Methyl Methacrylate In Toluene Research Articles

Sulfur-Free Radical RAFT Polymerization of Methacrylates in Homogeneous Solution: Design of exo-Olefin Chain-Transfer Agents (R-CH2 C(=CH2 )Z).

In this work, the development of exo-olefin compounds (R-CH2 C(=CH2 )Z) as chain-transfer agents for the sulfur-free reversible addition-fragmentation chain transfer (RAFT) radical polymerization of methacrylates in homogeneous solution is described. A series of exo-olefin compounds with a methyl methacrylate (MMA) dimer structure as the R group and a substituted α-methylstyrene unit as the -CH2 C(=CH2 )Z (Z: Ph-Y) group were synthesized and used for the radical polymerization of MMA in toluene and PhC(CF3 )2 OH. These compounds underwent transfer of the CH2 C(=CH2 )Z group via addition-fragmentation of the propagating methacryloyl radical. More electron-donating (Y) substituents, such as methoxy and dimethylamino groups, produced polymers with narrower molecular weight distributions. A continuous monomer addition method further improved molecular weight control and enabled the synthesis of colorless, sulfur-free, multiblock copolymers of methacrylates in homogeneous solutions.

Sulfur‐Free Radical RAFT Polymerization of Methacrylates in Homogeneous Solution: Design of exo‐Olefin Chain‐Transfer Agents (R−CH2C(=CH2)Z)

AbstractIn this work, the development of exo‐olefin compounds (R−CH2C(=CH2)Z) as chain‐transfer agents for the sulfur‐free reversible addition‐fragmentation chain transfer (RAFT) radical polymerization of methacrylates in homogeneous solution is described. A series of exo‐olefin compounds with a methyl methacrylate (MMA) dimer structure as the R group and a substituted α‐methylstyrene unit as the −CH2C(=CH2)Z (Z: Ph−Y) group were synthesized and used for the radical polymerization of MMA in toluene and PhC(CF3)2OH. These compounds underwent transfer of the CH2C(=CH2)Z group via addition‐fragmentation of the propagating methacryloyl radical. More electron‐donating (Y) substituents, such as methoxy and dimethylamino groups, produced polymers with narrower molecular weight distributions. A continuous monomer addition method further improved molecular weight control and enabled the synthesis of colorless, sulfur‐free, multiblock copolymers of methacrylates in homogeneous solutions.

Partitioning effect of nitrogen catalyst into polymerizing particles on dispersion reversible chain transfer catalyzed polymerization (dispersionRTCP) of methyl methacrylate in supercritical carbon dioxide and organic solvents

Reversible chain transfer catalyzed polymerization (RTCP) in dispersion polymerization system (dispersion RTCP) of methyl methacrylate (MMA) was performed with N-iodosuccimide (NIS) as a nitrogen catalyst in supercritical carbon dioxide (scCO2). The solubility of NIS in scCO2 can be controlled by tuning the pressure, and this led to promote NIS partitioning into polymerizing particles. As a result, the molecular weight distribution control was successfully improved by decreasing the NIS solubility in the medium by tuning the scCO2 at a low pressure of 20 MPa. On the other hand, at the same NIS concentration, a solution RTCP of MMA in toluene as a homogeneous polymerization system did not proceed with a controlled/living manner. The importance of NIS partitioning into the polymerizing particles was also confirmed in hexane as well as scCO2 medium. From these results, it was clarified that the NIS catalyst partitioning into the polymerizing particles as main polymerization loci is a key factor to control the molecular weight distribution in the dispersion RTCP of MMA in scCO2. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 613–620

CdS–Oleic Acid Quantum Dots as Long‐Wavelength Photoinitiators in Organic Solvent and Preparation of Luminescent, Colloidal CdS/Polymer Nanocomposites

