Polymerization Of Epoxides Research Articles

Controlled polymerization of epoxides: Metal‐free ring‐opening polymerization of glycidyl phenyl ether initiated by tetra‐n‐butylammonium fluoride in the presence of protic compounds

AbstractMetal‐free controlled ring‐opening polymerization of glycidyl phenyl ether (GPE) was achieved using tetra‐n‐butylammonium fluoride (Bu4NF) as an initiator in the presence of water and ethanol as chain transfer agents (CTAs). Number‐averaged molecular weight of poly(GPE) increased with an increase of [GPE]0/([Bu4NF]0 + [CTA]0) values, showing relatively narrow molecular weight distributions. NMR spectroscopic analysis exhibited a formation of ethoxy groups as well as FCH2 at the initiating polymer chain‐end when ethanol was used as the CTA in the polymerization. These results indicate that Bu4NF acts as a catalyst as well as the initiator for this polymerization system. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Exploration of Cocatalyst Effects on a Bimetallic Cobalt Catalyst System: Enhanced Activity and Enantioselectivity in Epoxide Polymerization

Organic ionic compounds were synthesized and investigated as cocatalysts with a bimetallic cobalt complex for enantioselective epoxide polymerization. The identities of both the cation and the anion were systematically varied, and the subsequent reactivity was studied. The nature of the ionic cocatalyst dramatically impacted the rate and enantioselectivity of the catalyst system. The ionic cocatalyst [P(N═P(N(CH2)4)3)4+][tBuCO2–] in combination with a bimetallic cobalt complex produced a catalyst system that exhibited the greatest activity and selectivity for a variety of monosubstituted epoxides.

Aluminum Nanoparticles Capped by Polymerization of Alkyl-Substituted Epoxides: Ratio-Dependent Stability and Particle Size

We report here on the polymerization of epoxide monomers on incipient aluminum nanoparticle cores and the effects of changing the epoxide-capping precursor and the metallic monomer ratio on the resultant stability and particle size of passivated and capped aluminum nanoparticles. When altering the ratio of aluminum to cap monomer precursor, nanoparticles capped with epoxydodecane, epoxyhexane, and epoxyisobutane show a clear decreasing trend in stability with decreasing alkane substituent length. The nanoparticle core size was unaffected by cap ratio or composition. PXRD (powder X-ray diffraction) and DSC/TGA (differential scanning calorimetry/thermal gravimetric analysis) confirm the presence of successfully passivated face-centered cubic (fcc) aluminum nanoparticles. We also report preliminary results from ATR-FTIR (attenuated total reflectance-Fourier transform infrared), (13)C CPMAS (cross-polarization/magic-angle spinning), and (27)Al MAS solid-state NMR (nuclear magnetic resonance) measurements. The most stable aluminum nanoparticle-polyether core-shell nanoparticles are found at an Al:monomer mole ratio of 10:1 with an active Al(0) content of 94%.

Influence of multidentate N-donor ligands on highly electrophilic zinc initiator for the ring-opening polymerization of epoxides

A set of multidentate ligands have been synthesized and used to stabilize the putative highly electrophilic zinc species initiating ring-opening polymerization (ROP) of cyclohexene oxide (CHO) and propylene oxide (PO). Reaction of the bidentate C 2-chiral bis(oxazoline) ligand ( R2,R3BOX: R 2 = (4 S)- tBu, R 3 = H ( a); R 2 = (4 S)-Ph, R 3 = H ( b); R 2 = (4 R)-Ph, R 3 = (5 S)-Ph ( c)) with Zn(R 1) 2 (R 1 = Et ( 1), Me ( 2)) led to the heteroleptic three-coordinate complexes ( R2,R3BOX)ZnR 1, 1a– c and 2a, which were isolated in 92–96% yield. Next, two pyridinyl-functionalized N-heterocyclic carbene (NHC) ligands have been designed and synthesized: the 1,3-bis(2-pyridylmethyl)imidazolinium salt ( d) and the protected NHC adduct 2-(2,3,4,5,6-pentafluorophenyl)-1,3-bis(2-pyridylmethyl)imidazolidine ( e). The reaction of ligands d and e with ZnEt 2 led directly to the formation of (NHC)ZnEt(Cl) 3d complex with ethane elimination and the adduct (NHC–C 6F 5(H))ZnEt 2 4e, respectively, in high yield. In situ combinations of selected complexes 1a– c, 3d and 4e with B(C 6F 5) 3 (1 or 2 equivalents) give active systems for ROP, with high productivity (3.3–5.9 10 6 g polym. mol Zn −1 h −1) and high molecular weight ( M n up to 132 10 3 g mol −1) for CHO polymerization. Although the in situ B(C 6F 5) 3-activated zinc species were not isolated, the sterically demanding BOX ligands ( 1c > 1b > 1a) and functionalized NHC ligands seem to enhance the stability of highly electrophilic zinc complexes over ligand redistribution, allowing a better control of the cationic ROP as reflected particularly for 3d and 4e complexes by their respective efficiency (42–88%).

