Ring-opening Polymerization Of Cyclic Ethers Research Articles

Borinane Boosted Bifunctional Organocatalysts for Ultrafast Ring-Opening Polymerization of Cyclic Ethers

Borinane Boosted Bifunctional Organocatalysts for Ultrafast Ring-Opening Polymerization of Cyclic Ethers

Modeling of Living Cationic Ring-Opening Polymerization of Cyclic Ethers: Active Chain End versus Activated Monomer Mechanism

Living cationic ring-opening polymerization of cyclic ethers in the presence of diol was modeled using the method of moments. A widespread kinetic model was developed based on previous experimental studies. Then, the moment and population balance of reactants were obtained. Modeling results were employed to study the influence of initiator and water amounts (as the impurity) as well as feeding policy in polymerization kinetics and final properties of the polymer. In addition, the sensitivity of modeling results to initiation, backbiting, and finally propagation via activated monomer reactions were investigated. Results showed the population of chains is the function of their precursors. In a typical polymerization, chains with diol functionality are the majority. Therefore, most of the polymerized monomers are incorporated into those chains. This makes the chains with diol functionality the determining group in Molecular Weight Distribution (MWD). The kinetics of polymerization and properties of the reactor’s product are highly dependent on the ratio of the rate of propagation via the Activated Monomer (AM) mechanism to the rate of propagation via active chain end (ACE). An increase in this ratio decreases the probability of occurrence of backbiting reaction. Therefore, cyclic dimers are less formed and MWD narrows. On the other hand, decreasing this ratio results in less diol reacted with protonated monomers. Consequently, the rate of regeneration of the initiator and hence the rate of polymerization is decreased. These findings give complete facts about the ring-opening syntheses of polyethers and are valuable for evolving new grades as well as optimization current processes.

ChemInform Abstract: Efficient Transition Metal‐Catalyzed Reactions of Carboxylic Acid Derivatives with Hydrosilanes and Hydrosiloxanes, Afforded by Catalyst Design and the Proximity Effect of Two Si—H Groups

AbstractReview: [89 refs.

Efficient Transition Metal-Catalyzed Reactions of Carboxylic Acid Derivatives with Hydrosilanes and Hydrosiloxanes, Afforded by Catalyst Design and the Proximity Effect of Two Si–H Groups

The discovery of the ruthenium cluster μ3,-(η2:η3:η5-acenaphythylene)Ru3(CO)7 (1), which is active in catalytic reactions involving Si–H bond activation, and the rate enhancement by the proximity effect of two Si–H groups enabled the reduction of carboxylic acid derivatives with hydrosilanes under mild reaction conditions. A judicious choice of the hydrosilane and of the additives led to a remarkably selective reduction. Besides simple reduction, the treatment of carboxylic acid derivatives with hydrosilanes in the presence of 1 led to new reactions involving several C–O and C–C bond-forming as well as C–O bond-cleavage steps. These reactions included polymerization, rearrangement, and aromatic substitution. The use of inexpensive 1,1,3,3-tetramethyldisiloxane (TMDS) facilitated the efficient reduction of amides to amines using either 1, commercially available platinum compounds, or environmentally friendly iron complexes. The conversion of tertiary amides into aldenamines was achieved by iridium catalysis. In the ruthenium-, iridium-, platinum-, and iron-catalyzed reduction of amides, the use of the reducing reagent polymethylhydrosiloxane (PMHS) resulted in self-encapsulation of the residual metal species into the formed silicone gel to give the ‘metal-free’ product in a straightforward way. 1 Introduction 2 Two Key Preliminary Investigations 2.1 A Ruthenium Cluster for Si–H Bond Activation 2.2 Proximity Effect of Two Si–H Groups for Rate Enhancement 3 Ruthenium-Catalyzed Reduction of Carboxylic Acid Derivatives 3.1 From Ketones to Less Reactive Carboxylic Acid Derivatives 3.2 Self-Encapsulation of the Residual Metals into Silicone Gel 4 Extension to C–O and C–C Bond-Forming Reactions 4.1 Reduction versus Ring-Opening Polymerization of Cyclic Ethers 4.2 Polymerization versus Rearrangement of Vinyl Ethers 4.3 Is ‘R3Si+’ Involved in the Reactions? 4.4 Applications of ‘R3Si+’-Mediated Reactions 5 Reductions with Unique Selectivity 6 Surfing the Periodic Table 7 Concluding Remarks

