Synthesis of cis,syndiotactic ROMP polymers containing alternating enantiomers

Ring-opening metathesis polymerization (ROMP) of rac-endo,exo-5,6-dicarbomethoxynorbornene (inter alia) yields a cis,syndio,alt-polymer, one in which the sequential units in the cis,syndiotactic polymer consist of alternating enantiomers. Cis selectivity arises through addition of the monomer to produce an all-cis-metallacyclobutane intermediate, while syndioselectivity and alternating enantiomer structures arise as a consequence of inversion of configuration at the metal center with each metathesis step.     

Novel multifunctional polymeric materials with predominant cis microstructures derived from α‐norbornenyl macromonomer and stable macroinitiator via ring‐opening metathesis polymerization and atom transfer radical polymerization

Novel star‐like polymeric materials with high cis content could be obtained by using α‐norbornenyl macromonomers and highly stable macroinitiators derived from an active norbornene derivative [5‐(2‐bromo‐2‐methylpropionylaminomethyl)bicyclo[2.2.1]hept‐2‐ene (NBBrMPAM)], which was synthesized by the reaction of norbornene methylene amine and 2‐bromo‐2‐methylpropionyl bromide. The α‐norbornenyl macromonomer (NBPMMA), which is polymethyl methacrylate containing norbornenyl end group, was prepared by atom transfer radical polymerization (ATRP) using NBBrMPAM as an initiator. Star‐like polynorbornene with high cis microstructure (cis/trans = 72/28) was obtained directly by ring‐opening metathesis polymerization of NBPMMA macromonomer having number molecular weight (Mn ) as low as 6.39 × 10³. Random ring‐opening metathesis copolymerization of NBPMMA and norbornene derivative containing carbazole group (NBCbz) was carried out at 25 °C by using Ru catalyst [(Cy₃P)₂Cl₂Ru = CHPh, Cy = cyclohexyl, Ph = phenyl]. High cis (cis/trans = 63/37) organo‐soluble star‐like random poly(NBPMMA‐co‐NBCbz) was successfully obtained with high number‐average molecular weight (Mn ) of 4.76 × 10⁴ and molecular weight distribution polydispersity index of 1.78. Organo‐soluble comb‐shaped copolymers with MMA could be successfully obtained using ATRP macroinitiator [poly(HNBBrMPAM)] in diluted macroinitiator solution with a concentration less than 3.64 × 10^?2 mol.L^?1. This is the first ever attempt to prepare novel star‐like organo‐soluble polymeric materials with high cis microstructure via the combination of ring‐opening metathesis polymerization and ATRP. Multimodification could be considered to be carried out by using the functional bromo group at the end of side chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3382–3392, 2006     

Living polymerization of aryl substituted acetylenes by MoCl5 and WCl6 based initiators: The ortho phenyl substituent effect

The polymerization of phenylacetylene initiated by MoCl₅ and WCl₆ based initiators was monitored directly in the NMR sample tube and demonstrated the presence of backbiting and intramolecular cyclization reactions. It was shown that the ratio of cis to trans structural units obtained by isomerization prior to double bond formation dictates the degree of backbiting and intramolecular cyclization reactions. This cis–trans ratio determines the length of cis–transoidal sequences present in the polymer backbone which are available for both backbiting and intrachain cyclization reactions. The cyclic trimers obtained in the metathesis polymerization of phenylacetylene are formed only through the cis–cisoidal-induced backbiting and/or intramolecular reactions. The o-trimethylsilylphenylacetylene follows a living mechanism of polymerization. This is due to the fact that the size of the ortho substituent suppresses the cis–transoidal to cis–cisoidal isomerization reactions and therefore eliminates the backbiting reactions. The steric hindrance provided by the size of the ortho substituent also eliminates interchain and intrachain reactions.     

