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1.
各向异性水凝胶在外界的响应刺激下可以具有不同的反应机制与驱动过程.本文综述了近期基于PNIPAM水凝胶智能响应驱动器的设计方法,总结了多种各向异性结构对驱动性能的影响,并对该领域所面临的挑战进行了讨论. 相似文献
2.
Koki Sano Dr. Yasuhiro Ishida Prof. Dr. Takuzo Aida 《Angewandte Chemie (International ed. in English)》2018,57(10):2532-2543
Owing to their water‐rich structures, which are similar to those of biological tissues, hydrogels have long been regarded as promising scaffolds for artificial tissues and organs. However, in terms of the structural anisotropy, most synthetic hydrogels are substantially different from biological systems. Synthetic hydrogels are usually composed of randomly oriented three‐dimensional polymer networks whereas biological systems adopt anisotropic structures with hierarchically integrated building units. Such anisotropic structures often play essential roles in biological systems to exhibit particular functions. In this context, anisotropic hydrogels provide an entry point for exploring biomimetic applications of hydrogels. Reflecting these aspects, an increasing number of studies on anisotropic hydrogels have been reported recently. This Minireview highlights the use and perspectives of these anisotropic hydrogels, particularly focusing on their preparation, structures, and applications. 相似文献
3.
Jia-Ni Jin Dr. Xi-Ran Yang Yan-Fang Wang Dr. Lei-Min Zhao Dr. Liu-Pan Yang Dr. Liping Huang Prof. Wei Jiang 《Angewandte Chemie (International ed. in English)》2023,62(8):e202218313
Many strategies have been developed for constructing anisotropic hydrogels, however, it remains a challenge to fabricate hydrogels with anisotropic nanocrystalline domains from intrinsically soft networks. Here, we report a naphthotube-based polyrotaxane-containing hydrogel that can be reinforced via mechanical training. During the training process, the hydrogel can adopt reorientation of polymer chains to form anisotropic structures driven by external uniaxial force. Due to the multiple hydrogen bonding sites and movable feature of naphthotube, the sliding of naphthotube on PEG chains simultaneously inducing the zipping of adjacent polymer chains to form densely anisotropic nanocrystalline domains through hydrogen bonded networks. Thus, the trained hydrogel exhibits an enhanced tension stress of ≈110 kPa, which realize a remarkable enhancement of ≈10 times compare to initial state. This study provides a new tactic for improving the mechanical performance of soft materials. 相似文献
4.
In the liquid crystalline (I.c.) state the backbone of l.c-polymers has to adapt an anisotropic conformation that is consistent with the I.c.-phase structure. For macroscopically uniformly aligned samples this anisotropic backbone conformation can be obtained by applying a suitable mechanical field on chemically crosslinked I.c-polymers. Introducing the network anisotropy a priori by synthesis, stable macroscopically aligned I.c.-networks can be realized. We have called these networks Liquid Single Crystal Elastomers (LSCE) because their physical properties resemble that of organic or inorganic single crystals. 相似文献
5.
Lian Chen Xianshuo Wei Feng Wang Shaoju Jian Weisen Yang Chunxin Ma Gaigai Duan Shaohua Jiang 《中国化学快报》2022,33(5):2635-2638
Stimuli-responsive hydrogels hold an irreplaceable statue in intelligent actuation materials because of their reversible stretchability and excellent biocompatibility. However, the poor mechanical performance and complicated fabrication process of anisotropic structures severely limit their further applications.Herein, we report a high-strength thermoresponsive wood-PNIPAM composite hydrogel actuator with complex deformations, through a simple in-situ polymerization. In this composite hydrogel a... 相似文献
6.
