基于多重动态共价键的环氧类玻璃网络的制备与性能

以三羟甲基丙烷三缩水甘油醚(TTE)为基体, 2,2′-(1,4-亚苯基)-双[4-硫醇1,3,2-二氧杂戊烷](BDB)和3,3-二硫代二丙酸(DTDPA)为交联剂, 通过环氧-巯基“点击”反应和环氧-羧酸酯化反应, 制备了基于多重动态共价键(硼酸酯键、 二硫键和酯键)的环氧类玻璃网络. 利用红外光谱和拉曼光谱对其结构进行了表征, 结果表明, 环氧类玻璃中不仅存在硼酸酯键、 二硫键和酯键, 还存在可逆氢键, 并且大量氢键的存在能提高环氧类玻璃的交联度. 对所得环氧网络的热稳定性、 热机械性能和力学性能进行了测试, 并对基于多重动态共价键环氧网络进行了自修复、 焊接、 形状记忆和再加工能力测试. 结果表明, 在80 ℃下可实现网络的完全自修复、 再加工与焊接, 且焊接后样品的力学性能(拉伸强度)恢复率在80%以上, 具有优异的功能性.     

Dual-responsive shape memory and self-healing ability of a novel copolymer from epoxy/cashew nut shell liquid and polycaprolactone

In this work, the blends of epoxy (EP) and polycaprolactone (PCL) with a bio-based curing agent, viz. cashew nut shell liquid (CNSL) were studied for their dual-responsive shape memory and self-healing behaviors. The suitable EP/CNSL weight ratio was observed at 70/30. The increase of PCL content up to 20 wt% in EP-CNSL matrix significantly enhanced the shape memory response to both thermal and chemical stimuli. All specimens showed 100% thermo-responsive shape recovery and the recovery time decreased with increasing PCL content. In the case of chemo-responsive shape memory, the immersion times spent for 100% shape recovery in water and methanol substantially decreased when PCL was added. Moreover, after thermal treatment, the EP-CNSL matrix with 20 wt% PCL showed significant self-healing ability with high tensile strength recovery at 93.70%. The EP-CNSL/PCL copolymer could be a promising alternative bio-related smart material for various applications such as dual-activated sensors and coatings with self-healing ability.     

Study on poly(ε‐caprolactone)‐based shape memory copolymer fiber prepared by bulk polymerization and melt spinning

In this paper, a poly(ε‐caprolactone) (PCL)‐based shape memory polyurethane fiber was prepared by melt spinning. The shape memory switching temperature was the melting transition temperature of the soft segment phase mainly composed of PCL at 47°C. The mechanical properties especially shape memory effect were explicitly characterized by thermomechanical cyclic tensile testing. The results suggest that the prepared fiber has shape memory effects. The prepared 40 denier shape memory fiber had a tenacity of about 1.0 cN/dtex, and strain at break 562–660%. The shape fixity ratio reached 84% and the recovery ratio reached 95% under drawing at high temperature and thermal recovery testing.¹ Finally, the fiber thermal/mechanical properties were measured using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Copyright © 2007 John Wiley & Sons, Ltd.     

Poly(urethane-oxazolidone): Synthesis, characterisation and shape memory properties

Poly(urethane-oxazolidone) were synthesized by reacting isocyanate-terminated oxazolidone with hydroxy-telechelic poly(tetramethylene oxide) (PTMO). The molar ratios of the reactants were varied to get polymers of varying oxazolidone and urethane compositons. The polymers were characterized by DSC, FTIR, XRD, dynamic mechanical thermal analysis and chemical analyses. An increase in the concentration of urethane and oxazolidone groups caused a decrease in tensile strength and elongation of the poly(urethane-oxazolidone). The polymers possessed crystallites of PTMO whose melting transition temperature decreased on enhancing the oxazolidone concentration. The polymers exhibited thermo-responsive shape memory properties, which was confirmed and quantified by cyclic tensile tests. The influence of oxazolidone modification and the consequent soft/hard segment variation on the thermal, mechanical, dynamic-mechanical and shape recovery properties of the resultant polymers was investigated. The oxazolidone moities conferred enhanced shape recovery and shape fixity to the polyurethane.     