AbstractPhotoexcitation of luminescent semiconductor quantum dots (QDs) generates an electron–hole pair, which can be utilized for photoinitiation of radical polymerization reactions. Here, oleic acid coated CdS QDs (CdS–OA) are demonstrated as successful photoinitiators in the absence of a protic solvent or a hole scavenger for the first time. This provides photopolymerization of hydrophobic methyl methacrylate in toluene, providing colloidal and strongly luminescent CdS/poly(methacrylic acid) (PMMA) hybrid structures with improved stability of the CdS. Besides, successful photopolymerization of poly(ethylene glycol)diacrylate at different excitation windows (320–480 and 400–500 nm) is demonstrated. This indicates that CdS–OA can act as a long‐wavelength initiator. Electron spin resonance (ESR) studies and control experiments suggest decarboxylation of the oleic acid as the initial source of the free radical. This method represents a unique and very simple way to create luminescent, small, stable, and colloidal QD/polymer hybrids.

The synthesis of (N1E,N4E)-N1,N4-bis(pyridine-2-YL) ethylene benzene-1,4-diamine and investigation of its efficiency as new binuclear catalyst complex in copper-based ATRP

(N1E,N4E)-N1,N4-bis(pyridin-2-yl) ethylene benzene-1,4-diamine (BPEBD) was synthesized by condensation of 2-acetyl pyridine and 1,4-diaminobenzene and its efficiency as a catalyst in Cu-based atom transfer radical polymerizations (ATRP) of methyl methacrylate (MMA) and styrene (S) was investigated. Linear first-order kinetic plots were obtained. However, there were induction periods. The apparent rate constant values of ATRP of MMA with CuCl/BPEBD catalyst system in toluene were found to be between 2.10 × 10−5 and 9.83 × 10−5 s−1, while they were between 6.67 × 10−6 and 3.30 × 10−5 s−1 in the case of acetonitrile, indicating the presence of a low radical concentration throughout the polymerizations. Low apparent rate constant values denote a good control over ATRP in general. Apparent rate constant vs [ligand]/[catalyst] ratio plots showed a maximum at the [ligand]/[catalyst] ratio of 1. In the ATRP of MMA in toluene, Mn,GPC values increased linearly with conversion and these molecular weight values were close to Mn,th in comparison to that of in acetonitrile. In the polymerization of S, the control of molecular weights was not good, although the reactions were first-order kinetics. Cyclic voltammetry measurements confirmed that CuCl/BPEBD complex in acetonitrile gives quasi-reversible redox couples, and copper (I) centers in CuCl/BPEBD binuclear catalyst complexes are readily oxidized and it potentially suits to facile ATRP.

Polymerization of methyl methacrylate by latent pre-catalysts based on CO2-protected N-heterocyclic carbenes

Various carbon dioxide-protected N-heterocyclic carbenes (NHCs) have been investigated with regard to their ability to act as thermally latent initiators for the polymerization of methyl methacrylate (MMA). Such CO2-protected NHCs, while completely inactive at room temperature, deliver poly(methyl methacrylate) (PMMA) in high yields upon heating and thus represent truly latent pre-catalysts. Polymerizations were conducted in the bulk, semi-bulk and in solution. Especially tetrahydropyrimidinium-2-carboxylates as well as 1,3-di(tert-butyl)imidazolium-2-carboxylate, both in combination with dimethylsulfoxide (DMSO), were identified as suitable pre-catalysts for the polymerization of MMA. With 1,3-di(tert-butyl)imidazolium-2-carboxylate in toluene, polydispersity indices (PDIs) as low as 1.3 and number-average molecular weights (Mn) of 500 000 g mol−1 could be realized. Tetrahydropyrimidinium-2-carboxylates in conjunction with DMSO resulted in lower molecular weights. Notably, isolated polymer yields up to 96% were possible in some cases, though yields proved to be sensitive to the structure of the initiators used. In principle, at least two different polymerization mechanisms are active. In the presence of DMF or DMSO, the formation of a solvent anion (e.g., DMSO−), which then reacts with the monomer, is proposed. What follows is that only highly basic NHCs work well under these conditions. In contrast, the polymerization of MMA in toluene or in the bulk is probably governed by the nucleophilicity of the NHC, rendering unsaturated, less basic NHCs more applicable. Both mechanisms are discussed.

