Synthesis and Photopolymerization of Silicon-Containing Multifunctional Oxetane Monomers

Abstract

A series of silicon-containing multifunctional oxetane monomers has been prepared and characterized. These monomers were compared among themselves and with other oxetane monomers with respect to their reactivity in photoinitiated cationic polymerization.     

Photoinitiated cationic polymerization of oxetane formulated with oxirane

Photoinitiated cationic polymerization of oxetane, oxirane (epoxide), and a formulation of both was carried out and their reactivity compared. To investigate a formulated system of oxetane and oxirane in photoinitiated cationic polymerization, computational and experimental methods were used. In the computational study, we employed a semiempirical molecular orbital method (AM1). On the other hand, the reactivities of each system were evaluated and compared experimentally by a real-time FT-IR method. The computational study reveals that oxetane seems to polymerize in S_N2 mechanism, but two possibilities, of S_N1 mechanism through the α-cleavage and of S_N2 mechanism through β-cleavage, are implied for oxirane. Using the real-time FT-IR method, the formulation of oxetane and oxirane was proved to possess rather high reactivities of oxetane toward photoinitiated cationic polymerization. The formulated system exhibited slightly lower number-average molecular weight than oxetane but higher than oxirane. These experimental observations are well explained in terms of the calculated reaction paths. © 1995 John Wiley & Sons, Inc.     

Structure and Reactivity Relationships in the Photoinitiated Cationic Polymerization of Oxetane Monomers

Abstract

A series of oxetane-containing monomers possessing several different types of functional groups has been prepared and characterized. These monomers were compared among themselves, and conclusions were drawn with respect to the influence of structure on their reactivities in photoinitiated cationic polymerization.     

Synthesis and Cationic Polymerization of Open-Chain and Cyclic Enol Ethers

Abstract

Several new open-chain and cyclic enol ether monomers were prepared using simple, straightforward procedures. The reactivities of these monomers were compared using both differential scanning photocalorimetry and Fourier transform real-time infrared spectroscopy. In general, these new monomers were found to possess excellent reactivity in photoinitiated cationic polymerization using a diaryliodonium salt photoinitiator.     

Aryl Epoxides as Accelerators for the Photopolymerization of Oxetane Monomers

Epoxides bearing aryl groups function as “kick-starters” to markedly accelerate the photoinitiated cationic ring-opening polymerization of oxetane monomers. Thus, it has been observed that the inclusion of a small amount of styrene oxide transforms a sluggishly polymerizing 3-mono- or 3,3-disubstituted oxetane monomer into one that undergoes rapid, exothermic polymerization. Mechanistic studies suggest that the activity of aryl epoxides as “kick-starters” is related to their ability to intercept photogenerated acids to form benzylic cations that rapidly initiate oxetane monomer polymerization by alkylation of the monomer.     

Synthesis and Cationic Photopolymerization of Novel Cycloaliphatic Epoxy Monomers Based on 5,6-Epoxy-1,3-oxepane

Abstract

A novel series of mono-, di-, and trifunctional monomers containing 5,6-epoxy-1,3-dioxepane groups were prepared along with a similar series of epoxycyclohexane monomers. The reactivities of the monomers were compared using both differential scanning photocalorimetry and Fourier transform real-time infrared spectroscopy. The novel monomers containing 5,6-epoxy-1,3-dioxepane groups were highly reactive in photoinitiated cationic polymerization but slightly less reactive than their counterparts based on epoxycyclohexane.     

Synthesis and cationic photopolymerization of alkoxyallene monomers

A series of cationically polymerizable mono-and difunctional alkoxyallene monomers have been prepared via the straight forward base catalyzed isomerization of the corresponding propargyl ethers. Rate studies conducted using real-time infrared spectroscopy showed that these monomers exhibit high reactivity in photoinitiated cationic polymerization. Monomers bearing a single alkoxyallene group undergo rapid polymerization to yield crosslinked polymers indicating that both double bonds react during polymerization. A mechanism has been proposed that explains this observation. © 1995 John Wiley & Sons, Inc.     

Photoinitiated cationic polymerization of limonene 1,2‐oxide and α‐pinene oxide

Limonene 1,2‐oxide (LMO) and α‐pinene oxide (α‐PO) are two high reactivity biorenewable monomers that undergo facile photoinitiated cationic ring‐opening polymerizations using both diaryliodonium salt and triarylsufonium salt photoinitiators. Comparative studies showed that α‐PO is more reactive than LMO, and this is because it undergoes a simultaneous double ring‐opening reaction involving both the epoxide group and the cyclobutane ring. It was also observed that α‐PO also undergoes more undesirable side reactions than LMO. The greatest utility of these two monomers is projected to be as reactive diluents in crosslinking photocopolymerizations with multifunctional epoxide and oxetane monomers. Prototype copolymerization studies with several difunctional monomers showed that LMO and α‐PO were effective in increasing the reaction rates and shortening the induction periods of photopolymerizations of these monomers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and cationic photopolymerization of epoxy‐functional siloxane monomers and oligomers

