Nanostructured Organic–Inorganic Composite Materials by Twin Polymerization of Hybrid Monomers

Forming two structurally different but associated polymer structures in a single step is a possible route for the production of nanostructured materials. By means of twin polymerization of specially constructed monomers consisting of two different covalently bonded building blocks (hybrid monomers), this route is realized. What is important is that two different macromolecular structures are formed from one monomer in a single process. The two polymers formed can be linear, branched, or cross‐linked structures. The molecular composition of the hybrid monomer defines the degree of cross‐linking of the corresponding macromolecular structures that is theoretically possible.     

Migration of Acrylic Monomers from Methacrylate Polymers – Establishing Parameters for Migration Modelling

Acrylic acid‐based and methacrylic acid‐based monomers are widely used for the manufacture of polymers, for polymer dispersions or for other specialty resins. Some of these applications cause interactions between the polymer and contact medium such as food contact materials, eyeglasses, contact lenses or toys. More specifically, migration of monomers from the polymer into the contact medium may occur, which needs to be evaluated for safety purposes. The objective of this study was to investigate the basic diffusion properties of acrylic polymers with respect to representative monomers in order to establish a scientific basis for migration modelling simulating the mass transport of monomers from the polymers when they are in contact with foods, human skin or body fluids such as sweat and saliva. For this purpose, 11 representative acrylic polymers containing five different acrylic monomers (MA, EA, BA, MMA and nBMA) were studied in extensive kinetic migrations experiments in contact with five different contact media (simulants) at three different temperatures (20°C, 40°C and 60°C). The simulants were selected according to the applications: toys were simulated by saliva simulant and articles coming in contact with human skin by sweat simulant. For food contact applications, water (aqueous foods), Miglyol 840 (Sasol, Witten, Germany) (fatty food) and Tenax® (Sigma‐Aldrich Corporation, Munich, Germany) (an adsorbent simulating dry foods) were selected. The diffusion coefficients (D) of the monomers in the polymer as well as partition coefficients between polymer and contact media were derived. It was found that those acrylic polymer materials used for rigid plastics applications exhibit extremely low diffusion behaviour, whereas acrylic polymer resins used for coating applications showed somewhat higher diffusion behaviour but this still at very low rates in comparison with other typical polymers used for the manufacture of food packaging materials. As a result, conservative polymer‐specific constants in support of migration modelling were established, and the specifications for the model general applicability were determined and specified. The parameter related to the polymers' intrinsic mobility is applicable to model migration of any other organic chemical substances, which may be present in acrylic polymers as potential migrants when they have comparable or higher molecular weights than the studied monomers. Copyright © 2012 John Wiley & Sons, Ltd.     

Emerging Multifunctional Metal–Organic Framework Materials

Metal?organic frameworks (MOFs), also known as coordination polymers, represent an interesting type of solid crystalline materials that can be straightforwardly self‐assembled through the coordination of metal ions/clusters with organic linkers. Owing to the modular nature and mild conditions of MOF synthesis, the porosities of MOF materials can be systematically tuned by judicious selection of molecular building blocks, and a variety of functional sites/groups can be introduced into metal ions/clusters, organic linkers, or pore spaces through pre‐designing or post‐synthetic approaches. These unique advantages enable MOFs to be used as a highly versatile and tunable platform for exploring multifunctional MOF materials. Here, the bright potential of MOF materials as emerging multifunctional materials is highlighted in some of the most important applications for gas storage and separation, optical, electric and magnetic materials, chemical sensing, catalysis, and biomedicine.     

