., director, Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, Mainz, Germany; Charles Daghlian Ph.D., manager, Electron Microscope Facility, Hanover, NH; and Markus Mezger, Ph.D., assistant professor, Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, Mainz, Germany, and the Institute of Physics, Johannes Gutenberg University Mainz, Mainz, Germany. Support for this research came in part from the National Science Foundation grant numbers CHE1449643 and CHE1565772. Shultz et al. "Single crystal Ih ice surfaces unveil connection between macroscopic and molecular structure" PNAS MS (May 2017) Article number: 03056R (2017) Published online May 9, 2017. DOI: 10.1073/pnas.1703056114 Tufts University, located on campuses in Boston, Medford/Somerville and Grafton, Massachusetts, and in Talloires, France, is recognized among the premier research universities in the United States. Tufts enjoys a global reputation for academic excellence and for the preparation of students as leaders in a wide range of professions. A growing number of innovative teaching and research initiatives span all Tufts campuses, and collaboration among the faculty and students in the undergraduate, graduate and professional programs across the university's schools is widely encouraged.
Figueira-Duarte T.M.,BASF |
Mullen K.,Max Planck Institute for Polymer Research
Chemical Reviews | Year: 2011
Pyrene's unique properties have inspired researchers from many scientific areas, making pyrene the chromophore of choice in fundamental and applied photochemical research. There has been an increased interest in the use of pyrene as organic semiconductor for application in materials science and organic electronics. Modification of the chemical structure by varying the substitution at different positions of the pyrene ring allows the control of the molecular architecture and thus the molecular packing, which renders the handling of pyrene substitution a key factor in pyrene-based semiconductors. Pyrene, as a blue-light-emitting chromophore with good chemical stability and high charge carrier mobility, appears to be a very attractive building block for light-emitting devices. The electrooptical properties of pyrene can be fine-tuned by introducing specific electron-donating or -accepting groups or, alternatively, by simply modifying the molecular architecture via substitution at the pyrene ring.
Kunz A.,Max Planck Institute for Polymer Research
Nature Materials | Year: 2016
In 1962, Mark and Helfrich demonstrated that the current in a semiconductor containing traps is reduced by N/Nt r, with N the amount of transport sites, Nt the amount of traps and r a number that depends on the trap energy distribution. For r > 1, the possibility opens that trapping effects can be nearly eliminated when N and Nt are simultaneously reduced. Solution-processed conjugated polymers are an excellent model system to test this hypothesis, because they can be easily diluted by blending them with a high-bandgap semiconductor. We demonstrate that in conjugated polymer blends with 10% active semiconductor and 90% high-bandgap host, the typical strong electron trapping can be effectively eliminated. As a result we were able to fabricate polymer light-emitting diodes with balanced electron and hole transport and reduced non-radiative trap-assisted recombination, leading to a doubling of their efficiency at nearly ten times lower material costs. © 2016 Nature Publishing Group
Mullen K.,Max Planck Institute for Polymer Research
ACS Nano | Year: 2014
The evolution of nanoscience is based on the ability of the fields of chemistry and physics to share competencies through mutually beneficial collaborations. With this in mind, in this Perspective, I describe three classes of compounds: rylene dyes, polyphenylene dendrimers, as well as nanographene molecules and graphene nanoribbons, which have provided a superb platform to nurture these relationships. The synthesis of these complex structures is demanding but also rewarding because they stimulate unique investigations at the single-molecule level by scanning tunneling microscopy and single-molecule spectroscopy. There are close functional and structural relationships between the molecules chosen. In particular, rylenes and nanographenes can be regarded as honeycomb-type, discoid species composed of fused benzene rings. The benzene ring can thus be regarded as a universal modular building block. Polyphenylene dendrimers serve, first, as a scaffold for dyes en route to multichromophoric systems and, second, as chemical precursors for graphene synthesis. Through chemical design, it is possible to tune the properties of these systems at the single-molecule level and to achieve nanoscale control over their self-assembly to form multifunctional (nano)materials. © 2014 American Chemical Society.
Spiess H.W.,Max Planck Institute for Polymer Research
Macromolecules | Year: 2010
In recent years major advances in generating, characterizing, and understanding macromolecular and supramolecular systems have been achieved. This has led to an enormous variety and complexity in polymer science. The traditional separation in terms of structure vs dynamics, crystalline vs amorphous, or experiment vs theory is increasingly overcome. As far as characterization of such materials is concerned, no experimental or theoretical/simulation approach alone can provide complete information. Instead, a combination of techniques is called for, and conclusions should be supported by results provided by complementary techniques. This Perspective discusses the kind of information that can be obtained by advanced solid state NMR and EPR spectroscopy, combined and/or compared with X-ray and neutron scattering as well as dielectric spectroscopy and computer simulation. The multi-technique approach is demonstrated by a number of examples including morphology, defects, heterogeneities in time scale and amplitude of motion, and local and collective dynamics in polymers of different architectures, biomacromolecules, and hybrid systems. © 2010 American Chemical Society.
