Polymerization Of Cyclohexene Oxide Research Articles

Synthesis of Mono- and Dinuclear Aluminum Complexes Bearing Aromatic Amino-Phenolato Ligands: A Comparative Study in the Ring-Opening Polymerization of Cyclohexene Oxide.

Dinuclear aluminum methyl complexes bearing aromatic diamine-bridged tetra(phenolato) ligands and the mononuclear aluminum methyl complex with the phenylamine-bridged bis(phenolato) ligand have been synthesized and characterized. Structure determination revealed that the Al-Al distances in these dinuclear aluminum complexes are tunable by the choice of the suitable aromatic backbone of the diamine-bridged tetra(phenolato) ligands. The catalytic behaviors of these mono- and dinuclear aluminum complexes for cyclohexene oxide (CHO) polymerization were investigated. The activities of these dinuclear Al complexes were observed to increase with the decrease of Al-Al distances, and the dinuclear Al complexes appeared to have better catalytic activity than the mononuclear Al complex, even if the Al-Al distance is as long as 9.401 Å. Dinuclear aluminum complex 2, with the shortest Al-Al distance (7.236 Å), showed the highest activity toward CHO polymerization with TOFs up to 6460 h-1 in neat CHO at 30 °C. Furthermore, comparative kinetic studies revealed that the polymerization is first-order for CHO concentration, and the reaction orders for initiator concentration are different for the mono- and dinuclear Al complexes. The polymerization mechanism study revealed that both the methyl and phenolate groups were involved in the initiation process.

Synthesis and characterization of Al (III)‐Zn (II) heterometallic complex and the application in ring‐opening polymerization of cyclohexene oxide

Four aluminum, zinc, and aluminum/zinc heterometallic complexes 1–4 stabilized by o‐phenylenediamine bridged poly (phenolato) ligands were synthesized and characterized. It was found that the reaction sequence has significant influence on the formation of the Al‐Zn heterometallic complex AlZnL1Me (4), which was prepared through successive complexation of poly (phenol) with ZnEt2 and AlMe3. The catalytic behaviors of complexes 1–4 for the ring‐opening polymerization of cyclohexene oxide (CHO) were investigated, and the heterometallic complex 4 showed significantly enhanced activity (TOF up to 410 min−1). Kinetic study was conducted; the activation energy (Ea) for formation of PCHO using 4 was determined to be 58.0 ± 6.5 kJ mol−1.

Block Copolymerization of Lactide and an Epoxide Facilitated by a Redox Switchable Iron‐Based Catalyst

AbstractA cationic iron(III) complex was active for the polymerization of various epoxides, whereas the analogous neutral iron(II) complex was inactive. Cyclohexene oxide polymerization could be “switched off” upon in situ reduction of the iron(III) catalyst and “switched on” upon in situ oxidation, which is orthogonal to what was observed previously for lactide polymerization. Conducting copolymerization reactions in the presence of both monomers resulted in block copolymers whose identity can be controlled by the oxidation state of the catalyst: selective lactide polymerization was observed in the iron(II) oxidation state and selective epoxide polymerization was observed in the iron(III) oxidation state. Evidence for the formation of block copolymers was obtained from solubility differences, GPC, and DOSY‐NMR studies.

Block Copolymerization of Lactide and an Epoxide Facilitated by a Redox Switchable Iron-Based Catalyst.

A cationic iron(III) complex was active for the polymerization of various epoxides, whereas the analogous neutral iron(II) complex was inactive. Cyclohexene oxide polymerization could be "switched off" upon in situ reduction of the iron(III) catalyst and "switched on" upon in situ oxidation, which is orthogonal to what was observed previously for lactide polymerization. Conducting copolymerization reactions in the presence of both monomers resulted in block copolymers whose identity can be controlled by the oxidation state of the catalyst: selective lactide polymerization was observed in the iron(II) oxidation state and selective epoxide polymerization was observed in the iron(III) oxidation state. Evidence for the formation of block copolymers was obtained from solubility differences, GPC, and DOSY-NMR studies.

Methoxyaryl substituted aluminum ketiminate complexes and its activity in ring opening polymerization processes

The synthesis of dimethyl aluminum (LoAlMe2) and chloromethyl aluminum (LoAlMeCl) complexes containing ketiminate ligand [(2-MeO)C6H4]N(H)C(Me)=CHC(Me)=O (LoH) is reported along with the preparation of Lo3Al from LoH and LiAlH4, and ionic [Lo′Al(thf)3]I from LoAlMe2 and I2. In the later complex the pseudooctahedral geometry of the aluminum ion by terdentate ligand {[(2-O)C6H4]NC(Me)=CHC(Me)=O}2− (Lo′), originated from Lo ligand by the methyl group abstraction, and three THF molecules are observed. Structures of these complexes were determined by X-ray techniques. The activity of LoAlMe2 and LoAlMeCl as initiators of ring opening polymerization of ε-caprolactone, trimethylene carbonate and l-lactide, and (co)polymerization of cyclohexene oxide and carbon dioxide was studied.