Stereoselectivity of the cyclooctene ring-opening polymerization

The stereoselectivity of the cyclooctene ring-opening polymerization in the presence of the tungsten hexachloride–tetraisobutylalumoxane (TBAO) catalyst system has been studied. The reaction conditions have been established in which the polymer chain isomerization is reduced to a minimum. Under these conditions the stereoselectivity is determined by an individual act of the monomer molecule insertion. The dependence of stereoselectivity on monomer concentration, number of active sites, and temperature has been investigated. The results obtained suggest that the cyclooctene polymerization is selective in favor of the geometrical configuration of the starting cycloolefin (the “retention” effect) by analogy with the previously reported metathesis of acyclic olefins. Considerations which support the idea that cis and trans units are reproduced by the same type of active sites are discussed. The experimental evidence indicates that in this case the stereoselectivity is determined by the difference in kinetics of two reaction paths of the monomer molecule insertion that lead to the formation of cis and trans units.     

Ring Opening Metathesis Polymerization of Bicyclic α,β‐Unsaturated Anhydrides for Ready‐to‐be‐grafted Polymers Having Tailored pH‐Responsive Degradability

Polymers having α,β‐unsaturated anhydrides as repeating units were synthesized by ring opening metathesis polymerization (ROMP). The anhydride moieties were ready‐to‐be‐grafted with amines to form acid‐labile cis‐α,β‐unsaturated acid amide linkages. The pH‐responsive reversible de‐grafting can be controlled by changing the intramolecular accessibility between acid and amide groups. The alendronate‐grafted ROMP polymers showed distinct pH‐dependent cytotoxicity according to the anhydride structures.     

Polymerization of 4-phenyl-1-butyne catalyzed by metathesis and Ziegler–Natta catalysts

The polymerization of 4-phenyl-1-butyne was carried out using metathesis and Ziegler-Natta catalysts. Especially, the Fe(acac)₃-AlEt₃ catalyst with toluene as a solvent produced an extremely high molecular weight polymer of M_w ≈ 10⁶. Solubility of the polymers at room temperature in organic solvents such as benzene, toluene, dichloromethane, chloroform, and THF was excellent despite their high molecular weights. It has been indicated that the polymer prepared by the Fe(acac)₃-AlEt₃ catalyst is of cis form with a high stereoregularity. © 1993 John Wiley & Sons, Inc.     

Contact metathesis polymerization (CMP)

Ring-opening metathesis polymerization (ROMP) has been used to investigate adhesive and coating formation via a general process called contact metathesis polymerization (CMP). This process involves applying a metathesis catalyst directly to the surface to be modified and initiating the polymerization by exposing this newly formed catalyst-coated surface to a monomer capable of undergoing ROMP, thereby creating an adhesive bond or coating. In this paper, we describe excellent primary adhesion results of bonding low surface energy elastomers to metals and themselves using ROMP as the operative chemistry. The elastomers natural rubber, EPDM, and Santoprene^® are difficult to bond using conventional methods, particularly in their post-vulcanized state. CMP yields rubber-tearing bonds to pre- and post-vulcanized elastomers at room temperature under ambient conditions in air, in the presence of moisture, and with minimal surface preparation using well-defined olefin metathesis catalysts.     

乙炔在钒催化体系下的聚合

本工作采用三乙酰基丙酮钒及二乙酰基氧钒同烷基铝组成的催化体系,研究了乙炔聚合的规律及聚乙炔成膜的条件,并初步研究了聚乙炔膜的链节结构、形态结构及室温电导率。     

Fatty acid derived phosphorus‐containing polyesters via acyclic diene metathesis polymerization

The acyclic diene metathesis (ADMET) polymerization of a phosphorus‐containing α,ω‐diene prepared from a plant oil derived building block is reported. Different ruthenium based metathesis catalysts and conditions were tested to optimize the ADMET polymerization of this monomer. Undecylenyl undecenoate was used as fully renewable comonomer to obtain polyesters with different phosphorus contents and to increase the renewable content of the final polymers. Copolymerization caused marked variations in the molecular weights leading to polyesters from 6 to 38 KDa. The effect of the ADMET polymerization temperature in the thermal properties of the copolymers was studied and their thermal degradation and flame retardant properties were evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5760–5771, 2009     

Stationary phases for chromatography prepared by ring opening metathesis polymerization

The chemistry of metathesis polymerization-derived stationary phases is summarized. Since both ring-opening metathesis and 1-alkyne polymerization triggered by well-defined transition metal alkylidenes are living polymerization methods, they allow for the controlled and highly reproducible synthesis of stationary phases in terms of both the nature and total content of the functional group(s) of interest. In addition, the high functionality tolerance of these polymerization techniques allows for creating chromatographic supports with an unprecedented diversity in terms of functional groups that may be introduced. Their applications in various areas of separation science such as SPE, ion-chromatography, RP chromatography, chiral chromatography, and the high-performance liquid chromatographic separation of biomolecules are summarized. Within the context of the latter topic, special attention will be given to metathesis polymerization-derived monolithic supports. Consideration will also be given to those aspects of polymer chemistry that are relevant to the separation performance of these supports.     

