Synthesis of block copolymers containing poly(ferrocenylmethyl methacrylate) units

Ferrocenylmethyl methacrylate (FMMA) has been polymerized by using LiAlH₄–tetramethyl-ethylenediamine initiation to form living polymers in high vacuum systems. The addition of methyl methacrylate or acrylonitrile to these living systems gave the block copolymers FMMA-block MMA and FMMA-block AN. The anions were not nucleophilic enough to initiate styrene polymerization. Therefore, living polystyrene was prepared (sodium naphthalide initiation in THF at ?78°C) and upon FMMA addition, styrene-block FMMA copolymers were formed. Extraction, precipitation, and gel-permeation chromatography studies were performed to examine the purity of the block copolymers.     

Synthesis of poly(methyl methacrylate) macromonomer

Anionic polymerization of methyl methacrylate (MMA) was carried out in tetrahydrofuran (THF) or THF/toluene mixture at ?78°C initiated by triphenylmethyl sodium or lithium as initiators. Highly syndiotactic PMMA of low polydispersity (M _w/m _n = 1.11–1.17) could be prepared with triphenylmethyl lithium in THF or THF/toluene mixture at ? 78°C. Moreover, PMMA macromonomer having one vinylbenzyl group per polymer chain was prepared by the couplings of living PMMA initiated by triphenylmethyl lithium with p-chloromethyl styrene (CMS) at ?78°C. The coupling reaction of living PMMA initiated by triphenylmethyl sodium with CMS was scarcely occurred.     

Reduction of Digallane [(dpp‐bian)Ga?Ga(dpp‐bian)] with Group 1 and 2 Metals

The reduction of digallane [(dpp‐bian)Ga? Ga(dpp‐bian)] ( 1 ) (dpp‐bian=1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene) with lithium and sodium in diethyl ether, or with potassium in THF affords compounds featuring the direct alkali metal–gallium bonds, [(dpp‐bian)Ga? Li(Et₂O)₃] ( 2 ), [(dpp‐bian)Ga? Na(Et₂O)₃] ( 3 ), and [(dpp‐bian)Ga? K(thf)₅] ( 7 ), respectively. Crystallization of 3 from DME produces compound [(dpp‐bian)Ga? Na(dme)₂] ( 4 ). Dissolution of 3 in THF and subsequent crystallization from diethyl ether gives [(dpp‐bian)Ga? Na(thf)₃(Et₂O)] ( 5 ). Ionic [(dpp‐bian)Ga]^?[Na([18]crown‐6)(thf)₂]⁺ ( 6 a ) and [(dpp‐bian)Ga]^?[Na(Ph₃PO)₃(thf)]⁺ ( 6 b ) were obtained from THF after treatment of 3 with [18]crown‐6 and Ph₃PO, respectively. The reduction of 1 with Group 2 metals in THF affords [(dpp‐bian)Ga]₂M(thf)_n (M=Mg ( 8 ), n=3; M=Ca ( 9 ), Sr ( 10 ), n=4; M=Ba ( 11 ), n=5). The molecular structures of 4 – 7 and 11 have been determined by X‐ray crystallography. The Ga? Na bond lengths in 3 – 5 vary notably depending on the coordination environment of the sodium atom.     

Titanium‐mediated living radical styrene polymerizations. V. Cp2TiCl‐catalyzed initiation by epoxide radical ring opening: Effect of solvents and additives

The effects of solvents, additives, ligands, and solvent in situ drying agents as well as catalyst and initiator concentrations have been investigated in the Cp₂TiCl‐catalyzed radical polymerization of styrene initiated by epoxide radical ring opening. On the basis of the solubilization of Cp₂Ti(III)Cl and the polydispersity of the resulting polymer, the solvents rank as follows: dioxane ≥ tetrahydrofuran > diethylene glycol dimethyl ether > methoxybenzene > diphenyl ether ≥ bulk > toluene ? pyridine > dimethylformamide > 1‐methyl‐2‐pyrrolidinone > dimethylacetamide > ethylene carbonate, acetonitrile, and trioxane. Alkoxide additives such as aluminum triisopropoxide and titanium(IV) isopropoxide are involved in alkoxide ligand exchange with the epoxide‐derived titanium alkoxide and lead to broad molecular weight distributions, whereas similarly to strongly coordinating solvents, ligands such as bipyridyl block the titanium active site and prevent the polymerization. By contrast, softer ligands such as triphenylphosphine improve the polymerization in less polar solvents such as toluene. Although mixed hydrides such as lithium tri‐tert‐butoxyaluminum hydride, sodium borohydride, and lithium aluminum hydride react with bis(cyclopentadienyl)titanium dichloride to form mixed titanium hydride species ineffective in polymerization control, simple hydrides such as lithium hydride, sodium hydride, and especially calcium hydride are particularly effective as in situ trace water scavengers in this polymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2015–2026, 2006     

