Leibniz Institute of Polymer Research

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTHyperbranched and Highly Branched Polymer Architectures—Synthetic Strategies and Major Characterization AspectsBrigitte I. Voit* and Albena LedererView Author Information Leibniz Institute of Polymer Research Dresden, Hohe Strasse 6, 01069 Dresden, Germany* E-mail: [email protected]; [email protected]Cite this: Chem. Rev. 2009, 109, 11, 5924–5973Publication Date (Web):September 28, 2009Publication History Received20 February 2009Published online28 September 2009Published inissue 11 November 2009https://pubs.acs.org/doi/10.1021/cr900068qhttps://doi.org/10.1021/cr900068qreview-articleACS PublicationsCopyright © 2009 American Chemical SocietyRequest reuse permissionsArticle Views17083Altmetric-Citations1035LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Chemical structure,Monomers,Organic polymers,Peptides and proteins,Polymers Get e-Alerts

Components that click: A large number of diverse dendrimers (see scheme) was prepared in almost quantitative yield by the click-chemistry transformation described in the title. In some cases filtration or solvent extraction was the only method required for purification in this highly efficient construction of the triazole units of the dendrimers.

In the last 12 years the field of hyperbranched polymers has been well established with a large variety of synthetic approaches and fundamental studies on structure and properties of these unique materials. However, new developments involving hyperbranched materials appeared recently, for example, different synthetic strategies, new reaction mechanisms, formation of more complex architectures, a deeper understanding of the branched structure and their kinetic development, and intensive studies on the material properties and possible applications. This demonstrates the high versatility and the possibilities that are still involved in hyperbranched polymers and render it one of the most active fields in polymer science with a very promising future. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2505–2525, 2000

Humans have long appreciated silk for its lustrous appeal and remarkable physical properties, yet as the mysteries of silk are unraveled, it becomes clear that this outstanding biopolymer is more than a high-tech fiber. This progress report provides a critical but detailed insight into the biomedical use of silk. This journey begins with a historical perspective of silk and its uses, including the long-standing desire to reverse engineer silk. Selected silk structure-function relationships are then examined to appreciate past and current silk challenges. From this, biocompatibility and biodegradation are reviewed with a specific focus of silk performance in humans. The current clinical uses of silk (e.g., sutures, surgical meshes, and fabrics) are discussed, as well as clinical trials (e.g., wound healing, tissue engineering) and emerging biomedical applications of silk across selected formats, such as silk solution, films, scaffolds, electrospun materials, hydrogels, and particles. The journey finishes with a look at the roadmap of next-generation recombinant silks, especially the development pipeline of this new industry for clinical use.

Hydrogen production using water electrolysers equipped with an anion exchange membrane, a pure water feed and cheap components (catalysts and bipolar plates) can challenge proton exchange membrane electrolysis systems as the state of the art.

Multiple biological, synthetic and hybrid polymers are used for multiple medical applications. A wide range of different polymers is available, and they have further the advantage to be tunable in physical, chemical and biological properties in a wide range to match the requirements of specific applications. This review gives a brief overview about the introduction and developments of polymers in medicine in general, addressing first stable polymers, then polymers with degradability as a first biological function, followed by various other functional and responsive polymers. It is shown up that biomedical polymers comprise not only bulk materials, but also coatings and pharmaceutical nano-carriers for drugs. There is subsequently an overview of the most frequently used polymer classes. The main body of the review then is structured according to the medical applications, where key requirements of the applications and the currently used polymer solutions are indicated.

The rapid development of microtechnology in recent times has increased the necessity for the development of devices, which are able to perform mechanical work on the micro- and macroscale. Among all kinds of actuators, the ones based on stimuli-responsive hydrogels, which are three-dimensional polymer networks strongly imbibed with water, deserve particular attention. This paper aims to provide a brief overview of stimuli-responsive hydrogel actuators with respect to their sensitivity to different stimuli, different kinds of deformation, the possibilities of generating different types of movement, as well as their applications.

