Showing papers on "Methyl acrylate published in 1996"

Diffraction of Visible Light by Ordered Monodisperse Silica−Poly(methyl acrylate) Composite Films

Abstract: Composites of ordered colloidal crystals of amorphous monodisperse silica particles in amorphous poly(methyl acrylate) (PMA) films selectively Bragg diffract visible light. The 153 nm diameter colloidal silica particles coated with 3-(trimethoxysilyl)propyl methacrylate form colloidal crystals in methyl acrylate (MA) monomer, and the crystal order is locked into place by polymerization of the MA. Bragg diffraction from the films is detected spectrophotometrically as narrow peaks of low percent transmission of visible light normal to the film plane. The diffraction wavelength is tuned by varying the d spacing of the crystal lattice and by varying the Bragg angle. Variation in the lattice spacing is achieved via the particle size or particle concentration, uniaxial stretching of the composite, and swelling the composite with monomers such as styrene or MA followed by photopolymerization of the imbibed monomers. Films that diffract from 434 to 632 nm have been prepared.

Mechanistic Studies of Catalytic Olefin Dimerization Reactions Using Electrophilic η3-Allyl−Palladium(II) Complexes

Abstract: The dimerization of olefins by well-defined cationic η3-allyl−palladium complexes of the type [(C3H5)Pd(L)(PR3)]+[BAr‘4]- (Ar‘ = [3,5-C6H3(CF3)2]; L = OEt2, H2O; R = cyclohexyl (Cy), n-butyl (nBu)) has been studied. These complexes react with ethylene or methyl acrylate at −80 °C with loss of L to form the η2-olefin complexes [(C3H5)Pd(η2-olefin)(PR3)]+[BAr‘4]- (olefin = H2CCH2, CH2CHC(O)OCH3). Upon warming, allyl−olefin coupling occurs. The dimerization of ethylene occurs rapidly at 0 °C with an observable ethyl−ethylene intermediate [(C2H5)Pd(C2H4)2(PCy3)]+[BAr‘4]-. Methyl acrylate reacts to form a stable acrylate chelate complex, [(CH3O(O)CCH2CH2)Pd(CH2CHC(O)OCH3)(PR3)]+[BAr‘4]-, which is the catalyst resting state for methyl acrylate dimerization which occurs at room temperature to give predominantly trans-dimethyl-2-hexenedioate.

Shape memory behaviors of crosslinked copolymers containing stearyl acrylate

Abstract: Shape memory polymers were prepared by copolymerizing stearyl acrylate and methyl acrylate. The principle of this shape memory effect is based on reversible order-disorder transition of the crystalline aggregates of stearyl moieties. A specific feature of this type of shape memory copolymer is that the transition temperature at which the polymer abruptly become soft and deforms can be controlled by changing the monomer composition, which enables one to adjust the shape memory effect at the desired temperature. Mechanism and process of the shape memory behaviors are discussed

Graft polymerization of methyl acrylate onto granular starch: Comparison of the Fe+2/H2O2 and ceric initiating systems

Abstract: Graft polymerizations of methyl acrylate (MA) onto granular cornstarch were carried out in water with both ferrous ammonium sulfate/hydrogen peroxide (FAS/H 2 O 2 ) and ceric ammonium nitrate (CAN) initiation. Starch concentrations were 10, 20, and 30% in water, and the amount of MA used was either 0.5, 1, or 2 mol per AGU of starch. Two concentrations of FAS/H 2 O 2 were used : 1 mol each of FAS and H 2 O 2 per 100 AGU of starch, and 1 mol per 1000 AGU. Significant amounts of acetone-extractable PMA homopolymer were produced, and homopolymer formation was especially high at the 1 : 100 ratio. Sharp exotherms were observed, and reaction mixtures reached maximum temperature within 2 min or less. Total conversions of MA to PMA were higher at the 1 : 100 ratio, and conversions in some polymerizations were nearly quantitative. CAN-initiated polymerizations were run under the same conditions used for FAS/H 2 O 2 ; however, the amount of CAN used was limited to 1 mol per 100 AGU because of low conversions at the 1 : 1000 ratio. Compared with FAS/H 2 O 2 , CAN gave more moderate exotherms ; and longer time periods were required for reaction mixtures to reach maximum temperature. CAN gave quantitative conversions of MA to PMA, but only low percentages of PMA homopolymer were observed. Differences between FAS/H 2 O 2 and CAN initiation are consistent with differences in the two initiation mechanisms. High levels of homopolymer produced on starch granule surfaces with FAS/H 2 O 2 could be seen in scanning electron micrographs and were also apparent in infrared spectra obtained with an attenuated total reflectance (ATR) cell. ATR spectra of acetone-extracted products indicated that the amount of PMA actually grafted to starch granule surfaces was similar with both initiating systems. Tensile properties of extruded ribbons prepared from these polymers did not vary greatly with the initiator used.

