Showing papers in "Macromolecular Rapid Communications in 2009"
TL;DR: This review is focused on the inherent advantages in using polymer vesicles over their small molecule lipid counterparts and the potential applications in biology for both drug delivery and synthetic cellular reactors.
Abstract: The ability of amphiphilic block copolymers to self-assemble in selective solvents has been widely studied in academia and utilized for various commercial products. The self-assembled polymer vesicle is at the forefront of this nanotechnological revolution with seemingly endless possible uses, ranging from biomedical to nanometer-scale enzymatic reactors. This review is focused on the inherent advantages in using polymer vesicles over their small molecule lipid counterparts and the potential applications in biology for both drug delivery and synthetic cellular reactors.
1,320 citations
TL;DR: Thermally reduced graphite oxides (TrGO) with specific surface areas of 600 to 950 m(2) · g(-1) were obtained by oxidation of graphite followed by thermal expansion at 600 °C.
Abstract: Exfoliation of expanded GO represents an attractive route to functionalized graphenes as versatile 2D carbon nanomaterials and components of a wide variety of polymer nanocomposites. Thermally reduced graphite oxides (TrGO) with specific surface areas of 600 to 950 m2 · g−1 were obtained by oxidation of graphite followed by thermal expansion at 600 °C. Thermal post treatment at 700 °C and 1 000 °C increased carbon content (81 to 97 wt.-%) and lowered resistivity (1 600 to 50 Ω · cm). During melt extrusion with PC, iPP, SAN and PA6, exfoliation afforded uniformly dispersed graphenes with aspect ratio > 200. In comparison to conventional 0D and 1D carbon nanoparticles, TrGO afforded nanocomposites with improved stiffness and lower percolation threshold. Recent progress and new strategies in development of functionalized graphenes and graphene-based nanocomposites are highlighted.
508 citations
TL;DR: This review presents ways to systematically improve charge carrier mobility by proper variation of the electronic and steric structure of the constituting molecules and to reach charge carrier mobilities that are close to and comparable to amorphous silicon.
Abstract: Organic semiconducting materials offer the advantage of solution processability into flexible films. In most cases, their drawback is based on their low charge carrier mobility, which is directly related to the packing of the molecules both on local (amorphous versus crystalline) and on macroscopic (grain boundaries) length scales. Liquid crystalline ordering offers the possibility of circumventing this problem. An advanced concept comprises: i) the application of materials with different liquid crystalline phases, ii) the orientation of a low viscosity high temperature phase, and, iii) the transfer of the macroscopic orientation during cooling to a highly ordered (at best, crystalline-like) phase at room temperature. At the same time, the desired orientation for the application (OLED or field-effect transistor) can be obtained. This review presents the use of molecules with discotic, calamitic and sanidic phases and discusses the sensitivity of the phases with regard to defects depending on the dimensionality of the ordered structure (columns: 1D, smectic layers and sanidic phases: 2D). It presents ways to systematically improve charge carrier mobility by proper variation of the electronic and steric (packing) structure of the constituting molecules and to reach charge carrier mobilities that are close to and comparable to amorphous silicon, with values of 0.1 to 0. 7 cm 2 . V -1 . s -1 . In this context, the significance of crosslinking to stabilize the orientation and liquid crystalline behavior of inorganic/organic hybrids is also discussed.
355 citations
TL;DR: Interestingly, in all blends, regardless of the way of introducing the nanotubes, the MWNTs were exclusively located within the PC phase, which resulted in much lower electrical resistivities as compared to PC or SAN composites with the same MWNT content.
Abstract: Multiwalled carbon nanotubes (MWNTs) have been introduced into blends of polycarbonate (PC) and poly(styrene-acrylonitrile) (SAN) by melt mixing in a microcompounder. Co-continuous blends are prepared by either pre-compounding low amounts of nanotubes into PC or SAN or by mixing all three components together. Interestingly, in all blends, regardless of the way of introducing the nanotubes, the MWNTs were exclusively located within the PC phase, which resulted in much lower electrical resistivities as compared to PC or SAN composites with the same MWNT content. The migration of MWNTs from the SAN phase into the PC phase during common mixing is explained by interfacial effects.
