Synthesis and Morphogenesis of Organic and Inorganic Polymers by Means of Biominerals and Biomimetic Materials

We have studied the simultaneous synthesis and morphogenesis of polymer materials with hierarchical structures from nanoscopic to macroscopic scales. The morphologies of the original materials can be replicated to the polymer materials. In general, it is not easy to achieve the simultaneous synthesis and morphogenesis of polymer material even using host materials. In the present work, four biominerals and three biomimetic mesocrystal structures are used as the host materials or templates and polypyrrole, poly(3‐hexylthiopehene), and silica were used as the precursors for the simultaneous syntheses and morphogenesis of polymer materials. The host materials with the hierarchical structure possess the nanospace for the incorporation of the monomers. After the incorporation of the monomers, the polymerization reaction proceeds in the nanospace with addition of the initiator agents. Then, the dissolution of the host materials leads to the formation and morphogenesis of the polymer materials. The scheme of the replication can be classified into the three types based on the structures of the host materials (types I–III). The type I template facilitates the hierarchical replication of the whole host material, type II mediates the hierarchical surface replication, and type III induces the formation of the two‐dimensional nanosheets. Based on these results, the approach for the coupled synthesis and morphogenesis can be applied to a variety of combinations of the templates and polymer materials.     

Template-directed control of crystal morphologies

Biominerals are characterised by unique morphologies, and it is a long-term synthetic goal to reproduce these synthetically. We here apply a range of templating routes to investigate whether a fascinating category of biominerals, the single crystals with complex forms, can be produced using simple synthetic methods. Macroporous crystals with sponge-like morphologies identical to that of sea urchin skeletal plates were produced on templating with a sponge-like polymer membrane. Similarly, patterning of individual crystal faces was achieved from the micrometer to nanometer scale through crystallisation on colloidal particle monolayers and patterned polymer thin films. These experiments demonstrate the versatility of a templating approach to producing single crystals with unique morphologies.     

Morphological and dimensional control via hierarchical assembly of doped oligoaniline single crystals

Single crystals of doped aniline oligomers are produced via a simple solution-based self-assembly method. Detailed mechanistic studies reveal that crystals of different morphologies and dimensions can be produced by a "bottom-up" hierarchical assembly where structures such as one-dimensional (1-D) nanofibers can be aggregated into higher order architectures. A large variety of crystalline nanostructures including 1-D nanofibers and nanowires, 2-D nanoribbons and nanosheets, 3-D nanoplates, stacked sheets, nanoflowers, porous networks, hollow spheres, and twisted coils can be obtained by controlling the nucleation of the crystals and the non-covalent interactions between the doped oligomers. These nanoscale crystals exhibit enhanced conductivity compared to their bulk counterparts as well as interesting structure-property relationships such as shape-dependent crystallinity. Furthermore, the morphology and dimension of these structures can be largely rationalized and predicted by monitoring molecule-solvent interactions via absorption studies. Using doped tetraaniline as a model system, the results and strategies presented here provide insight into the general scheme of shape and size control for organic materials.     

SiO2/聚合物核壳型杂化粒子及其空心结构的制备

SiO2/聚合物核壳型杂化粒子及其空心结构以其独特的形貌在药物控制释放、催化剂载体、生物医药等领域应用前景广阔,引起了人们的广泛关注。本文着重从乳液聚合法、仿生矿化法等制备方法角度阐述了SiO2/聚合物核壳型杂化粒子及其空心结构的研究进展。乳液聚合制备SiO2/聚合物核壳型杂化粒子简单易行,一般需要预先合成SiO2纳米粒子,其合成过程通常需要一些非理想的条件,如高温高压、极端pH、昂贵或有毒的有机试剂等,而且预先合成的SiO2粒子无法与聚合物实现100%匹配,即总有纯的聚合物粒子存在。相比之下,原位仿生矿化法制备SiO2杂化粒子不仅在环境条件下可进行,而且能够精确控制其纳米尺度的形态及分级有序结构。目前对材料科学家来讲,要使人工合成SiO2/聚合物杂化粒子实现像自然生物硅那样优异的性能,仍然是很大的挑战。     