Reactivity of N-Phenyl-1-Aza-2-Cyano-1,3-Butadienes in the Diels−Alder Reaction

Abstract: It is found that N-phenyl-2-cyano-1-azadiene 4, prepared via a two-step, one-pot, sequence from acrylanilide, undergoes efficient [4 + 2] cycloaddition with a complete range of electron rich, electron poor, and neutral dienophiles under remarkably mild thermal conditions (90-120 degrees C for 20-48 h). Regiospecific formation of the alpha-cycloadduct wherein the dienophile substituent is alpha to nitrogen is observed for vinyl ethers and styrene, whereas the Diels-Alder reactions with methyl acrylate and methyl vinyl ketone (MVK) produce alpha/beta mixtures in which the alpha-cycloadduct is the major regioisomer (approximately 4-5:1). An essentially identical reaction pattern was observed in the Diels-Alder reaction of N-(p-methoxyphenyl)-2-cyano-1-azadiene 18 and the 4-methyl-substituted azadiene 27. For compound 19 derived from cycloaddition of 18 with ethyl vinyl ether, facile conversion to the dihydropyridine 21 through loss of EtOH on brief acid treatment was also noted. The 2,4-cis-disubstitution pattern confirmed by X-ray diffraction for the major cycloadduct 29 isolated from the reaction of 27 with styrene provides evidence for the endo mode of cycloaddition in the Diels-Alder reaction of N-phenyl(aryl)-2-cyano-1-azadienes. Calculation of the frontier orbital energies and coefficients, as well as the transition state geometries for the [4 + 2] cycloaddition of N-phenyl-2-cyano-1-azadiene 4 with methyl vinyl ether, styrene, and MVK were carried out at the RHF AM1 level (MOPAC, Version 5.0). The FMO treatment indicates that the reaction of 4 with methyl vinyl ether occurs under LUMO(diene) control, whereas in contrast, the corresponding cycloaddition with MVK occurs preferably under HOMO(diene) control. A high degree of asynchronicity is observed in the calculated transition states for reaction of 4 with the three representative dienophiles. In all cases the transition states leading to the alpha-cycloadducts are lower in energy than those giving the beta-products. However, at the AM1 level the exo cycloaddition mode is found to be the preferred, this result contrasting with experimental results for azadiene 27.

Poly(ethylene-co-butyl acrylate). Phase Behavior in Ethylene Compared to the Poly(ethylene-co-methyl acrylate)-Ethylene System and Aspects of Copolymerization Kinetics at High Pressures

Abstract: Cloud point data for poly(ethylene-co-butyl acrylate) (EBA)−ethylene and poly(ethylene-co-methyl acrylate) (EMA)−ethylene mixtures are presented to 250 °C and 2600 bar as a function of butyl acrylate (BA) content from 5.2, 17.0, 25.2, 40.3, and 100 mol % BA and of molecular weight, and as a function of methyl acrylate (MA) content from 10, 18, 31, 41, and 100 mol % MA. Cloud point pressures initially decrease with increasing BA content at rate of ∼17 bar/mol % BA up to ∼40 mol % BA and then they remain relatively constant with further increases in BA content. The cloud point pressures increase with increasing weight-average molecular weight (Mw), at a rate of ∼4 bar/10000 Mw. However, cloud point pressures for the EMA−ethylene mixtures initially decrease as the MA content increases to ∼20 mol % but then increase rapidly as the MA content is further increased. In fact, it is not possible to dissolve poly(methyl acrylate) in ethylene to 240 °C and 2600 bar, although poly(butyl acrylate) readily dissolves in...

