生物橡胶的研究进展

2010年中国成为世界第二大经济体,这意味着中国需要更多的橡胶资源以满足其经济的快速发展。橡胶材料可以通过两个来源得到,一个是源自巴西橡胶树的天然橡胶,一个是源自化石资源的合成橡胶。我国的天然橡胶资源非常短缺,而合成橡胶又不可持续发展。因此,利用太阳能发展生物橡胶是中国橡胶工业可持续发展的未来。生物橡胶包含两大类材料,一类是生物基工程弹性(Bio-based engineering elastomer,BEE),它将可再生的生物质资源发酵得到衣康酸等生物基单体,再经化学合成得到的一类新的弹性体,或者将生物质发酵得到的生物基单体如异丁醇等进一步转化为传统单体如异丁烯等,再经过化学合成得到传统的弹性体;第二类是天然橡胶,包括三叶橡胶和第二天然橡胶(Second natural rubber,SNR),例如蒲公英橡胶、银菊橡胶以及我国特有的杜仲橡胶。本文将对生物基工程弹性体和第二天然橡胶进行综述,由于三叶橡胶的研究历史悠久、文献众多,在此不再综述。     

丁腈橡胶的配位硫化

在丁腈橡胶中引入无机金属盐粒子,通过腈基与金属离子之间的固相配位反应来实现丁腈橡胶的配位硫化,创建了一个完全不同于传统硫磺硫化体系的新型非共价键配位交联的橡胶网络体系.同时制备了具有优异的力学性能的配位硫化橡胶材料,既可以作柔性的橡胶材料使用,也可以作为韧性、脆性的塑料材料使用.本文就影响配位交联反应的两个关键因素(金属盐粉末的粒径和丁腈橡胶的丙烯腈含量)进行了探讨,提出了提高配位硫化效率的办法(结晶水、增塑剂等).     

丁腈羟型聚氨酯弹性体的分子结构设计与电机械性能研究

本文对端羟基聚丁二烯丙烯腈液态橡胶(丁腈羟，HTBN)进行端基化改性，合成带不同光活性端官能团的遥爪型丁腈羟(HTBN)预聚物，并最终通过光固化制备了不同分子链结构的丁腈羟型聚氨酯(BNPU)介电弹性体。研究表明，随着前驱体HTBN分子链长度的增加，固化交联后BNPU弹性体的线性链缠结网络密度增加，使得弹性体的模量(Y)和断裂伸长率(E_B)分别最高增加到1.89 MPa与112.26%,同时使弹性体的玻璃化转变温度(T_g)降低。根据活性封端基团的不同，采用季戊四醇三丙烯酸酯(PETA)封端的HTBN预聚物，光固化后的BNPU弹性体内部形成较大体积位阻的局部交联区域，可使BNPU弹性体的T_g升高，热分解速率降低，同时相分离导致的界面极化增强，从而进一步提升弹性体介电性能：使BNPU弹性体样品在10³ Hz频率下介电常数(ε′)最高达到807,介电损耗保持在1以下。最终局部大位阻交联结构和一定量的氰基结构可协同赋予BNPU弹性体优异的综合电机械性能，克服了纯聚氨酯和高交联度丁腈橡胶模量大、易击穿的问题。     

热固性树脂韧性的改进途径及其增韧机理

本文系统地综述了加入无机填料、弹性体及热塑性塑料;与热塑性塑料形成半IPN(Semi-Interpenetruting Polymer Network);改变交联网的化学结构;控制分子交联状态的不均匀性等增加热固性树脂韧性的途径。并对以上几种增韧途径的机理及其橡胶改性体系相分离的热力学和动力学判据也进行了讨论。     

氢键交联超分子聚合物材料：从结构性能到功能应用

高分子材料的大量消耗与持续积累已经在全球范围内造成了严重的环境污染与资源浪费.发展可修复、可循环、可降解和可回收的新一代高分子材料是解决上述挑战的根本途径.基于动态可逆的非共价键将聚合物链段进行交联可以有效地构建这些材料.本专论系统总结了我们课题组在氢键交联超分子聚合物材料方面的系列研究进展.基于多重氢键的协同性与动态性、氢键与动态共价键的协同,以及材料微相结构的调控,发展了系列兼具高强度与高韧性的超分子聚合物材料,实现了材料的修复、循环、降解与回收;不仅突破了非共价交联高分子材料力学性能弱的瓶颈,而且化解了高分子材料强度与韧性的矛盾.相关研究为发展传统高分子材料的可持续替代品提供了新的思路.同时,发展了系列基于氢键交联的功能超分子聚合物材料,展示了其在柔性电子、固态锂电池及水下黏合剂等方面的应用.     

