New ROMP Synthesis of Ferrocenyl Dendronized Polymers

First‐ and second‐generation Percec‐type dendronized ferrocenyl norbornene macromonomers containing, respectively, three and nine ferrocenyl termini are synthesized and polymerized by ring‐opening metathesis polymerization using Grubbs' third‐generation olefin metathesis catalyst with several monomer/catalyst feed ratios between 10 and 50. The rate of polymerization is highly dependent on the generation of the dendronized macromonomers, but all these ring‐opening metathesis polymerization reactions are controlled, and near‐quantitative monomer conversions are achieved. The numbers of ferrocenyl groups obtained are in agreement with the theoretical ones according to the cyclic voltammetry studies as determined using the Bard–Anson method.     

Nanostructured polymer composite nanoparticles synthesized in a single step via simultaneous ROMP and ATRP under microemulsion conditions

Ring‐Opening Metathesis Polymerization (ROMP) and Atom‐Transfer Radical Polymerization (ATRP) were carried out simultaneously under microemulsion conditions with 1st generation Grubbs catalyst playing a double role: ROMP initiator and ATRP controlling agent. Starting from two distinct microemulsions—one containing the monomers and the other the catalyst—well‐defined composite nanoparticles with z‐average hydrodynamic diameter smaller than 50 nm were prepared. Depending on the monomers droplet composition, homopolymers blends or graft‐copolymers were synthesized in a one‐pot, one‐step, one‐catalyst approach. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4014–4027, 2009     

Phenylenevinylene Block Copolymers via Ring‐Opening Metathesis Polymerization

Fully conjugated block copolymers containing 1,4‐ and 1,3‐phenylenevinylene repeating units can be prepared by the sequential ring opening metathesis polymerization of strained cyclophanedienes, initiated by ruthenium carbene complexes (Grubbs metathesis catalysts). The molecular weight of the constituent blocks can be tightly controlled by changing the catalyst to monomer ratio and the volume fraction of the block copolymers independently tailored by the ratio of the monomers employed. Extensive phase separation between the constituent blocks is observed in thin films of these polymers by atomic force microscopy and efficient energy transfer between blocks containing 1,4‐ and 1,3‐phenylenevinylene units can be seen in the photoluminescence of these materials.

     

活性开环歧化聚合合成梳形聚合物

综述了近年来利用活性开环歧化聚合反应合成规整结构梳形聚合物的研究工作进展。     

Unprecedented ROMP activity of low-valent rhenium-nitrosyl complexes: Mechanistic evaluation of an electrophilic olefin metathesis system

The reaction of [Re(H)(NO)2(PR3)2] complexes (1 a: R = PCy3; 1 b: R = PiPr3) with [H(OEt2)2][BAr(F)4] ([BAr(F)4] = tetrakis{3,5-bis(trifluoromethyl)phenyl}borate) in benzene at room temperature gave the corresponding cations [Re(NO)2(PR3)2][BAr(F)4] (2 a and 2 b). The addition of phenyldiazomethane to benzene solutions of 2 a and 2 b afforded the moderately stable cationic rhenium(I)-benzylidene-dinitrosyl-bis(trialkyl)phosphine complexes 3 a and 3 b as [BAr(F)4]- salts in good yields. The complexes 2 a and 2 b catalyze the ring-opening metathesis polymerization (ROMP) of highly strained nonfunctionalized cyclic olefins to give polymers with relatively high polydispersity indices, high molecular weights and over 80 % Z configuration of the double bonds in the chain backbone. However, these complexes do not show metathesis activity with acyclic olefins. The benzylidene derivatives 3 a and 3 b are almost inactive in ROMP catalysis with norbornene and in olefin metathesis. NMR experiments gave the first hints of the initial formation of carbene complexes from [Re(NO)2(PR3)2][BAr(F)4] (2 a and 2 b) and norbornene. In a detailed mechanistic study ESI-MS/MS measurements provided further evidence that the carbene formation is initiated by a unique reaction sequence where the cleavage of the strained olefinic bond starts with phosphine migration forming a cyclic ylide-carbene complex, capable of undergoing metathesis with alternating rhenacyclobutane formation and cycloreversion reactions ("ylide" route). However, even at an early stage the ROMP propagation route is expected to merge into an "iminate" route by attack by the ylide function on one of the N(NO) atoms followed by phosphine oxide elimination. The formation of phosphine oxide was confirmed by NMR spectroscopy. The proposed mechanism is supported further by detailed DFT calculations.     