Robust Superhydrophobic/Superoleophilic Wrinkled Microspherical MOF@rGO Composites for Efficient Oil–Water Separation

Graphene/MOF‐based composite materials in three‐dimensional (3D) architectures are promising for the treatment of oil‐containing wastewater by absorption owing to their intrinsic properties of graphene and metal‐organic frameworks (MOFs), such as high porosity, ultralow density, and facilely tailored superwettability. In this study, novel wrinkled 3D microspherical MOF@rGO composites with both superhydrophobic and superoleophilic properties were developed by embedding MOF nanoparticles between graphene oxide (GO) nanosheets, followed by high‐temperature reduction self‐assembly. The microspherical composites feature a unique micro/nano hierarchy consisting of crumpled reduced GO (rGO) nanosheets intercalated with well‐dispersed MOF nanoparticles. Combined with the superwettability and abundant meso/microporosity, the peculiar architectures of wrinkled ZIF‐8@rGO microspheres show very fast absorption rates and high sorption selectivity for organic solvents and oils from water.     

仿生矿化增强材料

近年来,随着材料科学领域的发展,机械性能优异且具有特定功能的有机-无机复合材料成为了研究热点。而天然的生物矿化过程产生了在自然界中分布广泛、结构特征多样性、机械性能优异的天然生物矿物,比如牙齿、骨骼、珍珠、贝壳、海胆刺、海洋红虫颚等。这些天然复合增强材料中的矿化组织结构特点和矿化机理为仿生设计与合成具有特定结构、特定功能和优异机械性能的材料提供了理论依据。通过模拟天然过程的仿生矿化方法,利用有机基质调控无机矿物成核生长为固态矿物,最终能够定向组装具有特定有序结构和先进功能的有机-无机复合材料。本文主要综述了自然界中通过生物矿化过程得到的高强度、高韧性的天然复合增强材料,以及受生物矿化增强现象的启发,在化学与材料仿生矿化合成中出现的一些有机-无机复合的增强材料。     

Hierarchical Proteinosomes for Programmed Release of Multiple Components

A facile route to hierarchically organized multicompartmentalized proteinosomes based on a recursive Pickering emulsion procedure using amphiphilic protein–polymer nanoconjugate building blocks is described. The number of incarcerated guest proteinosomes within a single host proteinosome is controlled, and enzymes and genetic polymers encapsulated within targeted subcompartments to produce chemically organized multi‐tiered structures. Three types of spatiotemporal response—retarded concomitant release, synchronous release or hierarchical release of dextran and DNA—are demonstrated based on the sequential response of the host and guest membranes to attack by protease, or through variations in the positioning of disulfide‐containing cross‐links in either the host or guest proteinosomes integrated into the nested architectures. Overall, our studies provide a step towards the construction of hierarchically structured synthetic protocells with chemically and spatially integrated proto‐organelles.     

Hierarchical CaCO3 Chromatography: A Stationary Phase Based on Biominerals

In biomineralization, acidic macromolecules play important roles for the growth control of crystals through a specific interaction. Inspired by this interaction, we report on an application of the hierarchical structures in CaCO₃ biominerals to a stationary phase of chromatography. The separation and purification of acidic small organic molecules are achieved by thin‐layer chromatography and flash chromatography using the powder of biominerals as the stationary phase. The unit nanocrystals and their oriented assembly, the hierarchical structure, are suitable for the adsorption site of the target organic molecules and the flow path of the elution solvents, respectively. The separation mode is ascribed to the specific adsorption of the acidic molecules on the crystal face and the coordination of the functional groups to the calcium ions. The results imply that a new family of stationary phase of chromatography can be developed by the fine tuning of hierarchical structures in CaCO₃ materials.     

Nanostructure synthesis using surfactants and copolymers

Self-assembled structures of surfactants and block copolymers provide a valuable tool for controlling nanostructure formation in polymers and inorganic solids. The past year has seen a huge number of different new nanoparticles and mesostructured solids. A high level of control of the mesoscopic and macroscopic morphologies has been reached for both polymer nanostructures and mesoporous inorganic materials. © 1999 Elsevier Science Ltd.     