卟啉-富勒烯络合物的合成

按照卟啉与富勒烯连接方式的不同,卟啉-富勒烯化合物可分为共价键连接和非共价键连接两种类型.共价键连接的卟啉-富勒烯化合物主要是通过环加成反应来合成,如1,3-偶极环加成反应、Diels-Alder环加成反应和Bingel-Hirsch环加成反应;非共价键连接的卟啉-富勒烯化合物主要是通过金属的轴向配位及氢键得到.本文综...     

热塑性弹性体的进展

一、引言近十年来,在聚合物科学中,嵌段共聚物的研究有着较快的发展。一些结构、分子量大小和分子量分布可控制的聚合物相继出现,其中又以热塑性弹性体最引人注目。最早的热塑性弹性体是1965年合成的一种新的苯乙烯—丁二烯的嵌段共聚物。它无需化学硫化,就具有交联、补强橡胶的特性,同时又能用一般热塑性聚合物的加工方法来加工成制品。热塑性弹性体这一名称也正是由此得来。     

热适性形状记忆聚合物

动态共价交联聚合物的研究具有悠久的历史,其早期的工作着眼于如何解决应力松弛带来的聚合物材料力学性能降低的问题.20世纪90年代以来,利用动态共价键来主动设计聚合物网络的特殊可适性逐渐成为研究主流,其中包括自修复和重加工性.然而,受到动态共价键的种类、通用性及所实现功能的特异性等限制,对于动态共价交联聚合物网络的研究尚停留在基础阶段.本文以本课题组近期在动态共价交联形状记忆聚合物的研究为基础,结合其他相关工作,展示了通用共价键(酯键及氨酯键)的动态可逆性,并利用其设计了具有特殊性能和潜在商业化价值的形状记忆聚合物.在此基础上,我们提出分子结构设计及宏观性能均不同于传统热塑性和热固性形状记忆聚合物的第3类形状记忆聚合物,即热适性形状记忆聚合物.     

运动鞋用橡塑材料的研究进展

橡塑材料在运动鞋制造过程中被普遍应用，总结了运动鞋制造过程中天然橡胶、丁苯橡胶、丁腈橡胶、氯丁橡胶、顺丁橡胶、再生橡胶、聚氯乙烯、聚烯烃弹性体、苯乙烯-丁二烯-苯乙烯弹性体、乙烯-醋酸乙烯共聚物、聚氨酯和嵌段聚醚酰胺树脂等橡塑材料的基本性能。分类别综述了相关橡塑材料近年的研究进展。指出未来运动鞋用橡塑材料将向着轻量化、功能化、智能化和环保化的方向发展。     

橡胶再生用解交联助剂研究进展

开发高效、低能耗、环境友好的橡胶再生方法对橡胶工业的绿色可持续发展具有重要意义。其中,废旧橡胶再生用解交联化学助剂的选择尤为关键。本文介绍了橡胶的再生机理,并根据作用机理分类,将解交联助剂归纳为自由基类、亲核类、相转移催化类、烯烃复分解类、催化类与氧化类等6类,总结了各类助剂的作用机理及研究进展,并讨论了其应用技术瓶颈。最后,展望了废旧橡胶再生利用面临的挑战和未来发展方向。     

硫酸铜含量对硫酸铜与丁腈橡胶之间配位交联反应的影响

利用丁腈橡胶(NBR)的可配位侧基——腈基(—CN)与金属盐硫酸铜(CuSO4)的铜离子(Cu2+)之间的配位反应制备了一种配位交联CuSO4/NBR.影响该配位交联反应的因素众多,如热压温度、热压时间、增塑剂等等,考察了CuSO4含量对其的影响.通过X射线光电子能谱(XPS)、动态力学分析(DMA)、差示扫描量热分析(DSC)等手段对CuSO4与NBR之间的配位交联反应进行了分析,并对所得配位交联的CuSO4/NBR进行了交联密度及力学性能的测试.结果发现,随CuSO4含量的不断增加,CuSO4与NBR的配位交联程度逐渐增强,且所得配位交联CuSO4/NBR显示出从典型橡胶到韧性塑料再到脆性塑料的力学转变特性.另外,通过扫描电子显微镜(SEM)及X射线能谱仪(EDX)对材料的微观结构进行了分析,发现CuSO4在聚合物基体中不仅充当交联剂的角色,而且还起着增强填料的作用.     