An Improved Synthetic Method for Preparing Polyoxyethylene Macromers and a Study of Their Copolymerization with Alkyl Acrylates

Polyoxyethylene macromers were synthesized by polymerization of ethylene oxide in dimethylsulfoxide by using potassium napthalide in tetrahydrofuran as initiator, followed by termination with methacroyl chloride. Potassium naphthalide is more active as an initiator than sodium naphthalide. The initiator in this case was confirmed to be of the monoanionic type. The molecular weight of the macromers can be varied from 2 × 10³ to 1.2 × 10⁴with M_w/M_n = 1.07-1.12. The macromers were characterized by UV, IR, and ¹H NMR, and copolymerized with butyl acrylate, methyl acrylate, or methyl methacrylate. The grafting efficiency can reach about 90%. The graft copolymers were purified by extractions and characterized by GPC, IR, and a Bruss membrane osmometer. The average grafting number of the copolymers varied from 10 to 15.     

Analysis of the end groups of poly(methyl methacrylate)

Methyl methacrylate polymerization by potassium hydride results in macromolecules with the methyl starting group. A side-reaction occurs during the process leading to potassium methoxide. It serves as the second initiator of the polymerization and gives macromolecules with the methoxy starting group. All macromolecules possess the methine group at the chain end after protonation. Potassium alkalide K⁻, K⁺(15-crown-5)₂ produces various active centres in the initial step of the polymerization. It results in macromolecules with the methyl, ethyl, methoxy and vinyl ether starting groups. However, the majority of macromolecules are formed on the species with two active centres. The termination reaction takes place during the polymerization, therefore, not all chains have the methine end group after protonation.     

Kinetic analysis based on the excluded-volume effect for radical polymerization

When the potential of average force based on the excluded volume affects the relative motions of the polymer radicals, the specific rate for bimolecular reaction between them can be approximated as k_t = const. (ns)^?a, where a = 0.153(2b ? 1), b being a constant in the Mark-Houwink equation, and n and s being degrees of polymerization. Introduction of such a rate into kinetic equation yields a relative molecular weight distribution: G(n) = (n/m)^2–2a exp {ph(m^1–a ? n^1–a)}, where m = (2/ph)^1/(1–a) is a degree of polymerization for the maximum in G(n) and ph is a parameter denoting kinetic character. Further, the relationship between polymerization rate R_p, monomer concentration [M], and initiator concentration [ε] is found to be: where σ is a parameter denoting primary radical termination and η and η? are viscosities for an arbitrary solvent and ?-solvent, respectively. These relationships are sufficiently applicable to the data obtained in the polymerizations of styrene and methyl methacrylate.     

Études calorimétriques en milieu solvant organique: III. Enthalpie de dilution de l'alanate de lithium LiAlH4 dans le tétrahydrofuranneen présence d'halogénure de lithium

Heats of dilution of lithium aluminum hydride in THF, in THFLiBr and in THFLiCl have been established. At a constant concentration of LiBr in THF, dilution of LiAlH₄ is exothermal, and consequently it is shown that lithium aluminum hydride is dissociated in THF.     

Defined Poly[styrene‐block‐(ferrocenylmethyl methacrylate)] Diblock Copolymers via Living Anionic Polymerization

Ferrocenylmethyl methacrylate (FMMA) is one of the very few metallocene‐based monomers that are promising candidates for truly living anionic polymerization. Nevertheless, FMMA homopolymers with a narrow polydispersity, or block copolymerization studies that result in satisfying blocking efficiencies, are unknown so far. Here we describe a procedure that leads to highly regular FMMA‐based polymers for the first time, characterized by polydispersity indices (PDI) of less that 1.05 and very high blocking efficiencies (>95%) in sequential copolymerization with styrene. Some of the obtained poly[styrene‐block‐(ferrocenylmethyl methacrylate)]s show unusual microphase morphologies, presumably the consequence of high T_gs causing ‘frustrated’ non‐equilibrium states.