25th Anniversary Article: Isoindigo‐Based Polymers and Small Molecules for Bulk Heterojunction Solar Cells and Field Effect Transistors

Driven by the potential advantages and promising applications of organic solar cells, donor‐acceptor (D‐A) polymers have been intensively investigated in the past years. One of the strong electron‐withdrawing groups that were widely used as acceptors for the construction of D‐A polymers for applications in polymer solar cells and FETs is isoindigo. The isoindigo‐based polymer solar cells have reached efficiencies up to ～7% and hole mobilities as high as 3.62 cm² V^?1 s^?1 have been realized by FETs based on isoindigo polymers. Over one hundred isoindigo‐based small molecules and polymers have been developed in only three years. This review is an attempt to summarize the structures and properties of the isoindigo‐based polymers and small molecules that have been reported in the literature since their inception in 2010. Focus has been given only to the syntheses and device performances of those polymers and small molecules that were designed for use in solar cells and FETs. Attempt has been made to deduce structure‐property relationships that would guide the design of isoindigo‐based materials. It is expected that this review will present useful guidelines for the design of efficient isoindigo‐based materials for applications in solar cells and FETs.     

Nitrogen‐Containing Microporous Conjugated Polymers via Carbazole‐Based Oxidative Coupling Polymerization: Preparation,Porosity, and Gas Uptake

Facile preparation of microporous conjugated polycarbazoles via carbazole‐based oxidative coupling polymerization is reported. The process to form the polymer network has cost‐effective advantages such as using a cheap catalyst, mild reaction conditions, and requiring a single monomer. Because no other functional groups such as halo groups, boric acid, and alkyne are required for coupling polymerization, properties derived from monomers are likely to be fully retained and structures of final polymers are easier to characterize. A series of microporous conjugated polycarbazoles ( CPOP‐2–7 ) with permanent porosity are synthesized using versatile carbazolyl‐bearing 2D and 3D conjugated core structures with non‐planar rigid conformation as building units. The Brunauer–Emmett–Teller specific surface area values for these porous materials vary between 510 and 1430 m² g^?1. The dominant pore sizes of the polymers based on the different building blocks are located between 0.59 and 0.66 nm. Gas (H₂ and CO₂) adsorption isotherms show that CPOP‐7 exhibits the best uptake capacity for hydrogen (1.51 wt% at 1.0 bar and 77 K) and carbon dioxide (13.2 wt% at 1.0 bar and 273 K) among the obtained polymers. Furthermore, its high CH₄/N₂ and CO₂/N₂ adsorption selectivity gives polymer CPOP‐7 potential application in gas separation.     

25th Anniversary Article: Progress in Chemistry and Applications of Functional Indigos for Organic Electronics

Indigo and its derivatives are dyes and pigments with a long and distinguished history in organic chemistry. Recently, applications of this ‘old’ structure as a functional organic building block for organic electronics applications have renewed interest in these molecules and their remarkable chemical and physical properties. Natural‐origin indigos have been processed in fully bio‐compatible field effect transistors, operating with ambipolar mobilities up to 0.5 cm²/Vs and air‐stability. The synthetic derivative isoindigo has emerged as one of the most successful building‐blocks for semiconducting polymers for plastic solar cells with efficiencies > 5%. Another isomer of indigo, epindolidione, has also been shown to be one of the best reported organic transistor materials in terms of mobility (～2 cm²/Vs) and stability. This progress report aims to review very recent applications of indigoids in organic electronics, but especially to logically bridge together the hereto independent research directions on indigo, isoindigo, and other materials inspired by historical dye chemistry: a field which was the root of the development of modern chemistry in the first place.     

Progress with Light‐Emitting Polymers

Light‐emitting polymers have been studied intensively as materials for light‐emitting diodes (LEDs). Here research efforts toward developing these materials for commercial applications are reviewed. The Figure shows the preferred two‐layer device structure for commercial polymer LEDs as well as polyfluorene, one of the polymers discussed.     

Rational Co‐Design of Polymer Dielectrics for Energy Storage

Although traditional materials discovery has historically benefited from intuition‐driven experimental approaches and serendipity, computational strategies have risen in prominence and proven to be a powerful complement to experiments in the modern materials research environment. It is illustrated here how one may harness a rational co‐design approach—involving synergies between high‐throughput computational screening and experimental synthesis and testing—with the example of polymer dielectrics design for electrostatic energy storage applications. Recent co‐design efforts that can potentially enable going beyond present‐day “standard” polymer dielectrics (such as biaxially oriented polypropylene) are highlighted. These efforts have led to the identification of several new organic polymer dielectrics within known generic polymer subclasses (e.g., polyurea, polythiourea, polyimide), and the recognition of the untapped potential inherent in entirely new and unanticipated chemical subspaces offered by organometallic polymers. The challenges that remain and the need for additional methodological developments necessary to further strengthen the co‐design concept are then presented.     