Enantioselective Epoxide Polymerization Using a Bimetallic Cobalt Catalyst

A highly active enantiopure bimetallic cobalt complex was explored for the enantioselective polymerization of a variety of monosubstituted epoxides. The polymerizations were optimized for high rates and stereoselectivity, with s-factors (k(fast)/k(slow)) for most epoxides exceeding 50 and some exceeding 300, well above the threshold for preparative utility of enantiopure epoxides and isotactic polyethers. Values for mm triads of the resulting polymers are typically greater than 95%, with some even surpassing 98%. In addition, the use of a racemic catalyst allowed the preparation of isotactic polyethers in quantitative yields. The thermal properties of these isotactic polyethers are presented, with many polymers exhibiting high T(m) values. This is the first report of the rapid synthesis of a broad range of highly isotactic polyethers via the enantioselective polymerization of racemic epoxides.

Aminimides Derived from Benzoylformic Acid Esters as Thermally Latent Base Catalysts

As a novel thermal latent anionic initiator for lower temperature applications, a new class of aminimide, 1,1-dimethyl-1-(2-hydroxypropyl)amine benzoylformimide (BFI), was synthesized from benzoylformic acid methyl ester in 95% yield, and its thermal rearrangement behavior was studied in detail. Thermal rearrangement of BFI proved to take place on heating above 80 °C via the Curtius rearrangement mechanism, generating the corresponding isocyanate, hydroxyamine, and their further reaction products. BFI proved to catalyze the polymerization of epoxides and epoxide/thiol system on heating above 80 °C. They exhibit both the long pot life and the low-temperature rapid polymerization in the presence of BFI which supported the promising applications of BFI as an efficient thermal latent base catalyst for anionically polymerizable/curable systems.

Redox initiated cationic polymerization: Silane‐N‐aryl heteroaromatic onium salt redox couples

AbstractIn this article, a new route for the synthesis of N‐aryl heteroaromatic onium salts by the direct copper catalyzed arylation of pyridine, substituted pyridines, isoquinoline, and acridine with diaryliodonium salts is described. It was demonstrated that these N‐aryl heteroaromatic onium salts undergo facile platinum or rhodium‐catalyzed reduction by silanes bearing SiH groups. The reduction of N‐aryl heteroaromatic onium salts generates Brønsted acids. When this redox reaction was carried out in situ in the presence of an appropriate monomer, cationic polymerization was observed. Using this approach, the cationic polymerizations of epoxides, oxetanes, 1,3,5‐trioxane, styrene, and vinyl ethers were carried out. The use of optical pyrometry to monitor the redox initiated cationic polymerizations of some representative multifunctional monomers is described. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

Allyl sulfonium salt as a novel initiator for active cationic polymerization of epoxide by shooting with radicals species

AbstractA rapid cationic polymerization of cyclohexene oxide that completed within a few minutes was achieved by a new initiation system that involves (1) a copper‐catalyzed reduction of benzoyl peroxide by an ascorbic acid derivative that generates free radicals and (2) capture of the radicals by allyl sulfonium salt having hexafluoroantimonate (SbF) as a counter anion, followed by fragmentation of sulfonium radical cation, from which a super acid HSbF6 was produced to initiate the rapid polymerization. The key factor in designing an efficient allyl sulfonium salt was attachment of an electron withdrawing ester group at the allyl group, of which ability to stabilize the formed radical can enhance the efficiency in trapping radicals by the allylic salt. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4178–4183, 2010

New Initiating Systems for Thermal Cationic Polymerization at Ambient Temperature with in situ Formation of Ag(0) Nanoparticles: A Silane/Silver Salt Combination

AbstractNew initiating systems for the thermal cationic polymerization of epoxides and vinyl ether derivatives are proposed. They are based on a silane/silver salt interaction, which ensures a good to excellent polymerization at room temperature. Moreover, the polymerization is much more efficient under air. The effects of the silane, silver salt, and monomer structures are investigated. Interestingly, silver nanoparticles Ag(0) are formed in situ. A coherent picture of the involved chemical mechanisms is presented.magnified image

Liquid Crystalline Organisation and Reaction Rate in the Formation of Liquid Crystal Thermoset Networks from Diepoxides and Dicyanates