Yong Yang A. Kloczkowski J. E. Mark B. Erman I. Bahar 《Colloid and polymer science》1994,272(3):284-292
It has been predicted that unusually good mechanical properties can be obtained by drying swollen networks of semi-rigid chains while they are in the deformed state, as described in several theoretical investigations [Macromolecules,23: 5335, 5341 (1990),24: 901 (1991)]. The present investigation involves the preparation of networks of this type from cellulose acetate (CA) and hydroxypropylcellulose (HPC), in order to test these concepts. The cross-linking required to maintain anisotropy during the drying process was obtained using formaldehyde, while the polymers were in either the anisotropic or isotropic state. Control of the cross-linking was obtained by studying the effects of the concentration of formaldehyde, temperature, and reaction time.The liquid-crystalline phase separations in CA and HPC, and in their networks, were studied with cross-polarized optical microscopy. CA and HPC showed anisotropic phases in trifluoroethanol and in methanol, respectively, and under shear the HPC systems exhibited the band textures associated with macroscopic orientation. In the case of the uncross-linked polymers, this band texture disappeared shortly after shearing was discontinued. The networks prepared by cross-linking the HPC in either liquid-crystalline solutions or in isotropic solutions also showed band textures, but these textures now persisted long after removal of the shearing stress. As shown in the following paper, the extensibility required in the proposed processing technique was highest for the networks prepared in the isotropic state, suggesting that these materials should have the greatest potential for dramatic improvements in mechanical properties. 相似文献
7.
《Liquid crystals》1998,24(1):71-82
Anisotropic networks, elastomers and gels exhibit piezoelectric, pyroelectric, ferroelectric and NLO properties of potential interest for use communication and processing technologies. The formation, properties and applications of such anisotropic, mainly liquid crystalline, networks are described. If some of the molecules in a liquid mixture contain at least two reactive groups which can be either photochemically or thermally polymerized, then crosslinked, anisotropic networks, elastomers and gels can be produced. Solid macroscopically aligned elastomers or networks can be formed as required beforehand or simultaneously by orientation of the sample. Anisotropic gels consist of a solid anisotropic network and non-covalently bonded, but strongly oriented domains of low molar mass liquid crystals. Anisotropic networks, elastomers preformed amorphous or liquid crystalline polymers incorporating additional reactive groups, which can be macroscopically oriented in the additional crosslinking reactions. Reversible networks, elastomers and gels can be prepared either non-covalently or covalently by thermally side group polymers and low molar mass molecules, liquid crystalline properties in the pure state. in many electro-optic devices for optical and gels can be prepared from liquid crystalline state and then fixed by reversible linkages between, for example, neither of which necessarily exhibit 相似文献
8.
Ultrasonic testing as a non-destructive evaluation (NDE) technique is newly introduced to characterize additively manufactured composite materials to identify their anisotropic mechanical properties, being especially facile, useful and accurate approach for dimensional dependent measurement. In this study, the immersion ultrasonic technique is employed to measure the energy loss of ultrasonic elastic waves, and wave propagation speed in the laser-sintered nanocomposite of carbon nanotube reinforced polyamine 12. The relationship of process-structure-property is revealed to establish the correlations between process parameters and energy loss of ultrasound, as well as mechanical moduli. The orientation-dependent wave attenuation and mechanical moduli of nanocomposites along three orthogonal directions are strongly associated with the layer-by-layer fusion induced microstructures and internal imperfections. This technique is capable of quantifying orientation-dependent mechanical properties such as moduli and attenuation without compromising additively manufactured parts, showing a high potential of quality control and safety inspection in end-use applications. 相似文献
9.