A series of difunctional silicon‐containing monomers were prepared with a novel method consisting of the monohydrosilation of an α,ω‐difunctional Si? H‐terminated siloxane with a vinyl‐functional epoxide or oxetane followed by the dehydrodimerization of the resulting Si? H‐functional intermediate. This method used simple, readily available starting materials and could be conducted as a streamlined one‐pot, two‐step synthesis. This novel method was also applied to the synthesis of several epoxy–silicone oligomers. The reactivities of these new monomers and oligomers were examined with Fourier transform real‐time infrared spectroscopy and optical pyrometry. Those monomers containing epoxycyclohexyl groups displayed excellent reactivity in cationic ring‐opening polymerization in the presence of lipophilic onium salt photoinitiators. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3056–3073, 2003     

The preparation of novel 1-propenyl ethers and their cationic photopolymerization

A series of nine difunctional 1-propenyl ether monomers bearing ether, ester, carbonate, and urethane groups were prepared based on trimethylolpropane diallyl ether as the starting material. The monomers were fully characterized and then subjected to photoinitiated cationic polymerization using diaryliodonium salts as photoinitiators. The course of the polymerizations was followed using Fourier transform real-time infrared spectroscopy and the relative reactivities of the various monomers were determined. It could be shown that the differences in reactivity could be related mainly to the basicity of the functional group introduced into the molecule. © 1996 John Wiley & Sons, Inc.     

Synthesis and Characterization of Bis(Isopropenylphenoxy)Alkanes and Bis(Vinylphenoxy)Alkanes: Two Classes of Highly Reactive,Photopolymerizable Monomers

Abstract

A novel and facile synthesis of difunctional, aromatic vinyl ether analogs is reported. These materials, which are conveniently prepared by the condensation of 4-acetoxystyrene or 4-isopropenylphenyl acetate with α, ω-dihaloalkanes in the presence of base, can be cationically polymerized using diaryliodonium or triarylsulfonium salts as photoinitiators to produce crosslinked polymers. Relative reactivities of the monomers toward cationic polymerization were studied using differential scanning photocalorimetry. The thermal stabilities of the polymers resulting from the photopolymerization of the difunctional, aromatic vinyl ether analogs were studied using thermogravimetric analysis.     

Redox initiated cationic polymerization of oxetanes

3,3‐Disubstituted oxetane monomers were found to undergo rapid, exothermic redox initiated cationic ring‐opening polymerization in the presence of a diaryliodonium or triarylsulfonium salt oxidizing agent and a hydrosilane reducing agent. The redox reaction requires a noble metal complex as a catalyst and several potential catalysts were evaluated. The palladium complex, Cl₂(COD)Pd^II, was observed to provide good shelf life stability while, at the same time, affording high reactivity in the presence of a variety of hydrosilane reducing agents. A range of structurally diverse oxetane monomers undergo polymerization under redox cationic conditions. When a small amount of an alkylated epoxide was added as a “kick‐start” accelerator to these same oxetanes, the redox initiated cationic polymerizations were extraordinarily rapid owing to the marked reduction in the induction period. A mechanistic interpretation of these results is offered. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1854–1861     

Propenyl ethers. II. Study of the photoinitiated cationic polymerization of propenyl ether monomers

The results of studies of the photoinitiated cationic polymerization of mono-, di-, and multifunctional propenyl ethers are reported in this article. Real-time infrared spectroscopy and differential scanning photocalorimetry were used to determine the reactivity of the monomers with respect to each other and in relation to other types of cationically polymerizable monomers. Propenyl ethers were observed to be highly reactive monomers in photoinitiated cationic polymerization undergoing very high conversions to polymer at very short irradiation times. Attempts were also made to correlate the structures of these monomers with their reactivity as well as to examine the effects of various experimental parameters on their photopolymerization. © 1993 John Wiley & Sons, Inc.     

Synergistic interaction of epoxides and N‐vinylcarbazole during photoinitiated cationic polymerization

A kinetic study was conducted of the independent photoinitiated cationic polymerization of a number of epoxide monomers and mixtures of these monomers with N‐vinylcarbazole. The results show that these two different classes of monomers undergo complex synergistic interactions with one another during polymerization. It was demonstrated that N‐vinylcarbazole as well as other carbazoles are efficient photosensitizers for the photolysis of both diaryliodonium and triarylsulfonium salt photoinitiators. In the presence of large amounts of N‐vinylcarbazole, the rates of the cationic ring‐opening photopolymerization of epoxides are markedly accelerated. This effect has been ascribed to a photoinitiated free‐radical chain reaction that results in the oxidation of monomeric and polymeric N‐vinylcarbazole radicals by the onium salt photoinitiators to generate cations. These cations can initiate the ring‐opening polymerization of the epoxides, leading to the production of copolymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3697–3709, 2000     

