Anionic Initiators Research Articles

Anionic Ring-Opening Alternating Copolymerizations of Bicyclic and Spirocyclic Bis(.gamma.-lactone)s with Epoxides via a Tandem Double Ring-Opening Isomerization of the Bislactones

Anionic copolymerizations of several bicyclic and spirocyclic bis(γ-lactone)s (1 and 2) with various epoxides (3) were carried out at 120 °C in THF in the presence of potassium tert-butoxide (4 mol %) as the anionic initiator. The copolymerizations of bicyclic bis(γ-lactone)s 1 (7-substituted 1,6-dioxabicydo[3.3.0]octa-2,5-diones) with glycidyl phenyl ether (3a) smoothly proceeded regardless of the structure of the substituent at the 7-position of 1 to give corresponding copolymers (4) in 44-78% yield. The structures of 4 were determined as the alternating copolymers by their IR and 1 H and 13 C NMR spectra. The copolymerization of spirocyclic bis(γ-lactone) 2a (1,6-dioxaspiro[3.3]octa-2,7-dione) with 3a was sluggish but was accelerated by addition of a crown ether (8 mol %) to the polymerization system to yield the alternating copolymer 5aa in 80% yield. The copolymerization of 2b (dibenzo derivative of 2a) with 3a gave 81% yield of the alternating copolymer 5ba in the absence of the crown ether. The copolymerizations of 1 or 2 with a variety of epoxides 3 were carried out, and the effect of the structure of 3 was examined. As a result, both the steric hindrance and polarity of 3 were suggested to influence the rate of the copolymerization. Thermal properties such as glass transition and 10% weight loss temperatures of the alternating copolymers 4 and 5 were evaluated by DSC and TGA.

Stereospecific and asymmetric polymerization of 1‐phenyldibenzosuberyl methacrylate with radical and anionic initiators

AbstractStereospecific and asymmetric (helix‐sense‐selective) polymerization of 1‐phenyldibenzosuberyl methacrylate (PDBSMA) was performed with radical and anionic initiators. A highly isotactic polymer having triad isotacticity greater than 97% was obtained by radical polymerization with (i‐PrOCOO)2 at 40°C. The radical polymerization of PDBSMA in (+)‐ and (‐)‐menthol gave (‐)‐and (+)‐polymers, respectively, whose optical activity is ascribed to the prevailing one‐handed helical conformation of a polymer chain. The radical copolymerization of PDBSMA with a small amount of an optically active monomer, (+)‐phenyl‐2‐pyridyl‐o‐tolylmethyl methacrylate, afforded an optically active copolymer with the prevailing one‐handed helical structure of PDBSMA sequences. Asymmetric anionic polymerization of PDBSMA was carried out with the complex of N, N′‐diphenylethylenediamine monolithium amide and a chiral ligand, (+)‐1‐(2‐pyrrolidinylmethyl)pyrrolidine in toluene at −78°C. The obtained polymer was highly isotactic and optically active due to nearly 100% one‐handed helical structure.

Polymerization of Trifluoroacetaldehyde Azine (1,1,1,6,6,6-Hexafluoro-3,4-diaza-2,4-hexadiene)

Trifluoroacetaldehyde azine (TFAcAz) was prepared as a new monomer and its polymerizabilities were studied. Poly(TFAcAz) was obtained by bulk polymerization with triethylamine at -20 °C, although only oligomers were obtained by typical anionic initiators. The structure and properties of the polymer were investigated by IR, Raman, and solid-state 13 C NMR spectroscopies, powder X-ray diffraction, and thermogravimetric analysis. The polymer is crystalline, composed of 1,2-addition units with pendant C=N double bonds, and decomposed to the monomer at about 200 °C.

Preparation of a Polystyrene Macromonomer with a Novel Anionic Initiator Containing an Olefinic Vinyl Group

Preparation of a Polystyrene Macromonomer with a Novel Anionic Initiator Containing an Olefinic Vinyl Group

Synthesis and Polymerization of Maleimides Containing a Cholesteryl Group

Two types of optically active N-(cholesteroxycarbonyl-n-pentyl)maleimide (ChP) and N-(cholesteroxycarbonyl-n-undecyl)maleimide (ChU) were synthesized and polymerized with radical and anionic initiators to obtain chiral polymers. Both copolymers contained different conformations, judging from CD spectra. Radical copolymerizations of ChP(M1) and ChU (M1) were performed with styrene (ST, M2), methyl methacrylate (MMA, M2) in toluene at 60°C. Monomer reactivity ratios (r1, r2) and Alfrey–Price Q–e were determined. Chiroptical properties for the original polymers were significantly influenced by the length of the methylene units. All hydrolyzed polymers were optically active, but specific rotations were very small.

