一种新的可控/活性自由基聚合方法——DPETTX调节苯乙烯自由基聚合研究

可控/活性自由基聚合(CLRP)自20世纪末以来获得了非常迅猛的发展,但由于已有方法的缺陷和局限,限制了其工业化规模应用.因此,开发可控、活性程度更高、更加简单实用且环境友好的CLRP新方法具有重要意义.本文制备了一种芳香环状硫醚化合物9-(1-苯乙基)-9-((1-苯乙基)硫基)-9H-硫杂蒽DPETTX,对其单独引发和与少量偶氮二异庚腈(ABVN)共同引发苯乙烯(St)聚合的行为进行了系统评价.结果表明,DPETTX可在高温(100℃)下单独引发St聚合,但引发效率较低;当其与少量ABVN共用时,可使St在低温下(55℃)聚合,聚苯乙烯(PS)的数均分子量(M_n)随转化率升高而不断增大,如摩尔比ABVN/DPETTX=0.05/1时,M_n从2.7万增长到4.6万.该基于DPETTX和少量ABVN的共引发体系,打开了一条开发新可控/活性自由基聚合体系的路径.     

Enhancing the thermoelectric performance through the mutual interaction between conjugated polyelectrolytes and single-walled carbon nanotubes

We present a method of constructing composites composed of conjugated polyelectrolytes(CPEs)and singlewalled carbon nanotubes(SWCNTs)to obtain a high-performing flexible thermoelectric generator.In this approach,three kinds of polymers,namely,poly[(1,4-(2,5-didodecyloxybenzene)-alt-2,5-thiophene](P1),poly[(1,4-(2,5-bis-sodium butoxysulfonate-phenylene)-alt-2,5-thiophene](P2),and poly[(1,4-(2,5-bis-acid butoxysulfonic-phenylene)-alt-2,5-thiophene](P3)are designed,synthesized and complexed with SWCNTs as thermoelectric composites.The electrical conductivities of the CPEs/SWCNTs(P2/SWCNTs,and P3/SWCNTs)nanocomposites are much higher than those of non-CPEs/SWCNTs(P1/SWCNTs)nanocomposites.Among them,the electrical conductivity of P2/SWCNTs with a ratio of 1:4 reaches 3686 S·cm^-1,which is 12.4 times that of P1/SWCNTs at the same SWCNT mass ratio.Moreover,CPEs/SWCNTs composites(P2/SWCNTs)display remarkably improved thermoelectric properties with the highest power factor(PF)of 163μW·m^-1·K^-1.In addition,a thermoelectric generator is fabricated with P2/SWCNTs composite films,and the output power and power density of this generator reach 1.37μW and 1.4 W·m;(cross-section)at△T=70 K.This result is over three times that of the thermoelectric generator composed of non-CPEs/SWCNTs composite films(P1/SWCNTs,0.37μW).The remarkably improved electrical conductivities and thermoelectric properties of the CPEs/SWCNTs composites(P2/SWCNTs)are attributed to the enhanced interaction.This method for constructing CPEs/SWCNTs composites can be applied to produce thermoelectric materials and devices.     

颜色指示法高通量筛选多相催化材料

介绍一种简单的组合化学技术, 用来筛选或优化多相催化反应中的催化剂. 在酯化反应中, 用甲基橙指示剂指示酯化反应的进程并对沸石的类型, 不同碳链的醇和酸的催化活性进行研究. 在光催化反应中, 选择甲基橙、罗丹明B作为反应物. 通过颜色变化, 对不同方法制备的TiO2进行高通量筛选.     

聚(3-羟基丁酸酯-co-3-羟基戊酸酯)改性及纤维成形北大核心CSCD

聚(3-羟基丁酸酯-co-3-羟基戊酸酯)(PHBV)是一种微生物发酵生产的热塑性聚合物。从物理、化学改性及其纤维成形两个方面综述了PHBV的研究进展。PHBV的物理改性主要有无机纳米粒子共混体系(PHBV/iNPs)、有机纳米晶共混体系(PHBV/oNPs)、高聚物共混体系(PHBV/Polymer)和绿色全降解共混体系;化学结构构筑主要包括接枝共聚改性、嵌段共聚改性、端基扩链改性等。从改性的手段及介质,分析了改性方法的优缺点。PHBV纤维的成形方法主要有熔融纺丝法、干法纺丝法及静电纺丝法。从PHBV纤维应用领域看,熔融纺纤维应用目标在于替代现有石油基相关产品,而静电纺纤维主要应用于开拓组织工程再生医学领域。最后,对PHBV今后的研究及发展提出了展望。     