Multiple levels hydrophobic modification of polymeric substrates by UV‐grafting polymerization with TFEMA as monomer

The hydrophobic solid surface modification with fluorine‐containing monomers has received tremendous attention because of its unique structure and excellent property. However, these hydrophobic films normally suffer from two major problems: one is weak interface interaction between fluoropolymers and substrates, and the other is the high cost of fluorine‐containing monomers. Herein, with the aim of feasible industrial application, a facile in situ UV photo‐grafting method is reported, which could ensure the formation of chemical bonds between fluoropolymer‐grafted layer and substrate with a low cost commercial 2,2,2‐trifluoroethyl methacrylate (TFEMA) as monomer. With low‐density polyethylene (LDPE) film as a model substrate, four kinds of poly‐TFEMA‐grafted layer are fabricated on LDPE films with different surface morphologies: polymer brush, polymer network, crosslinked nanoparticles, and a micro‐ and nanoscale hierarchical structure. The experimental results showed that the water contact angles (CAs) of the LDPE films grafted with polymer brush, polymer network, and crosslinked nanoparticles were (103 ± 2)°, (95 ± 2)°, and (122 ± 2)°, respectively, which were much higher than that of LDPE film. The introduction of micro‐ and nanoscale hierarchical structures can dramatically improve the surface roughness, which will further enhance the film hydrophobicity, and the water CA can reach as high as (140 ± 1)°. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1059–1067     

Directed Nanoparticle Assembly through Polymer Crystallization

Nanoparticles can be assembled into complex structures and architectures by using a variety of methods. In this review, we discuss recent progress of using polymer crystallization (particularly polymer single crystals, PSCs) to direct nanoparticle assembly. PSCs have been extensively studied since 1957. Mainly appearing as quasi-two-dimensional (2D) lamellae, PSCs are typically used as model systems to determine polymer crystalline structures, or as markers to investigate the crystallization process. Recent research has demonstrated that they can also be used as nanoscale functional materials. Herein, we show that nanoparticles can be directed to assemble into complex shapes by using in situ or ex situ polymer crystal growth. End-functionalized polymers can crystallize into 2D nanosheet PSCs, which are used to conjugate with complementary nanoparticles, leading to a nanosandwich structure. These nanosandwiches can find interesting applications for catalysis, surface-enhanced Raman spectroscopy, and nanomotors. Dissolution of the nanosandwich leads to the formation of Janus nanoparticles, providing a unique method for asymmetric nanoparticle synthesis.     

Multifunctional polyacrylonitrile‐ZnO/Ag electrospun nanofiber membranes with various ZnO morphologies for photocatalytic,UV‐shielding,and antibacterial applications

New multifunctional polyacrylonitrile (PAN)‐ZnO/Ag composite electrospun nanofiber membranes consisting of pineal‐type, flower‐type, and sea‐urchin‐type ZnO morphologies were prepared using a single‐capillary electrospinning technique, hydrothermal ZnO synthesis, and Ag reduction. The various ZnO architectures exhibited differences in photocatalytic activity and UV‐shielding efficiency, and were ranked as follows: sea‐urchin type > flower type > pineal type. Sea‐urchin‐type ZnO features a higher surface‐to‐volume ratio than other ZnO architectures do because of its distinctive structure, thus yielding higher performance. The present study demonstrated that self‐standing PAN‐ZnO/Ag composite fiber membranes, especially those with the sea‐urchin‐type ZnO structure, can be applied in multifunctional textiles such as water purification filters and antibacterial and UV‐shielding clothes. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 262–269     

Modulating the stacking modes of nanosized metal–organic frameworks by morphology engineering for isomer separation

Modulating different stacking modes of nanoscale metal–organic frameworks (MOFs) introduces different properties and functionalities but remains a great challenge. Here, we describe a morphology engineering method to modulate the stacking modes of nanoscale NU-901. The nanoscale NU-901 is stacked through solvent removal after one-pot solvothermal synthesis, in which different morphologies from nanosheets (NS) to interpenetrated nanosheets (I-NS) and nanoparticles (NP) were obtained successfully. The stacked NU-901-NS, NU-901-I-NS, and NU-901-NP exhibited relatively aligned stacking, random stacking, and close packing, respectively. The three stacked nanoscale NU-901 exhibited different separation abilities and all showed better performance than bulk phase NU-901. Our work provides a new morphology engineering route for the modulation of the stacking modes of nano-sized MOFs and improves the separation abilities of MOFs.

