Cationic Photocrosslinkable Polydimethylsiloxane. III. Synthesis and Photocrosslinking of Polydimethylsiloxane Bearing Oxetane Groups

Abstract

From 3-hydroxymethyl-3-methyl oxetane, we synthesized three oxetane monomers with allylic, diethoxysilane or triethoxysilane functions. These monomers allowed us to prepare different polydimethylsiloxanes bearing oxetane groups by two routes. One is hydrosilylation of allylic monomer on hydrogeno polydimethylsiloxane, with different percentages of Si-H bonds. The second route is a condensation of α,ω-dihydroxy polydimethylsiloxane with di and tri ethoxysilane monomers. By using a photocalorimeter, we studied the kinetic of cationic photopolymerization of a polydimethylsiloxane bearing 7.4% oxetane functions. Influence of temperature in the range 35 to 125°C showed a maximum conversion for 80°C due to an increase in transfer and termination reactions.     

The Synthesis,Characterization, and Photoinitiated Cationic Polymerizaton of Difunctional Oxetanes

Abstract

Seven novel difunctional oxetane monomers have been prepared and characterized using standard spectroscopic techniques. The photoinitiated cationic polymerization of these seven monomers was carried out and their reactivity compared to a typical diepoxide monomer. In these studies the reactivities of the various oxetane monomers were evaluated and compared by three different techniques: gel time measurements, differential scanning photocalorimetry, and real time infrared spectroscopy. It was observed that the difunctional oxetanes are generally more reactive than their structurally similar epoxide counterparts in photoinitiated cationic polymerization.     

Terpolymerization of Cyclic Ethers with Cyclic Anhydride

Abstract

A unique solution polymerization and polymer family have been discovered in the ring-opening terpolymerization of three heterocyclic monomers initiated by organometallic compounds, particularly trialkylaluminum. The products have repeating ether-ester-ester linkages along the chain and are alternating terpolymers, … ABCABCABC…, of three different monomers A, B, and C. Monomer A is a four- or five-membered cyclic oxide, such as tetrahydro-furan or oxocylobutane (oxetane). Monomer B is an epox-ide, and Monomer C is a cyclic acid anhydride. Many epoxides and anhydrides participate in the polymerization which enables the preparation of alternating terpolymers containing various substituents and unsaturatlons at regu-lar intervals along the chain. The alternating sequence can be near-perfect or less so depending on the initial monomer charge ratio. Evidence of the alternating struc-ture was obtained by chemical and NMR analyses of polymer sampled at intermediate and final conversions, and by glass transition temperatures.     

Hybrid acrylate‐oxetane photopolymerizable systems

Simultaneous free radical and cationic photopolymerizations of mixtures of multifunctional acrylate and oxetane monomers were carried out to provide hybrid interpenetrating network polymers. The use of “kick‐started” oxetanes in which oxetane monomers are accelerated by the use of small amounts of certain highly substituted epoxides provides dual independent radical and cationic systems with similar rates of photopolymerization leading to homogeneous interpenetrating networks. The combined photopolymerizations are very rapid and afford crosslinked network films that are colorless, hard, and transparent. The networks display no indications of phase separation. The use of this technology in various applications such as coatings, 3D imaging, and for composites is discussed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 594–601     

Electroinitiated Polymerization of 3,3-BIS(N-Carbazolylmethyl)Oxetane

Abstract

3,3-Bis(N-carbazolylmethyl)oxetane, a cyclic compound with carbazolyl substituents closely linked to the oxetane ring, was polymerized by electrochemical initiation in aprotic polar solvents using a quaternary ammonium salt as electrolyte. Colored polymers were obtained as thin films deposited on the anode and were characterized by IR, ¹H NMR, and thermogravimetry. The data obtained refute the classical cationic polymerization of oxetanes.     

Oligomeric Branched Polyethers with Multiple Hydroxyl Groups by Cationic Ring-Opening Polymerization for Inorganic Surface Modification

Summary: Cationic ring-opening polymerization of cyclic ethers (also esters and acetals) substituted with hydroxyl groups leads to branched multihydroxyl polymers. When 4-membered hydroxysubstituted oxetanes or 5-membered hydroxysubstuituted oxolanes (or lactone and 1,3-dioxolane) are used as monomers the polymerization products have limited molecular weights (about 1000). Polymerization of these monomers leading in situ to oligomeric products was used for inorganic surface modification. Successful polymerizations of oxetane as well as considered as difficult to polymerize 5-membered hydroxysubstituted cyclic monomers initiated from montmorillonite clay and silica nanoparticles surfaces were performed.     

