Crystal‐to‐Crystal Synthesis of Helically Ordered Polymers of Trehalose by Topochemical Polymerization

The synthesis of crystalline helical polymers of trehalose via topochemical azide–alkyne cycloaddition (TAAC) of a trehalose‐based monomer is presented. An unsymmetrical trehalose derivative having azide and alkyne crystallizes in two different forms having almost similar packing. Upon heating, both the crystals undergo TAAC reaction to form crystalline polymers. Powder X‐ray diffraction (PXRD) studies revealed that the monomers in both the crystals polymerize in a crystal‐to‐crystal fashion; circular dichroism (CD) studies of the product crystals revealed that the formed polymer is helically ordered. This solvent‐free, catalyst‐free polymerization method that eliminates the tedious purification of the polymeric product exemplifies the advantage of topochemical polymerization reaction over traditional solution‐phase polymerization.     

Fabrication of Large Single Crystals for Platinum‐Based Linear Polymers with Controlled‐Release and Photoactuator Performance

Preparation of large single crystals of linear polymers for X‐ray analysis is very challenging. Herein, we employ a coordination‐driven self‐assembly strategy to secure the appropriate head‐to‐tail alignment of anthracene moieties, and for the first time obtained large‐sized Pt‐based linear polymer crystals through a [4+4] cycloaddition of anthracene in a single‐crystal to single‐crystal fashion. Using X‐ray diffraction to determine the polymer crystal structure, we found that both the polymerisation and depolymerisation steps proceed via a stable intermediate. Taking advantage of the temperature‐dependent slow depolymerization, the Pt‐based linear polymer showed potential as a sustained release anticancer drug platform. Utilizing the reversible contraction effect of unit‐cell volume upon irradiation or heating, the stimuli‐responsive crystals were hybridized with polyvinylidene fluoride to obtain a “smart material” with outstanding photoactuator performance.     

Synthesis and Reversible Hydration of a Pseudoprotein,a Fully Organic Polymeric Desiccant by Multiple Single‐Crystal‐to‐Single‐Crystal Transformations

A diphenylalanine derivative, N3‐Phe‐Phe‐NHCH2CCH, was designed for topochemical azide–alkyne cycloaddition (TAAC) polymerization. This dipeptide adopted β‐sheet arrangement as designed, in its crystals, but the azide and alkyne were not fitly aligned for their topochemical reaction. However, the voids present around these groups allowed them to attain a reactive geometry upon heating and their consequent TAAC polymerization to a pseudoprotein in a single‐crystal‐to‐single‐crystal (SCSC) fashion. This motion led to the creation of channels in the product crystal and it absorbed water from the surroundings to fill these channels as H‐bonded water wire. The pseudoprotein undergo reversible hydration/dehydration in SCSC fashion many times under mild conditions: hydration at low relative humidity and dehydration at low temperature. Vapor sorption analyses suggest that this fully organic polymer might be useful as an energy‐efficient desiccant material for controlling indoor humidity.     

开环易位聚合合成瓶刷聚合物

瓶刷聚合物是一类具有独特侧链结构的梳形聚合物。功能性瓶刷聚合物在光子晶体、表面活性剂、医药载体、防污涂层以及智能材料等领域具有良好的应用价值。通过开环易位聚合合成瓶刷聚合物的方法具有合成步骤简单、聚合物接枝密度高和侧链组成均一等优点,在控制聚合物组成、分子量和分散性等方面具有显著优势。本文基于开环易位聚合,简述了合成瓶刷均聚物以及嵌段型、混合型和核-壳型三种类型的瓶刷共聚物的方法,并介绍了合成精确结构的瓶刷聚合物的新进展。     

Modular Approach to Degradable Acetal Polymers Using Cascade Enyne Metathesis Polymerization

A modular synthetic approach to degradable metathesis polymers is presented using acetal‐containing enyne monomers. The monomers are prepared in a short and divergent synthetic sequence that features two points of modification to tune polymerization behavior and introduce molecular cargo. Steric and stereochemical elements are critical in the monomer design in order to provide rapid and living polymerizations capable of generating block polymers. The developed polyacetal materials readily undergo pH‐dependent degradation in aqueous mixtures, and the rate of hydrolysis can be tuned through post‐polymerization modification with triazolinedione click chemistry. This presents a new scaffold for responsive metathesis polymers that may find use in applications that requires controllable breakdown and release of small molecules.     

Photocontrolled Synthesis of n-Type Conjugated Polymers

Current approaches to synthesize π-conjugated polymers (CPs) are dominated by thermally driven, transition-metal-mediated reactions. Herein we show that electron-deficient Grignard monomers readily polymerize under visible-light irradiation at room temperature in the absence of a catalyst. The product distribution can be tuned by the wavelength of irradiation based on the absorption of the polymer. Conversion studies are consistent with an uncontrolled chain-growth process; correspondingly, chain extension produces all-conjugated n-type block copolymers. Preliminary results demonstrate that the polymerization can be expanded to donor–acceptor alternating copolymers. We anticipate that this method can serve as a platform to access new architectures of n-type CPs without the need for transition-metal catalysis.     