基于聚丙交酯的多嵌段聚氨酯的形状记忆性能和生物相容性

制备了以聚丙交酯(PLA)为软段, 2,4-甲苯二异氰酸酯(TDI)与乙二醇(EG)反应产物为硬段的多嵌段聚氨酯(PLA-PU), 并对其形状记忆效应和生物相容性进行了研究. 形状压缩50%的样品从起始恢复温度(22~37 ℃)开始, 在10 ℃范围内可以恢复到起始形状, 形变恢复率接近100%, 形变恢复力最大值达到1.5~4 MPa. 细胞培养实验结果初步证明PLA-PU的细胞相容性与PLA相当, 因而有可能用作植入形状记忆医疗器械材料.     

基于多重可逆作用的自修复聚氨酯弹性体的制备及性能

在聚氨酯主链上引入可逆二硫键, 同时使用硼酸构建的硼酸酯键作为可逆交联点, 使聚氨酯内部形成交联网络结构, 制备了一种兼具高强度、 高韧性及高修复效率的自修复聚氨酯弹性体. 红外光谱、 动态力学分析、 力学测试、 电子显微镜及修复测试结果表明, 制备的自修复聚氨酯具有硬而韧的特性, 原样强度高达23.3 MPa, 断裂伸长率可达1177%, 并且修复条件温和, 剪断拼接的试样经60 ℃, 24 h修复后可恢复99%的原样强度, 且该修复过程可重复多次进行. 此外, 该材料还具有多通道修复特性, 通过热修复或水辅助热修复的方式均可实现材料的修复, 并且水辅助热修复速率更快.     

新型光、 热双响应形状记忆聚合物的制备与性能

通过多巴胺表面原位聚合反应修饰玻璃微珠, 利用X光电子能谱仪(XPS)和傅里叶变换红外光谱仪 (FTIR)对修饰前后玻璃微珠表面的化学组成进行了表征, 用热失重分析仪(TGA)对其热稳定性进行了测试, 并利用透射电子显微镜(TEM)和扫描电子显微镜(SEM)对其形貌进行了观察; 研究了改性玻璃微珠对形状记忆共混物聚己内酯和聚氨酯(PCL/TPU)的热性能、 力学性能和形状记忆性能的影响. 结果表明, 成功制备了表面包覆聚多巴胺的玻璃微珠(PHGM), 改性玻璃微珠的加入不仅增强了复合材料的力学性能(当改性玻璃微珠含量为3%时, 材料的拉伸强度提高到53.3 MPa, 杨氏模量提高到178.4 MPa), 还赋予了复合材料优异的光热效应. 所制备的形状记忆复合材料在808 nm近红外光的照射下, 可以在短时间内(7 s)升高到材料的开关温度并回复到初始形状.     

A Robust Self-healing Polyurethane Elastomer Enabled by Tuning the Molecular Mobility and Phase Morphology through Disulfide Bonds

Elastomers with outstanding strength, toughness and healing efficiency are highly promising for many emerging fields. However, it is still a challenge to integrate all these beneficial features in one elastomer. Herein, an asymmetric alicyclic structure adjacent to aromatic disulfide was tactfully introduced into the backbone of polyurethane(PU) elastomer. Specifically, such elastomer(PU-HPS) was fabricated by polycondensing polytetramethylene ether glycol(PTMEG), isophorone diisocyanate(IPDI) and p-hydroxydiphenyl disulfide(HPS) via one-pot method. The molecular mobility and phase morphology of PU-HPS can be tuned by adjusting the HPS content. Consequently, the dynamic exchange of hydrogen and disulfide bonds in the hard segment domains can also be tailored. The optimized sample manifests outstanding tensile strength(46.4 MPa), high toughness(109.1 MJ/m3), high self-healing efficiency after fracture(90.3%), complete scratch recovery(100%)and good puncture resistance. Therefore, this work provides a facile strategy for developing robust self-healing polymers.     