烯烃共聚酯的合成与表征

通过环辛烯、环辛二烯和降冰片烯与ω-十一烯酸乙二醇二酯的易位共聚合及氢化反应合成了烯烃共聚酯.改变聚合条件,可控制烯烃共聚酯的分子量、极性单体插入率和熔融温度等性质.两段聚合过程适于制备高分子量的烯烃共聚酯,聚合物收率达90%,极性单体的插入率大于10%,熔融温度高达120℃.     

Oligometallic template strategy for ring-closing olefin metathesis: highly cis- and trans-selective synthesis of a 32-membered macrocyclic tetraoxime

An oligometallic template effect was observed on the cis/trans selectivity of a 32-membered macrocyclic tetraoxime in ring-closing olefin metathesis of an acyclic diallyl derivative H4L; the metathesis of heterotrinuclear complex LZn2M (M=Ca2+, La3+) afforded the cis isomer, whereas uncomplexed H4L gave the trans isomer.     

Fast tandem ring-opening/ring-closing metathesis polymerization from a monomer containing cyclohexene and terminal alkyne

We report extremely fast tandem ring-opening/ring-closing metathesis polymerization of a monomer containing two rather unreactive functional groups: cyclohexene and a terminal alkyne. When a third-generation Grubbs catalyst was used at low temperature, this tandem polymerization produced polymers with controlled molecular weights and narrow polydispersity indices. To explain this extremely fast polymerization, its reaction mechanism was studied. This new type of controlled polymerization allowed for the preparation of block copolymers using other conventional living metathesis polymerizations. The diene on the backbone of the polymer was postfunctionalized by sequential Diels-Alder and aza-Diels-Alder reactions, which led to selective functionalization depending on the stereochemistry of the diene.     

烯烃易位聚合研究新进展环烯烃开环易位聚合和非环二烯易位聚合

本文综述了近年来环烯烃开环易位聚合和非环二烯易位聚合研究新进展，并以活性开环易位聚合催化剂作了详细概述。     

The polymerization of 3-chloro-1-propyne and 3-bromo-1-propyne with Mocl5 and WCL6 based initiators and the structure of the resulting polymers

The WCl₆ and MoCl₅ initiated polymerizations of 3-chloro-1-propyne and 3-bromo-1-propyne were performed in both halogenated and aliphatic non-nucleophilic and in aromatic nucleophilic solvents. The structure of the obtained polymers suggested that the polymerization reaction occurs in two steps. In both nucleophilic and non-nucleophilic solvents, the first step consists of the metathesis polymerization of 3-chloro(bromo)-1-propyne followed by electrophilic cis–trans isomerization leading to polymers containing trans-cisoidal allyl chloride or bromide structural units. When the polymerization is performed in non-nucleophilic solvents, in the second step an intramolecular electrophilic addition followed by elimination takes place. The resulting polymers contain a highly conjugated cyclopentadiene ladder structure. When the polymerization is performed in nucleophilic aromatic solvents, the intramolecular electrophilic addition competes with the electrophilic substitution of the solvent resulting in polymers containing high concentrations of arylpropenyl structural units. Subsequently, depending on the nucleophilicity of the polymerization solvent, the polymer structure contains structural units based on cyclopentadiene and/or arylpropenyl groups.     