Analysis of the 1H and 13C NMR spectra of poly( t-butyl-ethylene oxide) and of block and statistical copolymers of t-butyl-ethylene oxide and ethylene oxide

Resonances in the 500 MHz 1H and 75.5 MHz 13C NMR spectra of poly( t-butyl-ethylene oxide) and of block and statistical copolymers of t-butyl-ethylene oxide and ethylene oxide prepared using an anionic initiator have been assigned with the aid of 2-dimensional COSY spectra and DEPT subspectral editing. Monomer placement occurs almost entirely by head-to-tail addition, and in the homopolymers, isotactic enchainment is approximately twice as favourable as syndiotactic. 13C chemical shifts have been rationalised by a simple substituent increment scheme.

Hydrocarbon‐soluble difunctional organolithium anionic initiators. A gas–liquid chromatographic study of the reaction of sec‐butyllithium with m‐divinylbenzene

AbstractQuantitative gas–liquid chromatography provides an efficient, novel technique for the kinetic study of the reaction between sec‐butyllithium and m‐divinylbenzene. The reaction of stoichiometric amounts of ultra‐high purity sec‐butyllithium with pure m‐divinylbenzene at −23°C produces an anionic initiator, 1,3‐bis(1‐lithio‐3‐methylpentyl)benzene, 2, without traces of monofunctional and polyfunctional impurities. The relative rates of formation of 2 with and without the presence of Lewis base, triethylamine, or Lewis acid, diethylzinc, were studied by gas–liquid chromatography. The presence of diethylzinc reduces the activity of sec‐butyllithium to such an extent that the reaction did not proceed beyond the monofunctional component stage, that is, the formation of m‐1‐lithio‐3‐methylpentylvinylbenzene, 1. The reaction of sec‐butyllithium with m‐divinylbenzene at −79°C with a 10mol% ratio of triethylamine to sec‐butyllithium yielded a homogeneous product with composition of 94% difunctionality and 6% monofunctionality, with the total disappearance of m‐divinylbenzene as observed by GLC. However, precipitation due to agglomeration was observed at 25°C at 100% conversion.The high purity 1,3‐bis(1‐lithio‐3‐methylpentyl)benzene initiator, 2, is effective for the polymerization of 1,3‐butadiene and allows the synthesis of polybutadienes with predictable molecular weights and narrow molecular weight distributions. Depending on the polymerization solvent, polybutadienes with microstructures ranging from 9 to 13% 1,2‐vinyl content were observed by 1H NMR analysis and FTIR spectroscopy. However, the presence of diethylzinc retards the rate of polymerization of 1,3‐butadiene, without any change in polymer microstructure. Triethylamine enhances the rate of 1,2‐enchainment without significant reduction in the 1,4‐enchainment of polybutadiene.

Efficiency of the sec-Butyllithium/m-Diisopropenylbenzene Diadduct as an Anionic Polymerization Initiator in Apolar Solvents

The 2/1 sec-BuLi/1,3-diisopropenylbenzene adduct has been prepared and evaluated as an effective, hydrocarbon soluble, difunctional initiator for the synthesis of polystyrene-polybutadiene-polystyrene (SBS) thermoplastic elastomers in cyclohexane or benzene solution. The MWD of both the PBD central block and the final block copolymer is narrow, and the expected molecular weight is obtained. However, mechanical testing, degradation of the PBD component, and use of an excess of s-BuLi compared to DIB suggest that the final copolymers are diblock instead of triblock as expected. The stoichiometric reaction of s-BuLi with DIB in an apolar solvent essentially results in the expected Li diadduct

13C NMR Characterization of Polymers from 2,2,2-Trifluoroethyl Methacrylate

In an attempt to develop structural characterisation of polymers from fluorinated acrylic derivatives, a detailed 13C NMR analysis of free radical and anionic poly(2,2,2-trifluoroethyl methacrylate) (poly(TFEM)) was performed as compared to relevant literature studies concerning the corresponding methyl methacrylate (MMA) polymers. On the other side, the moderately syndiotactic microstructure of the poly(TFEM) samples fits very well with that of corresponding poly(MMA) samples and can be interpreted on the basis of the same statistical distribution of triads. Thus it appears that the presence of the –CH2–CF3 group does not affect in a determining way the stereochemistry of the polymerization. According to this final statement, anionic initiators give prevailingly isotactic poly(TFEM) as detected by 13C NMR.

