双硫键和双硒键在自修复聚氨酯脲弹性体中的应用

为解决自修复聚氨酯脲(PUU)弹性体兼具高修复效率和优异力学性能的问题,提出在PUU弹性体主链引入动态双硫键或双硒键。以聚碳酸酯二醇(PCDL)为软段,异佛尔酮二异氰酸酯(IPDI)为硬段,分别以胱胺(CY)、硒代胱胺(SeCY)和1,6-己二胺(HDA)为扩链剂,通过溶液法制备3种PUU弹性体,即含动态双硫键的PUU试样(SPU)、含动态双硒键的PUU试样(SePU)和对照组PUU试样(CPU)。通过红外、X射线衍射、拉伸测试、光学显微、热分析等对3种试样的结构和性能进行表征。结果表明,SPU的力学性能和自修复性能达到较好的平衡,拉伸强度和断裂伸长率分别达到53.1 MPa和400.5%,80℃修复12 h后的自修复效率分别为87.2%和75.7%;SePU具有最优的自修复性能,80℃修复12 h后的自修复效率达到98.9%和95.3%。     

基于双硫键的自修复聚氨酯研究进展

归纳了基于双硫键的自修复聚氨酯的制备方法、自修复机理和过程以及相应的表征手段;总结了双硫键自修复聚氨酯在自修复效率、相关结构和力学性能等方面的研究状况,展望了其发展前景,指出了其研究方向。     

基于两种双硫键自修复聚氨酯制备及性能

以异佛尔酮二异氰酸酯(IPDI)和双(2-羟基乙基)二硫醚(DTBO)为硬段,聚四氢呋喃(PTMG)为软段,β-巯基乙醇(ME)为封端剂,制备巯基封端且含双硫键的聚氨酯(PUR)预聚物,利用巯基易氧化的特点,用H2O2/NaI进行氧化,合成分子链内和分子链端均含有双硫键的自修复交联PUR.采用傅立叶变换红外光谱仪、差示...     

一种基于动态双硫键的自修复聚氨酯弹性体的制备与性能

以聚丙二醇(PPG)、异佛尔酮二异氰酸酯(IPDI)和含硫扩链剂胱氨酸二甲酯(CDE)为原料,固定摩尔比为1∶3∶2,采用预聚体法制备含硫自修复聚氨酯弹性体(SPU),对SPU进行红外光谱测试、拉曼光谱测试、力学性能和自修复性能测试、划痕修复观察和DSC测试。结果表明,SPU为非晶结构,微相分离程度低;切割50%深度后,通过拉伸强度测试得出其在60℃的自修复效率达到89.8%,原因是动态双硫键的交换反应和分子链的高运动能力(硬段玻璃化转变温度<60℃)。     

基于二硫键和氢键的自修复聚氨酯弹性体的制备、改性及其应用

以聚丙二醇（PPG）为软段,异佛尔酮二异氰酸酯（IPDI）为硬段构建聚氨酯主链,然后将1,4-丁二醇（BDO）和2,2’-二氨基二苯二硫醚（DTDA）作为扩链剂嵌入聚氨酯主链中,制备一种具有高强度、刺激条件温和且能快速修复的基于二硫键和氢键协同作用的聚氨酯（PU）弹性体。采用红外光谱、拉曼光谱、热分析、力学测试及光学显微观察对其结构和性能进行表征,研究了软硬段比、修复时间和修复温度对PU力学性能和自修复性能的影响。实验结果发现,所制备的PU具有很高的断裂伸长率（2398%）、断裂强度（8.84MPa）以及抗穿刺性能。同时PU在温和的刺激条件下具有优异的自修复性能,其修复效率与修复时间和修复温度呈正比,硬段质量分数为44.26%的试样经70℃加热3h后,断裂强度可恢复到原始试样的92.7%。再处理试验的结果表明,该PU可以通过热压实现循环利用,回收率高达98.8%。此外,该自修复PU弹性体可作为柔性基底应用于可穿戴传感器来监测人体肢体运动。     

红外光谱法研究聚氨酯脲氢键

采用间苯二胺为扩链剂制备聚氨酯脲,研究其力学性能。随着硬段含量的增加,产物的硬度和强度均增加,而断裂伸长率下降。并用红外光谱法对氢键化程度进行表征,结果表明：随着硬段含量的增加,其脲羰基区氢键化程度增加。     