Shape memory effects of poly(ethylene terephthalate-co-ethylene succinate) random copolymers

Random copolymers based on terephthalate acid, succinic acid and ethylene glycol, with thermally induced shape memory, were synthesized via melt polycondensation. The chemical structures of these poly(ethylene terephthalate-co-ethylene succinate) copolymers (PET-co-ES) were ascertained by ¹H NMR spectroscopy. The thermal and viscoelastic characteristics of these copolymers were studied in terms of the succinic acid content using differential scanning calorimetry and dynamic mechanical analysis. The shape memory effects of the copolymers were examined using the strain test. The experimental results suggested that all copolymers exhibited shape memory above the glass transition temperature and that the highest shape recovery rate was 90%. The shape recovery rates of all test samples declined with the number of cycles. This decrease in the shape recovery rate may result from the change in the degree of polymer orientation and/or crystallinity during repeated testing.     

Investigation on Structures and Properties of Shape Memory Polyurethane/Silica Nanocomposites

In this study, high performance shape memory polyurethane (SMPU)/silica nanocomposites with different silica weight fraction including SMPU bulk, 3%, 4.5%, 6%, 7.5%, 10%, were prepared by sol‐gel process initiated by the solid acid catalyst of p‐toluenesulfonic acid (PTSA). Field emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM) observation show that the silica nanoparticles are dispersed evenly in SMPU/silica nanocomposites. Tensile test and dynamic mechanical analysis (DMA) suggest that the mechanical properties and the glass transition temperature (T_g) of the nanocomposites were significantly influenced by silica weight fraction. Thermogravimetric analysis (TGA) was utilized to evaluate the thermal stability and determine the actual silica weight fraction. The TGA results indicate that the thermal stability can be enhanced with the hybridization of silica nanoparticles. Differential scanning calorimetry (DSC) was conducted to test the melting enthalpy (ΔH) and the results suggest that the ΔH was markedly improved for the SMPU/silica nanocomposites. Thermomechanical test was conducted to investigate the shape memory behavior and the results show that the shape fixity is improved by hybridization of silica and good shape recovery can be obtained with the increasing of cycle number for all the samples.     

Mechanical and shape memory performance of shape memory polyurethane-based aligned nanofibers

In recent years, shape memory polyurethane (SMPU) as a smart material has been used in various applications owing to its desirable shape memory effect and biocompatibility. In this study, unidirectional SMPU nanofibers are innovated by electrospinning to clarify the mechanical and shape memory properties with nanofiber directions. The results showed that when the nanofiber alignment degree is 0° (parallel to the tensile direction), the aligned SMPU nanofibers achieved the obvious improvement of tensile strength (increased to 135%) and elastic modulus (increased to 313%), compared with the random SMPU nanofiber. Moreover, the developed aligned nanofibers exhibited good ability against stress relaxation and creep under constant strain or constant stress conditions in cyclic loading. The aligned SMPU nanofibers with a 0° alignment degree exhibited excellent shape memory properties with shape recovery rates larger than 93% and shape fixity rates larger than 90%, and a dramatic increase of shape recovery stress.     

Design and development of self-repairable and recyclable crosslinked poly(thiourethane-urethane) via enhanced aliphatic disulfide chemistry

Thermoset polymer elastomers that are capable of autonomous repairability upon physical damage at ambient temperature are highly desirable because of their thermal and environmental resistance, outstanding mechanical toughness and stability. To aim at this goal, we demonstrated that tris(diethylamino)phosphine was initially proven as an efficient catalyst for the aliphatic disulfide exchange at mild condition. By making use of the aliphatic disulfide bond reshuffling and elasticity of polyurethane elastomers, the inherently cross-linked polysulfide-based poly(thiourethane-urethane) elastomers were prepared and exhibited the ability to mend without extrinsic stimuli in the presence of phosphorus catalyst at room temperature after artificially damaged. The self-healing efficiency via the mechanical recovery approach was investigated to be mainly dependent upon the cross-linking density of polysulfide and hard segments chemistry, which in turns determined the molecular chain diffusion and reshuffling that was corroborated by the stress-relaxation study. The thermoset elastomer based on asymmetric diisocynate showed a maximum self-healing efficiency of 85.6% compared to 71.6% for the elastomer with symmetric monomer building blocks. The self-healable polymer was confirmed to be recyclable and reprocessable through a cut-compression processing cycle under a quite mild pressure and temperature thanks to the disulfide bond reshuffling. Meanwhile, the recycled thermoset elastomer well maintained the mechanical properties to its original material.     