Li C.,Max Planck Institute for Polymer Research |
Wonneberger H.,Max Planck Institute for Polymer Research
Advanced Materials | Year: 2012
Perylene imides have been an object of research for 100 years and their derivatives are key n-type semiconductors in the field of organic electronics. While perylene diimides have been applied in many electronic and photonic devices, their use can be traced back to the first efficient organic solar cell. By functionalizing different positions of the in total 12 positions (four peri, four bay, and four ortho-positions) on the perylene core, perylene imides with significantly different optical, electronic and morphological properties may be prepared. Perylene imides and their derivatives have been used in several types of organic photovoltaics, including flat-, and bulk-heterojunction devices as well as dye-sensitized solar cells. Additionally perylene imides-based copolymers or oligomers play an important role in single junction devices. In this review, the relationship between the photovoltaic performance and the structure of perylene imides is discussed. 1 st (yesterday), 2 nd (today) and 3 rd (tomorrow) generation perylene imides, their designated material properties, and photovoltaic performance in organic solar cells are presented and discussed in this review. This class of chromophores has developed alongside photovoltaics and with the promises that the latest generation of perylene imides holds, they will continue to play a major role in the future. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Henson Z.B.,University of California at Santa Barbara |
Mullen K.,Max Planck Institute for Polymer Research |
Bazan G.C.,University of California at Santa Barbara
Nature Chemistry | Year: 2012
Organic semiconducting materials based on polymers and molecular systems containing an electronically delocalized structure are the basis of emerging optoelectronic technologies such as plastic solar cells and flexible transistors. For isolated molecules, guidelines exist that rely on the molecular formula to tailor the frontier (highest occupied or lowest unoccupied) molecular orbital energy levels and optical absorption profiles. Much less control can be achieved over relevant properties, however, as one makes the transition to the ensemble behaviour characteristic of the solid state. Polymeric materials are also challenging owing to the statistical description of the average number of repeat units. Here we draw attention to the limitations of molecular formulae as predictive tools for achieving properties relevant to device performances. Illustrative examples highlight the relevance of organization across multiple length scales, and how device performances - although relevant for practical applications - poorly reflect the success of molecular design. © 2012 Macmillan Publishers Limited. All rights reserved.
Hinderberger D.,Max Planck Institute for Polymer Research
Topics in Current Chemistry | Year: 2012
Synthetic polymers belong to the vast realm of soft matter and are one of the key types of materials to address societal needs at the beginning of the twenty-first century. Polymer science progressively addresses questions that deal with tuning mesoscopic and macroscopic structures and functions of polymers by understanding the effects that govern these systems on the nanoscopic level. EPR spectroscopy as a local, sensitive, and extremely specific magnetic resonance technique in many cases shows sensitivity on well-suited length-(0-10 nm) and time scales (μs-ps) and can deliver unique information on structure, dynamics, and in particular function of polymeric systems. A short review of recent literature is given and the power of simple EPR methods, especially CW EPR performed on a low-cost benchtop spectrometer, to elucidate complex polymeric materials is shown with specific examples from thermoresponsive polymer systems. These bear great potential in molecular transport and biomedical applications (e.g., drug delivery) and insights into interactions between carrier and small molecule are fundamental for designing and tuning these materials. © 2011 Springer-Verlag Berlin Heidelberg.
Schneider D.,Max Planck Institute for Polymer Research
Nature Materials | Year: 2016
Spider dragline silk possesses superior mechanical properties compared with synthetic polymers with similar chemical structure due to its hierarchical structure comprised of partially crystalline oriented nanofibrils. To date, silk’s dynamic mechanical properties have been largely unexplored. Here we report an indirect hypersonic phononic bandgap and an anomalous dispersion of the acoustic-like branch from inelastic (Brillouin) light scattering experiments under varying applied elastic strains. We show the mechanical nonlinearity of the silk structure generates a unique region of negative group velocity, that together with the global (mechanical) anisotropy provides novel symmetry conditions for gap formation. The phononic bandgap and dispersion show strong nonlinear strain-dependent behaviour. Exploiting material nonlinearity along with tailored structural anisotropy could be a new design paradigm to access new types of dynamic behaviour. © 2016 Nature Publishing Group
Tsao H.N.,Max Planck Institute for Polymer Research |
Mullen K.,Max Planck Institute for Polymer Research
Chemical Society Reviews | Year: 2010
In this tutorial review, different film microstructures, commonly termed morphologies, into which the organic semiconductor polymers self-assemble macroscopically are presented, together with their corresponding influence on charge carrier mobility and hence transistor behaviour. It will be clarified how various chemical design approaches and solution processing methods enable the manipulation of polymer morphology, leading to improvements in transistor performance. Ultimately, it is illustrated that the directional alignment of polymers form oriented fiber-like films, yielding one of the highest mobilities reported so far for polymer transistors. Based on these observations, a prediction is made concerning which kind of morphology is expected to reach the best charge carrier mobility. © 2010 The Royal Society of Chemistry.