Martin Glodde

Bio: Martin Glodde is an academic researcher from University of Pennsylvania. The author has contributed to research in topics: Liquid crystal & Dendrimer. The author has an hindex of 12, co-authored 15 publications receiving 1764 citations.

Self-organization of supramolecular helical dendrimers into complex electronic materials

Abstract: The discovery of electrically conducting organic crystals1 and polymers1,2,3,4 has widened the range of potential optoelectronic materials5,6,7,8,9, provided these exhibit sufficiently high charge carrier mobilities6,7,8,9,10 and are easy to make and process. Organic single crystals have high charge carrier mobilities but are usually impractical11, whereas polymers have good processability but low mobilities1,12. Liquid crystals exhibit mobilities approaching those of single crystals and are suitable for applications13,14,15,16,17,18, but demanding fabrication and processing methods limit their use. Here we show that the self-assembly of fluorinated tapered dendrons can drive the formation of supramolecular liquid crystals with promising optoelectronic properties from a wide range of organic materials. We find that attaching conducting organic donor or acceptor groups to the apex of the dendrons leads to supramolecular nanometre-scale columns that contain in their cores π-stacks of donors, acceptors or donor–acceptor complexes exhibiting high charge carrier mobilities. When we use functionalized dendrons and amorphous polymers carrying compatible side groups, these co-assemble so that the polymer is incorporated in the centre of the columns through donor–acceptor interactions and exhibits enhanced charge carrier mobilities. We anticipate that this simple and versatile strategy for producing conductive π-stacks of aromatic groups, surrounded by helical dendrons, will lead to a new class of supramolecular materials suitable for electronic and optoelectronic applications.

Designing libraries of first generation AB3 and AB2 self-assembling dendrons via the primary structure generated from combinations of (AB)(y)-AB3 and (AB)(y)-AB2 building blocks.

Abstract: Structural analysis of three libraries of up to five generations of self-assembling dendrons based on AB3, AB2, and combinations of AB3 with AB2 building blocks (Percec et al. J. Am. Chem. Soc. 2001, 123, 1302) facilitated the discovery of several nanoscale lattices previously unknown for organic compounds (3-D Pm3n cubic, 3-D P42/mnm tetragonal, and a crystallographically forbidden 12-fold symmetry liquid quasicrystal) and provided fundamental correlations between the molecular structure of the dendron and the shape and the diameter of the supramolecular dendrimers which, in these experiments, were limited to less than 75 A. That study concluded that alternative design principles should be elaborated for the assembly of supramolecular dendrimers of larger dimensions. Here we report design principles, synthesis and analysis of first and higher generations AB3 and AB2 self-assembling dendrons, based on various primary structures, and combinations of (AB)y−AB3 and (AB)y−AB2 (i.e., from nondendritic AB wher...

Synthesis, structural analysis, and visualization of poly(2‐ethynyl‐9‐substituted carbazole)s and poly(3‐ethynyl‐9‐substituted carbazole)s containing chiral and achiral minidendritic substituents

Abstract: The synthesis of 2-ethynyl-9-substituted carbazole and 3-ethynyl-9-substituted carbazole monomers containing first-generation chiral and achiral dendritic (i.e., minidendritic) substituents, 2-ethynyl-9-[3,4,5-tris(dodecan-1-yloxy)benzyl]carbazole (2ECz), 3-ethynyl-9-[3,4,5-tris(dodecan-1-yloxy)benzyl]carbazole (3ECz), 2-ethynyl-9-(3,4,5-tris[(S)-2-methylbutan-1-yloxy]benzyl)carbazole (2ECz*), and 3-ethynyl-9-{3,4,5-tris[(S)-2-methylbutan-1-yloxy]benzyllcarbazole (3ECz*), is presented. All monomers were polymerized and copolymerized by stereospecific polymerization to produce cistransoidal soluble stereoisomers. A structural analysis of poly(2ECz), poly(2ECz*), poly(3ECz), poly(3ECz*), poly(2ECz*-co-2ECz), and poly(3ECz*-co-3ECz) by a combination of techniques, including 1 H NMR, ultraviolet-visible, and circular dichroism spectroscopy, thermal optical polarized microscopy, and X-ray diffraction experiments, demonstrated that these polymers had a helical conformation that produced cylindrical macromolecules exhibiting chiral and achiral nematic phases. Individual chains of these cylindrical macromolecules were visualized by atomic force microscopy.

