基于乙炔基-苯并噁嗪单元双重交联反应的聚酰亚胺树脂的制备与性能

为开发可低温固化的聚酰亚胺树脂, 通过分子结构设计将苯并噁嗪单元引入聚酰亚胺树脂中, 合成了含苯并噁嗪单元及乙炔基封端的双官能化新型聚酰亚胺预聚体(PIBzA). 经高温处理, 苯并噁嗪单元发生开环交联, 同时, 乙炔基端基发生三聚成环反应, 从而在固化树脂中形成双重交联网络结构. 苯并噁嗪单元的引入使聚酰亚胺树脂最快固化反应温度降低约32 ℃, 有效降低了固化温度. 同时, 苯并噁嗪单元的引入未大幅度降低树脂的耐热稳定性, 其玻璃化转变温度(T_g)介于266~290 ℃之间, 5%热失重温度(T_d,5%)接近500 ℃, 依然可以满足耐高温复合材料的应用需求. 此外, PIBzA固化树脂具有低介电特性, 其介电常数k介于2.3~3.0, 介电损耗介于0.002~0.008, 可满足透波复合材料及先进微电子封装材料的应用需求.     

胶黏剂中的化学*——2020年美国国家化学周活动介绍及启示

重点介绍2020年美国国家化学周——“胶黏剂中的化学”实验活动,对科学阅读和采访未来科学家活动作简要介绍。以此得出本次化学周活动对我国化学教学的几点启示:(1)大概念视角,加深结构化认识;(2)扎根实践,提高应用意识;(3)鼓励探析,深化本质意识;(4)跨界科学,渗透STSE理念;(5)精选主题,凸显微型项目;(6)勤研善思,塑造优秀品格。     

Insight into the reaction mechanism of sulfur chains adjustable polymer cathode for high-loading lithium-organosulfur batteries

Small molecules with adjustable sulfur atoms in the confined structure were acted as precursor for the synthesis of polymer cathodes for lithium-organosulfur batteries.Among them,poly(diallyl tetrasulfide)(PDATtS)delivered a high capacity of 700 mAh g^-1,stable capacity retention of 85%after 300 cycles,high areal capacity~4 m Ah cm^-2 for electrode with up to 10.3 mg cm^-2 loading.New insight into the reaction mechanism of PDATtS electrode that radicals arisen from the homolytic cleavage of S-S bond in PDATtS reacted with Li+to generate thiolates(RSLi)and insoluble lithium sulfides(Li₂S)or lithium disulfide(Li₂S₂)was clearly verified by in-situ UV/Vis spectroscopy,nuclear magnetic resonance(NMR)studies and density-functional theory(DFT)calculations.Therefore,based on the unique reaction mechanism,problems of rapid capacity fading due to the formation of soluble polysulfide intermediates and their serious shuttle effect in conventional lithium-sulfur(Li-S)batteries was totally avoided,realizing the dendrite-free lithium sulfur batteries.This study sets new trends for avenues of further research to advance Li-S battery technologies.     

杂原子B—ZSM—35沸石的干法合成,表征及CO＋H2反应性能的研究

首次利用吸附态模板剂在Ｎａ２Ｏ－ＳｉＯ２－Ｂ２Ｏ３－ＤＥＡ干粉体系中合成了杂原子Ｂ－ＳＺＭ－３５沸石，ＸＲＤ，ＳＥＭ，ＩＲ，及ＣＯ加氢反应研究了其物理化学特性。结果表明，Ｂ原子同晶取代Ａｌ原子进入ＺＳＭ－３５沸石骨加。     

羟基锆及锆铝交联粘土的合成与表征

制备了锆交联粘土和锆铝交联粘土。锆交联粘土制备条件的研究表明，直接用ＺｒＯＣｌ２．８Ｈ２Ｏ水溶液作交联剂，延长老化时间和增大交联剂浓度有利于制备大比表面积高温有序的锆交联粘土。     

Syntheses and Studies of PEG-b-PNIPA Block Polymers

ＳｙｎｔｈｅｓｅｓａｎｄＳｔｕｄｉｅｓｏｆＰＥＧ┐ｂ┐ＰＮＩＰＡＢｌｏｃｋＰｏｌｙｍｅｒｓＣＡＯＷｅｉ－ｘｉａｏ＊＊ａｎｄＺＨＡＮＧＴａｏ（ＣｏｌｅｇｅｏｆＣｈｅｍｉｓｔｒｙａｎｄＭｏｌｅｃｕｌａｒＥｎｇｉｎｅｒｉｎｇ，ＰｅｋｉｎｇＵｎｉｖｅｒｓｉｔ...     