Facile fabrication of highly flexible,porous PEDOT: PSS/SWCNTs films for thermoelectric applications

High-performance organic composite thermoelectric(TE)materials are considered as a promising alternative for harvesting heat energy.Herein,composite films of poly(3,4-ethyienedioxythiophene):poly(styrene sulfonate)/single-walled carbon nanotubes(PEDOT:PSS/SWCNTs)were fabricated by utilizing a convenient solution mixing method.Thereafter,the as-prepared hybrid films were treated using sulfuric acid(H₂SO₄)to further optimize the TE performance.Film morphological studies revealed that the sulfuric acid treated PEDOT:PSS/SWCNTs composite samples all possessed porous structures.Due to the successful fabrication of highly conductive networks,the porous nano-architecture also exhibited much more excellent TE properties when compared with the dense structure of the pristine samples.For the post-treated sample,a high power factor of 156.43μW·m^-1·K^-2can be achieved by adjusting the content of CNTs,which is approximately 3 orders of magnitude higher than that of the corresponding untreated samples(0.23μW·m^-1·K^-2).Besides,the obtained films also showed excellent mechanical flexibility,owing to the porous nanostructure and the strong p–p interactions between the two components.This work indicates that the H₂SO₄ treatment could be a promising strategy for fabricating highly-flexible and porous PEDOT:PSS/SWCNTs films with high TE performances.     

利用化学指示剂在多相催化反应中进行高通量筛选

 介绍了一种简单的组合化学技术,该技术利用催化反应中产物或反应物导致的化学指示剂的颜色变化快速地指示反应进程. 选用甲基橙为指示剂,分子筛为催化剂,考察了不同反应条件下羧酸的酯化反应,并用气相色谱和高效液相色谱分析方法对实验结果进行验证. 结果表明,利用化学指示剂进行的高通量颜色筛选结果与色谱检测结果很好地吻合,该方法具有简单和高效的特点,可应用于对化学指示剂敏感的反应.     

反相液相色谱法测定农药中氯菊酯

建立反相液相色谱法测定农药中氯菊酯含量的方法.采用C18反相色谱柱(250 mm×4.6 mm,5μm),以甲醇–水溶液(体积比为9:1)为流动相,流量为0.8 mL/min,检测波长为230 nm,柱温为35℃,进样体积为10μL,以外标法测定农药中氯菊酯的含量.氯菊酯的质量浓度在1～200μg/mL范围内与色谱峰面...     

铪掺杂对锆钛酸钡钙陶瓷电学性能的调控

用固相反应法制备了B位Hf掺杂的Ba_0.95Ca_0.05 Zr_0.05Ti_0.95-xHf_x (BCZ_0.05T_(0.95-x)-xH) (x=0、0.02、0.04、0.06和0.08)陶瓷。研究B位同时含有Hf、Zr、Ti三种元素时,BCZ_0.05T_(0.95-x)-xH陶瓷的相结构变化与电学性能的差异。XRD测试结果表明：Hf₄₊^融入晶格,造成晶格膨胀。BCZ_0.05T_(0.95-x)-xH(x=0、0.02)陶瓷的XRD测试结果表明,该体系中存在明显的四方相与正交相共存的多晶型相转变(PPT),但正交相逐渐转变为主晶相;BCZ_0.05T_(0.95-x)-xH (x=0.04、0.06)陶瓷的XRD结果表明,四方相进一步减少,三方相却逐渐增加;当x继续增大到0.08时,XRD测试发现该体系只存在正交相和三方相结构。SEM测试发现,随着Hf的掺杂量增加,晶粒尺寸逐渐减小。剩余极化随Hf掺杂量的增加先增大再减小,在x为0.02时取得最大值,Hf掺杂显著降低矫顽场(Ec)。压电测试结果表明BCZ_0.05T_0.96-0.04H陶瓷具有最大压电系数(d₃₃=259 pC/N)。