Acyclic metathesis during ring-opening metathesis polymerization of cyclopentene

‘Living’ ring-opening metathesis polymerization (ROMP) permits the synthesis of narrow-distribution homopolymers and well-defined block copolymers - provided no side reactions occur. However, acyclic metathesis between the chain end and double bonds in the polymer backbone competes with propagation during ROMP of cyclopentene, even with a mild Mo catalyst, though the rate constant is some 1600-fold smaller. ‘Dead’ chains in the reaction mixture can also be attacked; the products of acyclic metathesis are tagged by quenching the ROMP reaction with pyrenecarboxaldehyde. The extent of acyclic metathesis can be minimized through proper choice of reaction conditions, permitting the synthesis of narrow-distribution polycyclopentene with 100 kg/mol molecular weight.     

Synthesis of latex particles by ring-opening metathesis polymerization

This paper reviews the recent discoveries that were achieved by our group in the field of particle synthesis via ring-opening metathesis polymerization (ROMP). Both polynorbornene and polybutadiene-based particles were prepared by the respective ROMP of norbornene and cyclooctadiene initiated by (PCy₃)₂Cl₂RuCHPh using several methods of polymerization in dispersed media, such as dispersion, suspension and miniemulsion. Depending upon the process implemented, particles size was found to range from 300 nm to 20 μm.     

Thermal- and photoinduced ring-opening metathesis polymerization (ROMP)/(PROMP): an efficient tool in polymer chemistry

Properties and applications of newly developed homogeneous ring-opening metathesis polymerization catalysts as well as photoinduced ring-opening metathesis polymerization catalysts are discussed. It is shown that simple alkyl complexes, e.g. [W(=NPh)(CH₂SiMe₃)₃Cl] as well as [Ru(arene)₂]²⁺ or [Ru(NC–R)₆]²⁺ complexes act as one-component Photo-ROMP initiators. Catalysts with good thermal latency are described for both classes. High quantum yields are observed for the photochemically induced solvation of Ru(II) complexes. Polymer structure and kinetic aspects of the reaction are consistent with [Ru(solvent)₆]²⁺ acting as the catalytically active species. The mechanism of aqueous ROMP with Ru(II) salts is discussed, which differs considerably from the classical ROMP reaction with Schrock-type catalysts in the sense that it is a chain reaction and not a living polymerization. Homo- and copolymers using exo-oxa-norbornene-carboximide ester derivatives were prepared with the ROMP technology and used, inter alia, to formulate very sensitive positive tone high-resolution microresists.     

钼基开环移位催化剂催化双环戊二烯聚合研究

分别用对甲基苯酚、壬基酚、2,6-二叔丁基-4-甲基苯酚、2,4,6-三溴苯酚和2,4-二硝基苯酚与五氯化钼(MoCl5)反应,制备出系列用于双环戊二烯(DCPD)开环移位聚合的钼-酚催化剂。考察了不同结构催化剂的活性及其在不同条件下对催化DCPD开环聚合的影响。以红外光谱和示差扫描量热分析表征了聚合产物的结构和性能。结果表明,产物中钼-对甲基苯酚的活性最高,其催化DCPD聚合的单体转化率为98.07%,交联度为90.44%。同时发现钼-酚催化剂催化DCPD聚合的凝胶时间随着Mo、Et2AlCl物质的量的增加和温度的升高而减小,而单体转化率和交联度则先增大后减小。     

POSS-enhanced shape-memory copolymer of polynorbornene derivate and polycyclooctene through ring-opening metathesis polymerization

A copolymer consisting of polycyclooctene (PCOE) and poly(5-norbornene-exo,exo-2,3-dicarboxylic anhydride) (PNBEDCA) was firstly synthesized through ring-opening metathesis polymerization, and then the obtained copolymer P(COE-co-NBEDCA) was readily modified by grafting reaction of NBEDCA units with polyhedral oligomeric silsesquioxanes (POSS) to afford a novel functionalized copolymer P(COE-co-NBEDCA-g-POSS), in which carboxyl and POSS as side chains attached to polynorbornene backbones. The copolymers were characterized by means of thermogravimetry, wide-angle X-ray diffraction, and stress–strain measurements. The shape memory effect of the copolymer was evaluated by dynamical mechanical analysis and shape recovery speed. Having the properties of the good shape fixity and the large shape recovery, the POSS-enhanced copolymer is expected to use as a potential shape memory material.     