316 citations
TL;DR: This review draws a rather comprehensive picture of how Suzuki polycondensation was discovered in 1989 and how it was subsequently developed into the most powerful polymerization method for polyarylenes during the last 20 years.
Abstract: This review draws a rather comprehensive picture of how Suzuki polycondensation was discovered in 1989 and how it was subsequently developed into the most powerful polymerization method for polyarylenes during the last 20 years. It combines insights into synthetic issues with classes of polymers prepared and touches upon aspects of this method's technological importance. Because a significant part of the developmental work was carried out in industry, the present review makes reference to an unusually large number of patents.
270 citations
TL;DR: Since lipase-catalyzed polyester synthesis provides a good opportunity for conducting "green polymer chemistry", the importance of this is described.
Abstract: Polyester synthesis by lipase catalyst involves two major polymerization modes: i) ring-opening polymerization of lactones, and, ii) polycondensation. Ring-opening polymerization includes the finding of lipase catalyst; scope of reactions; polymerization mechanism; ring-opening polymerization reactivity of lactones; enantio-, chemo- and regio-selective polymerizations; and, chemoenzymatic polymerizations. Polycondensation includes polymerizations involving condensation reactions between carboxylic acid and alcohol functional groups to form an ester bond. In most cases, a carboxylic acid group is activated as an ester form, such as a vinyl ester. Many recently developed polymerizations demonstrate lipase catalysis specific to enzymatic polymerization and appear very useful. Also, since lipase-catalyzed polyester synthesis provides a good opportunity for conducting "green polymer chemistry", the importance of this is described.
250 citations
TL;DR: It is believed that the following three molecular design criterions should be considered in designing triple-shape memory polymers with optimum TSME: well-separated thermal transitions, a strong interface, and an appropriate balance of moduli and relative ratios between the layers (or microphases).
Abstract: Bilayer polymers that consist of two epoxy dual-shape memory polymers of well-separated glass transition temperatures have been synthesized. These bilayer epoxy samples exhibit a triple-shape memory effect (TSME) with shape fixities tailorable by changing the ratio between the two layers. The triple-shape fixities of the bilayer epoxy polymers can be explained by the balance of stress between the two layers. Based on this work, it is believed that the following three molecular design criterions should be considered in designing triple-shape memory polymers with optimum TSME: 1) well-separated thermal transitions, 2) a strong interface, and 3) an appropriate balance of moduli and relative ratios between the layers (or microphases).
249 citations
TL;DR: FTIR spectra suggest that the triple helical structure of collagen was conserved after dissolution and electrospinning, and simple binary mixtures of phosphate-buffered saline and ethanol have been found to be highly effective for electrosp spinning.
Abstract: Nanofiber scaffolds of collagen have been fabricated via electrospinning using benign solvent systems as a replacement for 1,1,1,3,3,3 hexafluoro-2-propanol Simple binary mixtures of phosphate-buffered saline and ethanol have been found to be highly effective for electrospinning FTIR spectra suggest that the triple helical structure of collagen was conserved after dissolution and electrospinning Crosslinking of the electrospun collagen scaffolds was achieved with standard methods
218 citations
TL;DR: The spectroscopy and the optical properties of the PAEs and in particular of the PPEs are dominated by their conformation, which is influenced by solid-state packing, solvent, temperature and other factors.
Abstract: Poly(aryleneethynylene)s (PAE) are easily synthesized, chemically stable, and color-responsive towards their surroundings. These superbly chromic polymers are attractive as active transducers in sensors and advanced organic electronic devices. PAEs are generally fluorescent with emission maxima ranging from 420-600 nm, and can be either water- or organo-soluble. PAEs from linear building blocks are rigid rod molecules and display a host of supramolecular arrangements in solution and in the solid state. The poly(para-phenyleneethynylene)s (PPE) are lyotropic or thermotropic smectic liquid crystalline. In the solid state, PPEs display lamellar supramolecular structures that lead to distinct stranded nanoscale morphologies. The spectroscopy and the optical properties of the PAEs and in particular of the PPEs are dominated by their conformation, which is influenced by solid-state packing, solvent, temperature and other factors. The presence of twisted and planar forms and their interconversion leads to attractive structure/property relationships; PAEs are of use as ingredients for advanced supramolecular materials.
