Haloaldehyde Polymers. XIV. Endgroups in Polychloral

Chloral polymers prepared by anionic polymerization have alkoxide endgroups as terminal ends at the end of this polymerization. The initiating anion has, as expected, no influence on the type of terminal group formed. Polychloral with terminal alkoxide ends degrades easily thermally to monomeric chloral. Alkoxide endgroups in polychloral do not readily react with alkylating or acylating agents, although partial stabilization has been observed when alkoxide-terminated polymers were allowed to stand for periods of time; the endgroups seem to react either with impurities or with excess chloral in side reactions. With protic acids, alkoxide-terminated polychloral is transformed into hydroxyl-terminated polymer of higher thermal stability. Studies of the initiation step of the chloral polymerization revealed that above the ceiling temperature of polymerization, strong nucleophiles, such as soluble tertiary butoxide, initiate quantitatively, but polymerization does not proceed until the mixture is cooled. When chloral is initiated with weaker nucleophiles such as chloride or carboxylates, the initiation equilibrium is not on the side of the initiated species, although it shifts effectively as polymerization proceeds; with carboxylates as initiators the ester group has been found incorporated as the initial endgroup in polychloral. With sufficient amounts of lithium tertiary butoxide as anionic initiator, polychloral of low molecular weight was prepared. This polymer does not react with end-capping reagents (other than PCl₅) as does high molecular weight polychloral; in spite of considerable effort it was not possible to prepare low molecular weight soluble polychloral or oligomeric polychloral. Polychloral prepared with cationic initiators is thermally more stable than unstabilized anionically initiated polychloral but is generally crumbly and incoherent. The end-groups of such polymers are usually hydroxyl endgroups. Identification of endgroups of the polymers has been done where possible by IR spectroscopy, for the initiation reaction by NMR spectroscopy, but for high molecular weight insoluble polymers almost exclusively by comparative thermal polymer degradation.     

Optically Active Particles of Chiral Polymers

Particles constructed by chiral polymers (defined as PCPs) have emerged as a rapidly expanding research field in recent years because of their potentially wide‐ranging applications in asymmetric catalysis, enantioselective crystallization, enantioselective release, amongst many others. The particles show considerable optical activity, due to the chirality of the corresponding polymers from which the particles are derived. This review article presents an overview on PCPs with emphasis on our group's recent achievements in the preparation of PCPs derived from optically active helical polymers and their applications. PCPs can be prepared via emulsion polymerization, precipitation polymerization, and suspension polymerization by starting from monomers. Emulsification of preformed chiral polymers and self‐assembly approaches also can lead to PCPs. Chiral polymer‐based core/shell particles, hollow particles, and magnetic particles are also covered because of their remarkable properties and significant potential applications.

     

Noncovalent Chiral Functionalization of Graphene with Optically Active Helical Polymers

Optically active helical substituted (co)polyacetylenes containing pendent pyrene groups are prepared and then noncovalently immobilized on graphene via π–π interactions. The resulting graphene composite is characterized by XRD, FTIR, Raman, circular dichroism, UV‐vis absorption, TEM, TGA, and fluorescent spectroscopy techniques. The helical polyacetylene endows graphene with the desired optical activity. Also interestingly, the dispersibility of the functionalized graphene in tetrahydrofuran is remarkably improved due to the presence of the helical polymer chains. The present methodology opens new opportunities and serves as a versatile platform toward preparing novel graphene‐based materials.

     

旋光性高分子的合成（下）

旋光性高分子的合成（下）刘引烽，华家栋（上海科技大学化学系，上海，２０１８００）４不对称聚合由外消旋手性单体制备旋光性高分子必须通过选择性聚合才能实现。选择性聚合是指外消旋的两个对映异构单体进行聚合时，由于体系中存在着某种不对称的诱导因素，其中之一比...     

Haloaldehyde Polymers. XIX. Degradation Behavior of Chloral Polymers

Thermal stability of samples of polychloral prepared with different initiators and treated with various endcapping agents was studied using differential thermogravimetric analysis (DTG). Four temperature regions at which maxima of DTG curves occur were identified. On the basis of the known mechanism of initiation and the possible mechanism of termination, the structures of both initial and terminal endgroups of individual polychloral samples were elucidated which enabled the identification of the specific temperature region of thermal degradation of polychloral molecules having a specific type of endgroup. These results were confirmed by studies of the DTG curves of chloral-isocyanate copolymers containing stable terminal fragments with a high content of urethane linkages.     