Physical chemistry of supramolecular polymer networks

Supramolecular polymer networks are three-dimensional structures of crosslinked macromolecules connected by transient, non-covalent bonds; they are a fascinating class of soft materials, exhibiting properties such as stimuli-responsiveness, self-healing, and shape-memory. This critical review summarizes the current state of the art in the physical-chemical characterization of supramolecular networks and relates this knowledge to that about classical, covalently jointed and crosslinked networks. We present a separate focus on the formation, the structure, the dynamics, and the mechanics of both permanent chemical and transient supramolecular networks. Particular emphasis is placed on features such as the formation and the effect of network inhomogeneities, the manifestation of the crosslink relaxation dynamics in the macroscopic sample behavior, and the applicability of concepts developed for classical polymer melts, solutions, and networks such as the reptation model and the principle of time-temperature superposition (263 references).     

Tensile strength of rubbers

A current theory of the tensile strength of rubbers invokes large-scale crosslink interchange at room temperature to explain the high tensile strengths of networks crosslinked with weak linkages. This mechanical lability of certain crosslinks has been assumed from their known thermal lability at higher temperatures. Relaxation of stress experiments at various elongations have been performed at room temperature on networks crosslinked with both weak and strong linkages. Our purpose was to detect mechanically induced crosslink slippage. We have found no evidence of any mechanical lability of weak crosslinks at room temperature. A hypothesis is presented which explains the high tensile strengths of rubbers crosslinked with weak linkages as resulting from an internally relaxed network formed by the thermal lability of the crosslinks at the vulcanization temperature. This theory is shown to be consistent with some previously unexplained experimental results.     

A facile and controllable synthesis of dual‐crosslinked elastomers based on linear bifunctional polydimethylsiloxane oligomers

Dual‐crosslinked supramolecular elastomers with the hybrid network consisting of hydrogen bonds and covalent bonds combine the reversibility of hydrogen bond and mechanical properties of covalent crosslinking network. In this article, isocyanate mixture is used as curing agent to prepare dual‐crosslinked elastomer based on bifunctional polydimethylsiloxane under mild condition. This method can effectively build up a hybrid network with the designed structure. A series of elastomers with same hydrogen bond density and variable covalent crosslinking degree are obtained. Swelling measurements and ¹H‐NMR spectra confirm the feasibility and controllability of curing method, the increasing of bifunctional isocyanate give rise to higher covalent crosslinking degree, improving the solvent resistance. The studies on viscoelastic property show that the introduction of an irreversible covalent crosslinking network stabilize the hybrid network, restrain the chain movement. The mechanical and self‐healing property studies reveal that the covalent crosslink significantly reinforce the whole network, while the reparable strength seems to mainly depend on the hydrogen bond density. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3760–3768     

Supramolecular polymers fabricated by orthogonal self-assembly based on multiple hydrogen bonding and macrocyclic host–guest interactions

Supramolecular polymers constructed by orthogonal self-assembly based on multiple hydrogen bonding and macrocyclic host-guest interactions have received increasing attention due to their elegant structures,outstanding properties,and potential applications.Hydrogen bonding endows these supramolecular polymers with good adaptability and reversibility,while macrocyclic host-guest interactions give them good selectivity and versatile stimuli-responsiveness.Therefore,functional supramolecular polymers fabricated by these two highly specific,noninterfering interactions in an orthogonal way have shown wide applications in the fields of molecular machines,electronics,soft materials,etc.In this review,we discuss the recent advances of functional supramolecular polymers fabricated by orthogonal self-assembly based on multiple hydroge n bonding and host-guest interactions.In particular,we focus on crown ether-and pillar[n]arene-based supramolecular polymers due to their compatibility with multiple hydrogen bonds in organic solution.The fabrication strategies,interesting properties,and potential applications of these advanced supramolecular materials are mainly concerned.     

Synergistic effect between POSS and fumed silica on thermal stabilities and mechanical properties of room temperature vulcanized (RTV) silicone rubbers

In this paper, both divinyl-hexa[(trimethoxysilyl)ethyl]-POSS (DVPS) and fumed silica were firstly introduced into polydimethylsiloxane (PDMS) system using as the cross-linker and the reinforcing filler respectively. And a series of novel RTV silicone rubbers synergistically enhanced by DVPS and fumed silica were prepared. The cross-linked networks in the novel RTV silicone rubbers have been studied by attenuated total reflection infrared spectroscopy, and the dispersions of POSS and fumed silica in these novel RTV silicone rubbers have been observed by means of scanning electron microscope (SEM). And thermal stabilities, thermo-oxidative stabilities and mechanical properties of these novel RTV silicone rubbers were studied by means of thermal gravimetric analysis and universal tensile testing machine, respectively. From the obtained results, it was found that synergistic effect between POSS-rich areas and fumed silica on thermal stability and mechanical property of RTV silicone rubber indeed existed. And the experimental results also exhibited that the thermal stabilities and mechanical properties of the novel RTV silicone rubbers were far better than those of the reference materials (DVPR and MTFR). The striking enhancements in thermal properties and improvements on mechanical properties of novel RTV silicone rubbers were likely attributed to the synergistic effect between POSS-rich domains and fumed silica. Meanwhile, it was found that the mechanical properties of RTV silicone rubbers prepared with a given amount of POSS cross-linker were enhanced with the increment of the loading amount of fumed silica.     