199 citations
TL;DR: In this article, the frontier orbital energy offsets in O/O' heterojunctions are determined using photoemission spectroscopies, how these energies change as a function of molecular environment, and the influence of interface dipoles on these frontier orbital energies.
Abstract: Heterojunctions created from thin films of two dissimilar organic semiconductor materials [organic/organic' (O/O') heterojunctions] are an essential component of organic light emitting diode displays and lighting systems (OLEDs, PLEDs) and small molecule or polymer-based organic photovoltaic (solar cell) technologies (OPVs). O/O' heterojunctions are the site for exciton formation in OLEDs, and the site for exciton dissociation and photocurrent production in OPVs. Frontier orbital energy offsets in O/O' heterojunctions establish the excess free energy controlling rates of charge recombination and formation of emissive states in OLEDs and PLEDs. These energy offsets also establish the excess free energy which controls charge separation and the short-circuit photocurrent (J(SC) ) in OPVs, and set the upper limit for the open-circuit photopotential (V(OC) ). We review here how these frontier orbital energy offsets are determined using photoemission spectroscopies, how these energies change as a function of molecular environment, and the influence of interface dipoles on these frontier orbital energies. Recent examples of heterojunctions based on small molecule materials are shown, emphasizing those heterojunctions which are of interest for photovoltaic applications. These include heterojunctions of perylenebisimide dyes with trivalent metal phthalocyanines, and heterojunctions of titanyl phthalocyanine with C(60) , and with pentacene. Organic solar cells comprised of donor/acceptor pairs of each of these last three materials confirm that the V(OC) scales with the energy offsets between the HOMO of the donor and LUMO of the acceptor ($E_{{\rm HOMO}^{\rm D} } - E_{{\rm LUMO}^{\rm A} }$).
194 citations
TL;DR: Energy transfer studies at the single molecule level provide a new tool to study electronic couplings in simple donor/acceptor dyads and conjugated polymers and applications of energy transfer in fluorescent and phosphorescent organic light emitting devices are discussed.
Abstract: In this review, we discuss investigations of electronic excitation energy transfer in conjugated organic materials at the bulk and single molecule level and applications of energy transfer in fluorescent and phosphorescent organic light emitting devices. A brief overview of common descriptions of energy transfer mechanisms is given followed by a discussion of some basic photophysics of conjugated materials including the generation of excited states and their subsequent decay through various channels. In particular, various examples of bimolecular excited state annihilation processes are presented. Energy transfer studies at the single molecule level provide a new tool to study electronic couplings in simple donor/acceptor dyads and conjugated polymers. Finally, energy transfer in organic electronic devices is discussed with particular emphasis on triplet emitter doped OLEDs and blends for white light emission.
TL;DR: A new generation of porous polymers was made for various energy-related applications, e.g., as fuel cell membranes, as electrode materials for batteries, for gas storage, partly from renewable resources, by reporting on a variety of different approaches to make high performing polymers porous.
Abstract: A new generation of porous polymers was made for various energy-related applications, e.g., as fuel cell membranes, as electrode materials for batteries, for gas storage, partly from renewable resources. This review intends to catch this emerging field by reporting on a variety of different approaches to make high performing polymers porous. This includes template techniques, polymers with inherent microporosity, polymer frameworks by ionothermal polymerization, and the polymerization of carbon from appropriate precursors and by hydrothermal polymerization. In this process, we try to not only identify the current status of the field, but also point to open question and tasks to identify the potentially relevant progress.
TL;DR: An encapsulation of the macromolecules inside the lumen of the biocompatible clay nanotubes coupled with the polyelectrolyte shell formation provides a novel formulation for the controlled release of bioactive agents.