AbstractSummary: The influence of the type of mesophase on the rate of reaction in amine curing or anionic polymerisation of mesogenic diepoxides, and in the cyclotrimerisation of mesogenic dicyanates has been investigated by isothermal DSC and IR‐spectroscopy. Epoxide/amine systems were found to react faster in the nematic than in the isotropic phase. Anionic polymerisation of epoxides is an example where increase of the reaction rate occurs with the transition from a mesophase of higher order (smectic) to phases with lower order (nematic, isotropic). For triaromatic dicyanates with one or three methyl groups at the central ring cyclotrimerisation is faster in the isotropic than in the nematic phase showing an increase of activation energy in the nematic phase with the number of methyl groups. A pronounced rate increase has been observed in the smectic phase as compared to the nematic phase for the unsubstituted triaromatic dicyanate. In this case activation energies in the two phases are comparable with those of non liquid crystalline dicyanates.

Isospecific polymerization of racemic epoxides: a catalyst system for the synthesis of highly isotactic polyethers

A highly active bimetallic cobalt catalyst system is reported for the polymerization of racemic terminal epoxides to yield isotactic polyethers.

Sensitization of Thianthrenium Salt for Cationic Polymerization of Epoxides

Sensitization of Thianthrenium Salt for Cationic Polymerization of Epoxides

Ring-Opening Polymerization of Imidazole Epoxides for the Synthesis of Imidazole-Substituted Poly(ethylene oxides)

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTRing-Opening Polymerization of Imidazole Epoxides for the Synthesis of Imidazole-Substituted Poly(ethylene oxides)Sean M. Ramirez, John M. Layman, Philippe Bissel, and Timothy E. Long*View Author Information Department of Chemistry, Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, Virginia 24061-0212*Corresponding author. E-mail: [email protected]Cite this: Macromolecules 2009, 42, 21, 8010–8012Publication Date (Web):October 8, 2009Publication History Received4 August 2009Revised25 September 2009Published online8 October 2009Published inissue 10 November 2009https://doi.org/10.1021/ma901745dCopyright © 2009 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1921Altmetric-Citations10LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (3 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Ethers,Monomers,Oxides,Polymers,Ring-opening polymerization Get e-Alerts

Negative tone molecular resists using cationic polymerization: Comparison of epoxide and oxetane functional groups

Two molecular resists with a common molecular glass core were synthesized and characterized to compare the differences between epoxide (oxirane) and oxetane functional groups for use in high resolution negative tone molecular resists. Both resists are able to obtain at least 50nm half-pitch at a sensitivity of 75μC∕cm2 under 100keV electron-beam lithography. Due to differences in the kinetics of the cationic polymerization of epoxides as compared to oxetanes, the epoxide functionalized resist (2-Ep) was able to obtain sub-25-nm half-pitch resolution with good line edge roughness (LER) of 2.9nm (3σ) while the oxetane resist (2-Ox) was limited to 50nm half-pitch resolution and exhibited higher LER (3σ) of 10.0nm. The polymerization of the oxetane functional group has slow initiation and fast propagation which leads to reduced performance in 2-Ox as compared to 2-Ep. While oxetane functionalized molecular resists can obtain reasonably good imaging performance, epoxide functional groups show more promise for use in next generation negative tone resists that have a good combination of resolution, sensitivity, and LER.

Polymerization of epoxy resins initiated by metal complexes

AbstractBACKGROUND: Processing parameters and material properties of epoxy resins can be vastly influenced by choice of curing agent. In this work, metal complexes were investigated as initiators for anionic and cationic epoxide polymerization. Systems for thermally induced and electron beam‐induced curing are described.RESULTS: Zinc or cobalt imidazole complexes of the type [M(imidazole)2(anion)2] are efficient initiators for anionic polymerization of glycidyl‐based epoxy resins. The complexes can be employed to prepare tailored resin systems ranging from fast curing systems at slightly elevated temperatures to systems with very high thermal latencies curable at temperatures far above 150 °C. Silver complexes [Ag(L)n]SbF6 (L = crown ether or alkene) are highly efficient initiators for cationic curing and low initiator contents of around 1% are sufficient to reach high degrees of crosslinking. The complexes are excellent initiators for both thermally induced and electron beam‐induced polymerizations.CONCLUSION: Metal complexes are powerful initiators for the homopolymerization of epoxy resins and can be designed not only for anionic and cationic polymerization but also for thermal and radiation curing. Based on this study and additional work, a library can be compiled which allows retrieval of optimized metal–ligand–anion combinations and adjustment of the initiators to the respective processing and material demands. Copyright © 2009 Society of Chemical Industry

Redox-Initiated Cationic Polymerization: Reduction of Dialkylphenacylsulfonium Salts by Silanes