Strong,Self‐Healable,and Recyclable Visible‐Light‐Responsive Hydrogel Actuators

The most pressing challenges for light‐driven hydrogel actuators include reliance on UV light, slow response, poor mechanical properties, and limited functionalities. Now, a supramolecular design strategy is used to address these issues. Key is the use of a benzylimine‐functionalized anthracene group, which red‐shifts the absorption into the visible region and also stabilizes the supramolecular network through π–π interactions. Acid–ether hydrogen bonds are incorporated for energy dissipation under mechanical deformation and maintaining hydrophilicity of the network. This double‐crosslinked supramolecular hydrogel developed via a simple synthesis exhibits a unique combination of high strength, rapid self‐healing, and fast visible‐light‐driven shape morphing both in the wet and dry state. As all of the interactions are dynamic, the design enables the structures to be recycled and reprogrammed into different 3D objects.     

A fluorescent supramolecular crosslinked polymer gel formed by crown ether based host-guest interactions and aggregation induced emission

Based on the combination of B21C7/dialkylammonium salt host-guest interactions and tetraphenylethylene(TPE)-based aggregation-induced emission(AIE) effect, a fluorescent supramolecular crosslinked polymer gel was successfully prepared. Compared with the solution of TPE-containing small molecules, this gel exhibited remarkable fluorescence enhancement due to the AIE effect of TPE units. The "gelation induced fluorescence emission" phenomenon can be explained by the hindered intramolecular rotation of phenyl rings of TPE. Because of the reversibility and stimuli-responsiveness of the B21C7/dialkylammonium salt host-guest interactions, the transition between the fluorescent supramolecular crosslinked polymer gel and the disassembled sol with very weak fluorescence can be realized by adding p H and thermal stimuli. This novel material contributes to the development of supramolecular chemistry, polymer science and fluorescent materials and offers a new method to construct functional supramolecular materials.     

Effect of nature and extent of crosslinking on swelling and mechanical behavior of styrene–butadiene rubber membranes

The influence of crosslink type and crosslink density on the swelling and mechanical behavior of styrene–butadiene rubber (SBR) membranes were studied in four aliphatic hydrocarbons. To vary the crosslink type and crosslink density, SBR was vulcanized by four different vulcanizing systems viz conventional, efficient, peroxide and a mixture of sulfur and peroxide. SBR vulcanizates having mono or disulfidic crosslinks (efficient system) exhibited the highest solvent uptake whereas those with C–C bonds (peroxide system) showed the lowest. SBR crosslinked by the mixed system showed superior mechanical properties in the unswollen, swollen and deswollen conditions. Arrhenius and thermodynamic parameters were evaluated from the diffusion data. Finally, a comparison between theoretical and experimental diffusion results was carried out.     

Azobenzene Based Photo-responsive Mechanical Actuator Fabricated by Intermolecular H-bond Interaction

Photo-responsive mechanical actuator is a class of stimuli-responsive materials transferring light to mechanical energy through macroscopic transformation. To fabricate photo-responsive mechanical actuator, soft polymeric materials crosslinked with functional bridging structures are desired. Supramolecular interaction is a relatively common way to fabricate crosslinked materials due to its excellent self-assembly performance. And azobenzene and derivatives are ideal candidates of photo-responsive materials because of the unique photo-induced trans-cis isomerization. Here, a new kind of crosslinked materials based on supramolecular interaction between 4,4'-dihydroxyazobenzene and chitosan is reported. Under 355 nm irradiation, the macroscopic bending of polymeric materials occurs rapidly due to the photo-isomerization of 4,4'-dihydroxyazobenzene. Meanwhile, the photo-responsive mechanical actuator can also lift weight which is up to 200 times that of the actuator itself, and convert energy from light to mechanical work efficiently. This report suggests a new kind of photo-responsive actuator based on supramolecular interaction and may be helpful to contribute a theoretical basis to the design and synthesis of photo-responsive mechanical actuator suitable for large-scale manufacturing industrialization in future.