Abstract: The use of tubular halloysite clay as a nanotemplate for layer-by-layer (LbL) shell assembly and its utilization for controlled release of drug macromolecules are studied. The LbL nanoshell allowed additional control for the sustained release of drug loaded halloysite tubes. The number of polymeric layers in the shell and molecular weight of the assembled polymers influences the drug release rate. Three bilayer shells of chitosan and gelatin of 15 nm thicknesses gave the best encapsulation and retardation in the release rate of dexamethasone. An encapsulation of the macromolecules inside the lumen of the biocompatible clay nanotubes coupled with the polyelectrolyte shell formation provides a novel formulation for the controlled release of bioactive agents.
TL;DR: End group modification of polymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization was accomplished by conversion of trithiocarbonate into reactive functions able to conjugate easily with biomolecules or bioactive functionality.
Abstract: End group modification of polymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization was accomplished by conversion of trithiocarbonate into reactive functions able to conjugate easily with biomolecules or bioactive functionality. Polymers were prepared by RAFT, and subsequent aminolysis led to sulfhydryl-terminated polymers that reacted in situ with an excess of dithiopyridyl disulfide to yield pyridyl disulfide-terminated macromolecules or in the presence of ene to yield functional polymers. In the first route, the pyridyl disulfide end groups allowed coupling with oligonucleotide and peptide. The second approach exploited thiol-ene chemistry to couple polymers and model compounds such as carbohydrate and biotin with high yield.
TL;DR: This feature article reviews the authors' work combined with highlighted specific aspects of polyaniline (PANI) macro/nanostructures, focusing on such issues as the new development of a hard-template method.
Abstract: This feature article reviews the authors' work combined with highlighted specific aspects of polyaniline (PANI) macro/nanostructures, focusing on such issues as the following. 1) The new development of a hard-template method. 2) Evaluation of a template-free method in universality, controllability, and simplicity as well as the self-assembly mechanism. 3) Multi-functionality based on a template-free method associated with other approaches. 4) Cooperation effect of a micelle soft-template and molecular interactions as a new tool to complex 3D microstructures assembled from 2D or 1D nanostructures. 5) Electrical and transport properties of a single PANI nanotube, as measured by a four-probe method. 6) Sensors guided by reversible switching wettability through a doping/de-doping process. An outlook is also briefly given.
TL;DR: The metal nanoparticle-PDMS films have a higher Young's modulus than pure PDMS films and also show enhanced antibacterial properties and could be used for a number of applications such as for catalysis, optical and biomedical devices and gas separation membranes.
Abstract: We demonstrate a simple one-step method for synthesizing noble metal nanoparticle embedded free standing polydimethylsiloxane (PDMS) composite films. The process involves preparing a homogenous mixture of metal salt (silver, gold and platinum), silicone elastomer and the curing agent (hardener) followed by curing. During the curing process, the hardener crosslinks the elastomer and simultaneously reduces the metal salt to form nanoparticles. This in situ method avoids the use of any external reducing agent/stabilizing agent and leads to a uniform distribution of nanoparticles in the PDMS matrix. The films were characterized using UV-Vis spectroscopy, transmission electron microscopy and X-ray photoemission spectroscopy. The nanoparticle-PDMS films have a higher Young's modulus than pure PDMS films and also show enhanced antibacterial properties. The metal nanoparticle-PDMS films could be used for a number of applications such as for catalysis, optical and biomedical devices and gas separation membranes.
TL;DR: Chain transfer to polymer (CTP) in conventional free-radical polymerizations (FRPs) and controlled radical polymerizations of n-butyl acrylate (BA) has been investigated using (13) C NMR measurements of branching in the poly(n- butyl Acrylate) produced, finding that the mol-% branches are reduced significantly in the controlled Radical polymerizations as compared to conventional FRPs.
Abstract: Chain transfer to polymer (CTP) in conventional free-radical polymerizations (FRPs) and controlled radical polymerizations (ATRP, RAFT and NMP) of n-butyl acrylate (BA) has been investigated using 13C NMR measurements of branching in the poly(n-butyl acrylate) produced. The mol-% branches are reduced significantly in the controlled radical polymerizations as compared to conventional FRPs. Several possible explanations for this observation are discussed critically and all except one refuted. The observations are explained in terms of differences in the concentration of highly reactive short-chain radicals which can be expected to undergo both intra- and inter-molecular CTP at much higher rates than long-chain radicals. In conventional FRP, the distribution of radical concentrations is broad and there always is present a significant proportion of short-chain radicals, whereas in controlled radical polymerizations, the distribution is narrow with only a small proportion of short-chain radicals which diminishes as the living chains grow. Hence, irrespective of the type of control, controlled radical polymerizations give rise to lower levels of branching, when performed under otherwise similar conditions to conventional FRP. Similar observations are expected for other acrylates and monomers that undergo chain transfer to polymer during radical polymerization.