Highly efficient one-pot/one-step synthesis of multiblock copolymers from three-component polymerization of carbon dioxide, epoxide and lactone.

It is a long-standing challenge to combine mixed monomers into multiblock copolymer (MBC) in a one-pot/one-step polymerization manner. We report the first example of MBC with biodegradable polycarbonate and polyester blocks that were synthesized from highly efficient one-pot/one-step polymerization of cyclohexene oxide (CHO), CO2 and ε-caprolactone (ε-CL) in the presence of zinc-cobalt double metal cyanide complex and stannous octoate. In this protocol, two cross-chain exchange reactions (CCER) occurred at dual catalysts respectively and connected two independent chain propagation procedures (i.e., polycarbonate formation and polyester formation) simultaneously in a block-by-block manner, affording MBC without tapering structure. The multiblock structure of MBC was determined by the rate ratio of CCER to the two chain propagations and could be simply tuned by various kinetic factors. This protocol is also of significance due to partial utilization of renewable CO2 and improved mechanical properties of the resultant MBC.

Polymerization of epoxides catalyzed by a mixed-valent iron trifluoroacetate [Fe3O(O2CCF3)6(H2O)3

The readily available mixed-valent iron trifluoroacetate complex [Fe2IIIFeII(µ3-O)(O2CCF3)6(H2O)3] is an effective catalyst for the polymerization of epoxides. A very small amount of the catalyst (1.0–0.01 mol%) could initiate the polymerization of cyclohexene oxide, cyclopentene oxide and epichlorohydrin. Based on quantitative end-group analysis by 19F NMR spectroscopy, a Lewis acid (LA⊕) catalyzed anionic reaction mechanism is proposed. Copyright © 2012 Society of Chemical Industry

Ring‐opening polymerization of cyclohexene oxide by recyclable scandium triflate in room temperature ionic liquid

AbstractIn this article, we provide a concept of a two‐phase polymerization system consisting of immiscible monomer and room temperature ionic liquid (IL). The catalyst is immobilized in the IL phase where polymerization takes place. The produced polymer is extracted by the monomer, and the remaining IL phase is catalytically active for more polymerizations. Thus, common volatile organic solvents are no longer needed. Ring‐opening polymerization of cyclohexene oxide (CHO) in 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate IL ([bmim][BF4]) using scandium triflate [Sc(OTf)3] catalyst serves as a realistic example of such concept. The yield of polyCHO in [bmim][BF4] is higher than that in bulk. IL containing Sc(OTf)3 can be used for at least three times. A circulatory polymerization process is carried out with added catalyst to keep a relatively high yield in following circulation processes. The assignments of proton signals of polyCHO in 1H NMR are discussed in detail. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Novel addition-fragmentation agent in cationic photopolymerization

The aim of present study is to examine the photo-initiation efficiency of N,N-dimethylacrylamide-based allylic ammonium salt as one component addition-fragmentation agent (cationic photoinitiator cum radical source) in free radical accelerated cationic polymerization. Novel addition-fragmentation agent (AFA), 2-(N,N-dimethylcarboxy-3-propenyl)(phenylcarbonyl-4-phenylene) dimethyl ammonium hexafluoroantimonate (DMPDA) was synthesized as cationic photoinitiator and its initiation efficiency was examined in polymerization of cyclohexene oxide (CHO), isobutyl vinyl ether (IBVE), and n-butyl vinyl ether (n-BVE) in CH2Cl2 solvent at wavelength λ > 290 nm. The rate of polymerization increases with the increase in initiator concentration and reaction time. The results demonstrate that DMPDA acts as an efficient photoinitiator (AFA) without use of radical source in free radical accelerated cationic polymerization.