Ultra‐Light and Scalable Composite Lattice Materials

Architected lattice materials are some of the stiffest and strongest materials at ultra‐light density (<10 mg cm^?3), but scalable manufacturing with high‐performance constituent materials remains a challenge that limits their widespread adoption in load‐bearing applications. We show mesoscale, ultra‐light (5.8 mg cm^?3) fiber‐reinforced polymer composite lattice structures that are reversibly assembled from building blocks manufactured with a best‐practice high‐precision, high‐repeatability, and high‐throughput process: injection molding. Chopped glass fiber‐reinforced polymer (polyetherimide) lattice materials produced with this method display absolute stiffness (8.41 MPa) and strength (19 kPa) typically associated with metallic hollow strut microlattices at similar mass density. Additional benefits such as strain recovery, discrete damage repair with recovery of original stiffness and strength, and ease of modeling are demonstrated.

     

Self‐Assembly of Functional Molecules into 1D Crystalline Nanostructures

Self‐assembled functional nanoarchitectures are employed as important nanoscale building blocks for advanced materials and smart miniature devices to fulfill the increasing needs of high materials usage efficiency, low energy consumption, and high‐performance devices. One‐dimensional (1D) crystalline nanostructures, especially molecule‐composed crystalline nanostructures, attract significant attention due to their fascinating infusion structure and functionality which enables the easy tailoring of organic molecules with excellent carrier mobility and crystal stability. In this review, we discuss the recent progress of 1D crystalline self‐assembled nanostructures of functional molecules, which include both a small molecule‐derived and a polymer‐based crystalline nanostructure. The basic principles of the molecular structure design and the process engineering of 1D crystalline nanostructures are also discussed. The molecular building blocks, self‐assembly structures, and their applications in optical, electrical, and photoelectrical devices are overviewed and we give a brief outlook on crucial issues that need to be addressed in future research endeavors.     

Morphosynthesis of Molecular Magnetic Materials

Although molecule‐based materials can combine physical and chemical properties associated with molecular‐scale building blocks, their successful integration into real applications depends also on higher‐order properties, such as crystal size, shape, and organization. New approaches involving templating and self‐ or facilitated assembly of nanoscale building blocks to prepare novel multifunctional molecular magnetic materials with complex form and organization are described.     

Photonic Glasses: A Step Beyond White Paint

Self‐assembly techniques are widely used to grow ordered structures such as, for example, opal‐based photonic crystals. Here, we report on photonic glasses, new disordered materials obtained via a modified self‐assembling technique. These random materials are solid thin films which exhibit rich novel light diffusion properties originating from the optical properties of their building blocks. This novel material inaugurated a wide range of nanophotonic materials with fascinating applications, such as resonant random lasers or Anderson localization.     

Optimal Reactivity and Improved Self‐Healing Capability of Structurally Dynamic Polymers Grafted on Janus Nanoparticles Governed by Chain Stiffness and Spatial Organization

Structurally dynamic polymers are recognized as a key potential to revolutionize technologies ranging from design of self‐healing materials to numerous biomedical applications. Despite intense research in this area, optimizing reactivity and thereby improving self‐healing ability at the most fundamental level pose urgent issue for wider applications of such emerging materials. Here, the authors report the first mechanistic investigation of the fundamental principle for the dependence of reactivity and self‐healing capabilities on the properties inherent to dynamic polymers by combining large‐scale computer simulation, theoretical analysis, and experimental discussion. The results allow to reveal how chain stiffness and spatial organization regulate reactivity of dynamic polymers grafted on Janus nanoparticles and mechanically mediated reaction in their reverse chemistry, and, particularly, identify that semiflexible dynamic polymers possess the optimal reactivity and self‐healing ability. The authors also develop an analytical model of blob theory of polymer chains to complement the simulation results and reveal essential scaling laws for optimal reactivity. The findings offer new insights into the physical mechanism in various systems involving reverse/dynamic chemistry. These studies highlight molecular engineering of polymer architecture and intrinsic property as a versatile strategy in control over the structural responses and functionalities of emerging materials with optimized self‐healing capabilities.     