Grafting Poly(methyl methacrylate) onto Polyimide Nanofibers via “Click” Reaction

Surface modification of azide-decorated polyimide (PI) nanofibers with well-defined alkyne-terminated poly(methyl methacrylate) (PMMA) was accomplished via the combination of atom transfer radical polymerization (ATRP) and "click" chemistry. In this work, PI nanofibers were prepared via electrospun polyamic acid (PAA), followed by thermal imidization. Grafting of PMMA onto PI nanofibers was accomplished in three steps: (1) choloromethylation and azidization of PI nanofibers; (2) preparation of alkyne-terminated PMMA by ATRP of methyl methacrylate in toluene using propargyl 2-bromopropionate as initiator; (3) click coupling between the azidized PI nanofibers and the alkyne-terminated PMMA under the catalysis of Cu(I)Br/N,N,N',N''-pentamethyldiethylenetriamine (PMDETA). Gel permeation chromatography (GPC), (1)H NMR, and Fourier transform infrared (FT-IR) all confirmed the structure of alkyne-terminated poly(methyl methacrylate). The modified surface was characterized by X-ray photoelectron spectroscopy (XPS) after each modification stage. XPS and scanning electron microscope (SEM) were utilized to confirm PMMA-functionalized PI nanofibers, showing polymer coatings present on the surface of PI nanofibers. PI-g-PMMA nanofibers exhibited a more significant reinforcing effect compared to that with ungrafted PI nanofibers.

Solid-supported synthesis of well-defined amphiphilic block copolymer from methacrylates

A new facile method for preparation of an amphiphilic block copolymer via a one-pot sequential atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) on solid support was developed. As a model homopolymerization for the solid-supported block copolymerization, ATRPs of MMA and HEMA in toluene and in 2-butanone/1-propanol solvent system were carried out, respectively. Crosslinked polystyrene beads bearing 2-bromoisobutyrate moieties successfully initiated the polymerizations of MMA and HEMA in controlled manner. On the basis of the successful results, the one-pot synthesis of amphiphilic block copolymer by changing the reaction medium was performed. After the ATRP of MMA in toluene at 90 °C for 1 h, the poly(MMA) formed on the beads were washed by continuous flow of 2-butanone/1-propanol under nitrogen with the aid of a glass filter in a U-shaped glass vessel. Then, 2-butanone/1-propanol, copper chloride (I), 2,2′-bipyridyl, and HEMA were added and heated at 50 °C for 48 h with shaking the vessel, followed by treatment with trifluoroacetic acid to isolate the well-defined amphiphilic block copolymer, poly(MMA-b-HEMA). These demonstrated the feasibility of the present strategy for well-defined synthesis of amphiphilic block copolymers via a one-pot procedure. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1990–1997, 2008

“Constrained Geometry” Titanium Complexes: Exceptionally Robust Systems for Living Polymerization of Methacrylates at High Temperature and Model Studies toward Chain Transfer Polymerization with Thiols

The 1:1 combination of Ti{CGC}Me2 (1; CGC = Me2Si(Me4C5)(tBuN)) with B(C6F5)3 was found to feature a so far unrevealed thermal robustness in methacrylate polymerization that enables it to operate in a broad temperature range (0−100 °C) with a living behavior. Highly effective (576 kg PMMA·mol Ti-1·h-1) and productive (monomer-to-Ti ratio up to 5000) homopolymerization of methyl methacrylate (MMA) and effective diblock and triblock copolymerization of MMA with butyl methacrylate (BMA) were thus achieved at 80 °C. The robust “constrained geometry” titanium system has been used to investigate thiols as possible chain transfer agents in MMA polymerization. Neutral alkylthiolato and thiophenolato complexes [Ti{CGC}(X)(Y)] (2, X = Me, Y = tBuS; 3, X = Me, Y = o-MeOC6H4S; 4, X = Y = iPrS; 5, X = Y = PhCH2S) have been synthesized by protonolysis of 1 with thiols and shown to polymerize MMA once activated by a Lewis acid such as B(C6F5)3. Combinations 1/B(C6F5)3/tBuSH polymerized quantitatively MMA in toluene to yield PMMAs with narrow polydispersity (Mw/Mn ≅ 1.10), but no effective chain transfer was evidenced, whatever the conditions used. The stoichiometric reaction of tBuSH and o-MeOC6H4SH with the cationic enolate complex [Ti{CGC}(O(OiPr)CCMe2)(THF)]+[MeB(C6F5)3]- (8) revealed that thiols do cleave the Ti−O(enolate) bond of 8 to give the alkylthiolato and thiophenolato titanium cationic species; however, this pathway proceeds remarkably slowly in comparison with that with a similar Zr−O(enolate) bond.

