三元巯基／乙烯基硅氮烷UV固化制备聚合物陶瓷前驱体

采用差光量热扫描研究了三元巯基化合物与乙烯基硅氮烷紫外光固化特性,结果表明,随着光引发剂浓度和辐照强度的增加,体系聚合速率增大,体系终止方式以自由基双基偶合终止为主。聚合反应为一级,且聚合速率与乙烯基浓度有关,而与巯基浓度无关。对制备的聚合物陶瓷前驱体的基本性能进行了分析,结果表明,玻璃化转变温度随巯基化合物用量的减少而降低,在巯基-乙烯基硅氮烷等摩尔比时,体系的固化度最大。     

三元巯基/乙烯基硅氮烷UV固化制备聚合物陶瓷前驱体

采用差光量热扫描研究了三元巯基化合物与乙烯基硅氮烷紫外光固化特性,结果表明,随着光引发剂浓度和辐照强度的增加,体系聚合速率增大,体系终止方式以自由基双基偶合终止为主。聚合反应为一级,且聚合速率与乙烯基浓度有关,而与巯基浓度无关。对制备的聚合物陶瓷前驱体的基本性能进行分析表明,玻璃化转变温度随巯基化合物用量的减少而降低,在巯基-乙烯基硅氮烷等摩尔比时,体系的固化度最大。     

由交替共聚物引发苯乙烯原子转移自由基聚合合成梳型聚苯乙烯

以苯乙烯与马来酰亚胺的交替共聚物引发原子转移自由基聚合合成梳型聚苯乙烯,研究了络合剂结构、催化剂浓度、引发剂官能度与活性、反应温度等对聚合可控性、反应速率、支化程度等的影响。分别用气相色谱跟踪单体转化率、三检测器凝胶渗透色谱跟踪聚合物分子量、特性黏数等的变化。结果表明,利用高活性引发剂将导致形成自由基浓度过高,从而通过双基偶合终止形成高分子量组分,但通过降低催化剂浓度对提高聚合可控性效果不明显,而采用低官能度或活性引发剂可提高可控性,但导致所得聚合物支化程度较低。采用高官能度引发剂在较低温度下反应则既维持可控性又获得高度支化聚合物。     

聚合物先驱体的结构对氮化硅陶瓷性能的影响

以紫外光固化巯基/乙烯基硅氮烷共聚体系制备了不同结构的聚合物陶瓷先驱体,高温裂解后得到氮化硅陶瓷,用X射线衍射仪,场发射扫描电镜和能谱仪等手段对巯基官能度、巯基化合物分子尺寸、巯基/乙烯基硅氮烷配比以及惰性填料进行了表征,研究了聚合物先驱体的结构对氮化硅陶瓷的结晶度和晶粒尺寸的影响,结果表明:巯基单体官能度和分子尺寸的增加导致先驱体陶瓷的结晶度提高以及平均晶粒尺寸降低;巯基单体相对含量的增加导致先驱体陶瓷的结晶度增加,乙烯基与巯基摩尔比为1:0.5时平均晶粒尺寸出现峰值;β-Si3N4粉体惰性填料的加入能明显抑制先驱体陶瓷的尺寸收缩.     

巯基-乙烯基点击反应在紫外光固化过程中的应用

巯基-乙烯基反应是点击化学中的一类重要反应,在紫外光固化过程中通过添加巯基化合物可以克服自由基聚合过程中的氧阻聚、光引发剂小分子碎片等,因而近年来在紫外光固化过程中引入巯基-乙烯基点击反应成为紫外固化材料领域的前沿研究内容。文中综述了近年来巯基-乙烯基点击反应在紫外光固化过程中的研究成果,详细介绍了巯基-乙烯基反应在紫外光固化过程中的优缺点、反应机理、分子选择及分子设计原理,最后对巯基-乙烯基反应在紫外光固化过程中的进一步应用前景做了展望。     

可光聚合的高官能度甲基丙烯酸酯单体的合成与表征

可光聚合的高官能度甲基丙烯酸酯单体以丁二醇为起始剂,与马来酸酐和甲基丙烯酸缩水甘油酯(GMA)逐步反应制备。红外光谱和核磁共振波谱对其结构进行表征,实时红外探讨了高官能度甲基丙烯酸酯单体的光聚合动力学,动态力学分析和热重分析研究了其固化膜的动态力学性能和热稳定性。结果表明,随着单体官能度的增加,其光聚合速率逐渐增加,最终双键转化率逐渐降低。储能模量、玻璃化转变温度及最高分解温度随着官能度数的增加而增大,G5固化交联后储能模量达27.9×108Pa,玻璃化转变温度为117.8℃,最高分解温度为405.4℃。官能度对不同基材的附着力基本没有影响,单体在聚碳酸酯(PC)板上的附着力最好,剥离率为1%,铅笔硬度5H。     