S,S-Dialkyl-S-phenacylsulfonium salts undergo facile reduction by silanes bearing Si−H groups in the presence of a noble metal catalyst. This redox couple can be employed as a convenient initiator system for the cationic polymerizations of epoxides, oxetanes and vinyl ethers. The polymerizations of these monomers can be carried out in a conventional manner with neat monomer or under solution conditions. In this communication we also report the novel use of a two-component redox system in which the silane is delivered as a vapor to a thin film monomer sample containing the sulfonium salt. Typically, the polymerizations are rapid and exothermic. The use of optical pyrometry (infrared thermography) as a convenient method with which to monitor and optimize the aforementioned cationic polymerizations is described. Studies of the effects of variations in the structures of the S,S-dialkyl-S-phenacylsulfonium salt, the silane and the type of noble metal catalyst on the polymerizations of typical vinyl and heterocyclic monomers were carried out.

Redox Initiated Cationic Polymerization: Reduction of Triarylsulfonium Salts by Silanes

A novel redox initiator system for carrying out the cationic polymerization of epoxide, oxetane and vinyl ether monomers has been developed. The redox couple is based on a triarylsulfonium salt as the oxidant with an organosilane as the reducing agent. The reaction between these two agents is markedly catalyzed by platinum and palladium complexes. Cationic polymerizations using this redox initiator system were carried out in a conventional manner with neat monomer or under solution conditions. This paper also describes the novel use of a two-component redox system in which the silane is delivered to the monomer sample in the vapor state. Optical pyrometry (infrared thermography) was employed as a convenient method with which to monitor the polymerizations. A study of the effects of variations in the structures of the triarylsulfonium salt, the silane and the type of noble metal catalyst were carried out. The use of this initiator system for carrying out commercially attractive cross-linking polymerizations for coatings, composites and electronic encapsulations is discussed.

Radical-Promoted Visible Light Photoinitiated Cationic Polymerization of Epoxides

Herein is described the development of a three-component photoinitiator system that employs the free radical promoted decomposition of diaryliodonium salts for the visible light induced cationic polymerization of epoxides. A long wavelength, titanium-complex free radical photoinitiator is used to generate radicals that abstract hydrogen atoms from benzyl alcohol synergists. The resulting benzyl radical species efficiently reduce diaryliodonium salts thereby generating oxycarbenium ions that spontaneously fragment to form the corresponding aldehyde and a Brønsted superacid. The superacid subsequently initiates the cationic ring-opening polymerization of a wide variety of epoxide monomers.

(η6‐N‐alkylcarbazole) (η5‐cyclopentadienyl) iron hexafluorophosphate salts in photoinitiated and thermal epoxy polymerization

Abstract(η6‐Carbazole)(η5‐cyclopentadienyl) iron hexafluorophosphate salts (CFS PF6) are capable of photoinitiating cationic polymerization of epoxy monomers directly upon irradiation with long‐wavelength UV light. To improve the solubility of CFS ferrocenium salts in epoxides, two CFS photoinitiators have been prepared: [cyclopentadiene‐Fe‐N‐buylcarbazole] hexafluorophosphate (C4‐CFS PF6) and [cyclopentadiene‐Fe‐N‐octylcarbazole] hexafluorophosphate (C8‐CFS PF6), bearing C4 and C8 alkyl chains, respectively, on the nitrogen atom. Studies with real‐time infrared spectroscopy have shown that C4‐CFS and C8‐CFS photoinitiators exhibit high efficiency in polymerization of 3,4‐epoxycyclohexylmethyl‐3,4‐epoxycyclohexane carboxylate (ERL‐4221) epoxy monomer, but lower efficiency in polymerization of di(2,3‐epoxypropyl)‐3,4‐epoxy‐1,2‐cyclohexanedioate (TDE‐85) epoxy monomer. Benzoyl peroxide (BPO) sensitizer was very effective in improving the photoinitiating activities of CFS in polymerization of both ERL‐4221 and TDE‐85. DSC studies have shown that C4‐CFS and C8‐CFS photoinitiators can also be employed as thermal initiators for the cationic ring‐opening polymerization of epoxides at moderate temperatures. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

High resolution negative tone molecular resist based on di-functional epoxide polymerization

There is an urgent demand for higher performance resists with superior resolution, sensitivity, and line edge roughness for both electron-beam and extreme ultraviolet lithography applications. Chemically amplified resists provide superior sensitivity compared to non-chemically amplified resists, but often suffer from resolution limitations and poor line edge roughness. A new class of negative tone chemically amplified molecular resists has been developed based on epoxide cross-linking that combines high sensitivity with low line edge roughness and excellent resolution. The most recent compound of this class (2-Ep) simultaneously demonstrates resolution of 25 nm half-pitch, sensitivity of 38 μC/cm 2, and line edge roughness (3σ) of 2.9 nm under 100 keV e-beam exposure.