Copolymerization of Fullerene (C60) and Methyl Methacrylate (MMA) using Triphenylbismuthonium Ylide as a Novel Initiator and Characterization of the Copolymers (C60-MMA)

Copolymerization of fullerene (C₆₀) with methyl methacrylate (MMA) was carried out using triphenylbismuthonium ylide (abbreviated as Ylide) as a novel initiator in dioxan at 60°C for 4 h in a dilatometer under a nitrogen atmosphere. The reaction follows ideal kinetics: R_p∝ [Ylide]^0.5[C₆₀]^?1.0[MMA]^1.0. The rate of polymerization increases with an increase in concentration of initiator and MMA. However, it decreases with increasing concentration of fullerene due to the radical scavenging effect of fullerene. The overall activation energy of copolymerization was estimated to be 57 KJ mol^?1. The fullerene-MMA copolymers (C₆₀-MMA) were characterized by FTIR, UV–Vis, NMR and GPC analyses.     

Quantum chemical modeling of the addition reactions of 1‐n‐phenylpropyl radicals to C60 fullerene

Modeling of the addition of various radicals to C₆₀ fullerene is currently an active research area. However, the radicals considered are not able to adequately model polymeric radicals. In this work, we have performed a theoretical study of the possible reactions of C₆₀ fullerene with 1‐n‐phenylpropyl radicals, which are used to model polystyrene radicals. Several possible ways of subsequent addition of up to four 1‐phenylpropyl radicals to C₆₀ have been analyzed, the structures of the intermediates have been defined and thermal properties, such as the activation enthalpies of the corresponding reactions, have been calculated using density functional theory with the approximation of PBE/3z. It is shown that the topology of the spin density distribution on the fullerenyl radical causes regioselectivity for further radical addition. According to the energetic characteristics of the reactions, we assume the possibility of formation of products of one‐, two‐, three‐, and four‐ addition of the growth radical to the fullerene core in radical polymerization of styrene in the presence of C₆₀ fullerene. © 2016 Wiley Periodicals, Inc.     

Kinetic and ESR studies on radical polymerization of methyl methacrylate in the presence of fullerene

The effect of fullerene (C₆₀) on the radical polymerization of methyl methacrylate (MMA) in benzene was studied kinetically and by means of ESR, where dimethyl 2,2′-azobis(isobutyrate) (MAIB) was used as initiator. The polymerization rate (R_p) and the molecular weight of resulting poly(MMA) decreased with increasing C₆₀ concentration ((0–2.11) × 10⁻⁴ mol/L). The molecular weight of polymer tended to increase with time at higher C₆₀ concentrations. R_p at 50°C in the presence of C₆₀ (7.0 × 10⁻⁵ mol/L) was expressed by R_p = k[MAIB]^0.5[MMA]^1.25. The overall activation energy of polymerization at 7.0 × 10⁻⁵ mol/L of C₆₀ concentration was calculated to be 23.2 kcal/mol. Persistent fullerene radicals were observed by ESR in the polymerization system. The concentration of fullerene radicals was found to increase linearly with time and then be saturated. The rate of fullerene radical formation increased with MAIB concentration. Thermal polymerization of styrene (St) in the presence of resulting poly(MMA) seemed to yield a starlike copolymer carrying poly(MMA) and poly(St) arms. The results (r₁ = 0.53, r₂ = 0.56) of copolymerization of MMA and St with MAIB at 60°C in the presence of C₆₀ (7.15 × 10⁻⁵ mol/L) were similar to those (r₁ = 0.46, r₂ = 0.52) in the absence of C₆₀. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2905–2912, 1998     

Simulation of Potentially Possible Reactions at the Initial Stages of Free-Radical Polymerization of Styrene and Methyl Methacrylate in the Presence of Fullerene C<Superscript>60</Superscript>

The quantum-chemical simulation of possible reactions occurring at the initial stage of the free-radical polymerizations of styrene and methyl methacrylate in the presence of fullerene C⁶⁰ is performed. The reactions of interaction between initiating and model short-chain growing radicals containing from one to three monomer units with fullerene are considered. It is shown that, at the initial stage of styrene polymerization, the addition of short-chain growing radicals to fullerene predominates (with respect to the reaction of chain propagation). In the case of methyl methacrylate polymerization in the presence of fullerene C⁶⁰, the induction period is absent because of a higher probability of the initiation and chain propagation reactions (compared with the chain-termination reaction of short growing poly(methyl methacrylate) chains on fullerene C⁶⁰). The formation of bis- and trisadducts of fullerene C⁶⁰ with short-chain styrene and methyl methacrylate growing radicals is analyzed. The quantum-chemical simulation results are confirmed by electron spectroscopy and ESR studies.     