A morphology engineering method was utilized to modulate the stacking modes of three nano-NU-901 materials, leading to different separation abilities for isomers.     

Controlled synthesis, growth mechanism and highly efficient solar photocatalysis of nitrogen-doped bismuth subcarbonate hierarchical nanosheets architectures

The synthesis and self-assembly of hierarchical architectures from nanoscale building blocks with unique morphology, orientation and dimension have opened up new opportunities to enhance their functional performances and remain a great challenge. This work represents tunable synthesis of various types of 3D monodisperse in situ N-doped (BiO)(2)CO(3) hierarchical architectures composed of 2D single-crystal nanosheets with dominant (001) facets by a one-pot template-free hydrothermal method from bismuth citrate and ammonia solution. Depending on the concentration of ammonia solution, the morphology of N-doped (BiO)(2)CO(3), including dandelion-like, hydrangea-like and peony flower-like microspheres, can be selectively constructed due to different self-assembly patterns of nanosheets. It was revealed that the ammonia played dual roles in the formation of N-doped (BiO)(2)CO(3) architectures. One is to hydrolyze bismuth citrate, and the other is to behave as a nitrogen doping source. The in situ doped nitrogen substituted for oxygen in (BiO)(2)CO(3) and subsequently narrowed the band gap, making N-doped (BiO)(2)CO(3) visible light active. Due to the special nanosheets architectures, the prepared various N-doped (BiO)(2)CO(3) materials exhibited especially efficient photocatalytic activity and high durability for the removal of NO in air under both visible and UV light irradiation. Based on the direct observation of the growth process with respect to phase structure, chemical composition and morphological structure, a novel growth mechanism is revealed, which involves a unique multistep pathway, including reaction-nucleation, aggregation, crystallization, dissolution-recrystallization, and Ostwald ripening. The facile synthesis approach and the proposed growth mechanism could provide new insights into the design and controlled synthesis of inorganic hierarchical materials with new or enhanced properties.     

Nanocomposites and macroscopic materials: assembly of chemically modified graphene sheets

Self-assembly of chemically modified graphenes (CMGs), including graphene oxide (GO), reduced graphene oxide (RGO) and their derivatives, has emerged as one of the most appealing strategies to develop unprecedented graphene-based functional materials. With the assistance of various non-covalent forces such as hydrogen bonding, ionic, amphiphilic and π-π interactions, CMGs decorated with multiple functional groups are favorable for assembly with different organic and inorganic components which can result in hierarchical composites possessing unique structures and functions. In this review, we will summarize the state-of-the-art self-assembly strategies that have been established to construct CMG based nanomaterials, including nanoparticles, nanospheres, nanofibers, nanorods, nanosheets, and macroscopic thin films, fibers and porous networks. The driving forces involved in the self-assembly process will be elucidated in the context. Further, we will also highlight several representative examples of applications regarding the self-assembled CMG based materials.     

Hierarchically Structured Porous Films of Silica Hollow Spheres via Layer‐by‐Layer Assembly and Their Superhydrophilic and Antifogging Properties

Raspberrylike organic/inorganic composite spheres are prepared by stepwise electrostatic assembly of polyelectrolytes and silica nanoparticles onto monodisperse polystyrene spheres. Hierarchically structured porous films of silica hollow spheres are fabricated from these composite spheres by layer‐by‐layer assembly with polyelectrolytes followed by calcination. The morphologies of the raspberrylike organic/inorganic composite spheres and the derived hierarchically structured porous films are observed by scanning and transmission electron microscopy. The surface properties of these films are investigated by measuring their water contact angles, water‐spreading speed, and antifogging properties. The results show that such hierarchically structured porous films of silica hollow spheres have unique superhydrophilic and antifogging properties. Finally, the formation mechanism of these nanostructures and property–structure relationships are discussed in detail on the basis of experimental observations.     

