Allyl Monomers Research Articles

Change of molecular mobility during formation of epoxy allylic interpenetrating polymer networks

The results of investigation of a change of molecular mobility in sequential and simultaneous curing of the compositions based on epoxy and allylic oligomers are given, using the pulse NMR spectroscopy method. It was established that by simultaneous formation of epoxy and allylic networks the mutual hindrances to the full conversion of reactive groups occur resulting in the increase of defects in the interpenetrating polymer network (IPN) structure and an increasing molecular mobility of all its fragments. In the case of polymerization of allylic component of the IPN, when the formation of epoxy network is basically fully completed, the increase of molecular mobility in the system is due to a decrease of the limit conversion degree of polymerizable groups in the allylic monomer.

Preservation of beech and spruce wood by allyl alcohol-based copolymers

Abstract Allyl alcohol (AA), acrylonitrile (AN), methyl methacrylate (MMA), monomers and monomer mixtures AA+AN, AA+MMA were used to conserve and consolidate Beech and Spruce. After impregnation, copolymerisation and polymerisation were accomplished by gamma irradiation. The fine structure of wood+polymer(copolymer) composites was investigated by Scanning Electron Microscopy (SEM). It was observed that copolymer obtained from AA+MMA monomer mixture showed the optimum compatibility. The compressional strength and Brinell Hardness Numbers determined for untreated and treated wood samples indicated that the mechanical strength of wood+copolymer composites was increased. It was found that the mechanical strength of the wood samples containing the AA+MMA copolymer was higher than the others. In the presence of P(AA/MMA), at highest conversion, the compressive strength perpendicular to the fibres in Beech and Spruce increased approximately 100 times. The water uptake capacity of wood+copolymer composites was observed to decrease by more than 50% relative to the original samples, and biodegradation did not take place.

Polymer-supported bis-cinchona alkaloid ligands for asymmetric dihydroxylation of alkenes—a cautionary tale

Careful work-up and purification of purported copolymers formed by free radical copolymerisation of a bis-cinchona alkaloid with methyl methacrylate shows that the level of incorporation of the bis-alkaloid into the polymer skeleton is below the detection limit of a routine nitrogen microanalytical protocol. This reluctance of the CC bonds in the bis-alkaloid to undergo copolymerisation with a methacrylate monomer is totally consistent with the well-known and extensively documented poor copolymerizability of allylic monomers. Direct free radical copolymerisation of allyl groups containing alkaloids and other allyl substituted optically active ligands is not therefore a general and simple option for the production of polymer-supported asymmetric catalysts.

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

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.

Alternating Copolymerization of 3,4-Epoxy-1-Butene and Derivatives with Maleic Anhydride

3,4-Epoxy-1-butene (I), prepared by the selective oxidation of butadiene, is an unusual difunctional monomer containing polymerizable vinyl and epoxy groups. As expected, free radical homopolymerization of I and its cyclic ketal derivatives was found to be very sluggish, as expected, for the allylic monomer structures. However, I was found to form alternating copolymers with maleic anhydride with both 1,2- and 1,5- enchainment observed. The structures of the alternating copolymers were observed to be solvent dependent with the in situ formation of cyclic ketals and their incorporation into the copolymers in polymerizations done in ketone solvents. Various cyclic ketal monomers derived from I readily formed alternating copoymers with maleic anhydride. Thermally activated self-crosslinking of these resins was observed.

Polymerisation kinetics of allyl monomers at low conversions

Free radical polymerisation kinetics of several mono- and di-allyl monomers were studied using FT-NIR, ESR and GPC techniques to measure the monomer conversion, nature and the concentration of the radicals and the polymer molecular weight, respectively. By manipulating the modulation amplitude of the ESR, the allyl radical and the propagating radical concentrations were estimated and these values were used to calculate the propagation, transfer, re-initiation and termination rate constants. The activation energy for the allyl radical termination reaction was found to be higher than that for the termination of other vinyl monomers. The percentage cyclization for the di-allyl monomers was estimated and for CR39 the value was found to be as high as 25%. A gel with a higher modulus was found to form in CR39 when the reaction rate was kept low.