TL;DR: It was felt by the scientific community that the critical mass was lacking to bring the field of polymer science to a similar level of competence, international competitiveness.
Abstract: Synthetic polymers were portrayed a mere curiosity by the leading organic chemists. They were considered an interesting but rather exotic playground by physical chemists and physics was barely interested in materials which showed such a complex and parameter dependent behavior as were polymers available in the years 1950–1970. And yet, polymers had become a major field of growth for the chemical industry worldwide and increasing amounts of polymers – frequently called ‘‘plastics’’ in a simplifying and generalizing context – were thrown into a seemingly unsaturable market. The reason was that synthetic polymers had developed into the growth engine for mass production of advanced technology products in rapidly growing markets of the automotive, aero space, electronics and packaging industries, just to mention a few of the important areas. In consequence, industry was in need to find scientifically trained experts and contacts to research groups who could assist in understanding the materials properties in response to the ever growing complex requests of the markets. This was particularly true in Germany where the chemical industry had become a major supplier of polymer materials for the world market in the late 1970s. The landscape of academic research in the field of polymers was rich but extremely scattered into small and highly specialized individual groups at the time. It was felt by the scientific community that the critical mass was lacking to bring the field of polymer science to a similar level of competence, international competitiveness
TL;DR: The novel HPAMAMs displayed bright fluorescence, and the emissions bands cover nearly the whole visible wavelength range, and they can be easily cleaved by 2-mercaptoethanol or glutathione, leading to a decrease in the fluorescence intensity.
Abstract: Disulfide-functionalized hyperbranched poly(amido amine)s (HPAMAMs) were synthesized by Michael addition polymerization of N,N'-cystaminebisacrylamide and 1-(2-aminoethyl)piperazine. The novel HPAMAMs displayed bright fluorescence, and the emissions bands cover nearly the whole visible wavelength range. When polymer solutions were excited at 330-385, 460-490, and 510-550 nm, blue, green, and red solutions were observed, respectively. The HPAMAMs are biodegradable and they can be easily cleaved by 2-mercaptoethanol or glutathione, leading to a decrease in the fluorescence intensity. Studies of applications of the biocompatible and biodegradable HPAMAMs in fluorescence imaging technology and biological science are in progress.
TL;DR: Questions and concepts in lipid membrane research can often be favorably addressed with highly simplified simulation models and among the topics discussed are membrane adhesion to substrates, mixed lipid bilayers, lipid curvature coupling, pore formation by antimicrobial peptides, composition-driven protein aggregation, and curvature driven vesiculation.
Abstract: The window of a few tens to a few hundred nanometers in length scale is a booming field in lipid membrane research, owing largely to two reasons. First, many exciting biophysical and cell biological processes take place within it. Second, experimental techniques manage to zoom in on this sub-optical scale, while computer simulations zoom out to system sizes previously unattainable, and both will be meeting soon. This paper reviews a selection of questions and concepts in this field and demonstrates that they can often be favorably addressed with highly simplified simulation models. Among the topics discussed are membrane adhesion to substrates, mixed lipid bilayers, lipid curvature coupling, pore formation by antimicrobial peptides, composition-driven protein aggregation, and curvature driven vesiculation.
TL;DR: Blue emission of oxygen-doped tertiary amine (triethylamine), a key unit of fluorescent poly(amido amine) dendrimer, was demonstrated and it was found that the fluorescence intensity could be further enhanced if the tertiaries amines locate densely in the d endrimer interior as the branching sites.