Anionic polymerization of methyl methacrylate by initiating systems based on lithium amides of various secondary amines

AbstractThe anionic polymerization of methyl methacrylate in toluene at −78 °C with lithium amides of various secondary amines (diisopropylamine, N‐isopropylaniline, N‐n‐butylaniline, indoline, and N‐ethyl‐o‐toluidine) as initiators was studied. The tacticity of the resulting poly(methyl methacrylate)s (PMMAs) was dependent on the kind of secondary amine, and highly isotactic PMMAs (91–93% mm) were obtained when lithium amides of N‐isopropylaniline and N‐n‐butylaniline were employed. The isotacticity of the PMMAs further increased up to 98% mm with initiating systems composed of the lithium amides, n‐butyllithium, and transition‐metal halides (WCl6, MoCl5, and NbCl5). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4405–4411, 2005

TBuOK/iBu3Al as New Initiating System for Controlled Anionic Polymerization of tert-Butyl Acrylate and Methyl Methacrylate

The combination of potassium tert-butoxide (tBuOK) and triisobutylaluminum (iBu3Al) (the tBuOK/iBu3Al system) initiated the anionic polymerization of tert-butyl acrylate (tBA) and methyl methacrylate (MMA) and controlled the polymerization with respect to molecular weights and molecular weight distributions (MWDs). Poly(tBA)s (Mn = 20 000−80 000) with narrow MWDs (Mw/Mn = 1.05−1.12) were obtained quantitatively in toluene at 0 °C for 1−2 h. The controlled character of the polymerization remained intact even at high temperatures up to 50 °C. MALDI−TOF-MS analyses of a low molecular weight poly(tBA) prepared with the initiating system revealed that the polymer had hydrogens at both chain ends. Block copolymerizations of tBA and MMA were also successful in toluene at 0 °C by using the initiating system, giving poly(tBA-b-MMA)s with various compositions of the two monomer units and narrow MWDs in high yield. Although the tBuOK/iBu3Al system failed to control the homopolymerization of MMA in toluene or THF, the use of diethyl ether (Et2O) as a solvent for the polymerization coupled with cesium fluoride (CsF) resulted in the quantitative formation of high molecular weight poly(MMA)s with narrow MWDs.

The in situ formation of a new initiator system for the syndiotactic anionic polymerization of methyl methacrylate in toluene at 0 °C

This paper reports on an efficient ‘in-situ’ one pot synthesis of an initiatior/ligand adduct, which can be used to initiate the anionic polymerization of methyl methacrylate in toluene at 0 °C. Predominantly syndiotactic PMMA is formed.