Poly(cyclohexene oxide)/clay nanocomposites by photoinitiated cationic polymerization via activated monomer mechanism

AbstractPoly(cyclohexene oxide) (PCHO)/clay nanocomposites were prepared by in situ photoinitiated activated monomer cationic polymerization. The polymerization of cyclohexene oxide through the interlayer galleries of the clay can provide distribution of the clay layers in the polymer matrix homogenously and results in the formation of PCHO/clay nanocomposites. The exfoliated structures were characterized by X‐ray diffraction spectroscopy, thermogravimetric analysis, transmission electron microscopy, and atomic force microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5328–5335, 2009

Novel allylic phosphonium salts in free radical accelerated cationic polymerization

In the present study, the synthesis and evaluation of novel allylic phosphonium salts as addition fragmentation agents in combination of conventional (photo-/thermal) free radical source for cationic polymerization are described. The amide based allylic phosphonium salts, namely 2-(N, N-dimethylcaboxy-propenyl) triphenylphosphonium hexafluoroantimonate (DMTPH) and 2-(morpholinocarboxy-propenyl) triphenyl phosphonium hexafluoroantimonate (MTPH) were synthesized and characterized. The thermal and photo-latency of these salts was examined with and without free radical sources in bulk polymerization of cyclohexene oxide (CHO) salts at 70 °C and λ > 290 nm irradiation, respectively. In presence of thermal free radical source, the order of activity was observed as PAT > BPO > AIBN. The order of activity of free radical sources on photopolymerization was found to be benzoin > benzophenone > TMDPO. In addition, photopolymerization of other cationically polymerizable monomers (such as n-butyl vinyl ether, isobutyl vinyl ether, N-vinyl carbazole and glycidyl phenyl ether) was also examined at λ > 290 nm irradiation. It is concluded that the rate of cationic polymerization can be accelerated using novel phosphonium salts with combination of free radical sources, by both thermal and photochemical mode.

Cationic polymerization of cyclohexene oxide by pentamethoxytrityl salts

Abstract—Polymerization of cyclohexene oxide (CHO) has been investigated in dichloromethane, using crystalline, soluble, and nonhygroscopic methoxy substituted trityl carbocationic salts having nonnucleophilic anions such as SbF 6 − and PF 6 − without cocatalysts or promoters at 25°C. The effects of salt counterion, photolysis time, and variation in salt concentration on the polymerization of CHO are discussed.

Cationic Polymerization of Epoxides using Novel Xanthenyl Phosphonium Salts as Thermo-latent Initiator

The present article describes the effect of steric and electronic factors on the efficiency of initiators based on novel xanthenyl phosphonium salts for cationic polymerization of epoxide monomers. 2-substituted (IH, ICl, IMe, and IOMe) xanthenyl phosphonium hexafluoroantimonate were synthesized and characterized by NMR (1H, 13C and 31P) and IR spectroscopy. The order of initiator activity in polymerization of glycidyl phenyl ether (GPE), was found as IH> ICl>IMe>IOMe. To understand the effect of steric factor, the polymerization of cyclohexene oxide (CHO) was performed and the order of activity was found as ICl>IH>IMe >IOMe. All the initiators were found to be latent at ambient temperature and initiates polymerization on thermal initiation. The order of initiator activity was influenced by electronic and steric factors in the system. The thermal stability of these salts was measured by Thermo gravimetric analysis (TGA). The solubility of the initiators in various organic solvents and epoxy monomers is also discussed.

Dithioester functionalization of poly(cyclohexene oxide) and its application to obtain block copolymers

A new method of introducing dithioester groups into the polymer chain of poly(cyclohexene oxide) is reported. It includes the use of diaryliodonium salt and an aromatic dithioacid as a redox couple to initiate the cationic polymerization of cyclohexene oxide. It was found that the dithioacid by itself cannot start the polymerization of cationic polymerizable monomers; however, in combination with a diaryliodonium salt, an exothermic reaction was produced, yielding a thiocarbonylthio-functionalized polyether. Thermal profiles of the redox polymerizations were determined by means of optical pyrometry. A preliminary study showed that when the poly(cyclohexene oxide) functionalized with dithioester groups was introduced into the radical polymerization of styrene, the polystyryl growing radicals reacted with the dithioester-functionalized polyether to form a block polymer. The amount of polyether actually incorporated into the block copolymer was calculated to be 70% of the initial amount of poly(cyclohexene oxide)/dithiobenzoic acid charged into the reactor. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Polymerization of cyclohexene oxide by methyl-4-[bis(4-bromophenyl)amino]benzoate cation radical salts

Methyl-4-[bis(4-bromophenyl)amino]benzoate cation radical salts having non-nucleophilic anions such as \( {\text{SbF}}^{ - }_{6} \), \( {\text{PF}}^{ - }_{6} \) and \( {\text{AsF}}^{ - }_{6} \) were newly prepared and found to be very active initiators for the polymerization of cyclohexene oxide at room temperature, in dichloromethane without any external stimulation. The effects of counter ion structure, salt and monomer concentration on the polymerization yield and molecular weight, and the mechanism of initiation are presented.