Modification of polyolefin surfaces by plasma-induced grafting

Abstract: Polar monomers have been grafted onto polyolefin surfaces with the aid of inert gas plasma. In the first stage, an inert gas plasma (argon plasma) was used to generate free radicals on the polyolefin surface. In the second stage, the plasma generator was turned off and a vinyl monomer introduced as a vapor. Monomer was surface grafted by free radical polymerization. After cleaning and drying, the samples were analyzed by XPS, IR, and contact angle. LD–PE was successfully grafted with acrylic acid, glycidyl methacrylate, methyl acrylate, and 2-hydroxy ethylacrylate. The grafting of acrylic acid was studied in more detail, and the rate of grafting was observed to increase with increasing monomer pressure and to decrease with time. The increasing of grafting temperature was found to reduce the degree of grafting. This last factor can be explained by the reduced concentration of monomer at the polymer surface or by a deactivation of surface radicals. © 1996 John Wiley & Sons, Inc.

Synthesis and photocrosslinking of maleimide‐type polymers

Abstract: Self-sensitizable photocrosslinking maleimide-type polymers were synthesized by using (N-cinnamoyloxymethyl)maleimide (1) as a maleimide having a photodimerizable group, nitrophenyl acrylate as a sensitizer monomer, and styrene or methyl acrylate. The fluorescence spectra of these polymers exhibit an excimer band around 455 nm. The excimer intensity of the polymers decreased mainly during the early irradiation time. This decreasing tendency was similar to the increasing tendency of the insoluble fractions of the polymers with irradiation time. These results suggest that the photocrosslinking reaction of the polymers occurs via an excimer formation of the cinnamoyl groups and can be traced by fluorescence spectroscopy.

Mechanical properties of a poly(methyl acrylate) nanocomposite containing regularly-arranged silica particles

Abstract: In an earlier investigation, poly(methyl acrylate) nanocomposites containing silica particles were found to have novel optical properties when the particles were regularly spaced rather than randomly located. The availability of these materials was used to determine whether there was any difference in the particles' reinforcing ability between ordered and random arrangements. The two types of composites were compared using near-equilibrium mechanical property measurements in uniaxial or equi-biaxial deformation, and dynamic mechanical properties measurements. It was found that having the filler particles regularly arranged had little effect on these properties, and that there was no anisotropy in their mechanical behavior. Related experiments could possibly be used to clarify the long-standing question of the importance of particle aggregation in elastomer reinforcement.

Radical polymerization and copolymerization of methyl α-(2-carbomethoxyethyl)acrylate, a dimer of methyl acrylate, as a polymerizable α-substituted acrylate

Abstract: Polymerization and copolymerization of methyl α-(2-carbomethoxyethyl)acrylate (MMEA), which is known as a dimer of methyl acrylate, were studied in relation to steric hindrance-assisted polymerization. The propagating polymer radical from MMEA was detected as a five-line spectrum and quantified by ESR spectroscopy during the bulk polymerization at 40–80°C. The absolute rate constants of propagation and termination (κp and κt) for MMEA at 60°C (κp = 19 L/mol s and κt = 5.1 × 105 L/mol s) were evaluated using the concentration of the propagating radical at the steady state. The balance of the propagation and termination rates allows polymer formation from MMEA. The polymerization rate of MMEA at 60°C was less than that of MMA by a factor of about 4 at a constant monomer concentration. Although no influence of ceiling temperature was observed at a temperature ranging from 40 to 70°C, addition-fragmentation in competition with propagation reduced the molecular weight of the polymer. The content of the unsaturated end group was estimated to be 0.1% at 60°C to the total amount of the monomer units consisting of the main chain. MMEA exhibited reactivities almost similar to those of MMA toward polymer radicals. It is concluded that MMEA is one of the polymerizable acrylates bearing a substituted alkyl group as an α-substituent. Characterization of poly(MMEA) was also carried out. © 1996 John Wiley & Sons, Inc.

