Anionic Polymerization Of Methyl Methacrylate Research Articles

Anionic polymerization of methyl methacrylate and chain-end modification via terminal-selective transesterification with bulky zincate

The anionic polymerization of methyl methacrylate (MMA) was investigated using dilithium tetra-tert-butylzincate (TBZL), which is a bulky zincate, as an initiator. Poly(methyl methacrylate) (PMMA) with a narrow molecular weight distribution was obtained by conducting the polymerization in toluene at −80 °C. Chain-end analysis revealed the formation of PMMA with a tert-butyl group at the α-end and a hydrogen atom at the ω-end. These results suggest the living nature of the present polymerization. However, a prolonged polymerization time or elevated temperature caused backbiting reactions. Postpolymerization modification of the formed PMMA was also investigated using TBZL as a transesterification catalyst. Chain-end analysis revealed that terminal-selective transesterification occurred only at the monomeric unit at the terminating chain end. Therefore, TBZL appears to play dual roles in the production of chain-end-modified PMMA: an initiator for anionic polymerization and a catalyst for terminal-selective transesterification.

Ambient Temperature Polymerization of Methyl Methacrylate Mediated by Ate Complexes

AbstractFinding catalysts that are both robust and highly active at room temperature can often be considered as a daunting challenge. Yet, these features are desirable for polymer synthesis as they allow to produce materials of interest easily and sustainably. Herein, commercial reagents are used to form in situ “ate” complexes which were found to be highly active in the room temperature anionic polymerization of methyl methacrylate. Also of particular interest is their ability to polymerize rac‐lactide, and even form block copolymers of poly(methyl methacrylate) and poly(lactic acid).

Synthetic and mechanistic aspects of anionic polymerization of methyl methacrylate using tetrabutyl ammonium thioimidate

AbstractThe tetrabutylammonium salts of ionic organo‐initiator containing N,N'‐diisopropylthiourea (TUA‐1) or N,N'‐diethylthiourea (TUA‐2) serve as inexpensive initiators for the anionic polymerization of methyl methacrylate (MMA) at room temperature. The molecular weights of obtained polymers are in the range of 1500–22,700 g mol−1 and the molecular weight distributions are fairly broad (Đ = 1.9–2.5) in optimized cases. The molar ratio of monomer to initiator can be achieved up to 800. Side‐reactions, for example, backbiting, transfer reactions result in the polymerization being a non‐living manner, thus leading to broad molecular weight distributions of the resulting polymers. The effects of counterion nature were also studied from the polymerization of MMA using TUA‐1 anion with sodium or potassium salts as counterions under identical conditions. Detailed investigation indicates that the polymerization proceeds via a sulfur anion initiated repeated 1,4‐Machael addition. In general, thioimidate initiators induced MMA polymerization feature certain induction periods, which is ascribed to slow addition thioimidate to CC double bond of MMA as a result of low initiator efficiency.

In situ synthesis of polymer-modified boron nitride nanosheets via anionic polymerization

Owing to their inherent inertness, covalent functionalization of hexagonal boron nitride nanosheets (BNNSs) proves very difficult, greatly limiting their potential applications. Herein, we report an one-pot in-situ synthesis of polymer-modified boron nitride nanosheets via reductive functionalization. Negatively charged boron nitride nanosheets, generated by a smooth reductive treatment in an electron-rich environment, are directly employed as an initiator to trigger in situ anionic polymerization of methyl methacrylate (MMA) monomers, avoiding the use of complex initiators. The successful grafting of polymethyl methacrylate (PMMA) chains onto BNNS surfaces is evidenced by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The functionalized boron nitride nanosheets formed via B-C bonding through this facile “grafting from” method exhibit excellent dispersibility in acetone. When used as a filler, the material shows remarkable mechanical reinforcement for polymeric composites. The reductive charge provides a simple and scalable route for versatile chemical modifications of BNNSs to tailor surface properties of BNNSs, which will find important applications in sensors, catalysis, composite coating, bioimaging and drug delivery etc.