Bilayer Networks within a Hydrogel Shell: A Robust Chassis for Artificial Cells and a Platform for Membrane Studies
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Divesh K. Baxani Dr. Alex J. L. Morgan Dr. William D. Jamieson Dr. Christopher J. Allender Prof. Dr. David A. Barrow Dr. Oliver K. Castell 《Angewandte Chemie (International ed. in English)》2016,55(46):14240-14245
The ability to make artificial lipid bilayers compatible with a wide range of environments, and with sufficient structural rigidity for manual handling, would open up a wealth of opportunities for their more routine use in real‐world applications. Although droplet interface bilayers (DIBs) have been demonstrated in a host of laboratory applications, from chemical logic to biosynthesis reaction vessels, their wider use is hampered by a lack of mechanical stability and the largely manual methods employed in their production. Multiphase microfluidics has enabled us to construct hierarchical triple emulsions with a semipermeable shell, in order to form robust, bilayer‐bound, droplet networks capable of communication with their external surroundings. These constructs are stable in air, water, and oil environments and overcome a critical obstacle of achieving structural rigidity without compromising environmental interaction. This paves the way for practical application of artificial membranes or droplet networks in diverse areas such as medical applications, drug testing, biophysical studies and their use as synthetic cells. 相似文献
10.
Supitchaya Iamsaard Emmanuel Anger Sarah Jane Aßhoff Alexis Depauw Stephen P. Fletcher Nathalie Katsonis 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(34):10062-10066
Liquid crystal polymer networks respond with an anisotropic deformation to a range of external stimuli. When doped with molecular photoswitches, these materials undergo complex shape modifications under illumination. As the deformations are reversed when irradiation stops, applications where the activated shape is required to have thermal stability have been precluded. Previous attempts to incorporate molecular switches into thermally stable photoisomers were unsuccessful at photogenerating macroscopic shapes that are retained over time. Herein, we show that to preserve photoactivated molecular deformation on the macroscopic scale, it is important not only to engineer the thermal stability of the photoswitch but also to adjust the cross‐linking density in the polymer network and to optimize the molecular orientations in the material. Our strategy resulted in materials containing fluorinated azobenzenes that retain their photochemical shape for more than eight days, which constitutes the first demonstration of long‐lived photomechanical deformation in liquid‐crystal polymer networks. 相似文献
11.
Toshiyuki Sasaki Shunichi Sakamoto Yuichi Takasaki Satoshi Takamizawa 《Angewandte Chemie (International ed. in English)》2020,59(11):4340-4343
Mechanical twinning changes atomic, molecular, and crystal orientations along with directions of the anisotropic properties of the crystalline materials while maintaining single crystallinity in each domain. However, such deformability has been less studied in brittle organic crystals despite their remarkable anisotropic functions. Herein we demonstrate a direction‐dependent mechanical twinning that shows superelasticity in one direction and ferroelasticity in two other directions in a single crystal of 1,3‐bis(4‐methoxyphenyl)urea. The crystal can undergo stepwise twinning and ferroelastically forms various shapes with multiple domains oriented in different directions, thereby affording a crystal that shows superelasticity in multiple directions. This adaptability and shape recoverability in a ferroelastic and superelastic single crystal under ambient conditions are of great importance in future applications of organic crystals as mechanical materials, such as in soft robotics. 相似文献
12.
Pere Castell Angels Serra Marina Gali Marta Giamberini Cossimo Carfagna 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):1-12
Novel epoxy‐terminated monomers based on imine groups were synthesized and their mesogenic properties studied. Aliphatic spacers of different lengths were introduced between the rigid unit and the glycidylic group, and their liquid‐crystalline behavior was examined. They were reacted with primary aromatic diamines inside a magnetic field so that the formation of anisotropic networks could be investigated. The influence of curing conditions and the structure of monomers and amines on the formation of liquid‐crystal thermosets were investigated. Thermosets with locked nematic textures were obtained in all cases. The influence of a 7.1 T magnetic field on the macroscopic orientation of these materials was studied, and mechanical properties of the resulting networks were evaluated by dynamic mechanical analysis. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1–12, 2003 相似文献
13.