Strengths and limitations of SAFT for calculating polar copolymer-solvent phase behavior

Abstract: Statistical associating fluid theory (SAFT) is used to calculate the cloud-point behavior of poly(ethylene-co-methyl acrylate) (EMA) copolymers (0-41 mol % methyl acrylate) in ethane, propane, butane, ethylene, propylene, 1-butene, chlorodifluoromethane, and dimethyl ether at temperatures to 250°C and pressures to 2,600 bar. Poor agreement is obtained between calculated and experimental data if the pure component EMA parameters used in SAFT are calculated using mixing rules that average polyethylene (PE) and poly(methyl acrylate) (PMA) parameters. Therefore, two of the three pure component parameters for all of the EMA copolymers are fixed to the values reported for PE and the third parameter, u°/k, for the copolymer containing 31 mol % methyl acrylate (EMA 31 ) is determined by fitting the EMA 31 -butane cloud-point curve. The value for (u°/k) PMA is then obtained using a mixing rule and the values of u°/k for all of the EMA copolymers are calculated. A good fit of all of the copolymer-solvent cloud-point curves is obtained using a temperature-independent mixture parameter, k ij . With this method of calculation it is possible to correlate cloud-point data with the SAFT equation of state if a small amount of experimental data are available.

1,4-Asymmetric Induction in the Chromium(II)- and Indium-Mediated Coupling of Allyl Bromides to Aldehydes.

Abstract: A series of allyl bromides bearing an ethereal stereogenic substituent at C-2 were synthesized from methyl acrylate. These were coupled with a range of aldehydes under chromium(II) chloride-mediated conditions to afford syn-4-alkoxyalkan-1-ols in good yield and diastereoselectivity. The effect of altering the nature of the ethereal group and alkyl substituent upon the diastereoselectivity of the reaction was also investigated. The relative stereochemistry was proved by X-ray structure analysis. The work was extended to replace the chromium(II) chloride with indium metal, and this also afforded syn-4-alkoxyalkan-1-ols in good yield and diastereoselectivity.

Time-Resolved Luminescence Anisotropy Studies of the Relaxation Behavior of Polymers. 1. Intramolecular Segmental Relaxation of Poly(methyl methacrylate) and Poly(methyl acrylate) in Dilute Solutions in Dichloromethane

Abstract: The intramolecular segmental relaxation behaviors of poly(methyl methacrylate) (PMMA) and poly(methyl acrylate) (PMA) in dilute dichloromethane solutions have been studied using time-resolved fluorescence anisotropy measurements (TRAMS). TRAMS have been made on two different spectrometers, incorporating a picosecond laser source and synchrotron, respectively, as excitation sources. Excellent agreement was achieved between the resultant relaxation data, generating confidence both in the spectroscopic procedures involved and in the various forms of analytical data retrieval applied. The relaxation characteristics of each polymer, over the temperature range 230-310 K, was adequately described by an exponential model for the anisotropy, for both acenaphthylene- and 1-vinylnaphthalene- based labels. The associated correlation times for segmental motion exhibited an Arrhenius dependence in the temperature range studied, giving activation energies of the order of 14 and 11 kJ mol-1 for PMMA and PMA, respectively, in dichloromethane. These values are considerably reduced compared to those which have been reported for either polymer in other solvents. The differences in activation parameters are too great to be explained on the assumption that the solvents function to provide frictional resistance alone to the polymer dynamics. It is tentatively suggested that both PMMA and PMA exhibit specific interactions with dichloromethane and/or other solvents, such as toluene. Alternatively, the naphthyl labels used to interrogate the macromolecular dynamics might experience specific interactions with the dichloromethane which distort the apparent behavior of the polymer.