Preparation of polymethyl methacrylate with well‐controlled stereoregularity by anionic polymerization in an ionic liquid solvent

AbstractThis study investigates the effect of ionic liquids (ILs) on the anionic polymerization of methyl methacrylate (MMA). Polymethyl methacrylate (PMMA), an isotactic polymer, is prepared by anionic polymerization at a high reaction temperature with an IL that acts as both solvent and additive. The most plausible reaction mechanism is determined using 1H NMR and Fourier‐transform infrared spectroscopy. The electrostatic interaction between MMA and the IL increases the apparent steric hindrance in MMA, resulting in the isotactic PMMA.

Synthesis of cyclic Poly(methyl methacrylate) via N-Heterocyclic carbene (NHC) initiated-anionic polymerization and subsequent ring-closing without need of highly dilute conditions

A cyclic polymethacrylate was prepared via the anionic polymerization of methyl methacrylate (MMA) initiated by a 1:1 adduct of methyl sorbate (MS) and a N-heterocyclic carbene (NHC) without the need for highly dilute conditions, because an α-terminal imidazolimium group is neighboring to the propagating anion during the polymerization. The polymerization proceeded quantitatively using methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) as the Lewis acid to give the poly (MMA) with the MS unit in the α-terminus, and an Mn of 7.2 × 103–29.1 × 103 with a molecular weight distribution (Mw/Mn = 1.16-1.56). From proton (1H) NMR and matrix assisted laser desorption/ionization (MALDI-TOF) mass spectra, coupled with size exclusion chromatography (SEC) of the poly (MMA) produced before and after ozonolysis of the internal carbon-carbon double bond in the MS unit, we found that ring-closing reaction was induced by nucleophilic substitution of the propagating anion to the neighboring carbon of the α-terminal carbenyl (imidazolimium) group to synthesize cyclic poly (MMA) following complete the monomer consumption.

Anionic living polymerization of alkyl methacrylate at ambient temperature and its mechanism research

ABSTRACTIn order to break through the bottleneck of anionic polymerization, polar monomers such as methyl methacrylate (MMA), ethyl methacrylate, butyl methacrylate, and hexyl methacrylate are subjected to anionic polymerization at room temperature in tetrahydrofuran (THF) using potassium tert‐butoxide (t‐BuOK) as the initiator. The polymerization of alkyl methacrylates is studied by multidetector gel permeation chromatography, proton nuclear magnetic resonance (1H‐NMR) and 13C‐NMR spectroscopy, and dynamic laser light scattering. It is found that t‐BuOK can initiate the living anionic polymerization of polar alkyl methacrylate, and the polymerization conversion almost reaches up to 100%. t‐BuOK exists into two kinds of agglomerates, whose hydrodynamic volumes are 10 and 80 nm, respectively. t‐BuOK in THF is similar to emulsion and has a critical active species concentration of about 0.0265 mol L−1 and does not depend on how much t‐BuOK is added. After the initiation of the polymerization, the large agglomerates of a loose and less regular structure that have occupied the main part of t‐BuOK are greatly reduced, but they do not continue to decrease until they disappear according to the equilibrium theory. Similarly, the active chain after initiation also will not aggregate again. Furthermore, t‐BuOK also has an active species with smaller average vibration size between cation and anion pairs, which can only initiate the polymerization of MMA with rather slow rate but cannot initiate other alkyl methacrylates. At last, because t‐BuOK can make the dormant species caused by side reactions to be revived, the anionic polymerization of MMA could obtain a high yield. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1130–1139

Polymerization Mechanism of Methyl Methacrylate Initiated by Ethyl Acetate/t-BuP4

The anionic polymerization of methyl methacrylate (MMA) was carried out using phosphazene base t-BuP4 and ethyl acetate (EA) as the catalyst and the initiator, respectively. Gas chromatography (GC), size exclusion chromatography (SEC) measurements, and nuclear magnetic resonance (NMR) analyses were used to reveal the polymerization mechanism and to confirm the polymer structure. The results confirmed the proposed polymerization mechanism and the polymer structure, while the initiator efficiency was low. Meanwhile, the initiation by methoxy anion coming from hydrolysis of the ester bond in MMA was also observed. As a result, there is a marked deviation between the theoretical molecular weight and the measured molecular weight, and it is essential to carry out the polymerization at excessive dosage of t-BuP4 for preparing polymers with narrow molecular weight distribution.