Colloidal gold has been studied for its potential application in medicine for centuries. However, synthesis and evaluation of various gold nanoparticles have only recently been met with a wide interest of scientists. Current studies confirm numerous advantages of nanogold over different nanomaterials, primarily due to highly optimized protocols for the production of gold nanoparticles of countless sizes and shapes, featured with unique properties. The possibility to modify the surface of nanogold particles with different targeting and functional compounds significantly broadens the range of their potential biomedical applications, with particular emphasis on cancer treatment. Functionalized gold nanoparticles exhibit good biocompatibility and controllable biodistribution patterns, which make them particularly fine candidates for the basis of innovative therapies. Considering the high amount of scientific data on nanogold, this review summarizes recent advances in the field of medical application of gold nanoparticles for the therapy of cancer.

As for nanofillers in general, the properties of carbon nanotube (CNT) -polymer composites depend strongly on the filler arrangement and the structure of the filler network. This article reviews our actual understanding of the relation between processing conditions, state of CNT dispersion and structure of the filler network on the one hand, and the resulting electrical, melt rheological and mechanical properties, on the other hand. The as-produced rather compact agglomerates of CNTs (initial agglomerates, >1 μm), whose structure can vary for different tube manufacturers, synthesis and/or purification conditions, have first to be well dispersed in the polymer matrix during the mixing step, before they can be arranged to a filler network with defined physical properties by forming secondary agglomerates. Influencing factors on the melt dispersion of initial agglomerates of multi-walled CNTs into individualized tubes are discussed in context of dispersion mechanisms, namely the melt infiltration into initial agglomerates, agglomerate rupture and nanotube erosion from agglomerate surfaces. The hierarchical morphology of filler arrangement resulting from secondary agglomeration processes has been found to be due to a competition of build-up and destruction for the actual melt temperature and the given external flow field forces. Related experimental results from in-line and laboratory experiments and a model approach for description of shear-induced properties are presented.

Challenge of developing new formulations of water-in-salt electrolytes are addressed<italic>via</italic>mixed cation strategy: cheaper (by at least an order of magnitude) and more soluble salts featuring alkali cations beyond lithium, such as potassium, are used to create the water-in-salt condition.

Abstract Co-continuous structures can be regarded as the coexistence of at least two continuous structures within the same volume. Blends with co-continuous structures may combine the properties of both components in a favorable way, for example, mechanical moduli. This review article deals with the identification, characterization, and properties of co-continuous structures as well as with the development of co-continuous structures during the melt blending process. Co-continuous structures usually can be formed within a composition region about the phase inversion composition, which mainly depends on the viscosity ratio. On the other hand, co-continuous structures can be found independent of composition as intermediate stages during the initial state of morphology development and during phase inversion process in blends in which the component finally forming the dispersed phase forms the matrix in early mixing states. In addition, even at low volume fractions of one component, stable co-continuous morphologies can be created using suitable processing conditions, forming long elongated interconnected structures that do not break up because of the flow. The interfacial tension plays an important role for the stability; a lower interfacial tension leads to broader composition ranges of co-continuous structures. Another factor enhancing the formation and stability of co-continuous structure is melt yield stress of one or both components of blends. In addition, this article reviews the stability of co-continuous structures during further processing and the influence of compatibilization on the structure formation and stability. Subsequently, two models describing the co-continuous composition range are discussed.

Drug delivery systems are molecular platforms in which an active compound is packed into or loaded on a biocompatible nanoparticle. Such a solution improves the activity of the applied drug or decreases its side effects. Dendrimers are promising molecular platforms for drug delivery due to their unique properties. These macromolecules are known for their defined size, shape, and molecular weight, as well as their monodispersity, the presence of the void space, tailorable structure, internalization by cells, selectivity toward cells and intracellular components, protection of guest molecules, and controllable release of the cargo. Dendrimers were tested as carriers of various molecules and, simultaneously, their toxicity was examined using different cell lines. It was discovered that, in general, dendrimer cytotoxicity depended on the generation, the number of surface groups, and the nature of terminal moieties (anionic, neutral, or cationic). Higher cytotoxicity occurred for higher-generation dendrimers and for dendrimers with positive charges on the surface. In order to decrease the cytotoxicity of dendrimers, scientists started to introduce different chemical modifications on the periphery of the nanomolecule. Dendrimers grafted with polyethylene glycol (PEG), acetyl groups, carbohydrates, and other moieties did not affect cell viability, or did so only slightly, while still maintaining other advantageous properties. Dendrimers clearly have great potential for wide utilization as drug and gene carriers. Moreover, some dendrimers have biological properties per se, being anti-fungal, anti-bacterial, or toxic to cancer cells without affecting normal cells. Therefore, intrinsic cytotoxicity is a comprehensive problem and should be considered individually depending on the potential destination of the nanoparticle.

