Thermal Polymerization Of Methyl Methacrylate Research Articles

INFLUENCE OF LEAD IONS ON PHOTOLUMINESCENT PROPERTIES OF POLYMETHYL METACRYLATE /(Zn,Pb)S/CdS/(Zn,Pb)S COMPOSITIONS

The paper presents the results of a study of the effect of lead ions on the photoluminescent properties of core / shell / shell nanostructures based on zinc and cadmium sulfides synthesized in situ during the formation of polyacrylate composition. ZnS/CdS/ZnS and (Zn,Pb)S/CdS/(Zn,Pb)S nanoparticles were obtained by colloidal synthesis in a medium of (poly) methyl methacrylate. Colloidal solutions are solidified to a glassy state by radical thermal polymerization of methyl methacrylate in a block. To initiate the polymerization, benzoyl peroxide was introduced into the solutions in an amount of 0.1% by weight of methyl methacrylate. The conclusion on the formation of nanosized particles of complex composition in the polymer matrix is made by comparing the luminescence and luminescence spectra of the compositions containing ZnS and CdS particles and their structure. In the photoluminescence spectra of the (poly) methyl methacrylate/(ZnS/CdS/ZnS) composition, two complex bands associated with crystal lattice defects of ZnS particles (380 - 530 nm) and CdS (530 - 840 nm) were detected. The excitation of photoluminescence occurs as a result of interband transitions of electrons in each of the semiconductor layers, as well as during transitions of electrons from the conduction band to defect levels located in the forbidden band of the semiconductor structure. In the luminescence excitation spectrum, they correspond to bands of various intensities in the range of 300–420 nm and 300–480 nm. From the overlap of the ZnS luminescence bands and the excitation of CdS luminescence, it was concluded that the radiation of the core is absorbed by the CdS coating layer and that energy is transferred from the levels of structural defects of ZnS to the levels of structural defects of CdS at the layer boundary. Doping of zinc sulfide layers with lead ions leads to a change in the luminescence spectrum in the region of 380 - 530 nm and the disappearance of the CdS luminescence band in the range of 530 - 840 nm. The observed changes are associated with defects that create Pb2+ ions in the crystal lattice of the ZnS outer shell and the screening of the (Zn,Pb)S shell of the inner layers from the penetration of exciting radiation.

Photoluminescence of (Zn, Pb, Mn)S Quantum Dots in Polyacrylate Matrix

Solutions of (Zn, Pb, Mn)S quantum dots with different molar ratios between cations are produced by colloidal synthesis in a methyl methacrylate (MMA) medium. By the thermal polymerization of MMA in a block, the colloidal solutions are converted into the vitreous state. The optical transparency of the poly(MMA)/(Zn, Pb, Mn)S composites at the wavelengths >500 nm reaches 90% at a thickness of the absorbing layer up to 5 mm. The photoluminescence of the composites in the spectral range 400–480 nm is defined by the recombination of electrons at the levels of defects of the ZnS crystal structure, and photoluminescence in the range 520–620 nm by the 4T1 → 6A1 electronic transition in Mn2+ ions. Photoluminescence excitation is a result of interband transitions in ZnS, with energy transfer from the conduction band of ZnS to the levels of Mn2+ ions. The luminescence spectrum depends on the molar ratio between Mn2+ and Pb2+ ions, the order of introduction of substances into the reaction mixture, and the excitation-radiation wavelength.

Ground Organic Particles of ca. 3 μm Size as Chromatographic Separation Media in High Performance Liquid Chromatography

A new chromatographic stationary phase was prepared by making a soft organic monolith based on thermal polymerization of methyl methacrylate and ethylene glycol di-methacrylate with an aid of gas evolution via decomposition of urea, and by crushing the monolith into particles. The original purpose of urea incorporation was formation of monolith particles with affluent mesopores, but the actual effect was reduction of the particle size to a proper range (mostly in the range of 1–5 μm with an average of ca. 3 μm), which was very crucial for improvement of separation efficiency. A series of washing processes (including common washing and reflux washing) were carried out to remove un-reacted materials and free oligomers. The columns were made by packing the organic monolith particles in glass-lined stainless-steel tubing and evaluated for their performance with the mixture of six aromatic compounds (3-phenyl-1-propanol, acetophenone, methyl benzoate, 2-nitroaniline, ethylbenzene, cumene). The overall number of theoretical plates (N) over 6 analytes based on 6 columns was 32,000 plates/column (107,000 plates/m, 9.4 µm plate height).