旋光性聚合物的铁电性能

旋光性高分子在结构上具有一定的空间特异性,因而可以有多种应用。根据铁电材料所必需具备的条件,经过特定的分子结构设计,可以使之具备铁电性能,据此,人们已合成了许多不同类型的铁电聚合物。本文按照铁电聚合物所处的聚集态不同,分别综述了具有铁电特性的晶态和液晶态旋光性聚合物的种类、结构特点及其铁电性能,分析讨论了影响液晶态旋光性聚合物的自发极化率和响应时间的因素。     

Optically Active Helical Vinylterphenyl Polymers: Chiral Teleinduction in Radical Polymerization and Tunable Stereomutation

Helical vinyl aromatic polymers are emerging as interesting chiral materials due to their dynamic tailorability, synthetic simplicity, and outstanding chemical and physical stabilities. This Personal Account discusses long‐range chirality transfer in the radical polymerization of vinylterphenyl monomers and tunable stereomutation of the resultant polymers. It begins with a general introduction to the design, synthesis, and characterization of helical poly{(+)‐2,5‐bis[4′‐((S)‐2‐methylbutyloxy)phenyl]styrene}, the first one of this series of polymers. Then, long‐range chirality transfer during radical polymerization of terphenyl‐based vinyl monomers is explained. After that, the chiroptical property control of the resultant polymers by means of the transition from kinetically controlled conformation to thermodynamically controlled conformation and external stimulus is described. This Personal Account concludes by discussing the advantages and disadvantages of the strategy of using vinylterphenyls to obtain optically active helical polymers and providing a short outlook, especially emphasizing the importance of tacticity on the chiroptical properties of polymers.     

旋光性高分子的旋光能力（下）

在（上）中，我们讨论了结构单元及其远程作用对旋光性高分子旋光能力的影响。由于高分子具有特殊的长链结构，因而链形态对旋光能力的贡献尤其引人注目。     

含金鸡钠碱的光活性聚合物：2.含辛可宁的两亲单体及其两亲聚合物

通过两亲单体２－丙烯酰胺基烷磺酸与辛可宁成盐后再聚合，或ＡＭＣｎＳ聚合成梳型两亲聚合物后再生ＣＮ成盐，可获得含辛可宁的两亲聚合物。ＡＭＣｎＳ－ＣＮ盐及其相应的两亲聚合物具有比ＣＮ好得多的溶解性，易溶于氯仿、ＴＨＦ、乙醇、ＤＭＦ和ＤＭＳ等极性不同的溶剂。ＡＭＣｓＳ－ＣＮ盐好得多的溶解性，易溶于氯仿、ＴＨＦ、乙醇、ＤＭＦ和ＤＭＳＯ等极性不同的溶剂。ＡＭＣｎＳ－ＣＮ盐在乙醇／氯仿（Ｖ／Ｖ＝１／２）中比旋     

手性环胍衍生物的合成

以L-天冬酰胺为原料经十步反应合成了光学纯的手性双环胍, 总收率为2.2%. 这一合成方法的优点是避免使用剧毒的硫光气和气味难闻的有机硫化物     

Synthesis of Optically Active P‐Chiral and Optically Inactive Oligophosphines

A series of optically active P‐chiral oligophosphines (S,R,R,S)‐ 2 , (S,R,S,S,R,S)‐ 3 , (S,R,S,R,R,S,R,S)‐ 4 , and (S,R,S,R,S,R,R,S,R,S,R,S)‐ 5 with four, six, eight, and 12 chiral phosphorus atoms, respectively, were successfully synthesized by a step‐by‐step oxidative‐coupling reaction from (S,S)‐ 1 . The corresponding optically inactive oligophosphines 1′ – 5′ were also prepared. Their properties were characterized by DSC, XRD, and optical‐rotation analyses. While optically active bisphosphine (S,S)‐ 1 and tetraphosphine (S,R,R,S)‐ 2 behaved as small molecules, octaphosphine (S,R,S,R,R,S,R,S)‐ 4 and dodecaphosphine (S,R,S,R,S,R,R,S,R,S,R,S)‐ 5 exhibited the features of a polymer. Furthermore, DSC and XRD analyses showed that hexaphosphine (S,R,S,S,R,S)‐ 3 is an intermediate between a small molecule and a polymer. Comparison of optically active oligophosphines 1 – 5 with the corresponding optically inactive oligophosphines 1′ – 5′ revealed that the optically active phosphines have higher crystallinity than the optically inactive counterparts. It is considered that the properties of oligophosphines depend on the enantiomeric purity as well as the oligomer chain length.     