降冰片烯类聚合物用于离子交换膜的研究进展

离子交换膜作为燃料电池以及液流电池的核心部件, 对电池的性能起着关键作用。由于开环易位聚合的降冰片烯类聚合物其主链中保留着双键, 而具有优越热稳定性和良好的可加工性, 逐渐成为离子交换膜材料的研究热点。本文综述了近年来基于开环易位聚合的降冰片烯类聚合物用于阳离子交换膜、阴离子交换膜和复合离子交换膜的研究状况, 分析了膜的结构组成与性能测试, 并与Nafion的性能进行了比较, 展望了降冰片烯类聚合物在离子交换膜领域的发展趋势。     

Novel fluorescent polynorbornenes with multi-functional armed structure by using highly stable block macroinitiators via a combination of living ring-opening metathesis polymerization and atom transfer radical polymerization

Novel organosoluble fluorescent polynorbornenes with multi-functional armed structure were designed and prepared by using highly stable block macroinitiators via a combination of living ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). A bromo-containing functional norbornene (NBMBr) was prepared from the Diels-Alder reaction of cyclopentadiene and allyl bromide. The diblock copolymer of 5-(N-carbazolyl methyl)bicycle[2.2.1]hept-2-ene (CbzNB) and NBMBr was successfully prepared using living ROMP and used as a novel macroinitiator [poly(CbzNB-b-NBMBr)] for ATRP. Carbazoyl-containing multi-functional armed copolymer with poly(methyl methacrylate) (PMMA) was prepared by using poly(CbzNB-b-NBMBr) as a macroinitiator for ATRP. Strong fluorescence emissions (370-450 nm) were observed in the low excimer-forming multi-functional armed fluorescent polynorbornenes. The fact is that low excimer-forming carbazole-containing polymeric compound would apparently be favorable in photoconductive materials. The multi-functional armed structure make this compound an attractive candidate for applications as multi-modified hole transport materials in molecular electronic devices. Multi-modification could be further considered to be carried out by using such a functional bromo group at the end of multi-arms.     

Aggregation behavior of new cyclic saturated copolymers synthesized via ring-opening metathesis polymerization

Cyclic saturated copolymers were prepared from 8-methyl-8-methoxycarbonyltetracyclo[4.4.0.1^2,5.1^7,10]dodec-3-ene (MMT) with polar ester group and dicyclopentadiene (DCP) without polar group. This procedure consisted of ring-opening metathesis polymerization (ROMP) followed by hydrogenation. Monomer reactivity of DCP was higher than that of MMT; the monomer reactivity ratio r_DCP/r_MMT varied from 2.135 to 1.159 in a temperature range from 80 to 130 °C. These kinetic results indicated that the copolymer had distribution of DCP composition in a macromolecule chain, which could provide the interesting aggregation behavior. The aggregation behaviors of the hydrogenated copolymer and the homopolymer in various solvents were also examined using dynamic light scattering (DLS) and static light scattering (SLS). DLS analysis indicated that the fast mode in each polymer is attributed to the diffusive motion of each single polymer chain, while the slow mode in the copolymer is caused by aggregated polymer. The aggregation degree of the copolymer decreased with increasing hydrophobicity of solvent, decreasing polymer concentration, decreasing molecular size of solvent and increasing temperature. Based on these findings, the mechanism of aggregation behavior was clarified that the DCP-rich unit in a macromolecule might be acting as core to give the aggregation in poor solvent.     

Radical ring-opening emulsion polymerization of vinylcyclopropanes

Radical emulsion polymerizations of vinylcyclopropanes, 1,1-bis(ethoxycarbonyl)-2-vinylcyclopropane (ECVCP) and 1,1-dichloro-2-vinylcyclopropane (CVCP) were examined. ECVCP underwent soap-free and soap-in emulsion polymerizations satisfactorily to afford the ring-opened polymer in good yields. Polymer emulsions were obtained in a spherical shape with single particle size distribution. Meanwhile, emulsion polymerization of CVCP proceeded in only a low conversion. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 497–501, 1998     

Elastomer polymer brushes on flat surface by bimolecular surface-initiated nitroxide mediated polymerization

The method of formation of well-defined polymer brushes based on the nitroxide mediated polymerization (NMP) of n-butyl acrylate (BA) initiated from a self-assembled mono-layers (SAMs) of an azoic initiator in the presence of a stable nitroxide radical is described. After preliminary qualitative characterization by X-ray photoelectron spectroscopy, the samples were studied by ellipsometry in order to determine the dry film thickness (initiator and polymer) and the grafting density of macromolecular chains. It is demonstrated, that in the presence of stable counter radical SG1, acting as chain growth moderator, the surface initiated NMP exhibits a living/controlled character permitting to control architectural parameters (e.g. degree of polymerization) of elastomer grafted polymer chains. The possibility to use the living control character of this type of polymerization to re-initiate grafted chains in order to increase the thickness of an elastomer thin film with conservation of the brushes regime has been demonstrated.     