Triple shape memory effect of foamed natural Eucommia ulmoides gum/high‐density polyethylene composites

This paper proposes a new technique for the preparation of foamed Eucommia ulmoides gum (EUG)/high‐density polyethylene (HDPE) shape memory composites and establishes the relationship between structures and properties in foamed shape memory composites. Eucommia ulmoides gum/HDPE shape memory composites are designed to memorize 2 temporary shapes by exploiting the different melting points of the 2 phases; the triple shape memory effect in the composites is investigated via mechanical measurements, thermal analysis, and shape memory behavior analysis. The results show that HDPE phase enables the composites to effectively memorize the first temporary shape and EUG phase contributes the second temporary shape. When the ratios of EUG and HDPE were 80/20 and 70/ 30, the composite exhibited satisfactory shape memory behavior with favorable shape fixity ratio and shape recovery ratio, in addition to excellent mechanical properties (tensile strength of 15 MPa, tear strength above 51 KN/m, and foam porosity of about 11%).     

High modulus ratio shape‐memory polymers achieved by combining hydrogen bonding with controlled crosslinking

A new type of poly(methyl acrylate)‐co‐(acrylic acid) (PMA‐AA) networks obtained by combining hydrogen bonding with controlled crosslinking exhibit full and rapid shape‐memory recovery. The structure, thermal properties, dynamical mechanical properties and shape‐memory effects of these networks were presented. High modulus ratios were achieved for the series of PMA‐AA networks based on intense self‐complementary hydrogen bonding in poly(acrylic acid) (PAA) segments. This lead to excellent shape‐memory effects with strain‐recovery ratio above 99%. Meanwhile, faster recovery speed was achieved by the synergistic effect of hydrogen bonding and controlled crosslinking compared to the linear PMA‐AA copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1241–1245, 2011     

Effects of graphene quantum dot (GQD) on photoluminescence,mechanical, thermal and shape memory properties of thermoplastic polyurethane nanocomposites

A group of shape memory polyurethane‐based nanocomposites containing graphene quantum dot nanoparticles (GQDs) were prepared via in‐situ polymerization method. GQD nanoparticles were synthesized by a facile and rapid microwave‐assisted method and characterized by Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction pattern, field emission scanning microscopy, transmission electron microscopy, and fluorescence analysis. Chemical structure and hydrogen bonding index (HBI_[C=O]) of the nanocomposites were analyzed via FTIR spectra. The results show that the incorporation of GQDs in PU matrix reduces HBI_(C=O) of nanocomposites. Crystalline structure and thermal properties of the nanocomposites were investigated by differential scanning calorimetry. As results indicate, nucleation effect of GQDs raises crystallinity content of the samples. Mechanical examinations indicate that incorporation of GQDs improves Young's modulus of the nanocomposites, while their elongation at break values are reduced. In addition, shape memory analyses reveal that the presence of GQDs in PU matrix increases the shape fixity ratios in nanocomposites.     

Ultra-robust,self-healable and recyclable polyurethane elastomer via a combination of hydrogen bonds,dynamic chemistry,and microphase separation

Flexibility, robustness, transparency, and recyclability are critical to the application of self-healing polymer materials in the field of flexible electronics. However, integrating all the above properties remains a huge challenge to date. In this work, we put forward a facile strategy to prepare polyurethane (PU) elastomer with ultra-high strength and self-healing performance based on hydrogen bonds, disulfide dynamic chemistry, and microphase separation at the same time. Three different self-healing PUs were obtained by introducing disulfide bonds and different types of hydrogen bonds. A robust, transparent, and recyclable PU with amino-terminated chain extender (PUA) with fast and efficient self-healing performance was prepared. The mechanical and self-healing properties of the PUA were effectively balanced by the synergistic effect of reversible interaction of disulfide bonds and the formation of microphase separated structure. The results indicated that the PUA exhibited high transparency up to 90% and excellent mechanical property, e.g. the tensile strength and elongation at break can reach 37.10 MPa and 1080%, respectively. Meanwhile, it can achieve a high self-healing efficiency of 96.8% at 80 °C for 4 h and maintain 84% of the initial mechanical strength even after four times of recycling. Moreover, the colloid graphite/PUA flexible strain sensor was prepared by the combination of colloid graphite and PUA, which can accurately detect both large and tiny scale deformations.     