Synthesis,characterization, and polymerization of propenyl ether analogues

A series of aromatic monomers bearing cationically polymerizable propenyl groups were prepared and characterized using the readily available starting materials: isoeugenol and o-allyl phenol. Monomers with both propenyl and vinyl ether functional groups were also synthesized by the reaction of these starting materials with chloroethyl vinyl ether. The reactivity of the resulting monomers in photoinitiated cationic polymerization was studied using differential scanning photocalorimetry and photogel point measurements. Their thermal properties were determined using thermogravimetric analysis. © 1994 John Wiley & Sons, Inc.     

The synthesis and cationic polymerization of multifunctional silicon-containing epoxy monomers and oligomers

Several series of multifunctional silicon-containing epoxide monomers and oligomers have been prepared using rhodium catalyzed hydrosilation reactions. Dialkyl and diarylsilanes can be condensed with vinyl epoxides to give high yields of the desired diepoxides while the hydrosilation of alkyl and aryl silanes yields a mixture of di and tri epoxy substituted products. The condensation of αω,? Si? H difunctional compounds with vinyl epoxides can be carried out regioselectively to give α-hydrogen-ω-epoxy intermediates, which can be further reacted with di and tri olefins bearing terminal double bonds to give a series of well characterized epoxy functional oligomers. An investigation of the photoinitiated cationic polymerization of the monomers and oligomers, which were prepared during the course of these studies, was carried out. © 1994 John Wiley & Sons, Inc.     

Reactivity of oxetane monomers in photoinitiated cationic polymerization

Studies of the onium salt photoinitiated cationic ring‐opening polymerizations of various 3,3‐disubstituted oxetane monomers have been conducted with real‐time infrared spectroscopy and optical pyrometry. The polymerizations of these monomers are typified by an extended induction period that has been attributed to the presence of a long‐lived tertiary oxonium ion intermediate formed by the reaction of the initially formed secondary oxonium ion with the cyclic ether monomer. Because the extended induction period in the photopolymerization of these monomers renders oxetane monomers of limited value for many applications, methods have been sought for its minimization or elimination. Three general methods have been found effective in markedly shortening the induction period: (1) carrying out the photopolymerizations at higher temperatures, (2) copolymerizing with more reactive epoxide monomers, and (3) using free‐radical photoinitiators as synergists. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3205–3220, 2005     

The use of platinum and rhodium catalysts for the preparation and cationic ring-opening polymerization of silicon-containing epoxides

Regioselective platinum and rhodium catalysts were employed for the preparation of novel silicon-containing polyethers. First, silicon-containing monomers bearing cycloaliphatic epoxy groups were prepared by a rhodium-catalyzed regioselective hydrosilation. Then these monomers were polymerized using a platinum-catalyzed, cationic, ring-opening polymerization to give the linear polyethers. The obtained polyethers were compared with polymers prepared by photoinitiated cationic ring-opening polymerization using onium salt photoinitiators and found to be identical. © 1993 John Wiley & Sons, Inc.     

PHOTOINITIATED CATIONIC POLYMERIZATION OF EPOXY MONOMERS IN THE PRESENCE OF POLY(3,4-EPOXY-1-BUTENE)

ABSTRACT

Hydroxyl-terminated poly(3,4-epoxy-1-butene) (polyEPB) is an interesting and highly useful agent for the acceleration of the photoinitiated cationic ring-opening polymerization of epoxide monomers. Kinetic investigations using real-time infrared spectroscopy have shown that the observed acceleration of the polymerization is due to two independent mechanisms. Crosslinking polymerization of epoxide monomers is accelerated due to an activated monomer mechanism that results in facile chain transfer due to interaction of the terminal hydroxyl groups of polyEPB with the growing oxonium ion chain ends. A second mechanism involving participation of polyEPB in a free radical chain induced decomposition of the onium salt photoinitiator is mainly responsible for the observed acceleration in the rate of polymerization. A large number of polymer-bound carbocationic species are generated by this mechanism that are capable of initiating polymerization of the epoxide monomer.     

Synthesis and cationic photopolymerization of 1-butenyl ether monomers

A new series of cationically polymerizable mono-, di- and multifunctional 1-butenyl ether monomers have been prepared in high yields by the ruthenium catalyzed isomerization of the corresponding crotyl (2-butenyl) ethers. Their straightforward synthesis and high reactivity in photoinitiated cationic polymerization make these monomers highly attractive for a variety of applications. Cationic polymerization rate studies showed that these monomers exhibited comparable reactivity to their related vinyl and 1-propenyl ether analogues. © 1995 John Wiley & Sons, Inc.