Cyclic polyphosphoesters synthesized by acyclic diene metathesis polymerization and ring closing metathesis

This article describes the synthesis of cyclic polyphosphoester (PPE) by the ring-closing metathesis (RCM) of different difunctional linear PPEs. Linear PPE precursors were prepared through a selective head-to-tail acyclic diene metathesis polymerization of phenyl dienephosphate monomer using 2-hydroxyethyl acrylate as a selective chain terminator, followed by the transformation of the terminal acrylate functional group into a hydroxyl group utilizing a thiol-Michael addition click reaction. These products were then reacted with the corresponding acyl chloride containing a vinyl end group. The subsequent end-to-end intramolecular coupling reaction was performed under highly dilute conditions. The successful transformation of the linear PPE precursors to cyclic PPE was confirmed by NMR spectroscopy and gel permeation chromatography. The thermal and flame retardant properties of linear and cyclic PPEs were investigated, and their thermal degradation and flame retardance were evaluated, as these are important features for future applications.     

A novel amphiphilic AB2 star copolymer synthesized by the combination of ring-opening metathesis polymerization and atom transfer radical polymerization

A new amphiphilic AB₂ star copolymer was synthesized by the combination of ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). Two different routes (methods A and B) were employed firstly to prepare the poly(oxanorbornene)-based monotelechelic polymers as the hydrophobic arm bearing dibromo-ended group via ROMP in the presence of two different terminating agents catalyzed by first generation Grubbs catalyst. The values of capping efficiency (CE) of the polymers were determined by NMR, which were 94% and 67% for methods A and B, respectively. Then, the dibromo-ended ROMP polymers were used as the macroinitiators for ATRP of 2-(dimethylamino)ethyl methacrylate (DMAEMA) to produce two hydrophilic arms. The prepared amphiphilic AB₂ star copolymers poly(7-oxanorborn-5-ene-exo,exo-2,3-dicarboxylic acid dimethyl ester)-block-bis[poly(2-(dimethylamino)ethyl methacrylate)] (PONBDM_n-b-(PDMAEMA_m)₂) with a fixed chain length of hydrophobic PONBDM and various hydrophilic PDMAEMA chain lengths can self-assemble spontaneously in water to form polymeric micelles, which were characterized by dynamic light scattering, atom force microscopy, and transmission electron microscopy measurements.     

Highly efficient ring-opening polymerization of tetrahydrofuran by anhydrous ferric chloride

Poly(tetramethylene ether glycol) (PTMG), widely used as a precursor in the fabrication of commodity polymers, is typically produced byacid-catalyzed polymerization of tetrahydrofuran (THF). Herein, we report a detailed investigation of the cationic ring-opening polymerization of THF catalyzed by ferric chloride (FeCl₃), which can be considered as a strong Lewisacid. The polymerization reactions were performed in the presence of acetic anhydride at 20°C with FeCl₃, which readily produced poly(tetramethylene ether glycol diester) (PTMG_DE). A maximum yield of 79.2% was obtained within 30 min using a FeCl₃ to acetic anhydride molar ratio of 5:4. The resulting polymers generally exhibited low molecular weights and a narrow polydispersity index and could be easily converted into PTMG using aqueous NaOH. In contrast with the FeCl₃-acetic anhydride system, other iron-based catalysts such as FeCl₂ and FeCl₃·6H₂O did not show any noticeable activity in the polymerization of THF. The proposed mechanism involves initiation of the acetyl cation generated by FeCl₃, propagation by nucleophilic addition of THF, and termination by the acetate anion, accounting for the high activity of the FeCl₃ catalyst for THF polymerization. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47999.     