Molecular Mass Characterization of Poly(4-Vinylpyridine)

Abstract Poly(4-vinylpyridine) samples, synthesized by anionic and radical initiators, have been characterized by Size Exclusion Chromatography, Light Scattering and Intrinsic Viscosity. The mobile phase used in SEC characterization was 50% methanol and 50% 0.1M LiNO3. Broad molecular weight distribution samples of P4-VP1 characterized via Low Angle Laser Light Scattering, have been used in the calibration of the SEC system. The polymers show different molecular weight distribution and high polydispersity. Mark-Houwink constants for P4-VP in the SEC mobile phase have also been obtained.

Controlled copolymer structures via anionic/insertion polymerization of cyclic carbonates

Cyclic carbonates are polymerized in a ring-opening fashion by means of anionic and insertion type initiatiors. Different hexacyclic carbonates are copolymerized in a random way when both monomers are added to the initiator simultaneously. Block copolymers are obtained when the monomers are added in sequential way. With anionic initiators cyclic carbonates are polymerized preferentially as compared with lactones while insertion initiators are less selective. A special case is the preparation of copolymers of carbonates with lactams. When the polycarbonate is formed first the lactam unit is inserted into carbonate bond to form urethane and ester bonds. Thus, eventually an alternating polyesterurethane is formed with negligible amount of carbonate, amide, and urea units. Moreover, the anionic ring-opening polymerization of cyclic carbonates may be combined with vinyl polymerization. In the case of group transfer polymerization a transformation of the active site to the non-metallic anionic initiation of the cyclic carbonate occurs.

Polymerization of N‐alkyl‐substituted itaconimides and N‐(alkyl‐substituted phenyl)itaconimides and characterization of the resulting polymers

AbstractN‐alkyl‐substituted itaconimides (RII) and N‐(alkyl‐substituted phenyl)itaconimides (RPhII) with various alkyl substituents were prepared and polymerized in the presence of a radical or anionic initiator to give high molecular weight polymers in high yields. The effects of the alkyl substituents on the polymerization reactivities were investigated. It has been revealed that RII and RPhII have the highest polymerization reactivity compared with other itaconic and citraconic derivatives including dialkyl itaconates and citraconimides. The structure and some properties of poly(RII) and poly(RPhII) were examined. These polymers were found to have excellent thermal stability, better than poly (dialkyl itaconate)s. © 1994 John Wiley & Sons, Inc.

Synthesis of macrocyclic polystyrene-polydimethylsiloxane block copolymers

A series of macrocyclic polystyrene (PS)-polydimethylsiloxane (PDMS) block copolymers and similar block copolymers was synthesized by sequential polymerization of styrene and hexamethyl cyclotrisiloxane (D3) initiated by a difunctional anionic initiator in THF at −78° followed by coupling with Cl2SiMe2 in very dilute (10−5 – 10−6 M) solutions. Total molecular weights ranged from about 2–85 × 103. The formation of monodisperse macrocyclic block copolymers was indicated by the lower (15–30%) hydrodynamic volume of the rings compared to that of the linear block copolymers. Carbon-13 and 29Si NMR likewise supported the absence of linear polymer in the macrocyclic block copolymer. The behavior of second virial coefficient A2 of the rings and the linears versus temperature was examined by static light scattering in cyclohexane. Below 20° the A2 for the linear polymer goes negative while that for the cycle remains positive. Dynamic light scattering (DLS) as a function of temperature also reflects that the cyclic polymers remain well solvated even down to 12°C. The DLS autocorrelation functions for the linear triblock however demonstrate the onset of aggregation and phase separation as the temperature is reduced below 20°C.

Copolymers with soft and hard segments based on 2,2‐dimethyltrimethylene carbonate and ε‐caprolactone

AbstractThermoplastic elastomers with ABA‐block structure, A representing the hard segment and B the soft segment, were prepared by ring‐opening polymerization from 2,2‐dimethyltrimethylene carbonate (DTC, 1) and ε‐caprolactone (ECL, 2) as monomers. Typical anionic initiators, viz. the dilithium salt of hydroxytelechelic poly(ethylene oxide) 200 (4) and of polytetrahydrofuran 1000 (5) and as an insertion initiator the bis(diethylaluminium) salt of triethylene glycol were used. The soft block is formed by a sequence of random (or tapered) structure comprising equimolar amounts of the two monomers and obtained by simultaneous polymerization of DTC and ECL. The hard blocks consist of highly crystalline poly(2,2‐dimethyltrimethylene carbonate) sequences. The thermal properties of the polymers depend on the sequence length, the content of heterodiads in the soft block and the thermal history of the samples. Copolymer films with short end blocks and high content of heterodiads show rubber‐elastic properties at normal conditions.

