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.     

Non-equilibrium molecular weight studies on the metathesis polymerization of cyclopentene initiated by WCl6AliBu3: Effect of catalyst ageing time

A study has been made of the molecular weight and distribution changes that take place during the polymerization of cyclopentene initiated by the non-living metathesis catalyst $\text{WCl}{}_6\text{AliBu}{}_3$. The system appears to be characterized by two distinct phases. In the first phase, the molecular weight distribution, which is bimodal, would appear to be kinetically controlled and the bimodal distribution to result from the presence of two kinetically independent metathesis species. The initial molecular weight distribution would, therefore, appear to be dependent upon the relative concentrations of these active species. The second phase of the polymerization is a slow conversion of the molecular weight distribution to that of an equilibrium distribution after a long reaction time.     

Ring-opening metathesis copolymerization of dicyclopentadiene and cyclopentene through reaction injection molding process

Copolymer of dicyclopentadiene and cyclopentene (CPE) is synthesized through ring-opening metathesis polymerization using the second-generation Grubbs catalyst. The influences of monomer composition, catalyst concentration, and reaction temperature on gelification time and monomer conversion have been investigated. Furthermore, the reaction injection molding process is employed to produce the copolymer of dicyclopentadiene and CPE. It has been found that postcuring process is necessary to achieve 100% monomer conversion. The incorporation of a small amount of CPE into the copolymers can reduce the weight loss rate in the TGA process and improve the mechanical properties. The effects of CPE fraction, catalyst concentration, and postcuring temperature on thermal stability and mechanical properties are discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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 diene metathesis polymerization: The synthesis of unsaturated polyketones

The first acyclic diene metathesis (ADMET) polymerization of unsaturated ketone containing monomers using the molybdenum catalyst, Mo(CHCMe₂Ph)(N-2,6-C₆H₃-i-Pr₂)[OCCH₃(CF₃)₂]₂ is reported. 6,6,8,8-Tetramethyl-1,12-tridecadiene-7-one undergoes homopolymerization; copoly-merizations are carried out with 1,9-decadiene and 2,12-dimethyl-2,12-dipentenylcyclododecan-1-one, 2,12-diallylcyclododecan-1-one, and trans-2,12-diallyl-2,12-dimethylcyclododecan-1-one These polymerizations are initiated under bulk conditions and are continued in solution. No evidence of Wittig chemistry is observed between the carbonyl functional group and the catalyst when a high degree of steric hindrance exists around the carbonyl moiety. Polymer structures were characterized by IR, ¹H NMR, and ¹³C NMR spectroscopy. Molecular weights were determined by endgroup analysis and gel permeation chromatography.     

Hydrogenation of ring opening metathesis polymerization polymers

Various methods of hydrogenating ring opening metathesis polymerization (ROMP) polymers were investigated as part of an effort to improve their stability and increase their usefulness as matrix materials for nanocluster synthesis. Hydrogenation with Pd/BaSO₄ catalyst in high-pressure hydrogen gas was only partly successful and limited to unfunctionalized polymers such as polymethyltetracyclododecene. Block copolymers containing phosphine or carboxylic acid functionalities were successfully hydrogenated by diimide generated in situ from p toluenesulfonylhydrazide. © 1995 John Wiley & Sons, Inc.     

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.     

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.     

Novel catalysts for the ring-opening metathesis polymerization of norbornene-type monomers

A novel family of metallate compounds has been developed for use in catalyst systems for the ring-opening polymerization of dicyclopentadiene (DCPD) and other norbornene-type monomers. Examples of these novel catalyst compounds are the organoammonium isopoly-and heteropolymetallates. Applications of these metallates in combination with alkylaluminum-type reducing cocatalysts are found in the production of both solution polymers, and cross-linked resins from reaction injection molding (RIM). These catalyst systems have significant advantages over prior art catalysts. They are highly soluble in DCPD and other norbornene-type monomers, thus eliminating the need for a reaction solvent. They also are insensitive to air and moisture, have unlimited shelf-life in solution in norbornene-type monomers, and do not function as Lewis acids. The chemistry of these catalyst systems is discussed, along with the benefits they provide to the properties of the final polymer products. © 1993 John Wiley & Sons, Inc.     

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.     

Ring-opening metathesis polymerization (ROMP) of norbornenyl-functionalized fatty alcohols

Novel biorenewable-based thermosets have been successfully synthesized by the ring-opening metathesis polymerization (ROMP) of norbornenyl-functionalized fatty alcohols derived from soybean oil (NMSA), Dilulin (NMDA), ML189 (NMMA) and castor oil (NMCA). The effects of the monomer structure on the polymerization process, and the thermal and mechanical properties of the resulting thermosets have been extensively investigated. The number of ROMP-reactive rings appended to the fatty acid chain and the viscosity play an important role in controlling the initiation and propagation processes of the polymerization and the final properties of the thermosets obtained. The thermosets have been characterized by Soxhlet extraction, DMA, TGA, and tensile tests. It has been found that polyNMDA and polyNMMA have best thermo-mechanical properties. Compared with polyNMSA, the polyNMDA and polyNMMA thermosets exhibit lower soluble fractions, and higher thermal stabilities and mechanical properties, because of more effective crosslinking; whereas, polyNMCA exhibits a higher soluble fraction, and lower thermal stability, resulting from incomplete polymerization of the more viscous NMCA monomer.     