Abstract: Blue emission of oxygen-doped tertiary amine (triethylamine), a key unit of fluorescent poly(amido amine) dendrimer, was demonstrated. It was found that the fluorescence intensity could be further enhanced if the tertiary amines locate densely in the dendrimer interior as the branching sites. Moreover, a solvatochromic phenol blue, instead of oxygen, is able to induce the blue fluorescence of the tertiary amino-branching sites based on a guaranteed host-guest complexation of phenol blue molecules and dendrimer interior.
TL;DR: This review article describes the preparation of polymer brushes by nitroxide-mediated radical polymerization using either the 'Grafting to' or the 'grafting from' approach, using TEMPO as a classical initiator.
Abstract: This review article describes the preparation of polymer brushes by nitroxide-mediated radical polymerization using either the 'grafting to' or the 'grafting from' approach. The use of TEMPO as a classical initiator is intensively described. More sophisticated nitroxides are also included in the discussion. Brush formation on flat surfaces such as wafers and also on particles is reported. Finally, some applications of polymer brushes are presented.
TL;DR: It is shown how computer simulations can contribute to a better understanding of the switching behavior of brushes and how polymer brushes can be used to create surfaces with switchable ultrahydrophobicity and wettability gradients.
Abstract: Mixed polymer brushes as functional ultra thin films for surface functionalization have an enormous potential to create a variety of smart, switchable, and multifunctional surfaces and thin films. It is shown how computer simulations can contribute to a better understanding of the switching behavior of brushes. Furthermore, it is described how polymer brushes can be used to create surfaces with switchable ultrahydrophobicity and wettability gradients, as well as functional layers for the immobilization of nanoparticles. Applications of these versatile and multifunctional brush coatings are envisioned in many areas including fluid control, microfluidics, and thin film sensors.
TL;DR: This feature article mainly focuses on recent developments in the field of supramolecular self-assembly of amphiphilic and double hydrophilic block copolymers (DHBCs) possessing nonlinear chain topologies, including miktoarm star polymers, dendritic-linear blockcopolymers, cyclic blockCopolymers and comb-shaped copolymer brushes.
Abstract: Supramolecular self-assembly of block copolymers in aqueous solution has received ever-increasing interest over the past few decades due to diverse biological and technological applications in drug delivery, imaging, sensing and catalysis. In addition to relative block lengths, molecular weights and solution conditions, chain architectures of block copolymers can also dramatically affect their self-assembling properties in selective solvents. This feature article mainly focuses on recent developments in the field of supramolecular self-assembly of amphiphilic and double hydrophilic block copolymers (DHBCs) possessing nonlinear chain topologies, including miktoarm star polymers, dendritic-linear block copolymers, cyclic block copolymers and comb-shaped copolymer brushes.
TL;DR: An ultra-fast fabrication of large-scale colloidal PCs via spray coating was demonstrated, and the latex spheres with hydrophobic core and hydrophilic shell resulted in strong hydrogen bonding interaction among latex spheres, which boosted latex arrangement during the spray procedure.
Abstract: An ultra-fast fabrication of large-scale colloidal PCs via spray coating was demonstrated. The latex spheres with hydrophobic core and hydrophilic shell were designed, and the latex shell with abundant COOH groups resulted in strong hydrogen bonding interaction among latex spheres, which boosted latex arrangement during the spray procedure. The resultant samples with area of 7 x 12 cm 2 were easily fabricated within 1 min on different substrates. This ultra-fast fabrication procedure would be of great importance for the practical application of PCs for optic devices and functional coatings.
TL;DR: The alkylthio side chains decrease the HOMO energy level of the polymers, which benefits the higher open circuit voltage of the polymer solar cells (PSCs) based on the polymer as donor.
Abstract: Two polythiophene derivatives with electron-donating alkylthio side chains, poly[(3-hexyl-thio)thiophene] (P3HST) and poly[(3-hexylthio)thiophene-alt-thiophene] (P3HST-co-Th) have been synthesized and characterized. Both P3HST and P3HST-co-Th show broader absorption peaks than poly(3-hexylthiophene). Meanwhile, the alkylthio side chains decrease the HOMO energy level of the polymers, which benefits the higher open circuit voltage of the polymer solar cells (PSCs) based on the polymer as donor. PSCs have been fabricated with the polymers as donor and [6,6]-phenyl C61 butyric acid methyl ester as acceptor (1: 1, w/w). The devices based on P3HST and P3HST-co-Th show an open circuit voltage of 0.63 V, and a power conversion efficiency of 0.34% and 0.5%, respectively, under the illumination of AM1.5, 80 mW · cm ―2 .