Precise Anionic Polymerization of Methyl Methacrylate: Simultaneous Control of Molecular Weight, Stereoregularity and End-Structure

Precise Anionic Polymerization of Methyl Methacrylate: Simultaneous Control of Molecular Weight, Stereoregularity and End-Structure

メタクリル酸メチルの精密アニオン重合 －分子量，立体規則性，末端構造の三元同時制御－

メタクリル酸メチルの精密アニオン重合 －分子量，立体規則性，末端構造の三元同時制御－

Anionic polymerization of methyl methacrylate by difunctional lithium amide initiators with trialkylsilyl protection

Dilithium diamides derived from silyl-protected diamines (that is, N,N′-bis(trimethylsilyl)-1,3-bis(aminomethyl)benzene and N,N′-bis(triisopropylsilyl)-1,3-bis(aminomethyl)benzene, 1a and 1b, respectively) were examined as difunctional initiators for the anionic polymerization of methyl methacrylate (MMA) in toluene with the aid of organoaluminum mediators. While the dilithium diamides in combination with tributylaluminum afforded the polymers in quantitative yields, the less sterically demanding silyl amide (1a) underwent 1,2-addition (carbonyl addition) during the initial stage of polymerization to form poly(MMA) (PMMA) containing the initiator fragment, with the methacryloyl group at the chain end as a minor component (26%). Dilithium diamide 1b, which contains triisopropylsilyl groups that prevent the 1,2-addition due to their steric bulkiness, afforded PMMA with a 1,3-xylylenediamine unit (initiation fragment) in the middle of the chain. H2/Pd-C-mediated cleavage of the diamine unit yielded PMMA with a half molar mass in a narrow molar-mass distribution, which provided proof of the equivalent reactivity of the two amide anions in 1b. Dilithium diamides of Me3Si- and i-Pr3Si-protection were examined as difunctional initiators for polymerization of methyl methacrylate (MMA) in toluene in combination with tributylaluminum. The less sterically demanding Me3Si-derivative underwent 1,2-addition (carbonyl addition) in the initial stage of polymerization to form type B poly(MMA) (PMMA) as a minor component (26%). The i-Pr3Si-derivative gave type A PMMA exclusively with the 1,3-xylylenediamine unit in the middle of the chain. H2/Pd-C-mediated cleavage of the diamine unit yielded PMMA with a half molar mass and narrow molar-mass distribution.

Direct Mechanistic Transformations from Isotactic or Syndiotactic Living Anionic Polymerizations of Methyl Methacrylate into Metal-Catalyzed Living Radical Polymerizations.

The mechanistic transformations from living anionic polymerizations into living radical polymerizations were examined after halogenating the growing terminal during the stereospecific living anionic polymerization of methyl methacrylate (MMA), directly forming a macroinitiator with a covalent carbon-halogen terminal for subsequent transition metal-catalyzed living radical polymerizations. The quantitative halogenation of the living isotactic or syndiotactic PMMA anion, prepared using tBuMgBr in toluene or diphenylhexyllithium (DPHLi) in THF, respectively, was achieved using CCl3Br or CCl4 as a halogen source in the presence of strong Lewis bases, such as 1,8-diazabicyclo[5.4.0]undec-7-ene, to generate stereoregular PMMA with a C-X (X = Br or Cl) bond. The halogenated terminal was then transformed into the radical species through a one-electron redox reaction of the ruthenium catalysts to allow the living radical polymerization of styrene or MMA, resulting in block copolymers that consisted of stereoregular PMMA and polystyrene segments or stereoblock PMMAs.

Anionic polymerization of MMA and renewable methylene butyrolactones by resorbable potassium salts