Acyclic diene metathesis polymerization: History,methods and applications

Acyclic Diene Metathesis (ADMET) polymerization was established decades ago and has since developed into a robust and reliable technique. A wide range of different, new materials exhibiting unique properties has been produced via ADMET polymerization since its development. This versatile technique allows, through the right combination of monomer design and choice of catalyst, the synthesis of various functional polymers in addition to a precise control over primary structure. Systematic studies on precise ADMET polymers have greatly contributed to a better understanding of how branch identity and its distribution along the polymer backbone affect the thermal/electronic properties, crystallization, molecular dynamics and morphology of different materials. This article presents an extensive review of how ADMET started, the mechanism that underlies the structural features of ADMET polymers and the different strategies and techniques that have been developed over the years to overcome common synthetic challenges. Monomer synthesis methods are also discussed in detail, providing an important overview of the limitations and advantages of using ADMET as a polymerization technique. Many examples are given of functional ADMET polymers that have been developed by research groups all over the world.     

Ring opening metathesis polymerization of 1,1-diphenyl-1-sila-cyclopent-3-ene

Summary 1,1-Diphenyl-1-silacyclopent-3-ene (I) has been polymerized by ring opening metathesis using tungsten hexachloride and either cyclopentene or cyclohexene as an initiator, with or without tetraphenyltin as a cocatalyst. The product polymer poly(1,1-diphenyl-1-sila-cis-pent-3-ene) (II) has been characterized by¹H,¹³C, and²⁹Si NMR and IR spectroscopy.     

Camphorquinone-amines photoinitating systems for the initiation of free radical polymerization

Results of the camphorquinone/hindered piperidines, visible-light photoinduced polymerization of triethyleneglycol dimethacrylate are presented. The effectiveness of piperidines as a coinitiator is compared with a few aliphatic amines and aromatic amines. The main objective in this research was to study the mechanism of photoinitiation of polymerization. Reactive radicals that initiate the polymerization are formed by a mechanism of hydrogen atom abstraction by the triplet state of camphorquinone, mediated by photoinduced electron transfer. The different efficiencies of the aliphatic amines and of the aromatic amines affecting photopolymerization are explained on the basis of the different quenching reactivities of the excited states of camphorquinone.     

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.     

Polydispersity control in ring opening metathesis polymerization of amphiphilic norbornene diblock copolymers

Ring opening metathesis polymerization (ROMP) with Grubbs's catalyst was used to synthesize narrow polydispersity (PDI)diblock copolymers of norbornene (NOR) and norbornenedicarboxylic acid (NORCOOH). Norbornene (NOR) and 5-norbornene-2,3,-dicarboxylic acid bis trimethylsilyl ester (NORCOOTMS) were used as precursor monomers for thepolymerization. [NORCOOTMS]_m/[NOR]_n was converted to [NORCOOH]_m/[NOR]_n by precipitating the polymer solution in a mixture of methanol, acetic acid, and water. The conversion to 5-norbornene-2,3-dicarboxylic acid was evidenced by ¹H NMR. By polymerizing the bulkier NORCOOTMS precursor monomer first, lower PDIs were observed for the completed [NORCOOH]_m/[NOR]_n block copolymers in comparison to copolymers where the NOR block was polymerized first. The PDI of the diblock copolymers of [NORCOOH]_m/[NOR]_n decreased with increase in block length ofthe precursor NORCOOTMS monomer. This study shows that the PDI can be controlled by selecting a monomer with appropriate functionality as the starting block of the block copolymer to control the rate of propagation, R_p, as an alternative of using additives to change the reactivity of the catalyst.     

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.     

Efficiency of initiation by azodiisobutyronitrile in the emulsion polymerization of styrene

Oil-soluble initiators can produce rates of emulsion polymerization similar to those obtained with the water-soluble initiators which are normally used. Although radicals are generated in pairs in the oil phase, escape of a radical to the aqueous phase leaves an isolated radical in the oil phase: this is the essential condition for an emulsion polymerization. A concentration of azodiisobutyronitrile was found which produced the same number of latex particles in the emulsion polymerization of styrene as was obtained with a typical concentration of potassium peroxydisulphate. The rate of nucleation of latex particles can then be equated to that obtained with the known rate of decomposition of peroxydisulphate. Comparison with the rate of decomposition of azodiisobutyronitrile shows its efficiency to be only 4% in emulsion polymerization in contrast with the efficiency of ～50% obtained in bulk or solution polymerization.