Cool-applied hot melt adhesive composition

Abstract: A carton, case or tray formed utilizing a hot melt adhesive composition said adhesive consisting essentially of a) 10 to 60% by weight of at least one ethylene n-butyl acrylate copolymer containing 25 to 45% by weight n-butyl acrylate and having a melt index of at least about 850; b) 20 to 60% of a rosin ester tackifying resin; c) 10 to 50% by weight of a microcrystalline or paraffin wax having a melting point of 65.5 to 93.2°C (150 to 200°F); d) 1 to 20% by weight of a polymeric additive selected from the group consisting of ethylene vinyl acetate containing 10 to 40 % by weight vinyl acetate, ethylene methyl acrylate polymers containing 10 to 28 % methyl acrylate, ethylene acrylic acid copolymers having an acid number of 25 to 150, polyethylene, polypropylene, poly-(butene-1-co-ethylene), and lower melt index ethylene n-butyl acrylate copolymers; and e) 0 to 1.5 % stabilizer, said adhesive characterized by a viscosity of less than 3000 cps at 135°C, fiber tearing bonds from within the range of -35 to 40°C.

Cycloaddition of 3-Amino-5-chloro-2(1H)-pyrazinones and Olefins: Ring Transformation into 3-Amino- or 6-Cyano-Substituted 2-Pyridinone Systems

Abstract: The cycloadducts formed from the Diels−Alder reaction of 3-amino-5-chloro-2(1H)-pyrazinones with methyl acrylate in toluene are subject to two alternative modes of ring transformation yielding either methyl 6-cyano-1,2-dihydro-2-oxo-4-pyridinecarboxylates, e.g. 12a,b (loss of amine substituent), or the corresponding 3-amino-6-cyano-1,2,5,6-tetrahydro-2-oxo-4-pyridinecarboxylates, e.g. 15a,b. From the latter compounds, 3-amino-2-pyridinones can be generated through subsequent loss of HCN. A mechanism accounting for the loss or retention of the amine substituent is based on (1) the effects observed for each reaction mode when varying the substituents in both reaction partners and (2) the exclusive retention of the amine substituent when replacing toluene with the basic solvent pyridine.

Stereospecific polymerization of N,N-diphenylacrylamide

Abstract: N,N-Diphenylacrylamide (DPAA) was polymerized with anionic and radical initiators in toluene and tetrahydrofuran. The tacticity of the obtained polymers (poly(DPAA)) was unable to be determined directly by NMR spectroscopy. Therefore, poly(DPAA) was carefully converted to poly(acrylic acid) by solvolysis in a mixture of concentrated sulfuric acid and methanol (60:40; by volume) at 90°C for 24 hours, followed by methylation with diazomethane. Under suitable conditions, the transformation was performed without change (racemization) of tacticity of the polymers. Diad tacticity of the derived poly(methyl acrylate) was determined by 1H NMR spectroscopy. Anionic polymerization using butyllithium in toluene afforded a polymer rich in meso diad (m=0.95), and that in tetrahydrofuran racemo diad (r=0.66). Radical polymerization in toluene afforded a polymer with the highest racemo diad content (r=0.85).

On the conformational preferences of α,β-unsaturated carbonyl compounds. An ab initio study

Abstract: Ab initio theoretical calculations have been performed at different computational levels in order to study the s-cis/strans conformational preference of a series of α,β-unsaturated carbonyl compounds: acrolein, methyl vinyl ketone, acryloyl fluoride, acryloyl chloride, acrylic acid, and methyl acrylate. The results obtained show that RHF/6-31G∗ geometries are adequate to reproduce the experimental values for the difference in energy between both conformers, provided a sufficiently high level, such as MP3/6-3114 + + G∗∗, is used in single point energy calculations. The role of steric and electronic effects on the conformational preference of this kind of compound is discussed.

