辐照交联聚甲基乙烯基硅氧烷的ESR谱研究

本文研究了GY-131医用级聚甲基乙烯基硅氧烷(PMVS)在辐照交联中的自由基产生和衰减的ESR潜,以及SiO₂填料对交联的影响。     

溶液法制备柔性压阻式传感器的研究进展

柔性压阻式传感器具有结构简单、易于制备、检测范围广等优势, 在可穿戴电子器件领域中扮演着非常重要的角色. 在制备柔性压阻式传感器的众多方法中, 溶液法由于操作简单、反应条件温和、材料的适用性广泛、易于规模化制备等优势, 成为极具发展前景的制备工艺. 在此基础上, 如何进一步提高柔性压阻式传感器的力学与电学性能也成为研究者们更加关注的话题. 另外, 制备图案化、微型化、规模化的传感器阵列为柔性压阻式传感器的应用范围拓展了新的道路. 本综述首先介绍了柔性压阻式传感器的工作原理与性能指标, 同时讨论了其性能指标对传感器在实际应用中的影响. 随后, 简单介绍了其构成材料, 并通过梳理近年来溶液法制备柔性传感器的研究成果, 选取了几种典型的溶液法制备方法进行重点介绍, 指出其具备的优势及目前存在的问题. 最后, 对溶液法制备柔性传感器的发展方向进行总结与展望.     

原位合成手性镍配合物中的阻转异构及磁性研究

阻转异构体是一类特殊的手性化合物. 利用轴手性配体制得的具有阻转异构行为的配合物在不对称催化等领域有广泛的应用. 相比之下, 通过原位反应由非手性底物制备这类手性配合物的报道较少, 而利用非轴手性化合物原位组装得到非轴手性阻转异构体的报道则更加罕见. 乙腈是一种廉价易得的基本化工原料, 在金属离子存在下活化乙腈分子是向有机分子中引入氰甲基的一种有效手段. 本文利用乙腈分子进攻2-二吡啶基酮获得了一例含有氰甲基官能团的配体dpkMeCN-H[dpkMeCN=cyanomethyl-di(pyridin-2-yl)methanol]. 在Ni^II和K^I的配位作用下, 该体系发生原位组装生成了一对阻转异构体. 磁性拟合结果表明镍离子之间主要为铁磁耦合, 且它们由于八面体畸变产生一定的零场分裂, 使手性镍配合物产生磁各向异性.     

超细SiO2填充聚甲基乙烯基硅氧烷的动态流变特性

研究粒子填充类聚合物体系的动态粘弹响应，可在较宽应变、温度、频率范围内获得有关体系分散状态及相互作用等结构信息。用粒径小、比表面积大的二氧化硅(SiO2)增强聚硅氧烷时，其独特的化学结构和表面特性对填充体系的静态和动态流变特性有显著影响，Payne等研究了碳黑增强硫化橡胶的动态粘弹性，迄今关于SiO2增强聚硅氧烷，尤其对未硫化体系动态流变特性研究很少报道。本文以超细、高比表面积且具多孔结构的SiO2填充聚甲基乙烯基硅氧烷(Polymethylvinylsiloxane，PMVS)，对室温下不同SiO2含量的SiO2/PMVS体系动态流变特性进行了研究。     

PMVS/SiO2复合体系中粒子表面处理对动态粘弹特性的影响

粘弹性是高分子材料最本质的特征,其与高分子结构的关系一直是多组分高分子材料研究的热点。目前,对于填料增强聚硅氧烷体系的研究主要集中于填料在聚合物中的分散以及增强机理等方面,而有关不同填料表面特性体系的粘弹响应的研究报道尚不多见．在前文报道未经表面处理的超细SiO2填充聚甲基乙烯基硅氧烷(Polymethylvinylsiloxane,PMVS)的粘弹性研究的基础上,本文采用双(γ-三乙氧基硅基丙基)四硫化物IBis(3-triethoxysilyl)tetrasul{ane,TESPT]对SiO2进行表面处理,并采用溶液共混法制备样品,研究了经表面处理的SiO2填充PMVS体系的动态粘弹行为,并探讨了其结构变化与粘弹响应的关系。     