Ring-opening polymerization of cyclic ethers initiated by benzazaphosphole-W(CO)5/silver hexafluoroantimonate

Ring-opening polymerization of cyclic ethers initiated by benzazaphosphole-W(CO)₅/silver hexafluoroantimonate

Ring-Opening Polymerization of Trimethylene Carbonate Catalyzed by Methanesulfonic Acid: Activated Monomer versus Active Chain End Mechanisms

The ring-opening polymerization (ROP) of trimethylene carbonate (TMC) initiated by water or n-pentanol and catalyzed by trifluoromethanesulfonic acid (HOTf) or methanesulfonic acid (MSA) has been investigated. In contrast with HOTf, MSA was found to afford poly(trimethylene carbonate) (PTMC) free of ether linkages even under forcing conditions. The comparison of the two acids substantiates further that activity does not simply correlate with acidity. Analysis of the resulting PTMC by Size Exclusion Chromatography (SEC), 1H NMR spectroscopy and mass spectrometry revealed the absence of molar mass control due to the formation of two polymer populations. This phenomenon was unambiguously attributed to the occurrence of two competitive mechanisms, namely Activated Monomer (AM) and Active Chain End (ACE). Such a situation is frequently encountered in the ROP of cyclic ethers, but is unprecedented for cyclic carbonates. Its deleterious impact on the polymerization control can be significantly reduced by maintai...

Curing properties of cycloaliphatic epoxy derivatives

In the cationic ring-opening polymerization of cyclic ethers, three major factors, i. e. ring strain, basicity and steric hindrance, are known to govern the reactivity. Considering from these three factors, cycloaliphatic epoxides seem to be the best candidate for the high performance formulations. In the commercial applications, 3,4-epoxycyclohexyl-3′,4′-epoxycyclohexene-carboxylate (ECC) is widely used as cycloaliphatic epoxy monomer. In ECC polymerization, the possibility of ester group participation was pointed out, which resulted in lower reactivity. The negative effect of ester group seems to be very important issue for improved reactivity. In this study, to clarify the effect of the ester group on the cationic polymerization, two di-functional monomers, 2,2-bis-(3,4-epoxycyclohexyl)-propane (CADE-1) and 3,3′-bicyclohexene-3,3′,4,4′-diepoxide (CADE-2), were selected as candidate for no-ester monomers and their reactivity in the photo-initiated cationic polymerization was investigated. Using photo-DSC and real time DRA method, reactivity comparison of them with ECC was conducted. High curing rate of CADEs, especially for low viscous CADE-2, was confirmed. The curing rate of highly viscous CADE-1 was effectively accelerated by addition of low viscous oxetane monomer.

Highly Efficient Catalytic Reactions via Activation of a Si—H Bond of Organohydrosilanes by Triruthenium Carbonyl Clusters Bearing Bridging an Acenaphthylene or Azulene Ligand

Highly efficient catalytic reactions have been achieved via activation of Si-H bonds of organohydrosilanes by triruthenium carbonyl clusters bearing bridging acenaphthylene or azulene ligands. A ruthenium complex, (μ2, η2:η3:η5-acenaphthylene) Ru3 (CO)7 (1) catalyzes hydrosilylation of ketones and aldehydes in solution at room temperature to form the corresponding silyl ether in high yields. Prior activation of the catalyst by excess amounts of the hydrosilane results in dramatic increase of the catalytic activity. Application of the hydrosilylation catalyzed by preactivated 1 to the reduction of carboxylic acids and their derivatives has provided efficient preparative methods for silyl and alkyl ethers from esters, silyl ethers from carboxylic acids, and amines from amides, which are hardly achieved with other transition metal catalysts. The cluster 1 also behaves as an active catalyst for ring-opening polymerization of cyclic ethers and cyclic siloxanes and addition polymerization of vinyl ethers, which are induced by hydrosilanes. Spectroscopic analysis of the polymers obtained reveals existence of an organosilyl moiety at the end group, which is useful for further chemical transformation of the formed polymer. Isolation, characterization, and reactions of possible catalytically active species help discussion on the reaction mechanisms, in which a triruthenium hydridosilyl cluster is involved in the catalytic cycle.