AbstractThree resorbable potassium salts of hydride (K[H]), enolate Me2CC(OiPr)OK (K[E]), and allyl K[1,3‐(SiMe3)2C3H3] (K[A]) have been investigated for controlled anionic polymerization of methyl methacrylate (MMA) and its cyclic analogs, naturally renewable methylene butyrolactones including α‐methylene‐γ‐butyrolactone (MBL) and γ‐methyl‐α‐methylene‐γ‐butyrolactone (MMBL). When used alone at ambient temperature in toluene, these salts exhibit no (K[H]) to low (K[A]) to modest (K[E]) polymerization activity. Mixing of K[H] and Al(C6F5)3 leads to the formation of an “ate” complex, K+[HAl(C6F5)3]−, which has been structurally characterized by X‐ray diffraction; this complex has a high polymerization activity producing atactic PMMA, but addition of another equiv of Al(C6F5)3 further enhances both the rate and the efficiency of the polymerization, now producing syndiotactic PMMA with a narrow molecular weight (MW) distribution of 1.04. The K[H]/2Al(C6F5)3 system also exhibits high activity for polymerization of (M)MBL. In sharp contrast, addition of Al(C6F5)3 to K[A] shuts down the polymerization at various temperatures. The most active, controlled, and syndioselective polymerization system in this series is K[E]/2Al(C6F5)3. Accordingly, the polymerization control and kinetics of this most effective system have been examined in more detail. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

ANIONIC POLYMERIZATION OF ALKYL METHACRYLATES INITIATED BY nBuCu(NCy2)Li

Anionic polymerization of methyl methacrylate (MMA), n-butyl methacrylate (nBMA) and glycidyl methacrylate (GMA) initiated by nBuCu(NCy2)Li (1) in tetrahydrofuran (THF) at –50°C to –10°C was investigated. It was found that the polymerization of MMA and nBMA initiated by 1 proceeded quantitatively in THF to afford PMMA and PBMA with polydispersity index 1.15–1.30 and nearly 100% initiator efficiencies at –10°C. The molecular weights increased linearly with the ratio of [monomer]/[1]. However, a post-polymerization experiment carried out on this system revealed a double polymer peak by GPC when fresh monomer was added after an interval of 10 min. Polymerization of styrene could be initiated by 1, but the initiator efficiency was low.

GPC observations of branching effects in anionic polymerization of methyl methacrylate: A preliminary study

AbstractThe anionic polymerization of methyl methacrylate was performed in tetrahydrofuran (THF) at −78°C, using sec‐butyllithium/1,1‐diphenylethylene (DPE) as the initiation system. The effects of polymerization time and initiator concentration on the branching reaction were studied. High vacuum was used to prevent contamination during the polymerization. Gel permeation chromatography (GPC) was used to characterize the branching effect qualitatively. Experimental results indicated that the monomer conversion reached more than 98% in a polymerization time of 10 min. The branching reaction occurred after high monomer conversion, resulting in a tail of high molecular weight in the GPC trace. This branching effect, observed by GPC, increased with polymerization time. Rapid termination was thus probably required immediately after all of the monomer was consumed in the preparation of a well‐defined PMMA without a high‐molecular‐weight tail in this diphenylbutylllithium/THF/−78°C system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Anionic polymerization of methyl methacrylate in an ionic liquid

AbstractAnionic polymerization reactions of methyl methacrylate (MMA) in ionic liquids were carried out by utilizing alkyl lithium initiators such as n‐butyl lithium (n‐BuLi) and diphenylhexyl lithium (DPHLi). The polymerization in ionic liquids having bis(trifluoromethyl sulfonyl)amide ([NTf2]) anion did not yield poly(MMA) (PMMA), because of the deactivation of the initiator due to an attack on the trifluoromethyl group. By using 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([C4mim][PF6]), the polymerization reactions proceeded. The PMMA prepared in [C4mim][PF6] gave low yields (5–9%), as compared with those (15–62%) obtained for PMMA prepared in tetrahydrofuran (THF), and the prepared PMMA had large polydispersity indices (≅2.0). The results obtained can be attributed to the high reaction temperature (0°C), in comparison to the common anionic polymerization temperature of MMA, −78°C, and the reaction between the initiator and the imidazolium cation. The initiator was considered to be deactivated because the hydrogen atom at the 2‐position of the imidazolium ring was withdrawn by the alkyl lithium initiator. The tacticity of the obtained PMMA, prepared in [C4mim][PF6] by utilizing DPHLi, was rich in mm triads, similar to that polymerized in toluene. Copyright © 2008 John Wiley & Sons, Ltd.