短碳纤维填充HDPE复合体系的渗流网络与压阻行为

研究了短碳纤维(Shortcarbonfiber,SCF)填充高密度聚乙烯(HDPE)导电复合体系的渗流(Percola-tion)与压阻行为(Piezoresistivebehavior,PRB),发现SCF经物理接触而形成的导电网络是复合材料导电的根源.体系的压阻行为呈现浓度依赖性.受压时SCF间隙的减小与渗流网络的局部破坏-重建过程随填料浓度、载荷大小和力学循环次数的变化而变化,导致PRB表现为电阻负压力系数(NPC)、电阻正压力系数(PPC)或两者兼有的现象.讨论了体系PRB的稳定性,发现由于HDPE基体的塑性永久形变,电阻-时间基线随着压缩循环的进行而发生漂移,多次循环可有效提高体系的压阻稳定性.     

碱水显影阻焊油墨研究—羧基与环氧基的反应

二元酸单甲酯;环氧化合物;碱水显影阻焊油墨研究—羧基与环氧基的反应     

轴不稳定手性配体的开发及其在不对称催化反应中的应用

轴不稳定配体应用于不对称催化有其独到的特点, 不同于传统的轴稳定手性配体. 综述了轴不稳定的噁唑啉、双膦、单膦、双羟基及N—O等配体的开发及其在不对称催化中的应用.     

亚相pH对气水界面上VE/DPPC单分子膜的影响

通过表面压－分子面积等温线的测定，考察了亚相ｐＨ对气水界面上的维生素Ｅ（ＶＥ）／二棕榈酰基磷脂酰胆碱单分子膜的影响。亚相ｐＨ降低不改变ＤＰＰＣ单分子膜的崩裂压，但使ＶＥ单分子膜的崩裂压明显增大，不改变ＶＥ单分子膜的平均分子面积，但使ＤＰＰＣ单分子膜凝缩，低表面压下，ＶＥ对ＤＰＰＣ单分子膜的膨胀作用在纯水上很小，在ｐＨ为１的亚相上则很明显，这提示在低ｐＨ的亚相上，ＶＥ／ＤＰＰＣ单分子膜中的极性头基间     

高位阻有机磷萃取剂的研究——Ⅰ.烃基膦酸单十六烷基酯的合成及其对钴(Ⅱ)、镍(Ⅱ)等金属离子的萃取性能

合成了6个具有高位阻特征的烃基膦酸单十六烷基酯萃取剂,并考察了它们对Co(Ⅱ)、Ni(Ⅱ)、Cu(Ⅱ)、Fe(Ⅲ)和Ca的萃取性能。萃取剂分子中烃基结构的变化对各种金属离子的萃取能力有着不同程度的影响。空间位阻较大的异丙基和环己基化合物具有比2-乙基己基膦酸单2-乙基己基酯(P507)更高的Co-Ni分离能力。     

聚氯乙烯/炭黑导电复合体系的压阻行为

研究了聚氯乙烯/炭黑(PVC/CB)导电复合体系在单轴压力作用下的压阻行为,发现CB含量对电阻-机械响应具有显著的影响.当CB含量低于渗流阈值时,PVC/CB复合材料呈现PPC效应;而高于渗流阈值时,呈现NPC效应.在渗流阈值附近,单轴压缩可诱导NPC效应的出现,或者抑制PPC效应.     

HDPE/CB高分子导电复合体系的单轴形变与压阻行为

根据基体形变及其与渗流网络结构之间的关系,研究了高密度聚乙烯(HDPE)/炭黑(CB)复合材料压阻行为的发生机制及其影响稳定性的力学因素.结果表明,单轴压阻行为的产生源于材料受外力变形而导致的渗流网络微结构变化,且这种变化强烈依赖于填料含量.当填料含量较低时(渗流阈值附近),体系电阻率随压力升高而表现为电阻正压力系数行为;当填料含量较高时,体系电阻率随压力升高显现电阻负压力系数效应.完全卸载的零压力下,电阻基线随压缩循环随循环次数增大而发生漂移,这种漂移与轴向残余压缩应变有关,可以通过增加循环次数来加以稳定.交联可以减小残余压缩应变,并抑制高填充复合体系电阻基线的漂移.     