On the plasma polymerisation of allyl alcohol: an investigation of ion–molecule reactions using a selected ion flow tube

Low power plasmas of allyl alcohol monomer (M) have been previously probed by mass spectrometry. Mechanisms describing the formation of solid-phase product, based on ion–molecule reactions, were proposed. Major mechanisms proposed initially involve the reaction of (M-H) + ion with M, followed by a sequence of secondary ion–molecule reactions. In this paper the feasibility of these reactions has been tested using a selected ion flow tube. Parent and product ions have been monitored as a function of M concentration, providing information on the reaction rate coefficient and branching ratios, respectively. Primary and secondary products have been distinguished. The new data support the mechanism proposed for the formation of dimers and trimers in the plasma phase. However, the identity of an m/z 81 cation, previously attributed to a purely hydrocarbon containing fragment, has been revised. This ion is a primary product arising directly from reaction of (M-H) + and M, and is most likely the pyrylium cation. This new information has resulted in a significant modification to the previously proposed scheme.

Radiation-induced crosslinking in polymer-polyfunctional monomer systems

The does dependence of crosslinking yields was determined for irradiated compositions of poly(vinyl chloride) and polyethylene with an allylic polyfunctional monomer (PFM). Therewith, the notion of the differntial crosslinking yield G*c was used. The dose dependence of G*c has a maximum for the investigated systems. The current consumption of allylic groups and PFM molecules was determined. In the investigated systems, the process of network formation proceeds through chain crosslinking of graft chains of poly-PFM. © 1996 John Wiley & Sons, Inc.

Radiation-induced network formation in polyvinyl chloride-polyfunctional monomer systems

Some aspects of the radiation polymerization of allylic polyfunctional monomers in mixtures with polyvinyl chloride have been investigated. The process proceeds through a stepwise formation of the network polymerizate from the polyfunctional monomer, reaction between the polymerizate and polyvinyl chloride and further crosslinking of polyvinyl chloride through reaction with residual allylic double bonds. The initiating radical for the first stage is a low-molecular weight radiolytic product of polyvinyl chloride (apparently, the chloro-radical). At higher initial monomer content the structure formed changes from that of a crosslinked copolymer to that of an interpenetrating network, during irradiation. In the presence of aliphatic plasticizer, the crosslinking density increases in irradiated compositions of polyvinyl chloride and polyfunctional monomers.

Optical Polymers with Special Birefringent Properties

In this paper the possibilities of generating static and dynamic birefringence in polymers are discussed with reference to results from the authors' laboratories. Orientation in polymers can be achieved either by orientation of monomers and polymerization of the oriented molecules under maintenance of the orientation or by orientation of isotropic polymers under the influence of physical forces. Copolymers of positive and negative birefringent components (allyl and methacrylic monomers) have been synthesized which show either an achromatic birefringent behavior or are without any birefringence. In addition, special allyl polymers have been studied which have very high stress-optical coefficients and can be used as acousto-optical modulators or as sensors.

Optical Polymers with Special Birefringent Properties

In this paper the possibilities of generating static and dynamic birefringence in polymers are discussed with reference to results from the authors' laboratories. Orientation in polymers can be achieved either by orientation of monomers and polymerization of the oriented molecules under maintenance of the orientation or by orientation of isotropic polymers under the influence of physical forces. Copolymers of positive and negative birefringent components (allyl and methacrylic monomers) have been synthesized which show either an achromatic birefringent behavior or are without any birefringence. In addition, special allyl polymers have been studied which have very high stress-optical coefficients and can be used as acousto-optical modulators or as sensors.