Anandkumar R. Kannurpatti Karin J. Anderson Jay W. Anseth Christopher N. Bowman 《Journal of Polymer Science.Polymer Physics》1997,35(14):2297-2307
Crosslinked polymer networks are used in a wide variety of applications. To use these materials effectively, a fundamental understanding of their structural evolution and the relationship between material properties and structure is essential. In this article, a novel technique employing “iniferters,” i.e., living radical polymerizations, to photopolymerize these networks is utilized to study the property and structural evolution of these highly desirable materials. Living radical polymerizations are used in this work since this technique avoids the problem of carbon radical trapping encountered while using conventional initiators. Dynamic mechanical measurements are performed on highly crosslinked methacrylate networks to glean information regarding their structural heterogeneity. By performing these measurements on homopolymerized samples at various stages of the reaction and on copolymerized samples of multifunctional methacrylates, the mechanical properties are characterized as a function of double bond conversion and comonomer composition. From such analyses, with respect to both temperature and frequency, quantitative conclusions regarding the structure of the networks are drawn. This effort is aimed at exploiting the living radical polymerizations initiated by p-xylylene bis(N,N-diethyl dithiocarbamate) (XDT), to study the mechanical property evolution and structural heterogeneity of crosslinked polymers which is nearly impossible otherwise. Polymers examined in this study include networks formed by homopolymerization of diethylene glycol dimethacrylate (DEGDMA) and polyethylene glycol 600 dimethacrylate (PEG600DMA) as well as copolymers of DEGDMA and PEG600DMA. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2297–2307, 1997 相似文献
14.
Eun Seon Kim Da Bin Song Kyoung Hwan Choi Jae Heung Lee Dong Hack Suh Woo Jin Choi 《Journal of polymer science. Part A, Polymer chemistry》2020,58(23):3358-3369
Pressure-sensitive adhesives (PSAs) demand the ability to simultaneously improve toughness and adhesion. However, these requirements of PSAs have remained a great challenge because robust and recoverable characteristics are usually contradictory properties of PSAs. Dual cross-linking networks developed by incorporating dynamic noncovalent bonds into chemical cross-linking networks have the potential to mitigate these requirements in a wide variety of applications including adhesives, hydrogels, and elastomers. Herein, a facile approach to achieve dual cross-linking networks of acrylic PSAs with excellent mechanical properties and high-adhesive performance that integrate physically cross-linked networks into chemically cross-linked networks is proposed. Diurethane acrylic monomer-pentaerythritol ethoxylate (DAM-PEEL) groups were introduced into the acrylic PSA system through photopolymerization. The PSA/DAM-PEEL dual cross-linking networks led to the development of the chemically cross-linked networks for both PSA and DAM via covalent bonds and the physically cross-linked networks between the amide groups of DAM and the hydroxyl groups of PEEL via hydrogen bonds. Consequently, the PSA/DAM-PEEL dual cross-linking networks were able to simultaneously improve the modulus and stretchability. This design strategy for developing dual cross-linking networks of materials could offer potential applications for various adhesive-related applications. 相似文献
15.
16.
Hang Liu Michaela Zagler Prof. Dr. Michael Nase Prof. Dr. Katharina Weber Prof. Dr. Joachim Albrecht 《Chemphyschem》2023,24(20):e202300671
The surface topography of biodegradable polymer foils is modified by mechanical imprinting on a submillimeter length scale. The created patterns strongly influence the wetting behavior and allow the preparation of hydrophobic surfaces with controlled solid-liquid interaction. A detailed analysis of anisotropic surface patterns reveals that the observed effect arises from a combination of topographical and compositional changes that are introduced to the surface. As a main result it is found that an individual combination of material and structure is required for the production of water-repellent biopolymer foils that are highly attractive for packaging applications. 相似文献
17.
Complex mechanical changes in response to an external trigger are pervasive in natural soft materials and often sought for applications. Be it the reversible stiffening of sea cucumber, the failure of a polymeric or colloidal gel under load, or the dissolution of a biosensing hydrogel upon target binding, mechanical transitions are typically enabled, and critically affected, by heterogeneous structures and reversible bonds. New possibilities to monitor evolving properties and to gain access to stress propagation with temporal and spatial resolution are being disclosed by mechanochromic molecules and molecular complexes, which transduce a mechanical stress into a light signal and act as built-in stress reporters. I will review recent strategies and identify future directions for the design of mechanically responsive soft networks and for their optical mapping, focusing particular attention on the emerging class of hydrogels based on DNA self-assembly. 相似文献
18.