Optically Active Organometallic Compounds of Transition Elements with Chiral Metal Atoms

Chiral transition metal atoms are not only present in tris-chelate complexes [M(LL)₃]ⁿ⁺, which were already resolved into the enantiomers by Alfred Werner, but also in organometallic half-sandwich complexes such as 1 with three- or four-legged piano-stool structure. These complexes have been tools in the elucidation of the spatial course of reactions and in organic syntheses. Applications in enantioselective catalysis are beginning to show up.     

主链光学活性聚合物与手性催化剂

自从 50年代早期发现 Ziegler- Natta催化剂以来 [1] ,立体有规聚合研究迅速发展 .80年代初 ,Kaminsky等 [2 ] 以手性配体锆化合物为催化剂 ,得到了高度等规的聚丙烯及聚 1 -丁烯 ,为 Ziegler-Natta催化剂均相化开拓了全新局面 .其后 Ziegler-Natta催化剂的一些链引发、链模板增长及终止机理 ,在均相条件下得以充分的研究 [3～ 5] .最近几年 ,又出现了用手性催化剂使无光学活性的单体聚合而成主链光学活性聚合物的研究 [6～ 8] ,并迅速成为金属有机化学家和高分子化学家关注的热点 .合成手性聚合物的研究 ,主要集中在模仿天然聚合物 ,阐…     

Attempt to Resolute Chiral Clusters by Optically Active Hydrazide

Due to the framework chirality optically active clusters can provide the proof that a cluster as a whole, and not one of its fragments, acts as a catalyst, most of the work have been directed to the synthesis of tetrahedron-type chiral clusters1-3. However, there remains another major problem to obtain the pure enantiomers. Although Vahrenkamp had obtained some pioneering results in this area before 19901, only several racemic chiral clusters have been separated into pure enantiomers until now…     

Haloaldehyde Polymers. XXX. Macromolecular Asymmetry as the Basis of Optical Activity in Polymers

The synthesis of polymers characterized by a preferred helical screw sense (macromolecular asymmetry) is a subject of considerable experimental interest. Here, we summarize our efforts toward the preparation of optically active polychloral in which asymmetry at the macromolecular level is the only factor contributing to the polymer's chiroptical properties. Through the use of chiral initiating species, we have prepared optically active polychloral with specific rotations reaching 4500° at the sodium D-line. The results of this work and the prospects for further investigation are outlined.     

Chiral Detection with Coordination Polymers

Coordination polymers and metal-organic frameworks are prime candidates for general chemical sensing, but the use of these porous materials as chiral probes is still an emerging field. In the last decade, they have found application in a range of chiral analysis methods, including liquid- and gas-phase chromatography, circular dichroism spectroscopy, fluorescence sensing, and NMR spectroscopy. In this minireview, we examine recent works on coordination polymers as chiral sensors and their enantioselective host-guest chemistry, while highlighting their potential for application in different settings.     

基于1,1'-联-2-萘酚衍生物的手性荧光传感器

具有光活性的1,1′-联-2-萘酚（BINOL）衍生物是近年来研究较多的C2轴不对称芳香化合物,不仅具有很强的手性诱导作用,而且在适合结构基团修饰下能产生很强的荧光,可作为一类有效而灵敏的荧光化学传感器。在与手性胺、氨基醇、氨基酸、α-羟基羧酸、手性醇和单糖等手性有机化合物作用时,该荧光化学传感器在不同识别位点接受客体分子、通过光诱导电子转移（PET）及电子交换能量转移（EET）等引起共轭高分子内能级发生变化,使得所有这些相互作用十分灵敏地在其发光强度和能量上反映出来,具体表现在化学传感器荧光增强与减弱或发射波长的变化上。本文总结了近年来1,1′-联-2-萘酚衍生物的荧光化学传感器在手性异构体识别领域的最新研究进展。     

Optically Active Chiral Auxiliary Benzyloxyphenylglycinol for Preparation of Oxazolidine and Its Derivatives

To investigate the recovery of amino alcohols as chiral auxiliaries, optically active p-benzyloxyphenylglycinol and its corresponding oxazolidine of 1-naphthylcarboxaldehyde were prepared. Grignard additions to the oxazolidine followed by electrophilic quench and acidic hydrolysis afforded an aldehyde( compound 8) (later it was reduced to an alcohol, compound 9) in an excellent enantiomeric excess and a good recovery of the chlral amino alcohol. This research provides a model study of chiral amino alcohols in solid phase asymmetric synthesis.