Фотолюминесценция квантовых точек (Zn, Pb, Mn)S в полиакрилатной матрице

Solutions of quantum dots (Zn,Pb,Mn)S with different mole ratio of cations were obtained by colloidal synthesis in methyl methacrylate (MMA) medium. By thermal polymerization of MMA in the block, colloidal solutions are transferred to the glassy state. The optical transparency of PMMA/(Zn,Pb,Mn)S compositions at wavelengths >500 nm reaches 90% with the thickness of the absorbing layer up to 5 mm. Photoluminescence of compositions in the spectral region of 400–480 nm is associated with electron recombination at the levels of defects in the crystal structure of ZnS, in the range of 520–620 nm with 4T1 → 6A1 electron transition in Mn2+ ions. Excitation of photoluminescence occurs as a result of interband transitions in ZnS and energy transfer from the conduction band of ZnS to Mn2+ ion levels. The luminescence spectrum depends on the molar ratio of Mn2+ and Pb2+ ions, the sequence of introduction of the components into the reaction mixture, the wavelength of the exciting radiation.

Calorimetric Method To Determine Self-Accelerating Polymerization Temperature (SAPT) for Monomer Transportation Regulation: A Heat Balance Approach

In our previous paper, kinetic parameters for the thermal polymerization of methyl methacrylate (MMA) inhibited with 4-methoxyphenol (MEHQ) were determined by isothermal and nonisothermal calorimet...

Synthesis and absorption and luminescence spectra of poly(methyl methacrylate):Cd(Mn,Pb)S composites

The reaction of cadmium, manganese, and lead trifluoroacetates with thioacetamide in methyl methacrylate yielded colloidal solutions of metal sulfides with different Cd(II): Mn(II): Pb(II) molar ratios. The colloidal particles were separated from solutions and examined by electron microscopy. Glassy polymer composites poly(methyl methacrylate):Cd(Mn)S and poly(methyl methacrylate):Cd(Mn,Pb)S were prepared by thermal polymerization of methyl methacrylate in the bulk. The transmittance of the composites at wavelengths larger than 480 nm is 92% at the sample thickness of 0.40 cm. The luminescence of the composites in the visible range is associated with cadmium sulfide. The corresponding absorption bands were recorded in the luminescence excitation spectra in the wavelength interval 300–450 nm. The effect of the matrix, Mn(II) and Pb(II) ions, and synthesis conditions on the absorption and luminescence properties of the composites was determined.

Preparation and luminescent properties of GdOF:Ce, Tb nanoparticles and their transparent PMMA nanocomposites

GdOF:Ce, Tb nanoparticles and their poly (methyl methacrylate) (PMMA) nanocomposites have been successfully prepared by a thermolysis route and thermal polymerization of methyl methacrylate (MMA) monomer, respectively. The obtained nanoparticles and nanocomposites are characterized by XRD, EDS, TEM, FTIR, TGA, UV–Vis and PL spectrum. The as-synthesized transparent GdOF:Ce, Tb/PMMA nanocomposites exhibit green photoluminescence under the irradiation of 254nm UV lamp due to the incorporation of luminescent GdOF:Ce, Tb nanoparticles into the PMMA matrix. The present route would provide a general strategy to prepare other functional nanocomposites.

Effect of electron-donating ability of terminal groups of cationic polymethine dyes on thermal polymerization of methyl methacrylate in solution

Thermal polymerizability of methyl methacrylate solution was examined in dimethylformamide in the presence of cationic symmetric and asymmetric polymethine dyes with different terminal electron-donating groups by dilatometric method. It was found that the polymethine dyes according to the electronic structure can initiate or inhibit the polymerization of methyl methacrylate both in the presence of standard initiator, azoisobutyronitrile, and in its absence by a radical mechanism. It was shown that the initiating ability was weakened with altering an electron-donating activating ability of terminal groups of dyes from the average level in both directions of its increasing or decreasing. The transition from symmetric to asymmetric dyes in the same structural type is accompanied by a loss of initiating ability. Based on the comparison of experimental kinetic data of polymerization of methyl methacrylate in the presence of dyes and quantum chemical calculations of electronic structure for dyes it was demonstrated that a HOMO energy value of an initiating dye must be higher and that of an inhibiting dye, lower than the methyl methacrylate value.