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTEngineering Functional Polymer Capsules toward Smart NanoreactorsJens Gaitzsch*†‡, Xin Huang*§, and Brigitte Voit*∥View Author Information† Department of Chemistry, University College London, London WC1H 0AJ, United Kingdom‡ Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Basel-Stadt, Switzerland§ School of Chemical Engineering and Technology, Harbin Institute of Technology, 150001 Harbin, Heilongjiang, China∥ Leibniz-Institut fuer Polymerforschung Dresden e.V., Hohe Strasse 6, 01069 Dresden, Saxony, Germany*E-mail: [email protected]*E-mail: [email protected]*E-mail: [email protected]Cite this: Chem. Rev. 2016, 116, 3, 1053–1093Publication Date (Web):August 31, 2015Publication History Received22 April 2015Published online31 August 2015Published inissue 10 February 2016https://pubs.acs.org/doi/10.1021/acs.chemrev.5b00241https://doi.org/10.1021/acs.chemrev.5b00241review-articleACS PublicationsCopyright © 2015 American Chemical SocietyRequest reuse permissionsArticle Views11977Altmetric-Citations337LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Copolymers,Membranes,Nanodevices,Polymers,Vesicles Get e-Alerts

Abstract Fifteen years of research on hyperbranched polymers in the group of Brigitte Voit are described, with a focus first on hyperbranched polyester synthesis and then on the addition and cycloaddition reactions used for the preparation of the hyperbranched structure. The characterization of structural details and bulk, solution, and thin‐film properties is highlighted, and steps toward the elucidation of a general property profile of hyperbranched polymers are discussed. Some effects of hyperbranched polymers in reactive formulations and blends and in thin films are addressed that can lead to applications in coatings, as additives, and in microelectronics or sensorics. The great progress possible in the last years is shown, but open questions and unsolved problems are also pointed out. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2679–2699, 2005

One of the key challenges in two-dimensional (2D) materials is to go beyond graphene, a prototype 2D polymer (2DP), and to synthesize its organic analogues with structural control at the atomic- or molecular-level. Here we show the successful preparation of porphyrin-containing monolayer and multilayer 2DPs through Schiff-base polycondensation reaction at an air-water and liquid-liquid interface, respectively. Both the monolayer and multilayer 2DPs have crystalline structures as indicated by selected area electron diffraction. The monolayer 2DP has a thickness of∼0.7 nm with a lateral size of 4-inch wafer, and it has a Young's modulus of 267±30 GPa. Notably, the monolayer 2DP functions as an active semiconducting layer in a thin film transistor, while the multilayer 2DP from cobalt-porphyrin monomer efficiently catalyses hydrogen generation from water. This work presents an advance in the synthesis of novel 2D materials for electronics and energy-related applications.

Environmental contamination is a major global challenge, and the effects of contamination are found in most habitats. In recent times, the pollution by microplastics has come to the global attention and their removal displays an extraordinary challenge with no reasonable solutions presented so far. One of the new technologies holding many promises for environmental remediation on the microscale are self-propelled micromotors. They present several properties that are of academic and technical interest, such as the ability to overcome the diffusion limitation in catalytic processes, as well as their phoretic interaction with their environment. Here, we present two novel strategies for the elimination of microplastics using photocatalytic Au@Ni@TiO2-based micromotors. We show that individual catalytic particles as well as assembled chains show excellent collection and removal of suspended matter and microplastics from environmental water samples.