Poly(methyl methacrylates) with Ruthenium Tris(bipyridine) Cores via NiBr2(PR3)2-Catalyzed Atom Transfer Radical Polymerization (ATRP)

Ruthenium(II) tris(bipyridine) complexes derivatized with six α-bromoester functional groups were used as multifunctional initiators for the bulk and solution (toluene) polymerizations of methyl methacrylate (MMA) and methyl acrylate (MA) using NiBr2(PPh3)2 and NiBr2(PBu3)2 as atom transfer radical polymerization (ATRP) catalysts. Both tertiary (1) and secondary (2) halide metalloinitiators were prepared for investigation. The resulting orange-colored polymers were characterized by gel permeation chromatography (GPC) in chloroform. The molecular weight distributions of the poly(methyl methacrylates) (PMMAs) were narrow (toluene, Mw/Mn = 1.1−1.3; bulk, Mw/Mn < ∼1.3 at <50% conversion). The presence of [Ru(bpy)3]2+ in the eluting polymers was verified by in-line, diode-array UV/vis spectroscopic analysis. For polymerizations of MMA in toluene at 80 °C using the tertiary initiator and NiBr2(PPh3)2 as the catalyst, Mn vs percent conversion and pseudo first-order kinetics plots were linear. Thus, these conditi...

Mechanism of catalytic chain transfer in the free-radical polymerisation of methyl methacrylate and styrene

The mechanism of catalytic chain transfer with bis(boron difluorodimethylglyoximate) cobaltate(II) (COBF) has been studied in the homopolymerisations of methyl methacrylate and styrene. The chain transfer constants were measured using both the Mayo and Chain Length Distribution (CLD) methods over a range of temperatures (40–70°C). The two methods generally agree within 10%. The high values of the chain transfer rate coefficients, ktr (∼107 for MMA), suggest the possibility that the reaction is approaching diffusion control. This is also supported by the high values obtained for the frequency factor (A ∼ 1010). The chain transfer rate coefficients for styrene are approximately two orders of magnitude lower than those obtained for MMA, which can be explained in terms of the formation of cobalt-carbon bonds and the accessibility of β-H sites for hydrogen abstraction from the two different radical chain ends in the case of styrene. High conversion, solution polymerisation experiments on methyl methacrylate in toluene reveal behaviour inconsistent with a simple catalytic mechanism and may suggest deactivation of the catalyst by solvent. On the assumption that the kinetics of catalytic chain transfer can be explained by a classical free-radical mechanism, it is possible to derive information on the chain length dependence of the average termination rate coefficient, 〈kt〉. Applying this approach to methyl methacrylate and styrene at different temperatures, we have found that the chain length effect on 〈kt〉 appears to be independent of both temperature and monomer type.

Mechanism of catalytic chain transfer in the free-radical polymerisation of methyl methacrylate and styrene

The mechanism of catalytic chain transfer with bis(boron difluorodimethylglyoximate) cobaltate(II) (COBF) has been studied in the homopolymerisations of methyl methacrylate and styrene. The chain transfer constants were measured using both the Mayo and Chain Length Distribution (CLD) methods over a range of temperatures (40–70°C). The two methods generally agree within 10%. The high values of the chain transfer rate coefficients, ktr (∼107 for MMA), suggest the possibility that the reaction is approaching diffusion control. This is also supported by the high values obtained for the frequency factor (A ∼ 1010). The chain transfer rate coefficients for styrene are approximately two orders of magnitude lower than those obtained for MMA, which can be explained in terms of the formation of cobalt-carbon bonds and the accessibility of β-H sites for hydrogen abstraction from the two different radical chain ends in the case of styrene. High conversion, solution polymerisation experiments on methyl methacrylate in toluene reveal behaviour inconsistent with a simple catalytic mechanism and may suggest deactivation of the catalyst by solvent. On the assumption that the kinetics of catalytic chain transfer can be explained by a classical free-radical mechanism, it is possible to derive information on the chain length dependence of the average termination rate coefficient, 〈kt〉. Applying this approach to methyl methacrylate and styrene at different temperatures, we have found that the chain length effect on 〈kt〉 appears to be independent of both temperature and monomer type.

New Ligands for the Living Isotactic Anionic Polymerization of Methyl Methacrylate in Toluene at 0 °C. 2. 7Li NMR Analysis of sec-Butyllithium Ligated by Lithium Silanolates

The mixed associated species {xsBuLi, (y − x)sBuMe2SiOLi} formed by reaction of sec-Butyllithium (sBuLi) with octamethylcyclotetrasiloxane (Me2SiO)4 in toluene have been used to initiate the anioni...