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     

Synthesis and cationic photopolymerization of new silicon‐containing oxetane monomers

The cationic photopolymerization of oxetane‐based systems containing silicon monomers was investigated. For this purpose, three new silicon‐containing oxetane monomers were synthesized through a simple and straightforward synthetic method. The silicon‐containing monomers were added to a typical oxetane resin, 3,3′‐[oxydi(methylene)]bis(3‐ethyloxetane), in concentrations of 1–5 wt %. They exploited a certain surface tension effect without affecting the rate of polymerization. Enrichment only on the air side was achieved, which induced hydrophobicity in the photocured films, depending on the monomer structure and concentration. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1415–1420, 2004     

Synthesis and cationic ring‐opening polymerization of oxetane monomer containing five‐membered cyclic carbonate moiety via highly chemoselective addition of CO2

The bicyclic amidinium iodide effectively catalyzed the reaction of carbon dioxide and the epoxy‐containing oxetane under ordinary pressure and mild conditions with high chemoselectivity to give the corresponding oxetane monomer containing five‐membered cyclic carbonate quantitatively. The cationic ring‐opening polymerization of the obtained monomer by boron trifluoride diethyl ether proceeded to give linear polyoxetane bearing five‐membered cyclic carbonate pendant group in high yield. The molecular weight of the polyoxetane was higher than that of polyepoxide obtained by the cationic ring‐opening polymerization of epoxide monomer containing five‐membered cyclic carbonate. The cyclic carbonate functional crosslinked polyoxetanes were also synthesized by the cationic ring‐opening copolymerization of cyclic carbonate having oxetane and commercially available bisoxetane monomers. Analyses of the resulting polyoxetanes were performed by proton nuclear magnetic resonance, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2606–2615     

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     

Investigations of the reactivity of “kick‐started” oxetanes in photoinitiated cationic polymerization

The ability of certain alkyl substituted epoxides to accelerate the photoinitiated cationic ring‐opening polymerizations of oxetane monomers by substantially reducing or eliminating the induction period altogether has been termed by us “kick‐starting.” In this communication, the rates of photopolymerization of several model “kick‐started” oxetane systems were quantified and compared with the analogous biscycloaliphatic epoxide monomer, 3,4‐epoxycyclohexylmethyl 3′,4′‐epoxycyclohexanecarboxylate (ERL). It has been found that the “kick‐started” systems undergo photopolymerization at rates that are at least two‐fold faster than ERL. These results suggest that “kick‐started” oxetanes could replace ERL in many applications in which high speed ultraviolet induced crosslinking photopolymerizations are carried out. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 586–593     

Light-induced polymerization of new highly reactive acrylic monomers

Acrylic monomers containing an oxetane, dioxolane, oxazolidone or carbonate group in their structural unit have been shown to copolymerize rapidly and extensively with a polyurethane-diacrylate, upon UV radiation. For the most reactive resin, 50% conversion was reached within 3 ms of exposure to a medium-pressure mercury lamp. The kinetics of these ultrafast polymerizations was studied quantitatively by infrared spectroscopy. The rate of polymerization, photosensitivity, and amount of residual acrylate in the cured polymer were determined for the various monomers studied, and compared to the values obtained with conventional mono-, di-, and triacrylates. The functional group introduced into the monomer unit was shown to have a drastic effect on both the reactivity and the physical characteristics of the photocrosslinked polymer. Soft and highly flexible low-modulus polymers were produced with the oxetane, dioxolane, and chlorinated monomers, while the carbonate-acrylate compounds lead to hard and glassy materials. © 1993 John Wiley & Sons, Inc.     

Infrared thermographic analysis on copolymerization of spiroorthoester with oxetane

Infrared (IR) thermography was employed to monitor temperature changes during the copolymerization of a spiroorthoester monomer with an oxetane monomer initiated with a benzyl sulfonium salt. The temperature changes in the polymerizations decreased with the increase of the initial feed ratios of the spiroorthocarbonate monomer. For instance, the temperature in the copolymerization of the equimolar mixture of both of the monomers increased only ～1 °C, whereas that in the homopolymerization of the oxetane monomer increased more than 20 °C. This result indicates that the copolymerization employing spiroorthocarbonate monomers effectively suppress temperature increase, which are responsible to shrinkage during cooling. The suppression of polymerization shrinkage by spiroorthocarbonate was also confirmed by density measurement of the polymers using a gas pycnometer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1388–1393, 2007.     