Self-assembly of semifluorinated dendrons attached to electron-donor groups mediates their π-stacking via a helical pyramidal column

Abstract: Semifluorinated first-generation self-assembling dendrons attached via a flexible spacer to electron-donor molecules induce π-stacking of the donors in the center of a supramolecular helical pyramidal column. These helical pyramidal columns self-organize in various columnar liquid crystal phases that mediate self-processing of large single crystal liquid crystal do mains of columns and self-repair their intracolumnar structural defects. In addition, all supramolecular columns exhibit a columnar phase at lower temperatures that maintains the helical pyramidal columnar supramolecular structure and displays higher intracolumnar order than that in the liquid crystals phases. The results described here demonstrate the universality of this concept, the power of the fluorous phase or the fluorophobic effect in self-assembly and the unexpected generality of pyramidal liquid crystals.

Quantification of modelling uncertainties in a large ensemble of climate change simulations

Abstract: Comprehensive global climate models1 are the only tools that account for the complex set of processes which will determine future climate change at both a global and regional level. Planners are typically faced with a wide range of predicted changes from different models of unknown relative quality2,3, owing to large but unquantified uncertainties in the modelling process4. Here we report a systematic attempt to determine the range of climate changes consistent with these uncertainties, based on a 53-member ensemble of model versions constructed by varying model parameters. We estimate a probability density function for the sensitivity of climate to a doubling of atmospheric carbon dioxide levels, and obtain a 5–95 per cent probability range of 2.4–5.4 °C. Our probability density function is constrained by objective estimates of the relative reliability of different model versions, the choice of model parameters that are varied and their uncertainty ranges, specified on the basis of expert advice. Our ensemble produces a range of regional changes much wider than indicated by traditional methods based on scaling the response patterns of an individual simulation5,6.

Functional liquid-crystalline assemblies: self-organized soft materials.

Abstract: In the 21st century, soft materials will become more important as functional materials because of their dynamic nature. Although soft materials are not as highly durable as hard materials, such as metals, ceramics, and engineering plastics, they can respond well to stimuli and the environment. The introduction of order into soft materials induces new dynamic functions. Liquid crystals are ordered soft materials consisting of self-organized molecules and can potentially be used as new functional materials for electron, ion, or molecular transporting, sensory, catalytic, optical, and bio-active materials. For this functionalization, unconventional materials design is required. Herein, we describe new approaches to the functionalization of liquid crystals and show how the design of liquid crystals formed by supramolecular assembly and nano-segregation leads to the formation of a variety of new self-organized functional materials.

Helical polymers: synthesis, structures, and functions

Abstract: 2.2.1. Polyisocyanates 6117 2.2.2. Polysilanes 6118 2.2.3. Polyacetylenes 6120 2.3. Foldamer-Based Helical Polymers 6124 2.3.1. Click Polymerization 6126 2.3.2. Ring-Closing Reaction 6126 2.4. Other Types of Helical Polymers 6127 2.4.1. π-Conjugated Helical Polymers 6127 2.4.2. Metallosupramolecular Helical Polymers 6128 2.5. Induced Helical Polymers 6130 2.5.1. Induced Helical Polyacetylenes 6130 2.5.2. Other Induced Helical Polymers and Oligomers 6132

Discotic liquid crystals: a new generation of organic semiconductors

Abstract: Discotic (disc-like) molecules typically comprising a rigid aromatic core and flexible peripheral chains have been attracting growing interest because of their fundamental importance as model systems for the study of charge and energy transport and due to the possibilities of their application in organic electronic devices. This critical review covers various aspects of recent research on discotic liquid crystals, in particular, molecular design concepts, supramolecular structure, processing into ordered thin films and fabrication of electronic devices. The chemical structure of the conjugated core of discotic molecules governs, to a large extent, their intramolecular electronic properties. Variation of the peripheral flexible chains and of the aromatic core is decisive for the tuning of self-assembly in solution and in bulk. Supramolecular organization of discotic molecules can be effectively controlled by the choice of the processing methods. In particular, approaches to obtain suitable macroscopic orientations of columnar superstructures on surfaces, that is, planar uniaxial or homeotropic alignment, are discussed together with appropriate processing techniques. Finally, an overview of charge transport in discotic materials and their application in optoelectronic devices is given (234 references).