DRY METHOD SYNTHESIS OF PURE SILICEOUS FORM OF ZEOLITE ZSM-35

IntroductionZeoliteZSM-35isclassifiedasfcrricritc(FER)t\pc.x'hicllalsoincludesZSM-ZI.ZSM-38andFER.Zeolitesofthist}'pcha\lcrclatit'CI}UlldiscrinlinablcXRDpattcnlswhichindicatetheirsinlilarit\'illst,u.tu,.,I11.Thehighsiliceousfonllsofthesezeolitesarcgcllcra…     

Systematic investigation of the aza-Cope reaction for fluorescence imaging of formaldehyde in vitro and in vivo

Increasing evidence has highlighted the endogenous production of formaldehyde (FA) in a variety of fundamental biological processes and its involvement in many disease conditions ranging from cancer to neurodegeneration. To examine the physiological and pathological relevance and functions of FA, fluorescent probes for FA imaging in live biological samples are of great significance. Herein we report a systematic investigation of 2-aza-Cope reactions between homoallylamines and FA for identification of a highly efficient 2-aza-Cope reaction moiety and development of fluorescent probes for imaging FA in living systems. By screening a set of N-substituted homoallylamines and comparing them to previously reported homoallylamine structures for reaction with FA, we found that N-p-methoxybenzyl homoallylamine exhibited an optimal 2-aza-Cope reactivity to FA. Theoretical calculations were then performed to demonstrate that the N-substituent on homoallylamine greatly affects the condensation with FA, which is more likely the rate-determining step. Moreover, the newly identified optimal N-p-methoxybenzyl homoallylamine moiety with a self-immolative β-elimination linker was generally utilized to construct a series of fluorescent probes with varying excitation/emission wavelengths for sensitive and selective detection of FA in aqueous solutions and live cells. Among these probes, the near-infrared probe FFP706 has been well demonstrated to enable direct fluorescence visualization of steady-state endogenous FA in live mouse brain tissues and elevated FA levels in a mouse model of breast cancer. This study provides the optimal aza-Cope reaction moiety for FA probe development and new chemical tools for fluorescence imaging and biological investigation of FA in living systems.

Systematic investigation of various homoallylamines reveals N-p-methoxybenzyl homoallylamine as the optimal 2-aza-Cope reaction moiety for development of highly efficient formaldehyde fluorescent probes for in vitro and in vivo imaging.     

Pure Graphene Oxide Vertical p–n Junction with Remarkable Rectification Effect

Graphene p-n junctions have important applications in the fields of optical interconnection and low–power integrated circuits. Most current research is based on the lateral p-n junction prepared by chemical doping and other methods. Here, we report a new type of pure graphene oxide (pGO) vertical p-n junctions which do not dope any other elements but only controls the oxygen content of GO. The I–V curve of the pGO vertical p–n junction demonstrates a remarkable rectification effect. In addition, the pGO vertical p–n junction shows stability of its rectification characteristic over long-term storage for six months when sealed and stored in a PE bag. Moreover, the pGO vertical p–n junctions have obvious photoelectric response and various rectification effects with different thicknesses and an oxygen content of GO, humidity, and temperature. Hall effect test results show that rGO is an n–type semiconductor; theoretical calculations and research show that GO is generally a p–type semiconductor with a bandgap, thereby forming a p–n junction. Our work provides a method for preparing undoped GO vertical p–n junctions with advantages such as simplicity, convenience, and large–scale industrial preparation. Our work demonstrates great potential for application in electronics and highly sensitive sensors.