Piezoresistive characteristics of single wall carbon nanotube/polyimide nanocomposites

A systematic study of the effect of single wall carbon nanotubes (SWCNTs) on the enhanced piezoresistive sensitivity of polyimide nanocomposites from below to above percolation was accomplished. The maximum piezoresistive stress coefficient (Π) of 1.52 × 10^?3 MPa^?1 was noted at just above the percolation threshold concentration (Φ ～ 0.05 wt %) of SWCNT. This coefficient value exceeds those of metallic piezoresistive materials by two orders of magnitude (4.25 × 10^?5 MPa^?1 for aluminum). The high piezoresistive characteristics appear to originate from a change in the intrinsic resistivity of the composite caused by the variation of the tunneling distance between conducting inclusions (SWCNTs) under compression or tension. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 994–1003, 2009     

纳米微晶纤维素对炭黑补强天然橡胶力学性能和动态性能的影响

采用酸水解工业微晶纤维素(MCC)制备纳米微晶纤维素(NCC),将其与天然胶乳共凝沉,混炼时加入炭黑(CB),制备了天然橡胶(NR)/NCC/CB复合材料,研究了NR/NCC/CB和NR/NCC/CB/RH(间苯二酚-六亚甲基四胺络合物)复合材料的力学性能和动态性能,并与NR/CB体系的性能进行对比.结果表明NCC可以均匀分散在天然橡胶基体中,且依拉伸方向取向,随着NCC替代炭黑的份数增加,Payne效应减弱,说明NCC本身并不构成强的填料网络,NR/NCC/CB与NR/CB比较,前者整体的网络化程度减弱,体系的损耗因子变化不大,NCC的加入改善了NR/CB的力学性能和抗屈挠龟裂性能,降低压缩疲劳温升和压缩永久形变,当NCC取代5～20 phr CB后,仍然保持高耐磨炭黑补强天然橡胶的耐磨耗性能.动态力学性能显示NR/NCC/CB的玻璃化转变温度较NR/CB变化不大,0℃的tanδ略有下降的同时60℃的tanδ明显降低.NR/NCC/CB/RH体系的Payne效应较NR/NCC/CB明显减弱,力学性能、抗屈挠龟裂性能和耐磨耗性能进一步改善,体系的压缩疲劳温升和压缩永久形变更小.     

单轴压力对高密度聚乙烯/碳黑导电复合材料电阻特性的影响

研究了高密度聚乙烯/炭黑导电复合材料在单轴压力作用下电阻的变化规律.结果表明,在低压力下,复合材料电阻随压力增加而降低;而在较高压力下则随压力增大而升高,分别呈现出所谓的“电阻负压力系数”和“电阻正压力系数”效应.电阻的压力依赖性以及由压缩引起的电阻不可回复性,被认为与外力作用下导电网络的重组与破坏有关.由此提出了导电复合材料单轴压力作用-电阻相互关系的唯象模型.     

Polymer microcantilever biochemical sensors with integrated polymer composites for electrical detection

Micro fabricated sensors based on nanomechanical motion with piezoresistive electrical readout have become a promising biochemical sensing tool. The conventional microcantilever materials are mostly silicon-based. The sensitivity of the sensor depends on Young's modulus of the structural material, thickness of the cantilever as well as on the gauge factor of the piezoresistor. UV patternable polymers such as SU-8 have a very low Young's modulus compared to the silicon-based materials. Polymer cantilevers with a piezoresistive material having a large gauge factor and a lower Young's modulus are therefore highly suited for sensing applications. In this work, a spin coatable and photopatternable mixture of carbon black (CB) and SU-8, with proper dispersion characteristics, has been demonstrated as a piezoresistive thin film for polymer microcantilevers. Results on percolation experiments of SU-8/CB composite and fabrication of piezoresistive SU-8 microcantilevers using this composite are presented. With our controlled dispersion experiments, we could get a uniform piezoresistive thin film of thickness less than 1.2 μm and resistivity of 2.7 Ω cm using 10 wt% of CB in SU-8. The overall thickness of the SU-8/composite/SU-8 is approximately 3 μm. We further present results on the electromechanical characterization and biofunctionalization of the cantilever structures for biochemical sensing applications. These cantilevers show a deflection sensitivity of 0.55 ppm/nm. Since the surface stress sensitivity is 4.1 × 10⁻³ [N/m]⁻¹, these cantilevers can well be used for detection of protein markers for pathological applications.     

