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光致形状记忆高分子材料是一类在室温、一定波长的光照条件下发生形变后,再次成型得到二次形状,通过另一波长光刺激手段的处理,又可使其发生形状回复,从而"记忆"初始形状的新型功能高分子材料。该类材料具有非接触性、瞬时性、精确性和清洁性等特点。这些独特的优点使得该类材料越来越受到研究者的关注。本文主要集中对近年来光诱导的形状记忆和形状改变高分子材料的研究现状进行简要的论述,重点是光化学反应型材料,如含肉桂酸基和偶氮苯基系列材料,分别介绍了这些材料的分类、特性、工作原理及潜在的应用。最后对光致型形状记忆高分子材料的存在问题、发展方向和应用前景进行了展望。 相似文献
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形状记忆聚合物是一种典型的智能材料,具有质轻、形变量大、可对多种刺激进行响应等优点.根据形状记忆过程的可逆性进行分类,形状记忆效应可以分为2种:单向与双向形状记忆效应.与不可逆的单向形状记忆过程相比,双向形状记忆过程是可逆的,样品不需要使用者进行再次变形,就可以在原始形状与临时形状之间进行可逆转换,因此其具有极高的实用价值与广阔的应用前景,受到各国研究人员的广泛关注,成为当前的研究热点之一.本文总结了近年来所研究的双向形状记忆结晶聚合物及其复合材料,包括恒外力条件下(外力≠0)的准双向形状记忆结晶聚合物,无外力条件下的双向形状记忆结晶聚合物及其复合材料.具体来说,前者包括在恒外力作用下的化学或物理交联的结晶聚合物.后者包括双层或核-壳聚合物复合材料、由分步交联得到的双网络交联结晶聚合物、化学交联的双组分结晶聚合物、具有较宽熔融转变的化学交联结晶聚合物与物理交联的结晶聚合物.重点关注了这些材料的制备方法、影响因素及相应的双向形状记忆机理,并对其研究前景进行了展望. 相似文献
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聚合物形状记忆材料作为一种重要的刺激响应材料,近10年内得到了快速的发展,出现了新的分类方向,机理解释、转变结构和应用。在航空航天、传感制动和生物医药等领域展现了优越的性能,研究成果受到了学术和工业上的极大重视,成为当今最富有活力的研究领域之一。本文全面总结了近期国内外学者对聚合物形状记忆材料的研究进展,阐述了聚合物形状记忆材料的记忆机理及分类和功能应用,并探讨了未来的研究前景和方向,以期为聚合物形状记忆材料的研究提供参考。 相似文献
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利用聚偏氟乙烯(PVDF)微小结晶的物理交联点作用,制备了形状记忆性能优异的聚偏氟乙烯/丙烯酸酯聚合物(PVDF/ACM)共混材料。为提高其形状回复应力,又将碳纳米管(CNT)引入该共混体系中,系统研究了PVDF/ACM/CNT三元体系纳米复合材料的制备、结构及性能。结果表明,碳纳米管在PVDF/ACM体系中分散均匀;在基本保持其形状记忆性能的前提下,加入质量分数为4%的CNT,材料在25℃时的储能模量由2000 MPa提高至3130 MPa。 相似文献
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对苯乙烯基形状记忆聚合物进行了拉伸实验研究,测定了该材料在25℃、30℃、40℃和50℃时的弹性模量和屈服极限.根据实验结果,建立了苯乙烯基形状记忆聚合物的材料参数方程,描述了苯乙烯基形状记忆聚合物在玻璃体转化过程中,材料参数和温度的关系.在假设形状记忆聚合物为各向同性材料的基础上,将Tobushi等建立的热力学本构方程从一维扩展到三维.基于有限元分析软件ABAQUS的二次开发功能,针对上述本构方程和材料参数方程,编写了可供ABAQUS调用的UMAT函数,并对苯乙烯基形状记忆聚合物实现形状记忆效应的高温变形、应力冻结和形状恢复等热力学过程,进行了有限元数值模拟分析. 相似文献
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Dr. Qi‐jian Zhang Prof. Jing‐hui He Hao Zhuang Prof. Hua Li Prof. Na‐jun Li Prof. Qing‐feng Xu Dr. Dong‐yun Chen Prof. Jian‐mei Lu 《化学:亚洲杂志》2016,11(10):1624-1630
Flexible memory devices have continued to attract more attention due to the increasing requirement for miniaturization, flexibility, and portability for further electronic applications. However, all reported flexible memory devices have binary memory characteristics, which cannot meet the demand of ever‐growing information explosion. Organic resistive switching random access memory (RRAM) has plenty of advantages such as simple structure, facile processing, low power consumption, high packaging density, as well as the ability to store multiple states per bit (multilevel). In this study, we report a small molecule‐based flexible ternary memory device for the first time. The flexible device maintains its ternary memory behavior under different bending conditions and within 500 bending cycles. The length of the alkyl chains in the molecular backbone play a significant role in molecular stacking, thus guaranteeing satisfactory memory and mechanical properties. 相似文献
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A. Amengual A. Isalgue F. Marco H. Tachoire V. Torra V. R. Torra 《Journal of Thermal Analysis and Calorimetry》1992,38(4):583-592