基于环糊精的高度支化聚合物

环糊精（CD）与高度支化聚合物都存在空腔结构,若将两者结合起来可构筑出含有两种不同疏水空腔且具有特异物理化学功能的高分子体系,并有望在分子包合与识别、药物控释、基因传输等领域得到新的应用。本文根据高度支化聚合物与环糊精结合方式的不同,从以环糊精为核的高度支化聚合物、外端悬挂环糊精的高度支化聚合物、高度支化聚合物的结构单元与环糊精包合、环糊精与客体分子包合后自组装成高度支化聚合物,以及用功能化的环糊精单体合成超支化聚合物等5个方面对其研究进展进行了总结和评述,并在此基础上展望了该类聚合物的研究方向和发展趋势。     

Facile Synthesis of Thiol‐Functionalized Long‐Chain Highly Branched ROMP Polymers and Surface‐Decorated with Gold Nanoparticles

The synthesis of thiol‐functionalized long‐chain highly branched polymers (LCHBPs) has been accomplished in combination of ring‐opening metathesis polymerization (ROMP) and thiol‐Michael addition click reaction. A monotelechelic polymer with a terminal acrylate and many pendent thiol groups is first prepared through adding an internal cis‐olefin terminating agent to the reaction mixture immediately after the completion of the living ROMP, and then utilized as an AB_n‐type macromonomer in subsequent thiol‐ene reaction between acrylate and thiol, yielding LCHBPs as the reaction time prolonged. Au nanoparticles are then covalently conjugated onto the surface of thiol‐functionalized LCHBP to fabricate novel hybrid nanostructures, which is shown as one interesting application of such functionalized metathesis polymers. This facile approach can be extended toward the fabrication of novel nanomaterials with sophisticated structures and tunable multifunctionalities.

     

Synthesis of polynorbornene‐poly(tert‐butyl acrylate) nanoparticles with original morphologies by tandem ROMP and ATRP in microemulsion

Composite latex particles based on homopolymers and graft‐copolymers composed of polynorbornene (PNB) and poly(tert‐butyl acrylate) (PtBA) were synthesized in microemulsion conditions by simultaneous combination of two distinct methods of polymerization: Ring‐opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). Only one commercial compound (first generation Grubbs catalyst) was used to initiate the ROMP of norbornene (NB) and activate the ATRP of tert‐butyl acrylate (tBA). Well‐defined nanoparticles with hydrodynamic diameters smaller than 50 nm were prepared with original morphologies depending on the monomer compositions, the type of combination (polymer blend or graft‐copolymer), and the conditions of microemulsion polymerizations. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of Oligosaccharide‐Branched Ribofuranan by Ring‐Opening Polymerization of a New Anhydroribo Trisaccharide Monomer

A new anhydroribotrisaccharide monomer, A2B3LR ( 1 ), was synthesized and ROP was carried out to elucidate the polymerizability and to obtain oligosaccharide‐branched polysaccharides with defined structures. The new trisaccharide monomer was found to be polymerized readily with BF₃ · OEt₂ as a catalyst at ?40 °C to give a lactose‐branched polymer. Copolymerization with ADBR gave the corresponding copolymers in good yields. After removal of protective benzyl groups, D ‐lactose‐branched ribofuranans with free hydroxyl groups were obtained in good yields. The structure of polymers was analyzed by ¹H, ¹³C, and two‐dimensional NMR measurements, suggesting that D ‐lactose‐branched ribofuranans had (1 → 5)‐α stereoregularity.