Emulsion co- and terpolymerization of styrene, methyl methacrylate, and methyl acrylate. I. Experimental determination and model prediction of composition drift and microstructure in batch reactions

Abstract: In Part I of this series the reactivity ratios of the comonomer pair methyl acrylate-methyl methacrylate were determined with low-conversion bulk polymerizations. It was shown that the binary reactivity ratios of the systems styrene-methyl acrylate, styrene-methyl methacrylate, and methyl acrylate-methyl methacrylate describe composition drift in low-coversion bulk terpolymerizations with these monomers reasonably well. A computer model was developed to simulate the composition drift in emulsion co- and terpolymerizations. The composition drift in two batch emulsion copolymerization systems (styrene-methyl acrylate and methyl acrylate-methyl methacrylate) and one emulsion terpolymerization system (styrene-methyl acrylate-methyl methacrylate) was investigated both experimentally and with the model. Experimental results were compared with model calculations. The copolymer chemical composition distributions (CCD) were determined with gradient polymer elution chromatography (GPEC®). This technique was also used for the first time to obtain information about the extent of composition drift in emulsion terpolymerizations. Cumulative terpolymer compositions were determined with 3H-NMR as a function of conversion and with this information the three-dimensional CCD was obtained. The composition drift was analyzed with respect to free radical copolymerization kinetics (reactivity ratios) and monomer partitioning. It was shown that in most emulsion copolymerizations the composition drift is mainly determined by the reactivity of the monomers and to a lesser extent by monomer partitioning, except in systems where there is a large difference in water solubility. The model predictions for cumulative terpolymer composition as a function of conversion and the three-dimensional terpolymer CCD showed excellent agreement with the experiments. The GPEC® elution chromatogram of the terpolymer was found to be in accordance with the predicted CCD and the experimentally determined CCD. © 1996 John Wiley & Sons, Inc.

Hot melt adhesives with excellent heat resistance

Abstract: A hot melt useful for packaging, comprising from about 10 % to about 30 % by weight of at least one copolymer of ethylene and methyl acrylate (both acrylates and methacrylates); from about 10 % to about 20 % by weight of at least one copolymer of ethylene and n-butyl acrylate (both acrylates and methacrylates), wherein the total polymer content does not exceed 40 % by weight, and the total ethylene n-butyl acrylate copolymer content does not exceed the total ethylene methyl acrylate copolymer content by percent weight in the adhesive; from about 20 % to about 60 % by weight of at least one tackifying resin selected from the group consisting of rosins and modified rosins and hydrogenated derivatives; aliphatic, cycloaliphatic and aromatic hydrocarbon resins and modified hydrocarbon resins and hydrogenated derivatives; terpenes and modified terpenes and hydrogenated derivatives; and mixtures thereof; from about 5 % to about 30 % by weight of at least one wax; and up to about 2 % by weight of an antioxidant; wherein the resultant adhesive has peel values greater than about 150 °F (about 65 °C).

Cross-Chain Transfer Rate Constants of Styrene-Terminated Radicals to Methyl Acrylate and Methyl Methacrylate

Abstract: The chain transfer-to-monomer dominated regime of the molar mass distribution of low-conversion emulsion copolymers of styrene and methyl acrylate and of styrene and methyl methacrylate of various compositions, prepared with varying initiator concentrations, was analyzed with size exclusion chromatography. By extrapolation of the values of the slope of the natural logarithm of the number molar mass distribution to zero initiator concentration, it was possible to determine the average chain-transfer coefficient as a function of composition. By calculation of the ratio of the concentrations of styrene-terminated radicals and methyl (meth)acrylate-terminated radicals with an appropriate propagation model, the values of the cross-chain transfer rate constants of styrene-terminated radicals to methyl acrylate and methyl methacrylate could be deduced. These values were interpreted in the light of newly gained insights into radical propagation and transfer reactions.