     

Preparation of samarimm(ii) sulfide by the reaction of samarium(II) bis[bis(trimethylsilyl)amide] with hydrogen sulfide

X-ray amorphous samarium(II) sulfide was prepared by the reaction of H₂S with samarium(II) bis[bis(trimethylsilyl)amide] (1) in THF at 10^–2 Torr. Compound1 was prepared by two methods: 1) the reaction of SmI₂ with lithium bis(trimethylsilyl)amide and 2) the reaction of samarium naphthalide with bis(trimethylsilyl)amine. SmS was transformed to the polycrystalline state with the lattice parametera = 5.92 Å by annealing at 400–500 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 241–243, February, 1995.     

Ferrocene-containing polymers. II. Radiation-induced copolymerizations of ferrocenylmethyl methacrylate with styrene,methyl methacrylate,and ethyl acrylate

Ferrocenylmethyl methacrylate (FMMA) was copolymerized with styrene (St), methyl methacrylate (MMA), and ethyl acrylate (EA) in benzene solution at 25°C by γ radiation. The reactions proceeded by a free radical mechanism, and monomer reactivity ratios were derived by the Tidwell–Mortimer method for St(M₁)–FMMA(M₂), r₁ = 0.35 and r₂ = 0.46; for MMA(M₁–FMMA)(M₂), r₁ = 0.85 and r₂ = 1.36; for EA(M₁)–FMMA(M₂), r₁ = 0.36 and r₂ = 3.03. The Q and e values of FMMA determined from copolymerization with St were 0.97 and 0.55, respectively. Terpolymerization of a MMA–FMMA–EA system based on the Alfrey–Goldfinger equations was studied. This is a typical terpolymerization system in which reactivities of the monomers obey the Q–e scheme. Comparing the results obtained here with those previously reported for other monomers, we concluded that FMMA is one of the most highly reactive monomers among alkyl methacrylates.     

Anionic polymerization of methacrylate monomers initiated by lithium dialkylamides

The anionic polymerization of methacrylate monomers has been investigated with lithium dialkylamides as initiators in THF and toluene, respectively. Theoretical arguments and previous studies of mixed aggregates of lithiated organic compounds support the complexity of these systems. Lithium diisopropylamide (LDA) shows the highest initiation efficiency (e.g., f = 75% in THF at −78°C). Interestingly enough, lithium chloride has a remarkable beneficial effect on the methacrylates polymerization in THF at −78°C, due to the formation of 1 : 1 mixed dimer with LDA, which promotes a well-controlled anionic polymerization (M_w/M_n = 1.05) with a high initiation efficiency (94%). The less bulky lithium–diethylamide (LDEA) is much less efficient (f = 26%), essentially as a result of some associated “dormant” species and side reactions on the carbonyl group of MMA. Although various types of ligands have been screened, no remarkable improvement of LDEA efficiency has been observed. Lithium bis(trimethylsilyl)amide (LTMSA) has also been used to increase the steric hindrance of the initiator. This compound is, however, unable to initiate the methacrylates polymerization, more likely because of a too low basicity and a too strong Li—N bond. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3637–3644, 1997     

Further Studies on the Anionic Copolymerization of Styrene and Glycidyl Methacrylate in Toluene