多官能度粉末涂料的合成及固化研究

以四甲基氯化铵为催化剂,双酚A型环氧树脂与环氧氯丙烷合成了多官能度的粉末状环氧树脂,然后以四丁基溴化铵为催化剂,将多官能度环氧树脂与丙烯酸反应生成多官能度环氧丙烯酸酯。讨论了催化剂对合成多官能度环氧丙烯酸酯的影响,并考察了多官能度环氧丙烯酸酯固化后的物理机械性能。采用IR、TGA、NMR和冲击试验等手段,对其结构和性能进行了研究。结果表明:环氧氯丙烷成功接枝到环氧树脂中,丙烯酸成功接枝到多官能度环氧树脂中,多官能度环氧丙烯酸酯具有更优良的物理机械性能和耐溶剂性,可以满足工业生产的要求。     

紫外光固化含氟聚氨酯弹性涂层的制备及性能研究

以异佛尔酮二异氰酸酯(IPDI)、端羟基聚丁二烯(HTPB)、1,4-丁二醇(BDO)和丙烯酸羟乙酯(HEA)为主要原料制备了双键封端的聚氨酯树脂,通过红外、核磁对聚氨酯的结构进行了表征,结果表明合成的聚氨酯结构明确;对合成的聚氨酯树脂进行氟改性,当氟单体用量增加到8%时,聚氨酯弹性涂层的铅笔硬度由2B提高到HB,光泽度由67.5°提高到78.2°,接触角由85.4°上升到108.3°;利用巯基-烯反应速率快、氧阻聚效应小的特点,在体系中加入多官能的巯基化合物,结果表明聚氨酯涂层的表干时间由32s缩短到12s,光泽度由78.2°提高到86.8°,铅笔硬度由HB提高到了H。     

巯基-烯点击反应制备含不同功能端基的环三磷腈衍生物

环三磷腈衍生物在阻燃添加剂、生物医药材料、电解液和液压油等领域有着广泛的应用前景,因此,近年来环三磷腈衍生物的功能化改性研究受到越来越多的关注。利用巯基化合物与丁香酚氧基环三磷腈在紫外光下的巯基-烯点击反应,制备了末端分别含有烷基、羟基和羧基等不同功能基团的系列环三磷腈衍生物,研究了反应时间、投料比和巯基反应物所带的端基官能团对反应的影响规律。发现此方法具有反应条件温和,反应时间短(≤30min),反应产率高(≥95%),可批量制备的优点;同时还可以将具有不同结构的功能基团定量的引入到目标产物中。对产物的热性能表征结果表明,C—S键的引入降低了环三磷腈衍生物的热稳定性,但产物的起始分解温度依然保持在300℃以上;末端基团的种类对产物的热稳定性和受热分解后的残炭量有一定影响。     

多官能度大分子交联剂对硅橡胶耐热性能的影响

以多官能度的聚甲基甲氧基硅氧烷(PMOS)作为大分子交联剂,与端羟基聚硅氧烷橡胶通过室温水解缩合反应而固化。多官能度的PMOS在硅橡胶中原位生成了大量高密度多官能度的PMOS相,使硅橡胶的交联密度增大。热重法(TG)测试表明,多官能度的PMOS交联硅橡胶500℃的质量残留率为66%,计算得出热降解反应级数为0.974、热降解反应表现活化能为78.0 kJ/mol。X射线光电子能谱分析(XPS)表明多官能度的PMOS相阻碍了硅橡胶的热降解反应,提高了硅橡胶的耐热性能。     

Stimulus-responsive fluidic dispersions of rod shaped liquid crystal polymer colloids

Electrically responsive liquid crystal polymer nanorods were fabricated by template synthesis. Liquid crystal monomers are templated by alumina membranes. Molecular ordering of the liquid crystal molecules resulted from the confinement in the sub-micron channels and this ordering can be captured permanently through photo-polymerization. Template removal and sonication result in individual rods that can be reoriented by applied electrical and magnetic fields. Such anisotropic particles have significant potential applications in electro-rheological fluids and in active mixing in microfluidic channels.     

Multifunctional polydiacetylene-graphene nanohybrids for biosensor application

Graphene nanosheet hybridized with polydiacetylene (PDA) can be used as the electrochemical biosensor applications. Self-assembly and photo-polymerization chemistry of diacetylenic monomers on reduced graphene oxide (RGO) for non-covalent functionalization were used for high solubility and further functionality of graphene in water necessary for biosensor application. This enables regular graphene micropatterns to be formed on large substrates with chemical bonding and biological interactions. The PDA/RGO nanohybrids demonstrated the formation of conjugated polymer on graphene for fluorescence and electrochemical detection. The optical and structural properties of PDA/RGO, characterized by UV-Vis, FT-IR, Raman, and photoluminescence spectrometers, demonstrated that PDA and RGO in PDA/RGO are connected by physical interactions. Further-functionalization action of PDA/RGO with biotin was verified in microfluidic biochip via biotin-straptavidin interaction. Here, the applicability of functionalized RGO in the biochip and biosensing platform based on fluorescence detection was confirmed. The electrochemical experiments showed the potential of functionalized RGO for use as an electrochemical biosensor, especially with the detection of an analyte at low concentration.     