多重响应性杂臂星型聚合物的RAFT聚合合成及性能研究

耦合先臂法("arm first")和可逆加成-断裂链转移(RAFT)自由基聚合制备以温度响应性聚(聚乙二醇甲醚丙烯酸酯-co-2-(2-乙氧基乙氧基)乙基丙烯酸酯)(POD)和p H响应性聚丙烯酸二甲氨基乙酯(PDMAEA)为臂,含二硫键的N,N'-双丙烯酰胱胺(BAC)为核的杂臂星型聚合物(MAS).采用傅里叶红外光谱(FTIR)、核磁共振氢谱(1H-NMR)和凝胶渗透色谱(GPC)对聚合物的结构、相对分子质量及分子量分布进行了表征.结果表明,该法能有效控制星型聚合物的合成(分子量分布指数PDI1.3).采用紫外可见吸收光谱法(UV-Vis)、动态光散射(DLS)考察了MAS在水中的相变行为.结果表明,随着臂PDMAEA含量的增加,星型聚合物的LCST增大.当臂POD与PDMAEA的摩尔投料比为5∶5时,聚合物浓度为1 mg/m L时其在纯水中的LCST为38.2℃.     

Synthesis of Responsive Two‐Dimensional Polymers via Self‐Assembled DNA Networks

Despite a growing interest in two‐dimensional polymers, their rational synthesis remains a challenge. The solution‐phase synthesis of a two‐dimensional polymer is reported. A DNA‐based monomer self‐assembles into a supramolecular network, which is further converted into the covalently linked two‐dimensional polymer by anthracene dimerization. The polymers appear as uniform monolayers, as shown by AFM and TEM imaging. Furthermore, they exhibit a pronounced solvent responsivity. The results demonstrate the value of DNA‐controlled self‐assembly for the formation of two‐dimensional polymers in solution.     

Synthesis of Functional Polymers by Post‐Polymerization Modification

Post‐polymerization modification is based on the direct polymerization or copolymerization of monomers bearing chemoselective handles that are inert towards the polymerization conditions but can be quantitatively converted in a subsequent step into a broad range of other functional groups. The success of this method is based on the excellent conversions achievable under mild conditions, the excellent functional‐group tolerance, and the orthogonality of the post‐polymerization modification reactions. This Review surveys different classes of reactive polymer precursors bearing chemoselective handles and discusses issues related to the preparation of these reactive polymers by direct polymerization of appropriately functionalized monomers as well as the post‐polymerization modification of these precursors into functional polymers.     

基团转移聚合法合成A-B型嵌段共聚物

用基团转移聚合法(GTP)合成嵌段共聚物是近年来国际上高分子研究的热门之一.在室温下制备嵌段共聚物是GTP的一大特点.本文利用三类不同GTP单体的活性差别^[1,2],控制适当的加料顺序及聚合条件,首次用GTP法合成含丙烯腈嵌段的A-B型共聚物并进行表征.     

新型萘/苝酰亚胺取代丁二炔衍生物的合成及拓扑聚合

经5步反应制备了萘/苝酰亚胺取代的端炔和碘炔单体, 通过Sonagashira偶联反应合成了2个新型对称丁二炔单体浅黄色粉末2-[4-(4-{4-[7-(庚-3-基)-1,3,6,8-四氧亚基-1,2,3,6,7,8-六氢异喹啉并[6,5,4-def]异喹啉-2-基]苯基}丁-1,3-二炔基)苯基]-7-(辛-4-基)-1,2,3,6,7,8-六氢异喹啉并[6,5,4-def]异喹啉-1,3,6,8-四酮(diNDI)和暗红色粉末2-[4-(4-{4-[1,3,8,10-四氧亚基-9-(二十三烷-12-基)-1,2,3,8,9,10-六氢异喹啉并[6',5',4':9,1,2]蒽并[6,5,10-def]异喹啉-2-基]苯基}丁-1,3-二炔基)苯基]-9-(二十三烷-12-基)-1,2,3,8,9,10-六氢异喹啉并[6',5',4':9,1,2]蒽并 [6,5,10-def]异喹啉-1,3,8,10-四酮(diPDI), 产率分别达60%和70%. 由于NDI和PDI基元的强吸电子作用, diNDI和diPDI表现较低的最低未占分子轨道(LUMO)能级, 分别为?3.80和?3.70 eV. 单晶数据表明, 萘酰亚胺基元的分子间氢键及π-π作用对diNDI分子堆积结构起主导作用, diNDI呈层状堆积模式. 由差示扫描量热(DSC)实验结果可知, diNDI丁二炔经加热可发生固态聚合. 加热条件下diNDI的紫外-可见吸收光谱及原位拉曼光谱特征峰以及在波长532 nm激光强度为10%的辐照条件下原位拉曼光谱特征峰的变化均表明diNDI微纳晶发生了非常规的1,4-加成聚合, 并且新生成的共轭主链是无序的, 同时发现激光辐照条件下更易促进聚合反应.     

Direct Synthesis of Pyridyl Disulfide‐Terminated Polymers by RAFT Polymerization

A trithiocarbonate RAFT agent was modified with a pyridyl disulfide group and used in the direct synthesis of endgroup pyridyl disulfide‐functionalized homo‐ and amphiphilic block copolymers of oligo(ethyleneglycol) acrylate (PEG‐A) and butyl acrylate (BA). Both the homo‐ and copolymerizations were found to be well controlled via the RAFT mechanism. The NMR analysis indicated that both the homopolymers of PEG‐A and the amphiphilic diblock copolymers of PEG‐A and BA possessed pyridyl disulfide terminal groups. A UV‐Vis absorption test revealed that the pyridyl disulfide endgroup of the polymer could be efficiently used to couple thiol‐bearing molecules to the polymer without the need for any post‐polymerization modification. This communication presents the first efficient direct synthesis of thiol‐reactive endgroup‐functionalized well‐defined polymers via the RAFT technique.