Sequential anionic copolymerization of styrene and glycidyl methacrylate (GMA) was performed with the protection of argon under normal pressure, where styrene, GMA, toluene, THF, n-butyllithium and a small amount of lithium chloride (LiCl) were used as first monomer, second monomer, solvent, polar reagent, initiator and additive, respectively. Polystyrene-b-poly(glycidyl methacrylate) diblock copolymers (PS-b-PGMA) with well-defined structure and narrow molecular weight distribution were prepared by the copolymerization reaction of poly(styryl)lithium with GMA under certain temperatures. The copolymers were characterized using gel permeation chromatography (GPC), ¹H-NMR, ¹³C-NMR, thin layer chromatography (TLC) and hydrochloric acid-dioxane argentimetric methods. The effects of additives, copolymerization temperature and THF dosage on the copolymerization were studied. No chain transfer reaction of anionic polymerization of styrene in toluene was observed. Slightly broader molecular weight distribution of PS-b-PGMA was observed with the increase the GMA repeat units. Using THF/toluene blend solvent could reduce the polydispersity index (M _w /M _n ) and dissolve the copolymer better than toluene alone. Lower temperature (< -40°C) and LiCl are required to prepare PS-b-PGMA with narrower molecular weight distribution.     

Anionic polymerization and copolymerization of S-methyl thiomethacrylate

S-Methyl thiomethacrylate (methyl thiolmethacrylate, MTMA) was polymerized with a variety of anionic initiators such as n-BuLi, octylpotassium, PhMgBr, and Et₂AlNPh₂ in toluene and THF. Stereoregularity of the polymer (PMTMA) was determined from the ¹H-NMR spectrum of poly(methyl methacrylate), which had been derived from PMTMA, because the α-methyl resonance in the ¹H-NMR spectrum of PMTMA was not satisfactorily solved owing to the overlap of pentad signals. The ¹³C-NMR spectrum of PMTMA also showed the splitting due to pentad sequences. Stereoregularity of PMTMA was always low compared with that of poly(methyl methacrylate), which was prepared under the same reaction conditions. MTMA was much more reactive than methyl methacrylate and methacrylonitrile in the copolymerization with n-BuLi in toluene and in THF at ?78°C. The lower stereoregulation of the polymerization of MTMA and the higher reactivity of MTMA were mainly ascribed to the higher resonance effect of MTMA.     

A Novel Efficient Ligand in Anionic Polymerization at Elevated Temperature

This work confirmed a novel ligand in the anionic polymerization, lithium phenoxide, which helped to improve the controllability of the polymerization. The stability of n‐BuLi against THF at 0°C was effectively improved by adding lithium phenoxide. More than 60% n‐BuLi in THF was alive with the presence of lithium phenoxide after stirring at 0°C for 20 min, compared to 2% under same conditions but without lithium phenoxide. The propagation of polymerization of styrene (St) and methyl methacrylate (MMA) were retarded after adding lithium phenoxide. And by adding more than 10 fold lithium phenoxide, completed conversion was achieved in the polymerization of MMA in THF at 0°C. The lithium phenoxide showed both promoting and inhibiting effects in the polymerization of isoprene (Ip): it promoted the formation of 3,4‐structure, while mitigated the formation of 1,2‐ and 1,4‐structures. In general, the polymerization rate of Ip was promoted by lithium phenoxide.     

Chemical reactions of cycloalkanespirohydantoins. Part 2. Synthesis of new 4-hydroxyimidazolidinone N3-substituted from cycloalkanespirohydantoins

N₃-Substituted hydantoins have been to undergo lithium aluminum hydride reduction (THF, room temperature, 5 hours) to give 4-hydroxy-2-imidazolidinones in good yields.     

Syntheses and electrochemistry of some transition metal complexes with 2-mercaptopyridine N-oxide and crystal structure of bis(2-mercaptopyridine N-oxide)nickel(II)

The complexes M(mpo)_n (M = Mn, Ni, n = 2; M = Fe, Co, n = 3) (Hmpo = 2-mercaptopyridine N-oxide) were prepared by reacting the appropriate metal chloride with either Nampo or dtpo [2,2-dithiobis(pyridine N-oxide)] in the presence of sodium methoxide. The structure of the complex Ni(mpo)₂ was determined by X-ray diffraction. The nickel atom is in a square planar environment of two mpo⁻ ligands in the cis configuration. The four complexes were investigated by physicochemical methods especially by ¹H NMR spectroscopy and cyclic voltammetry.     