Synthesis of di‐ and tetra‐adducts by addition of polystyrene macroradicals onto fullerene C60

Br‐terminated polystyrenes of controlled molar masses and low polydispersities prepared by atom transfer radical polymerization (ATRP) can be converted to macroradicals using an appropriate catalytic complex (CuBr/bipyridine/100 °C). The addition of this macroradicals PS° to 6–6 bonds of C₆₀ follows a specific atom transfer radical addition mechanism that favors the grafting of even number of chains onto the fullerene core. This peculiar mechanism, resulting from the properties of C₆₀, offers an easy synthetic route toward well‐defined di‐ and tetra‐adducts. In these adducts the disturbance of the electronic structure of the fullerene is kept at its minimum, as only one double bond needs to be opened on the C₆₀ to add two PS chains and only two double bonds are converted to single bonds in the tetra‐adduct. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3456–3463, 2004     

Interaction of fullerene C60 with allylbenzene and allyl chloride

The reaction between allyl compounds and fullerene C₆₀ has been investigated via dilatometry under the conditions of free-radical polymerization. It has been shown that the rate of a variation in the volume of the reaction mixture plotted versus the concentration of fullerene C₆₀ is described by a curve with a minimum. It has been established that, in the presence of fullerene and the allyl monomer, the polymerization of methyl methacrylate proceeds without any induction period. It has been concluded that allyl radicals interact with fullerene C₆₀.     

Branched poly(methyl methacrylates) modified by C60 fullerenes

The poly(methyl methacrylates) of branched structure with a covalently bonded fullerene were synthesized by three-dimensional radical polymerization of methyl methacrylate with triethylene glycol dimethacrylate or allyl methacrylate in toluene containing C₆₀. The kinetics of copolymerization of methyl methacrylate with multifunctional co-monomers in the absence of fullerene is compared with that in its presence. The physicochemical characteristics and thermal stability of the obtained copolymers are also compared. The electron spin resonance (ESR) method was applied to study the kinetics of accumulation of the fullerene radicals in the course of the (co)polymerization of methyl methacrylate.     

Stable radical adducts of diisopropylphosphoryl radicals with fullerene complexes (η2-C60)Os(CO)(PPh3)2(CNBut) and (η2-C70)Os(CO)(PPh3)2(CNBut)

It was determined by ESR spectroscopy that the UV irradiation of toluene solutions containing Hg[P(O)(OPrⁱ)₂ and the complex (²-C₆₀)Os(CO)(PPh₃)₂(CNBu^t) produces six stable regioisomeric adducts of phosphoryl radicals with complexes, which are not demetallated under UV irradiation and do not dimerize in the absence of UV irradiation. This is caused by the addition of the phosphoryl radicals to the carbon atoms of fullerene localized near the metal-containing moiety. The addition of the phosphoryl radicals to (²-C₇₀)Os(CO)(PPh₃)₂(CNBu^t) gives rise to the formation of nine stable regioisomeric radical adducts. A comparison of the composition of regioisomers of the radical adducts of C₇₀ with the phosphoryl radicals, which were formed directly from C₇₀ and from the radical adducts of ²-C₇₀)Os(CO)(PPh₃)₂(CNBu^t) by the demetallation of the latter, revealed an orienting effect of the osmium-containing moiety on the addition of the phosphoryl radicals to the fullerene complex.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1968–1972, September, 2004.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

On the initial stage of the free-radical polymerizations of styrene and methyl methacrylate in the presence of fullerene C<Subscript>60</Subscript>

It has been demonstrated experimentally and theoretically that the essentially different inhibiting effects of fullerene C₆₀ on the initial stage of the polymerizations of styrene and methyl methacrylate (including complete hampering of styrene polymerization throughout a long induction period) are of common kinetic nature. The difference arises from the competition between C₆₀ and the monomer not for initiating radicals but for radicals originating from the monomer; that is, the difference stems from the competition between the chain propagation reactions and the termination reactions on fullerene molecules. As a consequence, the further development of the process is determined by the relative reactivities of the radicals toward C₆₀ and towards their parent monomers.     