Heidi Jahandideh Jun-Ray Macairan Aram Bahmani Mathieu Lapointe Nathalie Tufenkji 《Chemical science》2022,13(31):8924
The anisotropic nature of ‘graphenic’ nanosheets enables them to form stable three-dimensional porous materials. The use of these porous structures has been explored in several applications including electronics and batteries, environmental remediation, energy storage, sensors, catalysis, tissue engineering, and many more. As method of fabrication greatly influences the final pore architecture, and chemical and mechanical characteristics and performance of these porous materials, it is essential to identify and address the correlation between property and function. In this review, we report detailed analyses of the different methods of fabricating porous graphene-based structures – with a focus on graphene oxide as the base material – and relate these with the resultant morphologies, mechanical responses, and common applications of use. We discuss the feasibility of the synthesis approaches and relate the GO concentrations used in each methodology against their corresponding pore sizes to identify the areas not explored to date.Due to their anisotropic nature, graphene nanosheets can be used to form 3-dimensional porous materials using template-free and template-directed methodologies. These fabrication strategies are found to influence the properties of the final structure. 相似文献
19.
Versatile Ferroelastic Deformability in an Organic Single Crystal by Twinning about a Molecular Zone Axis
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Dr. Emile R. Engel Prof. Dr. Satoshi Takamizawa 《Angewandte Chemie (International ed. in English)》2018,57(37):11888-11892
Ferroelasticity involves the generation of spontaneous strain in a solid by the application of mechanical stress. The phenomenon has been well‐studied in metal alloys but relatively neglected in organic solid‐state chemistry. Herein we present multiple discrete modes of mechanical twinning and a mechanistic analysis of ferroelasticity in 1,4‐diethoxybenzene. Single crystals of the compound can be almost freely deformed, as multiple different twin domains are generated simultaneously. Within each domain, single‐crystal character is preserved. Such extremely versatile, ferroelastic deformability is unprecedented in single crystals of any kind and defies the fragility and anisotropic mechanical behaviour of most organic crystals. The dissipated energy and critical stress associated with twinning deformation in 1,4‐diethoxybenzene suggests that organic solids could be developed for absorbing weak mechanical shocks in such applications as mechanical damping and soft robotics. 相似文献
20.
Ji Won Hwang Kyung Nam Kim Joon Hyun Nam Hyun Wook Jung Jung Kwon Oh 《Journal of polymer science. Part A, Polymer chemistry》2014,52(21):3060-3068
Photo‐induced thiol‐ene crosslinked polymeric networks have been extensively explored in constructing a variety of new materials with enhanced mechanical properties for optical, biomedical, and sensing applications. Toward the broad applications, however, tunable mechanical properties are greatly desired. Here, an effective approach utilizing high‐molecular‐weight methacrylate copolymers having pendant thiol and vinyl groups (MCPsh and MCPenes) to modulate thermal and mechanical properties of photo‐induced thiol‐ene crosslinked materials is reported. The MCP copolymers are synthesized by an industrially friendly polymerization method, followed by post‐modification including either a facile coupling reaction or reductive cleavage. Upon UV irradiation, thiol‐ene reactive blends of MCPsh and MCPenes yield highly crosslinked materials through the formation of flexible sulfide linkages. These polysulfide‐crosslinked materials based on rigid MCP backbones exhibit enhanced mechanical properties. Further, their thermal and mechanical properties are tuned by modulating monomer compositions of MCPs as well as varying numbers of pendant SH or vinyl groups (i.e., extent of crosslinking densities). This approach is versatile and effective for development of high performance polymeric materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3060–3068 相似文献