Stable Electrooptical Guest-Host Polymers Based on Crosslinked Allyl Compounds

Abstract Novel nonlinear optical (NLO) guest-host polymers were prepared by means of a two-step polymerization of multifunctional aromatic allylic monomers. A soluble prepolymer obtained in the first step was doped with the NLO-azo dye 2-((4-(2-hydroxyethyl)-ethylamino)-phenylazo)-3,5-dicyano-4-methylthiophene and aligned by means of corona poling while the polymer network was formed via thermal polymerization in the second step. The crosslinking reaction was followed by film thickness measurements. For example, in a 6 hours' polymerization at 140°C a long-term stable material based on poly(triallyl isocyanurate) was obtained. An order parameter of φ ≈ 0.3 was deduced from absorption measurements. An electrooptical coefficient of r 33 ≈ 10 pm/V (at a wavelength of 785 nm) was determined.

Rheology and Photo-Cross-Linking of Thiol−Ene Polymers

A dynamic rheological technique, Fourier transform mechanical spectroscopy (FTMS), was used to monitor in real time the evolving rheological properties during UV cross-linking of two thiol−ene systems. These systems comprised a trifunctional thiol (trimethylolpropane tris(2-mercaptoacetate)) together with a trifunctional allyl monomer (triallyl isocyanurate) and a tetrafunctional thiol (pentaerythritol tetrakis(2-mercaptoacetate)) with the same allyl monomer. FTMS, in conjunction with specially designed quartz plates, provided an in situ method to elucidate the effects of temperature and monomer functionality on the photoinitiated polymerization of these systems. It was found that the tetrafunctional thiol system cross-linked at a faster rate than the trifunctional thiol system over the temperature range (25−50 °C) studied. Moreover, increasing the temperature increased the cross-linking rates for both systems. The Winter−Chambon criterion was applied to determine the gel point and the two parameters which characterize the material at its gel point, the gel stiffness, S, and the relaxation exponent, n. The gel stiffness was found to be greater for the trifunctional thiol system, which was consistent with the higher value of conversion calculated from the Flory−Stockmayer theory of gelation. Relaxation exponents of 0.80 and 0.81−0.82 were determined for the tri- and tetrafunctional thiol systems, respectively, indicating similar fractal structures at the gel point. These relaxation exponents were also invariant over the temperature ranges studied, suggesting that the cross-linking mechanisms remained unchanged with temperature. From the temperature dependence of the gel times, apparent activation energies of 6.6 and 14 kcal/mol were calculated for the tri- and tetrafunctional thiol systems, respectively.

Unsaturated polyester resins containing allylic monomers

Unsaturated polyester resins containing allylic monomers

Photocrosslinking of polypropylene: the effect of different photo-initiators and coagents

Crosslinking of polypropylene (PP) induced by photoreduced (benzophenone. xanthone and 2-methyl anthraquinone) and photofragmentated (halogenated sulphur, phosphorus and hydrocarbon derivatives) substances was studied. It was found that high gel content could be obtained in PP using sulphur monochloride, sulphuryl chloride, trichlorethylene and tetrachlorethylene as photoinitiators. The gel yield in the presence of photoreduced initiators increases if acryloyloxy polyfunctional monomers are used as PP photocrosslinking promoters, whilst the effect of allylic monomers is comparatively small. Temperature increase was shown mainly to depress PP crosslinking efficiency and to enhance photothermal degradation, although increased gel yield was attained if PP containing photoreduced initiators combined with allylic monomers was exposed to UV light at temperatures up to 140 °C. DSC studies showed that the melting temperature and the heat of fusion of PP photocrosslinked in the molten state or recrystallized after crosslinking were decreased substantially with gel content, especially if photofragmented chlorides are used as initiators. Investigation of photocrosslinked PP tensile properties at ambient temperatures revealed the increase of Young's modulus and yield stress along with catastrophic decrease of strain at break. At increased testing temperatures ( T > 80 °C) the ductility of photocrosslinked PP is enhanced and its tensile properties noticeably surpass those of uncrosslinked samples.