We describe an experimental set-up of high resolution thermal analysis (HRTA) activated by Peltier effect and computer-controlled by the signal processing that allows a high resolution programming of the temperature and a reproducibility better than ±0.01 deg.The basic equipment is suitable for studying the behaviour of the shape memory alloys (i.e. Cu based alloys). We also describe the applications of the system, which allows to build up a calorimetric system (heat flux or conduction calorimetry) (resolution 1.5 W) or a stress-strain-temperature system of 20 N of maximum charge (resolution around 1 mN and 0.1 m.CICYT projects MAT89-407-C03-01 and PETRI-90 are gratefully acknowledged. H. T. acknowledges the DGICYT (sabbatic program) for financial aid in international cooperation. The enlightening discussions with Dr. F. C. Lovey (Centro Atomico Bariloche - Argentina) are also acknowledged. 相似文献
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Remembering more than one permanent shape is an attractive research topic for shape memory materials (SMMs). In this paper, multiple crystalline shape memory polyurethanes (SMPUs) are prepared with PCL10000 and PTMG2900 by a three‐step polymerization method. DSC and WAXD results show that the obtained polyurethane contains, simultaneously and independently, two kinds of crystals. In addition, it is confirmed through DMA analysis that reversible soft phase and hard domains are formed in the PCL‐PTMG based SMPU system; and two‐step modulus decreases at low temperature range can be obtained in the SMPU with suitable mass proportion of PCL to PTMG, e.g., 1:7. Thus, shape memory effect (SME) can be achieved in this system. Moreover, it is found that the PTMG soft segment dominates the shape memory effect when the PCL mass is lower than that of PTMG; while the PCL soft segment dominates the SME when PCL mass is higher than that of PTMG; and a two‐step programing shape recovery can be achieved when the mass proportion of PCL/PTMG reaches a balance value, e.g., 3:5. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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The effect of cationic groups within hard segments on shape memory polyurethane (SMPU) fibers was studied and the cyclic tensile testing was conducted to assess the shape memory effect. Mechanical properties, hard segment crystallization, and dynamic mechanical properties of SMPU ionomer fibers composed of 1,4‐butanediol (BDO), N‐methyldiethanolamine (NMDA), 4,4′‐methylenebis(phenyl isocyanate) (MDI), and poly(butylene adipate)diol (PBA) were investigated using a universal tensile tester, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The results demonstrate that only 2 wt% NMDA can significantly change the glass transition temperature of the soft segment phase. DSC shows that the ionic group within hard segments can facilitate the crystallization of hard segments in unsteamed SMPU ionomer fibers. But for steamed fiber specimens, this effect is insignificant. Moreover, the ionic groups in hard segments with different hard segment contents (HSC) have different effects. In unsteamed fibers with 64 wt% HSC, 2 wt% NMDA increases the glass transition of soft segments from 63.5 to 70.6°C. However, in fibers with 55 wt% HSC, the glass transition temperature is lowered from 46.7 to 33.5°C. The post‐treatment, high‐pressure steaming is an effective way to remove the internal stress and subsequently improve the dimensional stability of SMPU ionomer fibers. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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J.B. Wachter V. Petkov D. Bilc K.M. Paraskevopoulos T. Torbrügge M.G. Kanatzidis 《Journal of solid state chemistry》2007,180(2):420-431