ルテニウムカルボニルクラスターを触媒として用いたヒドロシリル化反応を基軸とする高活性触媒反応

Highly efficient catalytic reactions have been achieved via activation of Si-H bonds of organohydrosilanes by triruthenium carbonyl clusters bearing bridging acenaphthylene or azulene ligands. A ruthenium complex, (μ2, η2:η3:η5-acenaphthylene) Ru3 (CO)7 (1) catalyzes hydrosilylation of ketones and aldehydes in solution at room temperature to form the corresponding silyl ether in high yields. Prior activation of the catalyst by excess amounts of the hydrosilane results in dramatic increase of the catalytic activity. Application of the hydrosilylation catalyzed by preactivated 1 to the reduction of carboxylic acids and their derivatives has provided efficient preparative methods for silyl and alkyl ethers from esters, silyl ethers from carboxylic acids, and amines from amides, which are hardly achieved with other transition metal catalysts. The cluster 1 also behaves as an active catalyst for ring-opening polymerization of cyclic ethers and cyclic siloxanes and addition polymerization of vinyl ethers, which are induced by hydrosilanes. Spectroscopic analysis of the polymers obtained reveals existence of an organosilyl moiety at the end group, which is useful for further chemical transformation of the formed polymer. Isolation, characterization, and reactions of possible catalytically active species help discussion on the reaction mechanisms, in which a triruthenium hydridosilyl cluster is involved in the catalytic cycle.

New Syntheses of Graft Copolymers Using the DPE-Technique: Cationic Graft Copolymerization

A new one-step synthesis of a set of macroinitiators for cationic polymerization via radical polymerization is presented. The macroinitiator consists of poly(meth)acrylate random copolymers with p-chloromethylstyrene. It was synthesized by controlled radical polymerization of a monomer mixture of (meth)acrylate and p-chloromethylstyrene in the presence of 1,1-diphenylethylene (DPE) using azobisisobutyronitrile (AIBN) as initiator. The resulting macroinitiators were used for the cationic ring-opening polymerization of cyclic ethers yielding graft copolymers which were characterized by GPC and NMR.

Molecular Design of Single Site Catalyst Precursors for the Ring-Opening Polymerization of Cyclic Ethers and Esters. 2. Can Ring-Opening Polymerization of Propylene Oxide Occur by a Cis-Migratory Mechanism?

From the reactions between 2,2‘-ethylidenebis(4,6-di-tert-butylphenol) and 2,2‘-methylidenebis(4-dimethyl-6-di-tert-butylphenol) and Et2AlCl the biphenoxide complexes [(O∼∼CHMe∼∼O)AlCl]2, 1, and [(O∼∼CH2∼∼O)AlCl]2, 2, have been isolated and characterized. These dimers are broken up by donor ligands, and the molecular structure of ethylidenebis(4,6-di-tert-butylphenoxide)AlCl(THF), 3, has been structurally characterized. Racemic 5,5‘-6,6‘-tetramethyl-3,3‘-di-tert-butyl-1,1‘-biphen-2,2‘-diol and Et2AlCl react in hexane to give [(O∼∼O)AlCl]2, compound 6, as a hydrocarbon insoluble white precipitate. In the donor solvent THF monomeric species are formed, and (O∼∼O)AlX(THF) has been crystallographically characterized, X = 20% Cl and 80% Et occupancy. Refluxing in THF favors X = Cl, compound 4. The reaction of Et2Al(OEt) with the biphenol gives (O∼∼O)AlEt(THF), 5, in the presence of THF by displacement of one ethyl and one ethoxide ligand. Compounds 1, 2, 3, 4, 5, 6, [(O∼∼CHMe∼∼O)Al(OiPr-d7)]2, and [Cp2Zr(OEt)(...

