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。     

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.     

Multi-metal cyanide catalysts for ring-opening polymerization of propylene oxide

Polymerizations of propylene oxide (PO) have been carried out by using a series of multi-metal metal cyanide (MMC) catalysts prepared by reacting ZnCl₂ and K₃[Co(CN)₆]₂, K₄Fe(CN)₆, K₃Fe(CN)₆ and/or K₂Ni(CN)₄ in the presence of tert-butyl alcohol and polytetramethylene ether glycol as complexing agents. The resulting MMC catalysts are characterized by elemental analysis, X-ray photoelectron spectroscopy, infrared spectroscopy and X-ray powder diffraction. The structure of MMC catalysts with broadened X-ray diffraction peaks is different from that of highly crystalline Prussian blue analogues of microporous crystalline materials due to the coordination of complexing agents. The PO polymerization behavior was tunable by changing with various metal cyanide salts after fixing a main catalyst component as ZnCl₂. Even if the basic structure of the MMC complexes is different each other, i.e. orthorhombic for Zn₂[Fe(CN)₆] and monoclinic for Zn₃[Fe(CN)₆]₂ and Zn₃[Co(CN)₆]₂, the chemical formulations become more complicated by forming MMC complexes through cyano bridges and complexing agents’ coordination and the structure more distorted from the defined crystal structures. All catalysts prepared by using K₃[Co(CN)₆]₂ showed very high activity once they were activated. Simply changing catalyst formulation by choosing different metal cyanide salts, catalytic activity, induction period, polymer molecular weight and its distribution and polymer viscosity could be tuned.     

Ring-opening metathesis polymerization of amino acid-functionalized norbornene diester monomers

Amino acid-derived novel norbornene diester derivatives, 5-norbornene-endo,endo-2,3-dicarboxylic acid bis((S)-2-N-(tert-butoxycarbonyl)aminopropyl) ester (1a), 5-norbornene-exo,exo-2,3-dicarboxylic acid bis((S)-2-N-(tert-butoxycarbonyl)aminopropyl) ester (1b), bis(N-α-(tert-butoxycarbonyl)-l-alanine) 5-norbornene-2,3-endo,endo-dimethyl ester (2a), bis(N-α-(tert-butoxycarbonyl)-l-alanine) 5-norbornene-2,3-exo,exo-dimethyl ester (2b) were synthesized and polymerized by the Grubbs catalyst, 2nd generation. Ring-opening metathesis polymerization of the monomers satisfactorily proceeded to give the polymers with fairly high molecular weights in good yields. The polymerization rate was not affected by the stereostructure of the monomers, endo,endo- and exo,exo-, while largely affected by solvents. The order of polymerization rate was as follows: acetone-d₆ > benzene-d₆ > DMF-d₇ ≈ CD₂Cl₂ > CDCl₃.     

Novel triazole-based aluminum complex for ring-opening polymerization of lactones

Novel triazole-based aluminum complex {O,O′-[4,5-P(O)Ph₂tz]-AlMe₂ was studied as the catalyst for the ring-opening polymerization of caprolactone (ε-CL) in chlorobenzene. In the presence of methanol, isopropanol, and bifunctional poly(ethylene glycol), the catalytic system produced polymers with high conversion (81–85 %) but broader distribution (M _w/M _n = 1.5–1.8). The system of catalyst and benzyl alcohol produced relative monodisperse PCLs (M _w/M _n ~ 1.2) with defined molecular weight at 1/1ratio, 60 °C and an initial concentration of ε-CL equal to 0.5 mol/L.     

Synthesis and cure kinetics of bisoxazoline monomers during cationic ring-opening polymerization

In this work, the synthesis and characterization of highly aromatic bisoxazoline (BOX) monomers containing diphenyl ether, furan, and thiophene backbones are presented. Preliminary investigations of the cure and reaction kinetics are performed to understand the impact of these moieties on polymerization and their glass transition temperatures. To do this, two catalysts are used, methyl triflate (MT) and dodecyl benzene sulfonic acid (DBS) to explore their role in controlling the cationic ring-opening polymerization (CROP) mechanism. Polymerization was monitored using non-isothermal differential scanning calorimetry and characterized according to the Kissinger and Ozawa models. Kinetic modeling using the Malek and Sestak-Berggren methods showed excellent agreement with experimental values and was used to determine reaction rate constants. The polymerization of BOX monomers in the presence of both MT and DBS is shown to be highly latent, being stable until the melting point is reached, after which reaction occurs rapidly.     