Synthesis of amphiphilic poly(methyl methacrylate‐ b‐ethylene oxide) copolymers from monohydroxy telechelic poly(methyl methacrylate) as macroinitiator

AbstractThe synthesis of well‐defined poly(methyl methacrylate)‐block‐poly(ethylene oxide) (PMMA‐b‐PEO) dibock copolymer through anionic polymerization using monohydroxy telechelic PMMA as macroinitiator is described. Living anionic polymerization of methyl methacrylate was performed using initiators derived from the adduct of diphenylethylene and a suitable alkyllithium, either of which contains a hydroxyl group protected with tert‐butyldimethylsilyl moiety in tetrahydrofuran (THF) at −78 °C in the presence of LiClO4. The synthesized telechelic PMMAs had good control of molecular weight with narrow molecular weight distribution (MWD). The 1H NMR and MALDI‐TOF MS analysis confirmed quantitative functionalization of chain‐ends. Block copolymerization of ethylene oxide was carried out using the terminal hydroxyl group of PMMA as initiator in the presence of potassium counter ion in THF at 35 °C. The PMMA‐b‐PEO diblock copolymers had moderate control of molecular weight with narrow MWD. The 1H NMR results confirm the absence of trans‐esterification reaction of propagating PEO anions onto the ester pendants of PMMA. The micellation behavior of PMMA‐b‐PEO diblock copolymer was examined in water using 1H NMR and dynamic light scattering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2132–2144, 2008

Anionic Polymerization of Methyl Methacrylate with the Aid of Lithium Trimethylsilanolate (Me3SiOLi) ‐ Superior Control of Isotacticity and Molecular Weight

AbstractHighly isotactic‐specific polymerization of methyl methacrylate (MMA) was developed by using a combined anionic initiator comprising α‐lithioisobutyrate (Li‐iPrIB) and a large excess of lithium trimethylsilanolate (Me3SiOLi), which afford, in particular, isotactic poly(methyl methacrylate) (PMMA) with isotactic triad content of up to 99.5% under the adjusted polymerization conditions. The polymerization system also exhibited a high activity such that isotactic PMMA with $\overline M _{\rm n}$ of over 800 000 and narrow molecular weight distribution ($\overline M _{\rm w} /\overline M _{\rm n}$ < 1.2) was obtained.magnified image

Chain transfer to ionic liquid in an anionic polymerization of methyl methacrylate

When methyl methacrylate is polymerized with alkyllithium as initiator in imidazolium ionic liquids, low molecular weight polymers are formed in high yield. The head-groups are, however, not those alkyl groups that are present in alkyllithium, but predominantly those that are originally present at 1-position in imidazolium cation indicating extensive chain transfer to imidazolium ionic liquid.

Living anionic polymerization of methyl methacrylate controlled by metal-free phosphazene catalyst as observed by small-angle neutron scattering, gel-permeation chromatography and UV–visible spectroscopy

Phosphazene (PZN) catalyst, PZN catalyst coexisting with a co-catalyst 1-hydroxycyclohexyl phenyl ketone (Irgacure 184; IRG) and polymethylmethacrylate (PMMA) (prepared by catalytic living anionic polymerization using the PZN catalyst and IRG) have been observed for the first time by small-angle neutron scattering (SANS) and UV–visible spectroscopy to elucidate the aggregation behavior of the PZN molecules themselves and the state of living chain ends in a living polymer solution. PZN catalyst in deuterated tetrahydrofuran (thf-d8) showed SANS curves fitted by a form factor for a sphere whose radius Rs is larger (1.4–1.6 nm) than a single PZN molecule (0.65 nm), indicating formation of PZN aggregates in thf-d8. In a nonpolar solvent, benzene-d6, Rs was even larger (3.1 nm), indicating formation of larger aggregates. By adding IRG to PZN solution, an excess scattering appeared in the SANS profile and a strong band emerged in the UV–visible spectrum. This result indicates strong interaction of IRG with PZN not only on a molecular scale but also on a mesoscopic scale. The SANS profile from the living polymer solution in thf-d8 was observed to be fitted by the sum of the profile for the aggregated PZN/IRG complex and that for Gaussian chains of PMMA. The molecular weight of the PMMA determined by SANS, 2100 g mol−1, was in agreement with that estimated from gel-permeation chromatography, indicating that the anionic living chain ends and their counter ions (PZN) are dissociated in thf-d8; thus, the chains are not associated into multiple-ion pairs.