KSb5S8 and its solid solution analogs with Rb and Tl were found to exhibit a reversible and tunable glass→crystal→glass phase transition. Selected members of this series were analyzed by differential scanning calorimetry to measure the effect of the substitution on the thermal properties. The solid solutions K1−xRbxSb5S8 exhibited clear deviations in melting and crystallization behavior and temperatures from the parent structure. The crystallization process of the glassy KSb5S8 as a function of temperature could clearly be followed with Raman spectroscopy. The thermal conductivity of both glassy and crystalline KSb5S8 at room temperature is ∼0.40 W/m K, among the lowest known values for any dense solid-state material. Electronic band structure calculations carried out on KSb5S8 and TlSb5S8 show the presence of large indirect band-gaps and confirm the coexistence of covalent Sb-S bonding and predominantly ionic K(Tl)?S bonding. Pair distribution function analyses based on total X-ray scattering data on both crystalline and glassy K1−xRbxSb5S8 showed that the basic structure-defining unit is the same and it involves a distorted polyhedron of “SbS7” fragment of ∼7 Å diameter. The similarity of local structure between the glassy and crystalline phases accounts for the facile crystallization rate in this system. 相似文献
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随着信息产业的高速发展,传统的存储技术已不能完全满足人们的需求。因此,对聚合物电存储材料与器件的研究应运而生。相对于传统的无机存储材料,基于聚合物的电存储材料与器件具有易加工、低成本、稳定性好、低功耗、可实现三维堆积以及高存储密度等优点,极有可能取代传统的无机半导体器件,显示出广阔的发展前景。本文介绍了聚合物电存储器件的一些基本原理及基本概念,并对存储器件几种主要的作用机制做了归纳; 根据器件的易失性与否,描述了闪存、一次写入多次读取及动态随机存储器件三类存储器件的存储特点,总结了聚合物电双稳材料及其在三类存储器件中应用的研究进展,探讨了这一研究领域需要解决的一些关键问题,最后展望了聚合物电存储材料与器件的研究和发展方向。 相似文献
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Phattarin Mora Hannes Schfer Chanchira Jubsilp Sarawut Rimdusit Katharina Koschek 《化学:亚洲杂志》2019,14(23):4129-4139
When dealing with smart polymers, in particular with shape memory polymers, the polymer type and composition specify the overall material properties and in particular the extent of the shape memory effect. Polybenzoxazines as a polymer with high potential for structural applications represent a promising component for materials with both shape memory effect and structurally interesting material properties. This minireview gives insight into how the shape memory effect, in particular the shape recovery event, is influenced by internal factors such as polymer structure, morphology and external factors such as filler addition. 相似文献
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Shape memory hybrids (SMH) have drawn significant attention because they allow an easy alternative for the design of shape memory materials with tailored properties or features. In this work, a shape memory hybrid was made, based on polyvinyl alcohol (PVA) as the elastic domain and 0D silver nanoparticles (Agnps) as the transition domain, a dissolution method of mixing both components, and evaporation of water afterward allowed the formation of films of the hybrid material. Two different size distributions of silver nanoparticles were used (13.7 ± 2.6 and 67.9 ± 14.1 nm), in order to study the effect of the size on the shape memory effect (SME) of the final SMH, under temperature stimuli. The materials obtained were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy, infrared spectroscopy (IR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. The crystallinity of PVA was slightly altered with the addition of Agnps. Finally, the shape memory effect was tested on both hybrid materials, resulting in a better response to temperature for the SMH prepared with Agnps of 68 nm, also the shape recovery time can be tuned varying both the increase of temperature and the size distribution of Agnps used. 相似文献