基于双硫键自修复高分子材料研究进展

自修复高分子材料是一种采用仿生思想制备的高分子材料,即当基体受损时能够在一定条件下实现自我修复。自修复高分子材料可分为外援型和本征型两种,本文重点介绍基于双硫键本征型自修复高分子材料的研究进展。综述了近年来国内外制备双硫键自修复高分子材料的方法及其修复机理,并对未来研究及发展进行了展望。     

硬段含量对聚氨酯和聚氨酯脲氢键化程度的影响

以PPG600,PPG2000,甲苯二异氰酸酯(TDI)和1,4-丁二醇(1,4-BD)为原料合成了聚氨酯(PU),通过改变PPG600,PPG2000配比调节产品硬段含量;以PPG2000,TDI和异佛尔酮二胺(IPDA)为原料合成了聚氨酯脲(PUU),通过调节TDI与IPDA在体系中的比例调节产品硬段含量。利用FT-IR,DSC,旋转黏度计研究了硬段含量对聚醚型PU和PUU的微观结构及黏度的影响。结果表明,随硬段含量提高,PU和PUU的氢键化程度均提高,PU较多地形成不完善的氢键,而PUU倾向于形成完善有序的氢键结构。此外随硬段含量增大,PU和PUU的黏度增大,PU软段的玻璃化转变温度升高。     

吡啶基聚氨酯的制备及其自修复性能研究

为探究氢键对聚氨酯性能的影响,以聚四氢呋喃、异氟尔酮二异氰酸酯、4,4’?二羟基联苯（HBD）和N³,N⁵?双（4?羟基苯基）吡啶?3,5?二甲酰胺（HPD）制备了2种类型的聚氨酯,并利用红外光谱仪（FTIR）、热重分析仪（TG）、万能力学试验机等对2种聚氨酯的化学结构、热稳定性、力学性能和自修复性能等进行了表征和测试。结果表明,2种聚氨酯均表现出了优异的自修复性能;60 ℃下,两者均30 min即可完成自修复;相较于以HBD为扩链剂制备的聚氨酯,以含有吡啶基团和酰胺基团的扩链剂（HPD）制备的聚氨酯表现出更优异的力学性能（拉伸强度为1.2 MPa）、更优异的热稳定性能（热降解活化能为230.3 kJ/mol）及更高的残炭率（800 ℃残炭率约为5 %）。     

Hydrolytic resistance of model poly(ether urethane ureas) and poly(ester urethane ureas)

Poly(ester urethane ureas) (PesURUs) and poly(ether urethane ureas) (PetURUs) synthesized from diphenylmethane-4,4′-diisocyanate and poly(butylene adipate) diol, and poly(tetramethylene oxide) diol or poly(propylene oxide) diol, respectively, were hydrolyzed at 70°C for various periods up to 16 weeks. Differences in thermal and mechanical properties of as-received dry samples are correlated with the number and strength of hydrogen bonds formed between urea/urethane groups of hard segments and polyester or polyether groups of soft segments. Gel permeation chromatography measurements show that the molar mass of linear PesURUs markedly decreases with the hydrolysis time, whereas that of linear PetURUs remains almost unaffected. PesURU crosslinked by polymeric isocyanate has lower crystallinity, but shows somewhat better resistance to hydrolysis than its linear counterpart because of its more stable three-dimensional molecular structure. Water uptake at 37°C, dynamic mechanical thermal analysis, and differential scanning calorimetry thermograms determined for redried hydrolyzed specimens concurrently show that advancing hydrolysis accounts for decrease in the crystallinity (if any) of soft polyester segments, in the efficacy of hydrogen bonding and in crosslinking density. Experimental data indicate that hydrolytic resistance of PetURUs is primarily determined by (1) the hydrolytic stability of individual types of present groups, (2) steric hindrances affecting the access of water molecules to these groups, and (3) the hydrophilicity of backbones. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 577–586, 1998     

Effect of chain extender on microphase structure and performance of self-healing polyurethane and poly(urethane-urea)