TL;DR: A pseudo dry spinning technique which allows precise control on fiber diameters and further allows deposition of fiber arrays in aligned configurations is presented and can be used towards developing strong textiles, biological scaffolds, and sensor networks.
Abstract: Polymeric nanofibers are finding increasing number of applications and hold the potential to revolutionize diverse fields such as tissue engineering, smart textiles, sensors, and actuators. Aligning and producing high aspect ratio fiber arrays (length/diameter > 2 000) in the sub-micron and nanoscale diameters has been challenging due to fragility of polymeric materials, thus making it difficult to deposit them as one dimensional structures functionally interfaced with other systems. Here, we present a pseudo dry spinning technique which allows precise control on fiber diameters and further allows deposition of fiber arrays in aligned configurations. Control on fiber diameters ranging from 50-500 nm and having lengths of several millimeters is achieved by altering the polymeric solution concentration. In the dilute and semi-dilute unentangled concentration domain droplets or beaded fibers are observed to form. Smooth uniform diameter fibers are observed to form at the onset of semi-dilute entangled concentration regime. For a given molecular weight, the increase in fiber diameter with increasing solution concentration is attributed to both the increase in the entanglement density and the decrease in the radius of gyration of solvated polymer molecules. Using this technique polymeric fiber arrays in single and multiple layers are demonstrated which can be used towards developing strong textiles, biological scaffolds, and sensor networks.
TL;DR: The review highlights different approaches to template organic materials as well as hybrid materials that find or are expected to find application in optoelectronic devices and summarized developments that take advantage of self-assembly processes to pattern hybrid materials.
Abstract: The review highlights different approaches to template organic materials as well as hybrid materials that find or are expected to find application in optoelectronic devices. The first templating approach focuses on the use of preformed nanoporous membranes as templates for organic materials and polymeric materials. Such nanoporous templates can be track-etched membranes, anodic aluminum oxide membranes and other variants thereof, or block copolymer templates. Further, opals have been described as templates. In the second part, we have summarized developments that take advantage of self-assembly processes to pattern hybrid materials. Examples are sol-gel templating techniques using amphiphiles, evaporation-induced self-assembly, lyotropic templating as well as templating from block copolymers. Both routes are very promising templating approaches for optoelectronic materials and represent complementary rather than competing techniques.
TL;DR: In this article, the authors reported the synthesis of soft polymeric colloids with sizes and shapes that mimic those of the human red blood cell (RBC) which exhibits extreme reversible deformability under flow.
Abstract: Recent advances in the synthesis of polymeric colloids have opened the doors to new advanced materials. There is strong interest in using these new techniques to produce particles that mimic and/or interact with biological systems. An important characteristic of biological systems that has not yet been exploited in synthetic polymeric colloids is their wide range of deformability. A canonical example of this is the human red blood cell (RBC) which exhibits extreme reversible deformability under flow. Here we report the synthesis of soft polymeric colloids with sizes and shapes that mimic those of the RBC. Additionally, we demonstrate that the mechanical flexibility of the colloids can be reproducibly varied over a large range resulting in RBC-like deformability under physiological flow conditions. These materials have the potential to impact the interaction between biological and synthetic systems.
TL;DR: The polysulfide oxidative sensitivity is put into the biological context of the development of new anti-inflammatory therapies through the review of 50 years of research on polys sulfur(II)-containing polymers.
Abstract: Sulfur(II)-containing polymers (polysulfides) combine flexible synthetic and processing techniques with a unique responsiveness to oxidants. Here, the polysulfide oxidative sensitivity is put into the biological context of the development of new anti-inflammatory therapies - the development of new anti-inflammatory methodologies, adopted interactions and the minimisation of foreign-body reactions - through the review of 50 years of research on polysulfide synthetic methodologies. Attention is paid to the identification of the most flexible and robust preparative techniques.