Comparison of 13C NMR spectra of polystyrenes having various tacticities and assignment of the spectra

13 C NMR spectra of polystyrene dissolved in o-dichlorobenzene at 150°C are clearly resolved and can be analyzed in terms of pentads and hexads. It is shown that the triad values in samples of polystyrene obtained from the C-1 part of the spectrum obey Bernoullian statistics, not only for samples prepared using radical, cationic and anionic initiators, but also for an atactic-rich polystyrene obtained with Cs dihydronaphtylide

Studies on helix‐sense‐selective copolymerization based on triphenylmethyl methacrylate

AbstractHelix‐sense‐selective copolymerizations based on triphenylmethyl methacrylate (TrMA) with methyl methacrylate (MMA), benzyl methacrylate (BzMA) and diphenylmethyl methacrylate (DPMMA) in the presence of the chiral anionic complex initiator (−)‐sparteine/9‐fluorenyl‐lithium (1) were investigated. The studies concentrated on the stereoregularity of the copolymers, the relative reactivity of the monomers, the specific rotation of the copolymers and the influence of the solvent on the copolymerization. The results show that the match of TrMA with MMA of smaller size would favour the form of the copolymer with isotactic one‐handed helix having higher specific rotation as compared with BzMA ad DPMMA in toluene, but the TrMA/MMA copolymer obtained in tetrahydrofuran possessed a very low specific rotation because of the action of the polar tetrahydrofuran on the anion complex.

A new family of ?ligated? anionic initiators for the ?living? polymerization of (meth)acrylic esters

A new family of ligands (dual σ-π ligand), i.e. chelating lithium alkoxides, Li-O-(CH2-CH2O)nCH3, is shown to be very effective in promoting the living anionic polymerization of methacrylic and acrylic esters, including a number of primary alkyl acrylates such as n-butyl acrylate and 2-ethylhexylacrylate.

Preparation of Amidoxime-Fiber Adsorbents Based on Poly(Methacrylonitrile) for Recovery of Uranium from Seawater∗

Abstract Polymerization of methacrylonitrile was performed with anionic initiators as reported in the literature. The molecular weight of the polymer produced using BuLi as initiator at 0 ± 2°C was on the order of 105. Maximum conversion was 97% with BuLi initiator. For comparison, methacrylonitrile was polymerized with diethylmagnesium in dioxane at 70°C. High-molecular weight polymers with 50–60% conversions were produced by diethylmagnesium initiator. The polymethacrylonitrile obtained by BuLi initiator was used for the fiber production process. The conversion of nitrile was performed by treatment with 3% NH2OH in MeOH at 80°C. The amidoxime-fiber adsorbent gave a large adsorption rate, such as 176 μg of U/g of adsorbent/day, in a batchwise seawater adsorption test. ∗ Dedicated to Prof. Iwao Tabushi.

Asymmetric polymerization of aromatic isocyanates with optically active anionic initiators

AbstractThe asymmetric anionic polymerization of o‐, m‐, and p‐methylphenyl isocyanates, p‐methoxyphenyl isocyanate, p‐chlorophenyl isocyanate, 2,6‐ and 3,4‐dimethylphenyl isocyanates, and 1‐naphthyl isocyanate was carried out using chiral anionic initiators such as the lithium salts of (−) ‐menthol, (−) ‐(2‐methoxymethyl) pyrrolidine, and (+) ‐1‐(2‐pyrrolidinylmethyl) pyrrolidine. Although o‐methylphenyl isocyanate gave an insoluble polymer and 2,6‐dimethylphenyl isocyanate afforded no polymer, the other monomers gave soluble polymers, which showed optical activity due to the prevailing helicity of the polymer chain induced by chiral initiator residues attached to the α‐end of the polymer chain. The molecular mechanics conformational calculation for a tetramer of m‐methylphenyl isocyanate supported the helical conformation of the main chain. The optical rotation of the polymers depended significantly on temperature. © 1994 John Wiley & Sons, Inc.

Synthesis of chiral and racemic functional polymers from glycidol and thioglycidol

AbstractRacemic and optically active protected glycidols (as 1‐ethoxyethyl ethers) are readily polymerized with anionic initiators (e.g., CsOH). Polymers with molecular weights up to 30 000 are obtained without cleavage of the protective group. Oligomers (degree of polymerization [DPn] 5 to 10) are prepared using an aluminium complex derived from a Schiff's base. The protected thioglycidol (synthesized from the protected glycidol) leads to very high‐molecular‐weight polymers (150 000–320 000) using anionic or anionic coordinated initiators. Copolymers of protected glycidol with ethylene oxide are obtained with KOH as initiator. Regeneration of hydroxyl groups in polymers is carried out with acidic cleavage. Treatment of protected polyglycidol with formic acid leads first to the formate of polyglycidol. Then, after saponification, pure polyglycidol is obtained. The use of aqueous hydrochloric acid leads directly to the free polymer.