In this work, four aliphatic chain extenders, hexanediol (HDO), hexane diamine (HDA), cystamine (CY), and cystine dimethyl ester (CDE), were chosen to synthesize four kinds of polyurethane and poly(urethane-urea)s (PUs), respectively. HDO extended polyurethanes, HDA extended poly(urethane-urea), CY extended poly(urethane-urea), and CDE extended poly(urethane-urea) were denoted as OPU, APU, CPU, and SPU, respectively. The effect of chain extender type on microphase structure and performance of four PUs was investigated. Our research showed that mechanical strength increased in the following order: OPU < SPU < CPU < APU, and self-healing performance increased in the opposite direction. This result is attributed to the increasing degree of microphase separation: OPU < SPU < CPU < APU. The optimal sample SPU has not only excellent mechanical properties (tensile strength of 27.1 MPa and elongation at break of 397.7%), but also exhibits superior self-healing performance (self-healing efficiencies of 95.3% and 93.5% based on tensile strength and elongation at break). The moderate degree of microphase separation between the soft segments and the hard segments, the introduction of disulfide bonds and low degree of hydrogen bonding are responsible for preparing a polyurethane or poly(urethane-urea) system with high mechanical strength and excellent self-healing performance simultaneously. This work provides useful information for us to develop self-healing polyurethane or poly(urethane-urea) materials in the future.     

Design and properties of dynamic self-healing polyurea molecule based on disulfide bonds

Although thermosetting polymer materials have excellent mechanical properties, they are less self-healing, recycling than thermoplastic polymer materials, which may cause a serious waste of resources. Herein, a series of polyurea materials with high mechanical strength, good properties of self-healing and recycling are prepared by adjusting the ratio of polyether polyol and introducing disulfides into the synthesis of polyurea prepolymer in an innovative way. The composite polyurea (FHPUA) materials with tensile strength over 47 MPa and elongation at break of 720% are prepared. The experimental results show that by adjusting the content of aromatic disulfide, the tensile strength is further increased to 52 MPa, and the heat resistance of the material is improved. Through five self-healing experiments, the surface of the material recovers as before even after continuous heating at 70°C for 1 h. In addition, the tensile strength of the material recovers 86.56% and the elastic modulus recovers 70.21% after four recycling experiments. In practical application, it is expected to fill the shortcomings of traditional polyurea such as micro cracks, short service life and poor performance, and have great potential applications in the fields of coating layer of heavy-duty conveyor belts, encapsulation film of electronic devices and building facade coating.     

Blends of polybenzoxazine/poly(acrylic acid): hydrogen bonds and enhanced performances

This work focuses on exploring the role of the additional hydrogen bond donor moiety‐containing polymer poly(acrylic acid) (PAA) in the hydrogen bonds and properties of polybenzoxazines. Thorough studies showed that PAA could not only decrease the curing temperature of benzoxazine resin, but also give additional hydrogen bond donors that were beneficial to the hydrogen bonding interactions and performances of polybenzoxazine/PAA blends. As the hydrogen bonds varied, the glass transition temperature and tensile modulus of the polymer blends changed in accordance with the hydrogen bonds. The results revealed that the introduction of the hydrogen bond donor moiety‐containing polymer was beneficial for hydrogen bonding interactions, which could improve the performances of polybenzoxazines. This novel insight is anticipated to be of help to researchers in the development of more polybenzoxazines and polybenzoxazine blends with enhanced properties. © 2017 Society of Chemical Industry     

基于动态硼酸酯键/氢键的自修复水凝胶的制备及性能

通过4-(溴甲基)苯基硼酸(PBA)和1-乙烯基咪唑(IL)的烷基化反应制备了苯硼酸离子液体(PBA-IL)单体。在2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)氧化纳米纤维素(CNF)的存在下，通过丙烯酰胺(AM)和PBA-IL的一步聚合反应，制备了一种具有半互穿网络结构的自修复导电水凝胶(PAM/PBA-IL/CNF)。通过1HNMR对PBA-IL的化学结构进行表征；通过FTIR、XPS、SEM对水凝胶的化学结构和物理形貌进行表征，并测试了水凝胶的拉伸性能、自修复性能和导电性能。结果表明，PBA-IL单体和水凝胶成功制备，且水凝胶具有典型的多孔结构。PAM/PBA-IL3/CNF水凝胶[3代表PBA-IL含量为30%，以AM、PBA-IL、CNF悬浮液、N,N’-亚甲基双丙烯酰胺(MBA)溶液、过硫酸铵(APS)的总绝干质量为基准]的断裂应力为335.1 kPa、断裂伸长率为1969.5%、断裂能为12.1 kJ/m²、自修复效率为95.43%(150 min)、电导率为6.38 mS/cm。     