Monomer sequencing and microstructural analysis on polymers of dimethyl norbornene dicarboxylate and 7‐oxanorbornene dicarboxylic derivatives employing ruthenium catalysts by ring‐opening metathesis polymerization

The physiochemical properties, comonomer sequencing, and regiospecificity of the linkages between monomeric units within homo/copolymers based on 5,6‐di‐substituted norbornene and 7‐oxanorbornene type monomers by ring‐opening metathesis polymerization are reported and correlated to their primary and secondary structural elements. In general, first‐generation Grubbs‐ I1 ruthenium catalyst generates polymers with high trans content that exhibits an extended secondary structure with exo,exo substituents, whereas second‐generation Grubbs‐ I2 catalyst produces polymers with high cis content that forms tight turns, resulting in a compact structure. Furthermore, I2 ‐produced polymers exhibit a high level of alternating cis–trans double bonds along their polymeric backbone. In stark contrast, both first‐ and second‐generation Grubbs catalysts display complete reversal in cis/trans selectivity when an oxygen atom is in position‐7 of the norbornene‐ring along with mono‐endo‐substitution in position‐5 or 6, and hence highlighting the importance of stereoelectronic complexation by the catalyst with the next incoming monomer for cis/trans selectivity. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2477–2501     

Synthesis and characterization of polyoctenamer with WCl6?e−?Al?CH2Cl2 catalyst system via ring‐opening metathesis polymerization

A typical low‐strain monomer, cyclooctene, was polymerized via ring‐opening metathesis polymerization with electrochemically produced active species. The structural properties of the polyoctenamer were determined by NMR, gel‐permeation chromatography and differential scanning calorimetry. Analysis of the polyoctenamer microstructure by ¹H and ¹³C NMR spectroscopy indicates that the polymer contains a highly cis stereoconfiguration of the double bonds (σ_c = 0.75). The resulting polymer is of low molecular weight and has a reasonably broad molecular weight distribution (M_w = 18 000, PDI = 1.9). The glass transition temperature and melting point of the polyoctenamer are ?11.3 °C and 36.5 °C respectively. Copyright © 2005 John Wiley & Sons, Ltd.     

Polymerization of isoprene with cobalt catalysts

The polymerization of isoprene with catalytic systems efficient for the cis polymerization of butadiene, i.e., cobalt 2-ethyl hexanoate-diethylaluminum chloride and cobalt 2-ethyl hexanoate-ethylaluminum sesquichloride, is studied. The catalysts are obtained via in situ mixing of the components or at a reduced temperature (0–5°C) in the presence of a small amount of the monomer. In situ polymerization proceeds with an induction period, whose duration depends on the polymerization conditions, or without this period if a preformed catalyst is used. In each case, the resulting polymer is characterized by a mixed microstructure with a predominant content of cis-1,4 units and 3,4 units.     

Polymerization of Cyclooctene in Benzene Initiated with a Metathesis Catalyst

Cyclooctene was polymerized in benzene at temperatures ranging from 10 to 80°C. The polymerization was initiated with the metathesis catalyst WCl₆/C₂H₅)AlCl₂/C₂H₅OH for initial monomer concentrations varying from 0.11 to 4.0 mol/L. Polymerization products obtained from the metathesis reaction and the alkylation of benzene were found. The metathesis products consisted of a high molecular weight polymer and cyclic oligomers of cyclooctene. The double bond content was the same as in the monomer. The alkylation products were characterized by the presence of an aromatic nucleus and a low double bond content. Benzene was found to react with the double bond of cyclooctene and the cyclic dimer. It may also lead to the formation of saturated oligomer consisting of short chains of cyclooctyl units. Their presence is not temperature dependent and increases with decreasing initial monomer concentrations. For initial monomer concentrations above 1.0 mol/L, the alkylation reaction cannot be detected.     

Functional Polyolefins: Poly(ethylene)‐graft‐Poly(tert‐butyl acrylate) via Atom Transfer Radical Polymerization From a Polybrominated Alkane

Poly(cis‐cyclooctene) is synthesized via ring‐opening metathesis polymerization in the presence of a chain‐transfer agent and quantitatively hydrobrominated. Subsequent graft polymerization of tert‐butyl acrylate (tBA) via Cu‐catalyzed atom transfer radical polymerization (ATRP) from the non‐activated secondary alkyl bromide moieties finally results in PE‐g‐PtBA copolymer brushes. By varying the reaction conditions, a series of well‐defined graft copolymers with different graft densities and graft lengths are prepared. The maximum extent of grafting in terms of bromoalkyl groups involved is approximately 80 mol%. DSC measurements on the obtained graft copolymers reveal a decrease in T_m with increasing grafting density.