Computational Evidence for Self-Initiation in Spontaneous High-Temperature Polymerization of Methyl Methacrylate

This paper presents computational evidence for the occurrence of diradical mechanism of self-initiation in thermal polymerization of methyl methacrylate. Two self-initiation mechanisms of interest were explored with first-principles density functional theory calculations. Singlet and triplet potential energy surfaces were constructed. The formation of two Diels-Alder adducts, cis- and trans-dimethyl 1,2-dimethylcyclobutane-1,2-dicarboxylate and dimethyl 2-methyl-5-methylidene-hexanedioate, on the singlet surface was identified. Transition states were calculated using B3LYP/6-31G* and assessed using MP2/6-31G*. The calculated energy barriers and rate constants with different levels of theory were found to show good agreement to corresponding data obtained from laboratory experiments. The presence of a diradical intermediate on the triplet surface was identified. When MCSCF/6-31G* was used, the spin-orbit coupling constant for the singlet to triplet crossover was calculated to be 2.5 cm(-1). The mechanism of monoradical generation via a hydrogen abstraction by both triplet and singlet diradicals from a third monomer was identified to be the most likely mechanism of initiation in spontaneous polymerization of methyl methacrylate.

Carbon Nanotube (CNT)–Polymethyl Methacrylate (PMMA) Composite Electrolyte for Solid-State Dye Sensitized Solar Cells

A novel carbon nanotube (CNT)-polymethyl methacrylate (PMMA) composite electrolyte was successfully synthesized by the thermal polymerization of methyl methacrylate (MMA) with CNTs for solid-state dye sensitized solar cells (DSSCs). The prepared CNTs-PMMA composite electrolytes were characterized by Fourior transformed-infrared (FT-IR) spectroscopy, field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and ionic conductivity. A strong bonding was observed between CNT and PMMA through ester bonding in the CNT-PMMA composite, resulting in the lowering of crystallinity and increasing the ionic conductivity of composite electrolyte. DSSCs fabricated with CNTs-PMMA composite electrolytes achieved relatively high conversion efficiency of 2.9% with an open circuit voltage (V(oc)) of 0.567 volt, short circuit current (I(sc)) of 8.9 mA/cm2 and fill factor of 61.8%, which is attributed to enhanced amorphicity and ionic conductivity due to the formation of strong bonding between CNT and PMMA molecules.

Synthesis and characterization of diblock, triblock, and multiblock copolymers containing poly(3‐hydroxy butyrate) units

AbstractA poly[(R,S)‐3‐hydroxybutyrate] macroinitiator (PHB‐MI) was obtained through the condensation reaction of poly[(R,S)‐3‐hydroxybutyrate] (PHB) oligomers containing dihydroxyl end functionalities with 4,4′‐azobis(4‐cyanopentanoyl chloride). The PHB‐MI obtained in this way had hydroxyl groups at two end of the polymer chain and an internal azo group. The synthesis of ABA‐type PHB‐b‐PMMA block copolymers [where A is poly(methyl methacrylate) (PMMA) and B is PHB] via PHB‐MI was accomplished in two steps. First, multiblock active copolymers with azo groups (PMMA‐PHB‐MI) were prepared through the redox free‐radical polymerization of methyl methacrylate (MMA) with a PHB‐MI/Ce(IV) redox system in aqueous nitric acid at 40°C. Second, PMMA‐PHB‐MI was used in the thermal polymerization of MMA at 60°C to obtain PHB‐b‐PMMA. When styrene (S) was used instead of MMA in the second step, ABCBA‐type PMMA‐b‐PHB‐b‐PS multiblock copolymers [where C is polystyrene (PS)] were obtained. In addition, the direct thermal polymerization of the monomers (MMA or S) via PHB‐MI provided AB‐type diblocks copolymers with MMA and BCB‐type triblock copolymers with S. The macroinitiators and block copolymers were characterized with ultraviolet–visible spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, cryoscopic measurements, and thermogravimetric analysis. The increases in the intrinsic viscosity and fractional precipitation confirmed that a block copolymer had been obtained. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1789–1796, 2004

Two-Stage Pseudoliving Radical Polymerization under the Influence of Triphenylmethyl Radicals

The kinetics and the mechanism of radical thermal polymerization of methyl methacrylate and styrene in bulk at 80°C initiated by hexaphenylethane (a source of triphenylmethyl radicals) were studied. It was found that polymerization of both monomers proceeded according to a two-stage pseudoliving mechanism. The first stage features the formation and accumulation of reactive oligomeric product due to a fast consumption of triphenylmethyl radicals in the reactions of initiation and termination of the growing chains. The oligomeric product reinitiates polymerization at the second stage. Polymerization in both systems is characterized by a successive increase in the molecular weights of the polymers up to high conversions. It was shown that at low concentration of triphenylmethyl radicals the pseudoliving mechanism of the polymerization is violated appreciably; the reasons for this phenomenon are discussed.