     

Advanced Developments in Cyclic Polymers: Synthesis,Applications, and Perspectives

Due to the topological effect, cyclic polymers demonstrate different and unique physical and biological properties in comparison with linear counterparts having the same molecular-weight range. With advanced synthetic and analytic technologies, cyclic polymers with different topologies, e.g. multicyclic polymers, have been reported and well characterized. For example, various cyclic DNA and related structures, such as cyclic duplexes, have been prepared conveniently by click chemistry. These types of DNA have increased resistance to enzymatic degradation and have high thermodynamic stability, and thus, have potential therapeutic applications. In addition, cyclic polymers have also been used to prepare organic–inorganic hybrids for applications in catalysis, e.g. catalyst supports. Due to developments in synthetic technology, highly pure cyclic polymers could now be produced in large scale. Therefore, we anticipate discovering more applications in the near future. Despite their promise, cyclic polymers are still less explored than linear polymers like polyolefins and polycarbonates, which are widely used in daily life. Some critical issues, including controlling the molecular weight and finding suitable applications, remain big challenges in the cyclic-polymer field. This review briefly summarizes the commonly used synthetic methodologies and focuses more on the attractive functional materials and their biological properties and potential applications.     

双环戊二烯反应注塑

作为一种新型工程材料,近年来聚双环戊二烯(polydicyclopentadiene, PDCPD)的研究备受关注。PDCPD多采用反应注塑成型工艺,需要在反应前有足够的储存稳定期以保证物料的混合和注模。本文介绍了不同催化体系的优缺点,着重阐述了极具应用前景的新兴Grubbs潜伏型催化剂最新进展,包括热触发型、化学触发型和光触发型等,并对其结构、性能及反应机理进行了详细分析。同时,围绕配体结构对催化特性的影响,对如何提高催化剂的潜伏性且保持其催化活性进行了对比和剖析。其中,螯合结构和O、S、N等杂原子基团的引入,提高了催化剂的潜伏性,但催化活性会有一定程度的下降。此外,还评述了聚双环戊二烯改性方面的相关研究,并对聚双环戊二烯产业发展的趋势进行了展望。     

Tandem Ring‐Opening–Ring‐Closing Metathesis for Functional Metathesis Catalysts

Use of a tandem ring‐opening–ring‐closing metathesis (RORCM) strategy for the synthesis of functional metathesis catalysts is reported. Ring opening of 7‐substituted norbornenes and subsequent ring‐closing metathesis forming a thermodynamically stable 6‐membered ring lead to a very efficient synthesis of new catalysts from commercially available Grubbs’ catalysts. Hydroxy functionalized Grubbs’ first‐ as well as third‐generation catalysts have been synthesized. Mechanistic studies have been performed to elucidate the order of attack of the olefinic bonds. This strategy was also used to synthesize the ruthenium methylidene complex.     

Coil-helix and sheet-helix block copolymers via macroinitiation from telechelic ROMP polymers

Coil-helix and sheet-helix block copolymers are synthesized by combining the ring-opening metathesis polymerization (ROMP) of norbornene or paracyclophanediene with the anionic polymerization of phenyl isocyanide. Key to the design is the use of an μ-ethynyl palladium (II) functionalized chain-transfer agent (CTA) that can be exploited in a stepwise manner for the termination of ROMP and the initiation of the anionic polymerization. Both the coil- and sheet-macroinitiators, and the ensuing covalent block copolymers, are analyzed using ¹H NMR spectroscopy and gel-permeation chromatography. In all cases, the Pd-end group is maintained and all polymers demonstrate a monomodal distribution with dispersities (Đ) of 1.1–1.4. The resulting helix-coil and helix-sheet block copolymers formed by the macroinitiation route still demonstrate their intrinsic properties (fluorescence, preferential helix-sense). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2991–2998     

Influence of topology on the gelation behavior of coordination polymers prepared via ROMP of macrocyclic olefins