Synthesis of core-shell nanoparticles using organic surface-functionalized gold and Au@SiO2 nanoparticles as multifunctional initiators in atom transfer radical polymerization

Gold and Au@SiO2 nanoparticles were synthesized and surface-functionalized by initiators for atom transfer radical polymerization (ATRP), either using a thiol or a trialkoxysilane anchor group for the immobilization of the initiating functionality. The thus obtained initiator-capped gold systems were applied in polymerizations of various monomers, such as styrene, methacrylic acid trimethyloxysilyl propylester and isoprene and copolymers thereof. The final inorganic-organic core-shell nanoparticles were characterized applying different techniques such as electron microscopy and light scattering. Kinetic studies of the polymerizations revealed that they were highly controlled and therefore the thickness of the polymer shell could be easily adjusted. The obtained nanoparticles formed stable suspensions in various organic solvents and can therefore be used as building blocks for polymer nanocomposites.     

一种新型PDLC薄膜电-光性能的研究

选用丙烯酸胆固醇酯/甲基丙烯酸β-羟乙酯/液晶复合体系,在紫外光照射下制备聚合物分散液晶薄膜.研究了两种丙烯酸酯类单体的配比对聚合物分散液晶薄膜的电-光性能的影响规律,由此确定了制备综合电-光性能优异的PDLC薄膜材料的最佳制备条件.     

Effect of molecular monomer structure on the composition and properties of BN via the preceramic polymer route

Boron nitride (BN) ceramics were prepared via the preceramic polymer route from two (alkylamino)borazine (AAB) monomers. The effect of monomer structure on the chemical composition, microstructure, oxidation resistance and high-temperature stability of BN was investigated. The two ceramics were characterized by elemental analysis (EA), IR, XPS, XRD, HRTEM and TGA. With similar composition, BN derived from symmetric monomer had a higher crystallinity and exhibited better oxidation resistance/high temperature stability. This is due to that the structure of symmetric molecular derived polymeric precursor is close to that of hexagonal BN (h-BN).     

Influence of molecular tilt angle on the SHG response of pyroelectric liquid crystal polymers

Second harmonic generation in novel pyroelectric liquid crystal polymers (PLCP) made from a series binary mixtures, was studied using 1100 nm as the fundamental wavelength. The PLCPs were prepared by photo-polymerization of binary mixtures of two monomers which exhibit a smectic C^* phase, A2c (4″-(R)-(−)-2-[(10-acrylo-yloxy)decyl]oxy-3-nitrophenyl 4-{4′-[(11-acryloyloxy)-undecyloxy]phenyl}benzoate) and Alb (4″-((R)-(+)-2-octyloxy)-3″-nitrophenyl 4-(4′-(11-acryloyloxy)undecyloxy)-phenyl)-benzoate). The highest d₁₆ and d₂₃ coefficients were found to be in the range 0.65–0.8 pm/V, and differed depending on the detailed preparation of the sample. All cases of polymers formed from the chiral smectic C* phase showed an SHG-signal with no external field present, indicating that polar order became fixed. The SHG-signal was found to increase with the tilt angle of the FLC molecules.     

Novel Additive Manufacturing Materials for Waste Heat Deduction

Herein, three material approaches, for the fabrication of thermally conductive and yet electrically insulating parts via additive manufacturing (AM) technologies, are described. Samples are prepared from light-curable resins, sol–gel-hybrid polymers, and thermoplastic materials using thermally conductive particles as fillers. AM sample preparation is done using vat photo-polymerization and material extrusion with subsequent measurements of thermal conductivity and electrical insulation properties. The main goal herein in addition to material development is the demonstration of manufacturing applicability including usage properties. Use cases are heat sinks for power electronics, which have to be thermally conductive to spread the generated heat and electrically insulating to ensure general functionality and long-term operation.     

Micro- and nanospheres from preceramic polymers: process parameters and size control

Polymeric and porous ceramic micro- and nanospheres were prepared by a simple solidification process with a liquid preceramic polymer in an oil–water-emulsification process. The system was composed of a water-crosslinkable poly(methoxymethylsiloxane) as the preceramic polymer and a linear hydroxyl-terminated poly(dimethylsiloxane) as a source for in situ water generation. Emulsification followed by subsequent curing was carried out via an ultrasonic treatment in the presence of surfactants and a crosslinking active organometallic catalyst. The rheological behavior of the polymeric base system was characterized and the crosslinking behavior was investigated as a function of catalyst concentration and temperature. Effects of composition and processing parameters such as energy input and type and concentration of the surfactant were determined with respect to the microstructure and particle size distribution of the obtained polymeric spheres. The particle diameters of the as-synthesized spheres were mainly in the sub-micron range. Pyrolysis was performed in argon atmosphere at 1073.15 K resulting in the formation of amorphous ceramics under shape retention.     

SiBNC体系陶瓷先驱体的研究进展

分别对SiBN、SiBC和SiBNC陶瓷先驱体及其单源先驱体的制备进行了综述。总的来说,陶瓷先驱体的制备可以分为两大类,即采用不同分子的共缩合和单源先驱体的缩聚两种路径。后者由于其单源先驱体分子具有最终陶瓷产物中所具有的组成和结构特征,并且这种特征能保持到最终的产物中,因而最受关注。同时对两种制备方法的发展前景作了初步的分析与讨论。