Polymers Move in Response to Light

Significant advances have recently been made in the development of functional polymers that are able to undergo light‐induced shape changes. The main challenge in the development of such polymer systems is the conversion of photoinduced effects at the molecular level to macroscopic movement of working pieces. This article highlights some selected polymer architectures and their tailored functionalization processes. Examples include the contraction and bending of azobenzene‐containing liquid‐crystal elastomers and volume changes in gels. We focus especially on light‐induced shape‐memory polymers. These materials can be deformed and temporarily fixed in a new shape. They only recover their original, permanent shape when irradiated with light of appropriate wavelengths. Using light as a trigger for the shape‐memory effect will extend the applications of shape‐memory polymers, especially in the field of medical devices where triggers other than heat are highly desirable.     

Nucleic Acids and Smart Materials: Advanced Building Blocks for Logic Systems

Logic gates can convert input signals into a defined output signal, which is the fundamental basis of computing. Inspired by molecular switching from one state to another under an external stimulus, molecular logic gates are explored extensively and recognized as an alternative to traditional silicon‐based computing. Among various building blocks of molecular logic gates, nucleic acid attracts special attention owing to its specific recognition abilities and structural features. Functional materials with unique physical and chemical properties offer significant advantages and are used in many fields. The integration of nucleic acids and functional materials is expected to bring about several new phenomena. In this Progress Report, recent progress in the construction of logic gates by combining the properties of a range of smart materials with nucleic acids is introduced. According to the structural characteristics and composition, functional materials are categorized into three classes: polymers, noble‐metal nanomaterials, and inorganic nanomaterials. Furthermore, the unsolved problems and future challenges in the construction of logic gates are discussed. It is hoped that broader interests in introducing new smart materials into the field are inspired and tangible applications for these constructs are found.     

Assembly and Self‐Assembly of Nanomembrane Materials—From 2D to 3D

Nanoscience and nanotechnology offer great opportunities and challenges in both fundamental research and practical applications, which require precise control of building blocks with micro/nanoscale resolution in both individual and mass‐production ways. The recent and intensive nanotechnology development gives birth to a new focus on nanomembrane materials, which are defined as structures with thickness limited to about one to several hundred nanometers and with much larger (typically at least two orders of magnitude larger, or even macroscopic scale) lateral dimensions. Nanomembranes can be readily processed in an accurate manner and integrated into functional devices and systems. In this Review, a nanotechnology perspective of nanomembranes is provided, with examples of science and applications in semiconductor, metal, insulator, polymer, and composite materials. Assisted assembly of nanomembranes leads to wrinkled/buckled geometries for flexible electronics and stacked structures for applications in photonics and thermoelectrics. Inspired by kirigami/origami, self‐assembled 3D structures are constructed via strain engineering. Many advanced materials have begun to be explored in the format of nanomembranes and extend to biomimetic and 2D materials for various applications. Nanomembranes, as a new type of nanomaterials, allow nanotechnology in a controllable and precise way for practical applications and promise great potential for future nanorelated products.     