High-efficiency self-repairing polyurethane based on synergy of disulfide bonds and graded hydrogen bonds

Designing an elastomer that possesses both mechanical strength and self-healing properties is a challenging. In this study, a polyurethane elastomer (PUSTP) was successfully synthesized, featuring disulfide bonds along the main chain and graded intermolecular hydrogen bonds. The results demonstrated that the mechanical properties of the polyurethane elastomer improved with an increase in the number of disulfide bonds increased. Specifically, when the molar ratio of disulfide bonds to IPDA was 5:5, the tensile strength of the composite elastomeric film was 5.22 MPa, with an elongation of 1820.26%. Furthermore, the material exhibited robust thermal stability after undergoing repair at 70°C for 12 h, the mechanical strength of the polyurethane membrane remained unchanged, showing outstanding self-healing capabilities. Additionally, the polyurethane film served as the substrate material for crafting self-healing conductive devices, which maintained excellent electrical conductivity even after damage repair. This flexible material, combining impressive mechanical recovery capabilities with electrical performance, holds significant promise for a wide array of applications.     

Phase-mixing and molecular dynamics in poly(urethane urea) elastomers by solid-state NMR

The dynamical heterogeneity in a series of 4,4′-dicyclohexylmethane diisocyanate-diethyltoluenediamine-poly(tetramethylene oxide) based poly(urethane urea) (PUU) elastomers was studied by solid-state nuclear magnetic resonance (NMR) methods. Extensive phase mixing was evidenced by the ¹H wideline signal, which can be approximately fitted by a single exponential model. ¹³C T₁ relaxation time measurements indicate that the hard segments (HS) exhibit some small-amplitude mobility, likely “activated” by neighboring soft segments (SS). Fitting of the time-domain wideline separation (TD-WISE) data was employed to characterize the extent of phase mixing, which revealed that a PUU elastomer contains four fractions: rigid-HS, mobile-HS, rigid-SS, and mobile-SS regions. For a variety of SS MWs, the dynamics and relative portions of rigid vs. mobile fractions among HS were substantially similar, while those for the SS exhibit large contrast. Furthermore, the dynamics in the rigid-SS fraction is at least an order of magnitude slower than that in mobile-SS for all PUUs. Greater phase-mixing substantially lowers the SS mobility, facilitating SS to undergo glass transition at high strain rates, thus can be key to enhancing dynamic mechanical strengthening.     

The effect of microstructure on the rate-dependent stress-strain behavior of poly(urethane urea) elastomers

Segmented poly(urethane urea) materials (PUUs) exhibit versatile mechanical properties and have drawn great interest due to their potential for protection against projectile impacts and blast loadings. To optimize the performance of PUUs for various high rate applications, specific features of their mechanical behavior have to be suitably tailored by altering the microstructure. Hence the micromechanisms governing the mechanical behavior must be identified, understood and leveraged. In this study, the effects of varying microstructure on the rate-dependent mechanical behavior were examined for select PUU materials. As expected, increasing the hard segment content increased the stiffness and the flow stress levels. Interestingly, it was observed that promoting phase mixing among the hard and soft segment domains of the PUU material greatly enhanced its rate-dependent stiffening and strain hardening behavior. These insights can help design PUUs for articles that manifest improved protective abilities under impact, while maintaining their flexibility during normal use. The potential applications for such materials are extensive, including face masks and goggles, which require excellent folding/un-folding capabilities, while also providing superior impact resistance.     

Electrospinning of linear and highly branched segmented poly(urethane urea)s

Electrospun fibrous mats were formed from linear and highly branched poly(urethane urea)s. The highly branched poly(urethane urea)s were synthesized using an A₂+B₃ methodology, where the A₂ species is an oligomeric soft segment. Since the molecular weight of the A₂ oligomer is above the entanglement molecular weight, the highly branched polymers formed electrospun fibers unlike typical hyperbranched polymers that do not entangle. Stress-strain experiments revealed superior elongation for the electrospun fibrous mats. In particular, the highly branched fiber mats did not fail at 1300% elongation, making the electrospun mats promising for potential applications where enhanced tear strength resistance is required.