Covalent modification of graphene oxide with polynorbornene by surface-initiated ring-opening metathesis polymerization

Surface-initiated ring-opening metathesis polymerization (SI-ROMP) was employed to prepare polymer-grafted graphene oxide (GO). Grubbs catalysts were immobilized onto GO surfaces followed by ROMP of norbornene from these active catalyst sites to result in polynorbornene (PNb)-functionalized GO (GO-PNb), whose structure and morphology were fully characterized by FTIR, Raman, NMR, XRD, TGA and SEM. The as-prepared hybrid material of GO-PNb is an intercalated layer structure with an improved solubility in organic solvents. Further epoxidation of double bonds along the PNb chains resulted in the epoxidized PNb-functionalized GO (GO-ePNb). The relatively low and irregular grafting ratio of PNb on GO measured by gravimetry mainly result from the effect of complex GO surfaces and the chain-transfer reactions in the polymerization process.     

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.     

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.     

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.     

New polyelectrolytes by ring-opening metathesis polymerization of norbornene derivatives with imidazolium functionalized oligo-alkylether pendant groups

Novel monomers are reported that are derived from norbornene functionalized with oligoethyleneoxy groups that carry imidazolium salts. These monomers were polymerized via ruthenium-catalyzed ring-opening metathesis polymerization in a variety of solvents, including ionic liquids, at different temperatures to give novel low T_g polymers. These polymers are expected to act as new polymer electrolytes.     

Castor oil-based thermosets with varied crosslink densities prepared by ring-opening metathesis polymerization (ROMP)

Two castor oil-based monomers, (1) norbornenyl-functionalized castor oil (NCO), which has ∼0.8 norbornene rings per fatty acid chain and (2) norbornenyl-functionalized castor oil alcohol (NCA), which has ∼1.8 norbornene rings per fatty acid chain, have been prepared. Ring-opening metathesis polymerization (ROMP) of different ratios of NCO/NCA using the 2nd generation Grubbs catalyst results in rubbery to rigid biorenewable-based plastics with crosslink densities ranging from 318 to 6028 mol/m³. Increased crosslink densities result in shorter gelation times, better incorporation of the monomers into the polymer network, and much less soluble materials in the bulk materials. The increased crosslink densities obtained by adding NCA enhance the thermal properties, including the glass transition temperature (T_g) and room temperature storage modulus, which increase from −17.1 °C to 65.4 °C and from 2.4 MPa to 831.9 MPa, respectively. The TGA results, where T₁₀ increased from 285 °C to 385 °C, illustrate that improved thermal stabilities can be obtained for thermosets with higher crosslink densities. Young’s modulus (11-407 MPa), tensile strength (1.6-18 MPa) and toughness (0.14-1.6 MPa) are also improved dramatically with higher crosslink densities.     

Aqueous ring-opening metathesis polymerization of exo-7-oxabicyclo [2.2.1] hept-5-ene-2,3-dicarboximide

The aqueous ring-opening metathesis polymerization of the exo-Diels-Alder adduct of furan and maleimide was accomplished using an “activated Ruthenium” catalyst present in the supernatant of a RuCl₃-catalyzed aqueous polymerization of furan-dimethylacetylene dicarboxylate adduct. The polymer was characterized by solution ¹H? and ¹³C-NMR, IR, DSC, and viscometry. Characterization revealed an intact imide group and the possibility of high-temperature applications. © 1993 John Wiley & Sons, Inc.     

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 nickel(II)-based catalysts for the polymerization of ethylene

A series of Ni(II)-based bidentate -diimine complexes bearing two alkyl (alkyl = methyl, ethyl and isopropyl) substituents on each imine aryl group were studied as precatalysts for the polymerization of ethylene. These new catalysts were observed to show high activity in combination with methyl aluminoxane (MAO) and produced high molecular weight polyethylenes. The effects of the steric bulk of ortho-aryl substituents of the ligand on the catalytic activity and the resulting polyethylene microstructure were investigated. Kinetics of polymerization was also studied by changing important parameters such as temperature and MAO concentration. The polymerization activity, polymer molecular weight and resulting polymer microstructure were drastically changed according to the catalyst structure modification and polymerization parameters.