聚甲基乙烯基硅氧烷/炭黑复合体系的电阻弛豫行为

考察了聚甲基乙烯基硅氧烷/炭黑(CB)复合交联体系在恒定压应力作用下以及完全卸载后的导电行为,发现电阻在恒定压应力作用下及完全卸载后均随时间非线性下降,呈现典型的电阻弛豫行为.根据电阻弛豫时间以及最大电阻弛豫幅度,分析了导电网络结构变化与电阻弛豫之间的关联,讨论了炭黑含量对电阻弛豫的影响.结果表明,在恒定压应力2~4MPa下,电阻弛豫具有两个与CB含量无关的弛豫时间,对应不同尺寸导电网络的结构变化.完全卸载后,基体形变回复造成导电网络发生结构弛豫,弛豫时间随CB含量增大而延长.     

The piezoresistive behaviors of polyethylene/foliated graphite nanocomposites

A conductive nanocomposite with an ordered conductive network and low-percolation threshold were prepared by adding foliated graphite (FG) nanosheets to high-density polyethylene (HDPE). The piezoresistive behavior of the nanocomposites was investigated under different pressure ranges. There existed a critical pressure below which composite resistance decrease with the increase of pressure and above which resistance increased sharply with increasing of pressure. The critical pressure is a function of the concentration of FG and the sensitivity of the change in resistivity against the applied pressure strongly depended on the FG content. The critical pressures of the nanocomposites with FG concentration at 6 vol.%, 11 vol.%, 12 vol.%, are about 7 MPa, 10 MPa, and 12 MPa, respectively. After repeated pressure treatment, there was a gradual decrease in the change of conducting structure although a permanent damage occurred due to the irreversible deformation of polymer matrix. As a result, the piezoresistive behavior of HDPE/FG nanocomposites tended to be constant under cyclic compression. The behavior was accounted for by an extension of tunneling conduction theory to which provides a good approximation to the piezoresistive effect.     

Conduction stability of high-density polyethylene/carbon black composites due to electric field action

Conduction stability of high-density polyethylene/carbon black (HDPE/CB) composites with a CB volume fraction slightly above the percolation threshold is studied in relation to electric field action at various ambient temperatures below the melting point of HDPE. It is found that resistance of the composites shows considerable changes after the electric field is switched off. Influence of irradiation crosslinking of HDPE on the conduction stability is also discussed.     

Monolithic polyimine vitrimer/graphene aerogel composites

Graphene-polymer composites have attracted great attention as sensing materials due to their tailorable electrical conductivity, physicochemical properties, and sensitivity to geometric and functional changes. Herein, we report the first example of cylindrical monolithic polyimine vitrimer/graphene composites with excellent mechanical, compressive, rehealable and recyclable, and piezoresistive properties via simple infiltration of polymer monomers into the pores of graphene aerogel followed by thermal curing. The composites exhibit excellent durable compressibility (negligible reduction in the compression properties even after 3000 consecutive compression cycles), rapid recovery to the original size upon stress released, high compressive strength (up to 1.2 MPa), and high conductivity (up to 79 S/m). Excellent piezoresistive properties were observed, displaying consistent and reliable change of the electrical resistance with the compression ratio. Furthermore, rehealing with ～100% recovery of the compressive strength and electric conductivity was achieved under mild rehealing conditions, which is highly desired but has rarely been reported for electronic materials. The facile strategy for fabrication of rehealable monolithic polymer/GAs can open new possibilities for the sustainable development of composites with high electrical conductivity for various applications such as sensing, health monitoring, and movement detection.