New Ligands for the Living Isotactic Anionic Polymerization of Methyl Methacrylate in Toluene at 0 °C. 1. Ligation of Butyllithium by Lithium Silanolates

sBuLi and tBuLi have been combined with a new family of ligands, i.e. lithium silanolates, and used as initiators for the ligated anionic polymerization (LAP) of methyl methacrylate (MMA) in toluene at 0 °C. Compared to other known μ-ligands, the accordingly formed Bu(Me2)SiOLi are more efficient stabilizers for the active centers. Under appropriate reaction conditions, a fast polymerization proceeds quantitatively without self-termination at 0 °C and leads to high molecular weight polymer of narrow molecular weight distribution (M̄w/M̄n < 1.2) and high isotacticity (90% isotactic triads).

Effect of bulkiness and lewis acidity of aluminium compounds on the anionic polymerization of methyl methacrylate in toluene

AbstractThe bulkiness and the Lewis acidity of added aluminium compounds strongly affect the polymerization of methyl methacrylate in toluene at −78°C. The polymerization strongly deviates from ‘ideal’ first‐order kinetics, i.e. the first‐order time‐conversion plots are kinked at low monomer conversions. Additionally, for the more bulky and more Lewis‐acid aluminium alkyls, the time‐conversion plots show a further downward curvature. This curvature is not the result of a termination reaction because the polymers are free of side products like β‐ketoesters or vinyl ketone units. The molecular weight distributions and tacticities of the resulting polymers are also affected. Dependent on the aluminium compound used, molecular weight distributions are in the range of 1.2 &lt; Mw/Mn &lt; 7, and the triad tacticity of the polymer can change from highly syndiotactic over atactic or heterotactic to highly isotactic.

Penultimate Unit Effects in Free-Radical Copolymerization. Number-Average Degree of Polymerization and Copolymerization Rate in Styrene/Methyl Methacrylate/Toluene System

Recently, Fukuda et al. showed from the measurements of absolute rate constants that in the free-radical copolymerization the propagation step obeys the penultimate model and the termination step is diffusion-controlled. Also Fukuda et al. proposed the “radical stabilization energy model” in the free radical copolymerization. To examine this copolymerization model, relationships between feed monomer composition f1 and number-average degree of polymerization Xn and between f1 and copolymerization rate Rp were investigated for the copolymerization of styrene and methyl methacrylate in toluene at 40°C. The composition of the copolymer F1 was determined by 1H NMR. The number-average molecular weight of the copolymer Mn was measured to calculate Xn by osmometry and size exclusion chromatography (SEC). By the so-called terminal model (the Mayo–Lewis model), the copolymer composition data was well described while the data of Xn and Rp Were not described. Alternatively, the model proposed by Fukuda et al. described well the composition data, the Xn data and the Rp data.

Kinetics of free radical solution polymerization of methyl methacrylate over an extended conversion range

AbstractThe low and intermediate conversion solution polymerization kinetics of methyl methacrylate in toluene and in 2‐butanone are investigated. For this purpose, repetitively applied laser pulses are employed to stimulate initiation, and quantitative near infrared spectroscopy is used to determine methyl methacrylate concentrations. The monomer concentration change per pulse is measured; it is shown how this information may be converted into coupled values of the rate coefficient for propagation kp, the rate coefficient for termination kt, and the total efficiency of (photo)initiation. In the present case kp is already known from independent investigations, which enables our pseudostationary state methods to yield kt directly. The major thrust of this paper, therefore, concerns the effect of solvent on kt: it is found that at both low and intermediate conversions, kt increases as the solvent concentration increases; possible causes of this are discussed. The effect of initial solvent fraction on the variation of kt with conversion is also reported. Although all our experimental measurements are carried out at an elevated pressure (1000 bar) and a single temperature (30°C), there is no reason for suspecting that our findings regarding solution polymerization termination should not be representative for polymerizations of methyl methacrylate (and other methacrylate monomers) in general.