Polymerization of Methyl Methacrylate in the Presence of Imidazole Derivatives. Kinetics and Polymer Structure

The kinetics of the polymerization of methyl methacrylate (MMA) in the presence of imidazole (Im), 2-methylimidazole (2MIm), or benz-imidazole (BIm) in tetrahydrofuran (THF) at 15–40°C was investigated by dilatometry. The rate of polymerization, R_p , was expressed by R_p = k[Im] [MMA]², where k = 3.0 × 10^?6 L²/(mol² s) in THF at 30°C. The overall activation energy, E_a , was 6.9 kcal/mol for the Im system and 7.3 kcal/mol for the 2MIm system. The relation between logR_p and 1 T was not linear for the BIm system. The polymers obtained were soluble in acetone, chloroform, benzene, and THF. The melting points of the polymers were in the range of 258–280°C. The ¹H-NMR spectra indicated that the polymers were made up of about 58–72% of syndiotactic structure. The polymerization mechanism is discussed on the basis of these results.     

Living cationic polymerization of isobutyl vinyl ether by EtAlCl2 in the presence of ether additives: Cyclic ethers,cyclic formals,and acyclic ethers with oxyethylene units

The living cationic polymerization of isobutyl vinyl ether (IBVE) was investigated in the presence of various cyclic and acyclic ethers with 1-(isobutoxy)ethyl acetate [CH₃CH(OiBu)OCOCH₃, 1 ]/EtAlCl₂ initiating system in hexane at 0°C. In particular, the effect of the basicity and steric hindrance of the ethers on the living nature and the polymerization rate was studied. The polymerization in the presence of a wide variety of cyclic ethers [tetrahydrofuran (THF), tetrahydropyran (THP), oxepane, 1,4-dioxane] and cyclic formals (1,3-dioxolane, 1,3-dioxane) gave living polymers with a very narrow molecular weight distribution (MWD) (M?_ω/M?_n ≤ 1.1). On the other hand, propylene oxide and oxetane additives resulted in no polymerization, whereas 1,3,5-trioxane gave the nonliving polymer with a broader MWD. The polymerization rates were dependent on the number of oxygen and ring sizes, which were related to the basicity and the steric hindrance. The order of the apparent polymerization rates in the presence of cyclic ether and formal additives was as follows: nonadditive ～ 1,3,5-trioxane ? 1,3-dioxane > 1,3-dioxolane ? 1,4-dioxane ? THP > oxepane ? THF ? oxetane, propylene oxide ? 0. The polymerization in the presence of the cyclic formals was much faster than that of the cyclic ethers: for example, the apparent propagation rate constant k in the presence of 1,3-dioxolane was 10³ times larger than that in the presence of THF. Another series of experiments showed that acyclic ethers with oxyethylene units were effective as additives for the living polymerization with 1 /EtAlCl₂ initiating system in hexane at 0°C. The polymers obtained in the presence of ethylene glycol diethyl ether and diethylene glycol diethyle ether had very narrow molecular weight distribution (M?_ω/M?_n ≤ 1.1), and the M?_n was directly proportional to the monomer conversion. The polymerization behavior was quite different in the polymerization rates and the MWD of the obtained polymers from that in the presence of diethyl ether. These results suggested the polydentate-type interaction or the alternate interaction of two or three ether oxygens in oxyethylene units with the propagating carbocation, to permit the living polymerization of IBVE. © 1994 John Wiley & Sons, Inc.     

Anionic polymerization of methyl methacrylate using tetrakis[tris(dimethylamino)phosphoranylidenamino] phosphonium (P5+) as counterion in tetrahydrofuran

A novel metal‐free initiator, i.e. the salt of the tetrakis[tris(dimethylamino)phosphoranylidenamino]phosphonium (P₅⁺) cation with the 1,1‐diphenylhexyl (DPH^–) anion was prepared by cation metathesis. It initiates a very fast and controlled anionic polymerization of methyl methacrylate in THF. Kinetic investigations between –20 and +20°C using a flow tube reactor provide nearly linear first‐order time‐conversion plots with half‐lives below 0.1 s, a linear dependence of the number‐average degree of polymerization, and rather narrow molecular weight distributions (M_w/M_n ≈ 1.2). ¹³C NMR measurements on a model of the active chain end (the P₅⁺ salt of ethyl isobutyrate) in THF‐d₈ show 15 and 25 ppm upfield shifts of the α‐carbon compared to the dimers and tetramers of the lithium ester enolate, respectively, indicating a non‐aggregated structure and an increased charge density on the α‐carbon.