Modification of carbon whisker surface by the grafting of polyethers: Cationic ring-opening polymerization of cyclic ethers initiated by acylium perchlorate groups on the surface

To modify the surface of a carbon whisker, i.e. a vapor-grown carbon fiber, the grafting of polyethers onto the surface by the ring-opening polymerization of cyclic ethers initiated by acylium perchlorate groups introduced onto the surface was investigated. The introduction of acylium perchlorate groups onto the carbon whisker was achieved by the reaction of silver perchlorate with surface acyl chloride groups, which were introduced by the treatment of surface carboxyl groups with thionyl chloride. It was found that the surface acylium perchlorate groups are capable of initiating the cationic ring-opening polymerization of cyclic ethers such as tetrahydrofuran (THF), styrene oxide and propylene oxide, and the corresponding polyethers are effectively grafted onto the carbon whisker, based on the propagation of the polymer from the surface. The rate of the polymerization increased with increasing polymerization temperature, but the percentage of polyether grafting decreased, because the chain transfer reaction of the growing polymer cation is accelerated at higher temperature. Poly(THF)-grafted carbon whiskers dispersed stably in a good solvent for poly(THF), such as THF, but precipitated immediately in a poor solvent. Therefore it is considered that grafted poly(THF) chains on the carbon whisker surface extend outside the surface in THF and interfere with the aggregation of carbon whiskers.

Cationic Grafting from Carbon Black. X. Graft Polymerization Initiated by Benzylium Perchlorate Groups Introduced onto a Carbon Black Surface

Abstract The cationic graft polymerization of various polymers from carbon black initiated by benzylium perchlorate groups introduced onto the surface was investigated. The introduction of benzylium perchlorate groups onto a carbon black surface was achieved by the reaction of silver perchlorate with benzyl chloride groups on the surface. Benzyl chloride groups were introduced by the treatment of carbon black with 3,3′-bischloromethylbenzoyl peroxide in carbon tetrachloride. It was found that the cationic polymerization of styrene is initiated by carbon black having benzylium perchlorate groups, and polystyrene is grafted from the surface based on the propagation of the polymer from the surface. The percentage of grafting increased to 130.1%. The weightaverage molecular weight of grafted polystyrene was estimated to be 5.0 × 103. Furthermore, benzylium perchlorate groups on carbon black have an ability to initiate the cationic ring-opening polymerization of cyclic ethers, such as tetrahydrofuran and epichlorohydrin, and lactones, such as ε-caprolactone and δ-valerolactone, to give polyether- and polyester-grafted carbon black, respectively. These polymer-grafted carbon blacks gave a stable colloidal dispersion in good solvents for grafted polymer.

Symposium on the Polymerization of Cyclic Ethers and Sulfides

Abstract Ring-opening polymerization of cyclic ethers and sulfides has long been exciting broad interest as a distinct area of specialization. Often it was useful to include discussions of these studies as part of other areas such as anionic or cationic polymerization However, these ring-opening polymerizations have likewise been the sole subject of successful symposia The time lapse since the previous such ACS sponsored symposium and the worldwide effort since then amply justified this American Chemical Society sponsored symposium held in Boston, Massachusetts, April 11 and 12, 1972. Judging from its reception, I felt it was a successful. and timely symposium. I think this attests to the considerable amount of good work being done in the area and to the advances that are being made. Not only are there a number of important products on the market based on this chemistry, but also considerable basic chemical knowledge has evolved, leading in turn to still more products.

Studies on the Ring-Opening Polymerization of Cyclic Ethers. Kinetics of Initiation Reaction by Triethyloxonium Tetrafluoroborate

Studies on the Ring-Opening Polymerization of Cyclic Ethers. Kinetics of Initiation Reaction by Triethyloxonium Tetrafluoroborate