Thermal Polymerization of Methyl Methacrylate at High Temperature

Abstract Kinetic studies of the bulk polymerization of methyl methacrylate at high temperature have been carried out first without any additives and then in the presence of 1-Butanethiol as a chain transfer agent. A pressurised dilatometric reactor operating at high temperature is used to determine the time-conversion curves at temperatures between 150 and 180°C. A two-stage polymerization is observed. The high polymerization rate obtained initially is attributed to traces of an initiating impurity, while the second, slower polymerization stage could be considered as the actual thermal polymerization. The chain transfer agent or an impurity it may contain also initiates the reaction. Therefore, the rates of both the initial polymerization and of the second stage are increased when the thiol is added. Experimental data on the degree of conversion versus time and on the final average molecular weight are used to determine the chain transfer constants to the monomer and to the mercaptan as well as the initiation rate constants. These constants are used to model the thermal polymerization of MMA at high temperatures where these initiation reactions can no longer be neglected, especially when an industrial polymerization process has to be optimized and controlled.

Effect of iron(III) oxide on the thermal polymerization of methyl methacrylate in low density polyethylene matrix

The effects of the temperature and fine particles of Fe2O3 upon methyl methacrylate (MMA) thermal polymerization in low density polyethylene (LDPE) matrix were investigated. The MMA mass increment in the composite matrix is a temperature dependent process. It reaches values 10 folds higher at 90°C compared to the mass increment at 60°C. The apparent polymerization rate is dependent of Fe2O3 concentration reaching a maximum at 0.17–0.26 % of Fe2O3 in the composite. The thermal process is catalysed by Fe2O3.

Radical grafting from carbon fiber surface: graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface

This paper describes the radical graft polymerizations of vinyl monomers from carbon fiber surface initiated by azo groups introduced onto the fiber surface. The carbon fiber used in this experiment was the polyacrylonitrile type. The introduction of azo groups onto the carbon fiber surface was achieved by the reaction of 4,4'-azobis (4-cyanopentanoic acid) with isocyanate groups which were previously attached onto the surface by the treatment of the fiber with tolylene 2,4-diisocyanate. The amount of surface azo groups introduced onto nitric acid-treated carbon fiber was determined to be 0.60 x 10-5 mol 9-1 by nitrogen analysis. The radical graft polymerization of methyl methacrylate (MMA) was tried. Though the thermal polymerization of MMA proceeded slightly in the absence or in the presence of untreated carbon fiber, the rate of the polymerization was considerably low. In contrast, the graft polymerization of MMA was initiated in the presence of the carbon fiber having surface azo groups, and part of r...

Synthesis and initiation/transfer properties of carbamoyl disulfides

AbstractThree model tetraalkylcarbamoyl disulfides were prepared and their initiation/transfer capabilities tested. The compounds studied were: bis(1‐piperidinecarbonyl) disulfide (1), bis(4‐(2‐hydroxyethyl)piperazine‐1‐carbonyl) disulfide (2), bis[N‐ethyl‐N‐(2‐(trimethylsiloxyethyl)‐carbamoyl)] disulfide (3). It was found that, in contrast to tetraalkylthiruam disulfides, the carbamoyl disulfides were not able to initiate free radical polymerization of methyl methacrylate (MMA) and styrene (ST), even at the highest temperatures applicable to these monomers. Apparently, the central S—S bond in carbamoyl disulfides is much stronger than the corresponding S—S bond in thiuram disulfides. Moreover, the carbamoyl disulfides are rather poor transfer agents. The transfer constants were estimated to be 2,5 10−3, 18.10−3 and 2,8. 10−3 for 1,2 and 3 in thermal polymerization of MMA at 110, 110 and 100°C, respectively, and 2,1. 10−3 for 3 in polymerization of MMA initiated with AIBN at 70°C. Chemistry aspects of synthesis and stability of hydroxy‐functionalized carbamoyl disulfides are discussed.