Synthesis and study of organic nitrates of heterofunctional series. 5. Synthesis of 3,3-bis(hydroxymethyl)oxetane mono- and dinitrates and 2,2-bis(hydroxymethyl)propane-1,3-diol (pentaerythritol) mono- and dinitrates

New procedures were developed for the synthesis of 3,3-bis(hydroxymethyl)oxetane dinitrate (1) by O-nitration of the corresponding glycol (3) or its mononitrate (6), which were prepared by the reactions of 2,2-bis(hydroxymethyl)propane-1,3-diol (pentaerythritol) (2) mono- (4) and dinitrates (5), respectively, with alkali. A new method was devised for the synthesis of compounds 4 and 5 by the reaction of tetraol 2 with concentrated HNO₃ in dichloroethane. The structures of compounds 1 and 6 were established by X-ray diffraction analysis.     

氧负离子聚合在超支化聚合物合成中的应用

近年来,氧负离子聚合得到较快发展,单体种类已经由酯基的β位上含有供电性杂原子的甲基丙烯酸酯类扩展到环氧类、甲基丙烯酸羟酯类单体.氧负离子引发这两类单体聚合,可以得到新型结构的超支化聚合物.对氧负离子引发合成超支化聚合物的机理及其应用进行了综述.     

A facile approach for the construction of the oxetane ring from 5α-acyloxy-Δ~(4(20)) - taxoids

An oxetane ring can be constructed from 5α-acyloxy-Δ4(20)-taxoids. Hie facile intramolecular acyl migration from 5- to 20-position under slightly basic conditions enabled the construction of the oxetane ring in a convenient short cut, whereas the acyl migration from 2- to 20-position left the 2-hydroxyl accessible to a later benzoylation. An unexpected five-mem-bered 4-O, 20- O sulfite ring was formed in the attempted construction of the oxetane ring with 5α-triflate as a leaving group. After the construction of the oxetane ring, treatment with strong base LiHMDS and acetyl chloride gave the expected 4-O-acetate while treatment with acetic anhydride and DMAP gave a 4-O-acetoacetate.     

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.     

Photoactivated Cationic Frontal Polymerization

Photoactivated cationic ring-opening polymerizations of certain oxirane and oxetane monomers take place in a frontal manner. The study of the frontal behavior of those monomers was conducted using a new analytical technique involving optical pyrometry that provides insight into the mechanism of these polymerizations.     

Synthesis,UV-curing Behavior and Surface Properties of New Fluorine-containing Aromatic Oxetane Monomers

In this paper,we combined high-end cationic UV-curable material with fluorinated chain obtaining a series of new fluorine-containing aromatic oxetane monomers via a mild nucleophilic substitution reaction.The structures and properties of monomers were characterized using 1H-NMR,19F-NMR,dynamic viscosity tests and differential scanning calorimetry (DSC).It was determined that all of the fluorinated monomers obtained had much lower viscosity and higher thermostability after the introduction of hexafluorobenzene.Then,UV-curable coatings were prepared using four fluorine-containing aromatic oxetane monomers (FOX1-4);the UV-curing kinetics,with three kinds of initiators,and properties of the cured films were evaluated using real-time Fourier transform infrared (FTIR) spectroscopy,water and diiodomethane contact angle tests,surface energy calculations and scanning electron microscopy (SEM).The FTIR spectroscopy results showed that the coatings possessed excellent conversion rate (＞ 99％ with liquid initiator PAG-201 in 150 s),and as the fluorine content increased,the monomers exhibited decreased mobility with the increasing viscosity and worse solubility with fluorinated monomers,resulting in a lower conversion rate.Moreover,the coatings possessed favorable hydrophobic and oleophobic properties and low surface energies owing to the fluoride chains floating to the membrane-air interface,which was also confirmed by discrete concave structures in SEM images.These new kinds of monomers can replace traditional fluorinated cationic monomers applied to the fingerprint resistant,fouling resistant,scratch resistant and anti-aging coatings,adhesives or printing ink materials.     

“Kick‐Starting” oxetane photopolymerizations

In the presence of small amounts of 2,2‐dialkyl‐, 2,2,3‐trialkyl‐, or 2,2,3,3‐tetraalkyl substituted epoxides such as isobutylene oxide, 1,2‐limonene oxide, and 2,2,3,3,‐tetramethyl oxirane, the photoinitiated cationic ring‐opening polymerizations of 3,3‐disubstituted oxetanes are dramatically accelerated. The acceleration affect was attributed to an increase in the rate of the initiation step of these latter monomers. Both mono‐ and disubstituted oxetane monomers are similarly accelerated by the above‐mentioned epoxides to give crosslinked network polymers. The potential for the use of such “kick‐started” systems in applications such as coatings, adhesives, printing inks, dental composites and in three‐dimensional imaging is discussed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2934–2946