UV curing of composites based on modified unsaturated polyester

AbstractSynthesis and photocrosslinking of glass fiber‐reinforced composites, based on epoxy acrylate‐modified unsaturated polyester, have been investigated. The efficiency of the photocrosslinking process for glass fiber laminates of the polyesters that contain different comonomers has been evaluated by measuring mechanical properties. The data show (i) that 2 mm thick laminates, containing 30–40% glass fiber mats, are cured with UV irradiation for 15 sec at room temperature in air; (ii) that multifunctional acrylate or acrylether monomers added to the polyester resin improve the tensile and flexural properties of the photocured product to a greater extent than do added allylic monomers, due to the different photocrosslinking mechanisms; (iii) that the physical properties of the photocrosslinked laminates are well correlated with the molecular weight of the polyester, the amount of multifunctional monomer added, and the glass fiber content. © 1994 John Wiley & Sons, Inc.

Investigations for obtaining semi‐interpenetrating polymer networks based on monomers of different reactivity toward radicals

AbstractClassically, the one‐step synthesis of interpenetrating polymer networks (IPNs) and related materials requires noninterfering polymerization modes to achieve distinct networks, held together by only physical entanglements. For the combination of (meth) acrylic and allylic monomers, both polymerizable by free radicals, a new in situ sequential synthesis for obtaining semi‐IPNs is proposed. Using specific initiators that decompose at two different temperatures, refractive index measurements, Fourier transform infrared spectroscopy, and dynamic mechanical analysis have shown that neat species are formed and that the two monomers do not copolymerize. © 1993 John Wiley & Sons, Inc.

Polymerization of allyl esters derived from long‐chain fatty acids and palm olein

AbstractAllyl esters of palm olein, palmitic, and oleic acids were synthesized by transesterification and esterification methods using KOH and absolute H2SO4 as catalysts, respectively. Three allyl esters, namely, allyl palmitate, allyl epoxystearate, and epoxidized allyl ester of palm olein, were successfully polymerized in the presence of t‐butyl perbenzoate at 120°C to obtain oligomers with the average number of backbone atoms approximately equal to the number of skeletal atoms of the long‐dangling side chains. The kinetic data of polymerization were conformed to the rate equation proposed by other workers. No oxirane cleavage was detected during the chain reaction. The melting behavior of these comb‐shaped polymers was compared with that of their respective allylic monomers. The polymer of epoxidized allyl ester of palm olein exhibits a glass transition temperature at 204.4 K. The critical molecular weights of the polymers of allyl esters investigated are predicted to be not lower than 104.

Copolymerization of methyl methacrylate and a novel allyl monomer

A novel monomer (TEP) having pendant carbamate groups was prepared by reacting equimolar quantities of 4-allyl-2-methoxyphenyl and phenol with tolylene diisocyanate (2,4- and 2,6-isomers). TEP was copolymerized with methyl methacrylate (MMA) in tetrahydrofuran solution at 65° using benzoyl peroxide as initiator. Copolymer compositions were determined by elemental analysis. The monomer reactivity ratios were found to be 1.45 ± 0.05 (MMA) and 1.0 ± 0.1 (TEP). A random copolymerization of MMA with an allyl monomer has so far not been reported. A two step decomposition was observed for all polymer samples in nitrogen.

Copolymers and terpolymers of sulfur dioxide with allyl monomers comprising groups absorbing ultraviolet irradiation

AbstractAlternating copolymers are obtained of sulfur dioxide with allyl phenyl ether, allyl p‐nitrophenyl ether, N‐allylbenzamide, N‐allyl p‐nitrobenzamide, allyl cinnamate and allyl o‐benzoylbenzoate. Copolymerizations proceed in high yield at ‐78°C in the presence of tert‐butyl hydroperoxide as initiator. However, copolymer yield is small for reactions initiated with 2,2′‐azoisobutyronitrile at 50–60°C. Ultraviolet spectra of the copolymers obtained show the presence of intense absorption bands in the range of 220 to 305 nm. SO2 terpolymers have been obtained with allyl ethers, allyl amides or allyl esters and 1‐heptene, 2‐methylpropene or methyl acrylate. The effect of the structure of the monomers on the reactivity in polymerizations involving SO2 is discussed on the basis of the composition of the products.