New azo-chromophore-containing multiblock poly(butadiene)s synthesized by the combination of ring-opening metathesis polymerization and click chemistry

A combination of ring-opening metathesis polymerization (ROMP) and click chemistry approach was utilized for the first time in preparation of multiblock copolymers. The dibromo-functionalized telechelic poly(butadiene) (PBD) was synthesized firstly by ROMP of 1,5-cyclooctadiene in the presence of a symmetrical difunctional chain transfer agent and transformed into diazido-telechelic PBD, which was then reacted with a dialkynyl-containing azobenzene chromophore via click reaction, producing novel multiblock PBDs collected by azobenzene groups and newly formed triazole moieties. The monomer and polymer were characterized by IR, UV-vis, LC/MS, and NMR techniques. The produced multiblock copolymers have molecular weights within 13.3 and 57.8 kDa, and their polydispersity indices ranging from 1.98 to 2.38 by gel permeation chromatography measurement. The multiblock PBDs containing azo chromophores and triazole moieties with or without hydrogen-bonding interreaction with 4,4′-dihydroxybiphenyl molecule exhibited different photoisomerization efficiency from trans to cis as observation in UV-vis spectroscopy. The morphologies of multiblock PBDs were also investigated by atom force microscopy.     

Controlled atom transfer radical polymerization of MMA onto the surface of high-density functionalized graphene oxide

We report on the grafting of poly(methyl methacrylate) (PMMA) onto the surface of high-density functionalized graphene oxides (GO) through controlled radical polymerization (CRP). To increase the density of surface grafting, GO was first diazotized (DGO), followed by esterification with 2-bromoisobutyryl bromide, which resulted in an atom transfer radical polymerization (ATRP) initiator-functionalized DGO-Br. The functionalized DGO-Br was characterized by X-ray photoelectron spectroscopy (XPS), Raman, and XRD patterns. PMMA chains were then grafted onto the DGO-Br surface through a ‘grafting from’ technique using ATRP. Gel permeation chromatography (GPC) results revealed that polymerization of methyl methacrylate (MMA) follows CRP. Thermal studies show that the resulting graphene-PMMA nanocomposites have higher thermal stability and glass transition temperatures (T_g) than those of pristine PMMA.     

Fabrication of magnetic nanofibers via surface-initiated RAFT polymerization and coaxial electrospinning

A simple and continuous approach for fabricating magnetic polyacrylonitrile nanofibers (MNFs) with the diameter of about 200 nm has been developed by combining surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization and coaxial electrospinning. The RAFT polymerization of acrylonitrile was carried out on the surface of RAFT agent immobilized Fe₃O₄ nanoparticles. The room-temperature saturation magnetizations of the prepared MNFs can be easily adjusted. In addition, the aligned fibers can be conveniently obtained via magnetic electrospinning using a specially designed fiber collector.     

丙交酯开环法合成聚乳酸工艺探讨

研究了丙交酯开环法合成聚乳酸的工艺路线,考察了反应温度、反应时间、催化剂用量等工艺条件对聚乳酸分子质量的影响,在优化工艺条件下可以得到高分子质量和高结晶度的聚乳酸。     

新型环境友好材料聚乳酸合成工艺研究

以工业乳酸为原料,采用开环聚合法对聚乳酸合成工艺进行系统研究,对传统工艺中的催化剂及投加方式作了改进。在丙交酯合成工艺中,采用ZnO/La2O3作催化剂并分2次顺序加入,明显提高了丙交酯的产率(达52%);在丙交酯开环聚合工艺中,采用辛酸亚锡甲苯溶液作催化剂,在反应温度为130—180℃,反应时间8h,体系真空度控制在0.098MPa的条件下,制备出聚乳酸的分子质量达到2.4×104g/mol,优于文献报道。     

Poly(thienylenevinylene) prepared by ring-opening metathesis polymerization: Performance as a donor in bulk heterojunction organic photovoltaic devices

Poly(3,4-dioctylthienylenevinylene) (PDOTV) was synthesised by ring-opening metathesis polymerization (ROMP) with controlled molecular weight. PDOTV has been used to fabricate organic photovoltaic devices in combination with phenyl C₆₁-butyric acid methyl ester (PCBM) for the first time. The devices show power conversion efficiency up to 0.18%. Optimal device performance was found at a film thickness of 100 nm and a ratio of PCBM to PTV of 2:1. External quantum efficiency (EQE) measurements, transient absorption spectroscopy and morphology studies were carried out to establish factors governing photovoltaic performance. These results suggest that the efficiency values for the devices were limited by the hole mobility and unexpected phase separation within the blend. Nevertheless, the results show that ROMP is a viable, alternative, synthetic strategy for preparing PTV donors for use in bulk heterojunction OPVs.