Hydroxy(tosyloxy)iodo]benzene as Thermal initiator for the Radical Polymerization of Methyl Methacrylate

Abstract The thermal polymerization of methyl methacrylate in a solution of N,N-dimethylacetamide has been studied using [hydroxy(tosyloxy)- iodo]benzene (HTIB) as the initiator. The rate of polymerization was a direct function of the monomer and initiator concentrations. The initiator and monomer exponent values expressing this dependence were found to be 1.0 and 0.8, respectively. The overall activation energy of polymerization was estimated to be 45 kJ·mol−-1. The polymerization was inhibited in the presence of hydroquinone. The effect of various solvents on the polymerization rate was studied. The polymer prepared with HTIB (0.47 × 10−3 mol·L−-1) had a number-average molecular weight of 138,000 and a glass transition temperature of 106°C. The polymer showed good thermal stability as determined by thermogravimetric analysis.

Sorption and thermal polymerization of vinyl monomers in low density polyethylene-iron (III) oxide composite

The nature of the species produced after sorption and thermal polymerization of acrylic acid, methyl methacrylate and 4-vinylpyridine in low density polyethylene-iron (III) oxide composite was investigated by Mossbauer and IR spectroscopies. The values of the Mossbauer parameters indicate no change in the oxidation state of iron (III) in the LDPE-Fe2O3 composite before and after sorption and thermal polymerization of the monomers. Acrylic acid interacts with iron (III) oxide particles yielding acrylates, hydroacrylates, polyacrylates and polyhydroacrylates. The iron (III) oxide particles remained unchanged after sorption and thermal polymerization of methyl methacrylate although some thermal polymerization is observed in the presence of Fe2O3-doped LDPE. Iron (III) oxide acts as catalyst for the radical polymerization of methyl methacrylate on LDPE-Fe2O3. The interaction of iron (III) oxide and 4-vinylpyridine after its sorption and thermal polymerization in LDPE-Fe2O3 is mainly by coordination bonding of the pyridine ring of the polymer to the iron of Fe2O3.

Triblock copolymers via thermal “macroiniferters”: Block copolymers of ethyl acrylate with methyl methacrylate or styrene

AbstractThe concept of macro iniferter (MI) was applied to realize the synthesis of triblock copolymers of ethyl acrylate (EA) with styrene (St) or methyl methacrylate (MMA), with EA forming the end blocks. The syntheses involved 3 steps. Secondary amine terminated poly(ethyl acrylate) was synthesisted by polymerization of EA in presence of butyl‐(2‐mercaptoethyl)ammonium chloride as a functional chain‐transfer agent. The macroamine so obtained was converted to the macrothiuram disulfide by reaction with CS2 and I2. Thermal polymerization of MMA or St in presence of this macroiniferter led to the respective triblock copolymers. The kinetics of polymerization of MMA and styrene using MI and two different chain lengths was done in limited concentration ranges. The kinetic parameters indicated that the iniferter action was not affected by the incorporation of the thiuram disulfide groups in the polymer backbone. Triblock copolymers of differing block lengths of hard and soft segments could be prepared by varying the chain length of the macroamine and the concentration of the iniferter in the reaction system. The copolymers were characterized by GPC analysis and spectral or elemental analyses. In the case of St, analysis showed formation of perfect triblocks, whereas for MMA, tendencies to form diblocks were observed on increasing the chain length of the iniferter‐forming block. DSC analyses showed demixing of the soft EA block and the hard central blocks.

Highly conductive poly(ethylene oxide)-poly(methyl methacrylate) blends complexed with alkali metal salts

Solid electrolytes of room temperature ionic conductivity exceeding 10 −5 S cm −1 were obtained by complexing NaI, LiI, LiBF 4 and LiClO 4 with blends prepared by thermal polymerization of methyl methacrylate in the presence of high molecular weight poly(ethylene oxide). All of the studied samples were thermally stable up to at least 60°C. Differential scanning calorimetry studies indicated that these electrolytes contained amorphous phases with very low glass transition temperatures. This is due to the plasticizing effect of the grafted copolymers formed during the polymerization. This is supposed to lead to high mobility of the charge carriers in the systems studied.