This work reports on the consequences of concatenation of two twin macrocycles on the gelation behavior of coordination polymers obtained via ring‐opening metathesis polymerization (ROMP) initiated by 2^nd generation Grubbs' catalyst. The influence of concatenation is evaluated by comparison with the behavior of a non‐interlocked model complex under the same reaction conditions. The suitability of the choice of the non‐interlocked model complex is discussed in terms of molecular structure and effective molarity (EM). It is found that concatenation has a primary role in the gelation process, resulting in lower critical gelation concentrations for the endotopic, interlocked complex compared with the exotopic, non‐interlocked one. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55, 1237–1242     

Sequence‐Controlled Polymers via Simultaneous Living Anionic Copolymerization of Competing Monomers

Natural macromolecules, i.e., sequence‐controlled polymers, build the basis for life. In synthetic macromolecular chemistry, reliable tools for the formation of sequence‐controlled macromolecules are rare. A robust and efficient chain‐growth approach based on the simultaneous living anionic polymerization of sulfonamide‐activated aziridines for sequence control of up to five competing monomers resulting in gradient copolymers is presented. The simultaneous azaanionic copolymerization is monitored by real‐time ¹H NMR spectroscopy for each monomer at any time during the reaction. The monomer sequence can be adjusted by the monomer reactivity, depending on the electron‐withdrawing effect by the sulfonamide (nosyl‐, brosyl‐, tosyl‐, mesyl‐, busyl) groups. This method offers unique opportunities for sequence control by competing copolymerization: a step forward to well‐engineered synthetic polymers with defined microstructures.

     

Living ROMP Synthesis and Redox Properties of Diblock Ferrocene/Cobalticenium Copolymers

Using the third‐generation Grubbs catalyst, the living ring‐opening metathesis polymerization of ferrocene/cobalticenium copolymers is conducted with theoretical numbers of 25 monomer units for each block, and their redox and electrochemical properties allow using the Bard–Anson electrochemical method to determine the number of metallocenyl units in each block.

     

烯烃易位聚合制备遥爪聚合物及嵌段共聚物

遥爪聚合物因其聚合物链的两端带有反应性官能团,可用于制备嵌段、接枝、星形、超支化等具有特殊结构的聚合物,其制备方法主要包括传统自由基聚合与可控/“活性”自由基聚合、阴离子聚合、阳离子聚合、易位聚合和缩合聚合等。相比于其他的传统聚合方法,烯烃易位聚合是一种较为温和的、产物分子量及结构可控的聚合方法。本文主要概述在各种链转移剂的存在下,采用环烯烃的开环易位聚合(ring-opening metathesis polymerization, ROMP)和非环二烯易位(acyclic diene metathesis, ADMET)聚合制备带有各种官能团的遥爪聚合物以及与其他活性聚合方法(NMRP、ATRP、RAFT、ROP等)相结合制备嵌段共聚物的研究进展。     

Antimicrobial Polymers Prepared by Ring‐Opening Metathesis Polymerization: Manipulating Antimicrobial Properties by Organic Counterion and Charge Density Variation

The synthesis and characterization of a series of poly(oxanorbornene)‐based synthetic mimics of antimicrobial peptides (SMAMPs) is presented. In the first part, the effect of different organic counterions on the antimicrobial properties of the SMAMPs was investigated. Unexpectedly, adding hydrophobicity by complete anion exchange did not increase the SMAMPs’ antimicrobial activity. It was found by dye‐leakage studies that this was due to the loss of membrane activity of these polymers caused by the formation of tight ion pairs between the organic counterions and the polymer backbone. In the second part, the effect of molecular charge density on the biological properties of a SMAMP was investigated. The results suggest that, above a certain charge threshold, neither minimum inhibitory concentration (MIC₉₀) nor hemolytic activity (HC₅₀) is greatly affected by adding more cationic groups to the molecule. A SMAMP with an MIC₉₀ of 4 μg mL^?1 against Staphylococcus aureus and a selectivity (=HC₅₀/MIC₉₀) of 650 was discovered, the most selective SMAMP to date.