Intermolecular interaction-induced hierarchical transformation in 1D nanohybrids: analysis of conformational changes by 2D correlation spectroscopy

We have examined both self-assembly and confinement effect in room-temperature ionic liquid (RTIL)-aluminum hydroxide hybrids (RAHs) to attain a fundamental understanding of special phenomena in nanoscale spaces as well as to design functional nanomaterials for practical applications. Phase-controlled one-dimensional (1D) RAHs were synthesized through a simple ionothermal process. The RAHs were hierarchically transformed in terms of the molecular structures, morphologies, and phases of the materials during the ionothermal process with respect to the concentration of RTIL. In addition to the hierarchical transformation, the RTIL/aluminum hydroxide nanohybrids revealed unexpected physical behaviors, including thermal transition variation of the RTIL in confined environments and a phase transition from nanosolid to nanoliquid affected by changes of the melting points. More importantly, intermolecular interaction induced-self-assembly and confinement effect of RTILs inside an integrated hybrid system, which have not been clearly explained to date, were analyzed by 2D infrared correlation spectroscopy (2D IR COS); dynamic behaviors of RTILs, i.e., sequentially spatial reorientation and kinetically conformational changes, were attributed to the interactions between RTILs and aluminum hydroxides. 2D IR COS offers a new way to interpret highly complex, veiled systems such as the formation mechanism of nanoparticles, biomineralization, self/supramolecular assembly, and nanoconfinement.     

Nanocomposite polymer hydrogels

The technological need for new and better soft materials as well as the drive for new knowledge and fundamental understanding has led to significant advances in the field of nanocomposite gels. A variety of complex gel structures with unique chemical, physical, and biological properties have been engineered or discovered at the nanoscale. The possibility to form self-assembled and supramolecular morphologies makes organic polymers and inorganic nanoparticles desirable building blocks for the design of water based gels. In this review, we highlight the most recent (2004–2008) accomplishments and trends in the field of nanocomposite polymer hydrogels with a focus on creative approaches to generating structures, properties, and function within mostly biotechnological applications. We examine the impact of published work and conclude with an outline on future directions and challenges that come with the design and engineering of new nanocomposite gels.     

Application of complex macromolecular architectures for advanced microelectronic materials

The distinctive features of well-defined, three-dimensional macromolecules with topologies designed to enhance solubility and amplify end-group functionality facilitated nanophase morphologies in mixtures with organosilicates and ultimately nanoporous organosilicate networks. Novel macromolecular architectures including dendritic and star-shaped polymers and organic nanoparticles were prepared by a modular approach from several libraries of building blocks including various generations of dendritic initiators and dendrons, selectively placed to amplify functionality and/or arm number, coupled with living polymerization techniques. Mixtures of an organosilicate and the macromolecular template were deposited, cured, and the phase separation of the organic component, organized the vitrifying organosilicate into nanostructures. Removal of the sacrificial macromolecular template, also denoted as porogen, by thermolysis, yielded the desired nanoporous organosilicate, and the size scale of phase separation was strongly dependent on the chain topology. These materials were designed for use as interlayer, ultra-low dielectric insulators for on-chip applications with dielectric constant values as low as 1.5. The porogen design, chemistry and role of polymer architecture on hybrid and pore morphology will be emphasized.     

Macroscopic Free‐Standing Hierarchical 3D Architectures Assembled from Silver Nanowires by Ice Templating

As macroscopic three dimensional (3D) architectures show increasing significance, much effort has been devoted to the hierarchical organization of 1D nanomaterials into serviceable macroscopic 3D assemblies. How to assemble 1D nanoscale building blocks into 3D hierarchical architectures is still a challenge. Herein we report a general strategy based on the use of ice as a template for assembling 1D nanostructures with high efficiency and good controllability. Free‐standing macroscopic 3D Ag nanowire (AgNW) assemblies with hierarchical binary‐network architectures are then fabricated from a 1D AgNW suspension for the first time. The microstructure of this 3D AgNW network endows it with electrical conductivity and allows it to be made into stretchable and foldable conductors with high electromechanical stability. These properties should make this kind of macroscopic 3D AgNW architecture and it composites suitable for electronic applications.