Ring-opening polymerization of cyclohexene oxide by a novel dicationic palladium catalyst

The synthesis of a novel, air- and moistures table dicationic palladium (II) complex, Pd(CH3CON-(2-pyridyl)2)(CH3CN)2+ 2(PF6 −)2 (1) is described. 1 crystallizes in the mononoclinic space group C2/m, a = 2391.11 (4), b = 1063.34(5), c = 1137.59(6) pm, α = 90°, β = 105.026(2)°, γ = 90°, Z = 4. Its use in the ring-opening polymerization (ROP) of cyclohexene oxide in comparison to the parent catalyst, dichloropalladium di(pyrid-2-yl)amide (2) was investigated. In contrast to 2, 1 shows excellent reactivity in the ROP of cyclohexene oxide, allowing a class-II living polymerization, however, it fails to polymerize propylene oxide.

Et(2)Al(+) alumenium ion-like chemistry. synthesis and reactivity toward alkenes and alkene oxides.

Inert weakly coordinating carborane anions, CB(11)H(6)X(6)(-) (X = Cl, Br), allow access to the long sought, highly electrophilic diethylaluminum moiety in Et(2)Al(CB(11)H(6)X(6)). X-ray crystallography reveals ion-like structural features reminiscent of the corresponding trialkylsilylium species. Et(2)Al(CB(11)H(6)X(6)) is a potent catalyst for the electrophilic ethenation of benzene, the polymerization of cyclohexene oxide, and the oligomerization of ethene to a low molecular weight, highly branched product.

A Novel Bifunctional Addition-Fragmentation Agent for Photoinitiated Cationic Polymerization

A novel addition-fragmentation agent (AFA), namely, 2-benzyl-2-(N,N-dimethyl-2-ethoxycarbonyl-1-propenyl) ammonium hexafluoroantimonate-1-(4-morpholinophenyl)-butane-1-one, for photoinitiated cationic polymerization was synthesized and characterized. With this compound, it is possible to initiate the cationic polymerization of cyclohexene oxide (CHO), butyl vinyl ether (BVE) and N-vinylcarbazole (NVC) photochemically at λ = 380 nm. The mechanism involves the formation of radicals from the alkylphenone moiety and the addition of these radicals to the allylic site and fragmentation of the AFA.

Synthesis and characterization of dienic salts as addition–fragmentation type initiators for cationic polymerization

Thiophenium pentadiene (TPD) and pyridinium pentadiene (PPD) salts with hexafluoroantimonate counteranion were prepared by reacting 5-bromo-1,3-pentadiene with thiophene and pyridine, respectively, and subsequent counteranion exchange with sodium hexafuoroantimonate, and characterized. The cationic polymerization of cyclohexene oxide (CHO) containing one of the dienic salts (TPD or PPD) and a respective free radical initiator was initiated upon thermolysis at 70°C or photolysis at λ > 300 nm. Benzoyl peroxide (BP), 2,2′-azobisisobutyronitrile (AIBN), phenylazotriphenylmethane (PAT), benzoin (B) and trimethoxybenzoyl dipenylacylphoshine oxide (TMDPO) were used as thermal and photochemical sources of free radicals. The contribution of addition-fragmentation and electron transfer meachanisms for the initiation is discussed.

Photochemically and thermally induced radical promoted cationic polymerization using allyl phosphonium salts

Three allylic triphenyl phosphonium salts, namely allylphosphonium (AP), methyl allylphosphonium (MAP) and ethoxy carbonyl allylphosphonium (ECAP) salts with a hexafluoroantimonate counter anion were synthesized and characterized. Their capability to act as initiators or coinitiators for the cationic polymerization of oxiranes such as cyclohexene oxide (CHO) and vinyl monomers such as butylvinyl ether and N-vinyl carbazole was examined. These monomers turned out to be polymerizable in the presence of ECAP provided free radicals are generated thermally at 70°C or photochemically at λ>350nm with the aid of appropriate radical sources. The polymerization of CHO was also induced thermally in the absence of radical sources only with ECAP at a very low rate, while all the three types of salts are ineffective in generating reactive species when irradiated at λ=268nm where the salts absorb the light. Regarding sources generating free radicals the mode of action of ECAP concerning promotion of the cationic polymerization seems to be based on the addition–fragmentation mechanism. Accordingly, a free radical adds to the carbon–carbon double bond and fragmentation of the adduct radical results in the formation of a reactive onium radical cation. The possibility of electron transfer mechanism was disregarded since nucleophilic triphenyl methyl radicals were not oxidized with the aid of phosphonium salts.