In material science of elastomers the influence of nanoscale and nanostructured filler particles is of utmost significance for the performance of innovative rubber products, i.e., passenger car tires with ultralow rolling resistance but high wet-grip performance. A better understanding of the physical characteristics of the filler–rubber interface and the filler–rubber interphase as well is necessary to improve the overall macroscopic properties of these elastomeric nanocomposites. Therefore, the surface energies and polarities of filler particles with different modified surfaces were measured by a modified Wilhelmy technique. In all cases the rubber matrix consisted of a solution - styrene butadiene copolymers, filled with 20 or 40 phr pyrogenic or precipitated silica grades with different surface modifications by silanes, and a carbon black sample as reference. A moving die rheometer was employed to observe the filler flocculation at elevated temperatures (160 °C) in rubber mixtures containing no curatives. A significant influence of the surface energy of the filler was noticed: the flocculation tendency increased with increasing difference in work of adhesion between filler and rubber. In dynamic mechanical measurements the influence of the filler/filler and the filler/polymer interactions were studied in cured S-SBR samples. Amplitude sweep experiments were carried out to investigate the temperature dependent nonlinear characteristics of the elastic and viscous moduli, which is commonly associated with a progressive breakdown of the filler network at higher strain amplitudes (Payne effect). Static measurements and relaxations test were accomplished by large scale strain experiments. A structural–phenomenological modeling of the long strain mechanical properties of these rubber compounds was done: the “layered fiber model”. This new model is based on the hypothesis that during deformation of the composites the polymer chains slipped off from the polymer interphase around the filler particles into the gaps between aggregates, where high-strength polymer fibers in an uniaxially oriented state are formed. We find new interesting correlations between the physicochemical properties of the filler/polymer interface and the macroscopic mechanical properties of the elastomeric materials.

Excessive production of inflammatory chemokines can cause chronic inflammation and thus impair cutaneous wound healing. Capturing chemokine signals using wound dressing materials may offer powerful new treatment modalities for chronic wounds. Here, a modular hydrogel based on end-functionalized star-shaped polyethylene glycol (starPEG) and derivatives of the glycosaminoglycan (GAG) heparin was customized for maximal chemokine sequestration. The material is shown to effectively scavenge the inflammatory chemokines MCP-1 (monocyte chemoattractant protein-1), IL-8 (interleukin-8), and MIP-1α (macrophage inflammatory protein-1α) and MIP-1β (macrophage inflammatory protein-1β) in wound fluids from patients suffering from chronic venous leg ulcers and to reduce the migratory activity of human monocytes and polymorphonuclear neutrophils. In an in vivo model of delayed wound healing (db/db mice), starPEG-GAG hydrogels outperformed the standard-of-care product Promogran with respect to reduction of inflammation, as well as increased granulation tissue formation, vascularization, and wound closure.

We design partially biodegradable thermoresponsive self-folding capsules capable of controlled capture and release of cells. The proof of principle is demonstrated on the example of star-like patterned polycaprolactone-poly(N-isopropylacrylamide) bilayers, which reversibly encapsulate/release yeast cells in response to a temperature signal.

The exceptional thermal conductivity of graphene is expected to endow polymer composites with ultrahigh thermal conductivities, which can be even similar to those of some metals such as stainless steel and aluminum alloy. The thermal conductivities of composites prepared by dispersing multilayer graphene (MLG) in epoxy matrix increase only by an order of magnitude over the pure epoxy. However, the improvement has been limited since the large interfacial thermal resistance exists between graphene and the surrounding epoxy. We have reported an extraordinary increase in thermal conductivity of the MLG/epoxy composites through the fabrication of the vertically aligned and densely packed MLG in the epoxy matrix. The ultrahigh thermal conductivity of 33.54 W/(m K) has been achieved in the aligned MLG/epoxy composite (AG/E). The thermal conductivity of AG/E exhibits a positive temperature response related to the aligned structure while increasing the temperature from 40 °C to 90 °C.