A Novel Method for Modification of SMPU by Micro-phase Separation Promoters

Shape memory polyurethane(SMPU)is a typical temperature-sensitive functional polymer having an excellent shape memory behavior1,which has been extensively studied since19882,10.B.K.Kim et al.3reported the effect of hard segment contents(HSC)and soft segment length(SSL)of SMPU on its modulus,hardness and recovery strain.They attributed these effects to its micro-phase separation of its soft segment and hard segment as well as its soft segment crystallization.F.K.Li et al.4found that high…     

Effect of SSL and HSC on morphology and properties of PHA based SMPU synthesized by bulk polymerization method

Searching new shape memory polymer and the associating synthesis technology are critical on the development of smart materials. In this paper, a comprehensive study on Poly(hexylene adipate) PHA being the soft segment of shape memory polyurethane (SMPU) was presented. Bulk polymerization method was employed to synthesize the SMPU with different soft segment length (SSL) and hard segment content (HSC). The influences of SSL and HSC on its morphology and thermomechanical property using DSC, DMA, POM, and shape memory behavior were presented here. The results indicate that the thermal properties, dynamic mechanic properties, and crystal morphology of SMPU are influenced significantly by SSL and HSC. And it is found that the shape fixity increases with SSL but decreases with HSC. On the other hand, the shape recovery decreases with both SSL and HSC, and the associated recovery temperature increases either with the increasing SSL or with decreasing HSC. Lastly, it is concluded that in the PHA‐based‐SMPU, the lower limiting value of SSL for polyurethane having shape memory effect is 2000; their response temperature varied with SSL and HSC, changing from 41.0 to 51.9 °C. Stable hard segment crystal are formed at above 30% HSC sample in bulk polymerization, but shape memory behavior can also be observed when its physical crosslink point are formed in the lower HSC PHA‐based‐SMPU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 444–454, 2007     

Click coupled graphene for fabrication of high‐performance polymer nanocomposites

An effective technique of using click coupled graphene to obtain high‐performance polymer nanocomposites is presented. Poly(ε‐caprolactone) (PCL)‐click coupled graphene sheet (GS) reinforcing fillers are synthesized by the covalent functionalization of graphene oxide with PCL, and subsequently the PCL‐GS as a reinforcing filler was incorporated into a shape memory polyurethane matrix by solution casting. The PCL‐click coupled GS has shown excellent interaction with the polyurethane matrix, and as a consequence, the mechanical properties, thermal stability, thermal conductivity, and thermo‐responsive shape memory properties of the resulting nanocomposite films could be enhanced remarkably. In particular, for polyurethane nanocomposites incorporated with 2% PCL‐GS, the breaking stress, Young's modulus, elongation‐at‐break, and thermal stability have been improved by 109%, 158%, 28%, and 71 °C, respectively. This click coupling protocol offers the possibility to fully combine the extraordinary performance of GSs with the properties of polyurethane. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Preparation of body-temperature-triggered shape-memory polyurethane with biocompatibility using isosorbide and castor oil

Shape memory polyurethanes (SMPUs) have attracted much attention in the biomedical field because they can easily control the transition temperature (T_trans) to shape memory and are biocompatible. In this study, a shape memory polyurethane with both biocompatibility and a T_trans close to the body temperature was synthesized by using natural derivatives of isosorbide and castor oil in place of petroleum-based materials. Isosorbide and castor oil were used to form net points, and polycaprolactone diol (PCL diol) acted as the switching segment. The synthesized four polyurethane (PCL diol/isosorbide/castor oil, PICU-1, 2, 3, 4) with different isosorbide contents exhibited desired thermal and mechanical properties. In the thermo-cyclic shape memory testing experiment, the PICU series demonstrated good shape memory property, with more than 95% shape recovery ratio (R_r) and more than 90% shape fixity ratio (R_f), and PICU-3 recovered its shape within 20 s in a 37 °C water bath. In addition, the PICU series proved to be safe materials with excellent biocompatibility, as indicated by the observed C2C12 cells viability and proliferation. The stent made with the PICU-3 film showed near complete magnetization at 37 °C within 18 s and proved to be a suitable self-expanding stent.