Promising Functional Materials Based on Ladder Polysiloxanes

Preparation of real ladder polysiloxanes (LPSs), including both oxygen‐bridged ladder polysilsesquioxanes (LPSQs) and organo‐bridged ladder polysiloxanes (OLPSs), had been a great challenge to polymer chemists from 1960 until the successful synthesis of LPSs via the supramolecular architecture‐directed stepwise coupling polymerization (SCP) in the early 1980s. This opened up a new field of LPS‐based advanced materials. As key building blocks, LPSs are used to construct a variety of polysiloxanes with special steric configurations and functions, such as mesomorphic LPSs, tubular polysiloxanes (TPs), and pseudo‐sieve‐plate polysiloxanes (pseudo‐SPSs). With excellent temperature and radiation resistance, good solubility, and fine optical and mechanical properties, all these polysiloxanes demonstrate very promising prospects in the advanced materials realm. Here, the synthesis of well‐ordered LPSs is presented and features of fishbone‐like and rowboat‐like liquid crystalline polysiloxanes are discussed. Special emphasis is given to typical applications of LPSs, TPSs, and pseudo‐SPSs in the areas of liquid crystal displays, microelectronics packaging, and nonlinear optical materials.     

石墨烯/功能聚合物复合材料

常规的聚合物与石墨烯组成复合材料时，聚合物的引入经常会损害石墨烯的一些性能，如降低石墨烯材料本征的高导电性、导热能力、高比表面积等，因此石墨烯/聚合物复合材料的应用也受到颇多限制。如果基于不同的应用，通过设计或选用具有特定性能的功能聚合物，可以有针对性地增强石墨烯某些特定的性质，提高石墨烯/聚合物复合材料的应用性能，减弱甚至消除复合材料应用的限制性。本文基于上述这一功能聚合物定义范畴，以石墨烯/聚合物复合材料中石墨烯的维度进行分类，包括三维网络结构石墨烯、二维薄膜结构石墨烯、一维纤维结构石墨烯，介绍并讨论石墨烯/功能聚合物复合材料的制备方法和当前的应用进展，并分析存在的问题及发展前景。      

Aligned two- and three-dimensional structures by directional freezing of polymers and nanoparticles

The preparation of materials with aligned porosity in the micrometre range is of technological importance for a wide range of applications in organic electronics, microfluidics, molecular filtration and biomaterials. Here, we demonstrate a generic method for the preparation of aligned materials using polymers, nanoparticles or mixtures of these components as building blocks. Directional freezing is used to align the structural elements, either in the form of three-dimensional porous structures or as two-dimensional oriented surface patterns. This simple technique can be used to generate a diverse array of complex structures such as polymer-inorganic nanocomposites, aligned gold microwires and microwire networks, porous composite microfibres and biaxially aligned composite networks. The process does not involve any chemical reaction, thus avoiding potential complications associated with by-products or purification procedures.     

High‐Performance All‐Polymer Solar Cells Enabled by an n‐Type Polymer Based on a Fluorinated Imide‐Functionalized Arene

A novel imide‐functionalized arene, di(fluorothienyl)thienothiophene diimide (f‐FBTI2), featuring a fused backbone functionalized with electron‐withdrawing F atoms, is designed, and the synthetic challenges associated with highly electron‐deficient fluorinated imide are overcome. The incorporation of f‐FBTI2 into polymer affords a high‐performance n‐type semiconductor f‐FBTI2‐T, which shows a reduced bandgap and lower‐lying lowest unoccupied molecular orbital (LUMO) energy level than the polymer analog without F or with F‐functionalization on the donor moiety. These optoelectronic properties reflect the distinctive advantages of fluorination of electron‐deficient acceptors, yielding “stronger acceptors,” which are desirable for n‐type polymers. When used as a polymer acceptor in all‐polymer solar cells, an excellent power conversion efficiency of 8.1% is achieved without any solvent additive or thermal treatment, which is the highest value reported for all‐polymer solar cells except well‐studied naphthalene diimide and perylene diimide‐based n‐type polymers. In addition, the solar cells show an energy loss of 0.53 eV, the smallest value reported to date for all‐polymer solar cells with efficiency > 8%. These results demonstrate that fluorination of imide‐functionalized arenes offers an effective approach for developing new electron‐deficient building blocks with improved optoelectronic properties, and the emergence of f‐FBTI2 will change the scenario in terms of developing n‐type polymers for high‐performance all‐polymer solar cells.