Effective dispersion of fullerene with methacrylate copolymer in organic solvent and poly(methyl methacrylate)

Dispersion of fullerene, C₆₀, by addition of polymethacrylate dispersant in methyl methacrylate (MMA) and incorporation of C₆₀ into poly(methyl methacrylate) (PMMA) were investigated. Copolymers synthesized by radical copolymerization of MMA and 2-naphthyl methacrylate (NMA), poly(MMA-co-NMA), effectively dispersed C₆₀ in MMA to form clusters of 20?nm. In these cases, addition of minimal 110 naphthyl groups per unit C₆₀ molecule afforded to give clusters with minimum of 20?nm sizes. Furthermore, block copolymers, poly(MMA-b-NMA) with MMA/NMA mole ratio from 12:1 to 20:1, also efficiently dispersed C₆₀ to give formation of clusters of 20?nm size by addition of minimal 40 naphthyl groups per unit C₆₀ molecule, which was corresponding to approximate nine layers of naphthyl group in block copolymer adsorbed on the surface of the cluster. Hybrid films of C₆₀/PMMA, prepared by casting of C₆₀-dispersed solution containing PMMA, exhibited absorbance at 400?nm linearly increased with C₆₀ content.     

Radical functionalization of [60]fullerene and its derivatives initiated by the C(CF3)2C6H4F radical

It was found that the 2-(p-fluorophenyl)hexafluoroisopropyl radical produced by thermal dissociation of the Polishchuk dimer [C(CF₃)₂C₆H₄F]₂ can withdraw, under mild conditions, the H atom from the methyl group of toluene and mesitylene to form the corresponding radicals, whose addition to [60]fullerene occurs more selectively than in the case of photochemical production of these radicals. Dynamics of the step-by-step multiaddition of the radicals to C₆₀ was studied by ESR. It was found that the addition of benzyl radicals affords adducts containing from 3 to 5 benzyl groups, whereas no spin-adducts with five addends were observed for more bulky 3,5-dimethylphenylmethyl radicals. The interaction of 3,5-dimethylphenylmethyl radicals with the metal complexes (η²-C₆₀[IrH(CO)(PPh₃)₂] and (η²-C₆₀[Pd(PPh₃)₂] was studied for the first time. It was shown that the palladium derivative undergoes only demetallation. In the case of the Ir complex, up to 3 radicals add to the fullerene ligand in the same hemisphere where the transition metal is coordinated. The reaction rates are ∼5 times lower than those for C₆₀. The ability of 2-(p-fluorophenyl)hexafluoroisopropyl radicals to dehydrogenate C₆₀H₃₆ was found. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1119–1123, June, 1999.     

Stereocontrol during the radical polymerization of methyl methacrylates with combined Lewis acids: Aluminium trichloride (AlCl3) and iron dichloride tetrahydrate

The radical polymerization of methyl methacrylate (MMA) was carried out in the presence of combined Lewis acids of the AlCl₃-FeCl₂ system. Compared with the polymerization produced in the presence of single Lewis acids, AlCl₃ or FeCl₂, the MMA polymerization in the presence of AlCl₃-FeCl₂ composite in CHCl₃ or 1-butanol produced a polymer with a higher isotacticity and in toluene produced a polymer with a much higher isotacticity (mm = 50%). The molecular weight and polydispersity of PMMA in the presence of Lewis acids were similar with those in the absence of Lewis acids, although Lewis acids decelerate the polymerization of MMA. The effects of the Lewis acids were greater in a solvent with a lower polarity. A possible stereocontrol mechanism of the polymerization was proposed. The Lewis acid composite of AlCl₃-FeCl₂ readily formed a complex with growing species. These complexes possessed apparent bulkiness that changes the direction of monomer addition to the growing radical center.     

Radical polymerization of styrene in the presence of C60

Radical polymerizations of styrene in the presence of C₆₀ have been conducted at 90°C in benzene using benzoyl peroxide (BPO) as initiator. The behaviors of C₆₀ are investigated by monitoring BPO concentration, C₆₀ content, and polymerization time. It is found that C₆₀ acts like a radical absorber which multiply absorbs primary radicals from BPO and propagating radicals. Therefore, in the presence of C the yield and molecular weight decrease significantly. However, the molecular weight distribution is narrowed down by its coupling characteristics. At the beginning of the reaction, owing to the radical-absorbing effect of C₆₀, it makes the chain-propagation restricted. However, the number of polystyrene chains added to C₆₀ increases with polymerization time. Direct dilatometric experiment proves that C₆₀ is mainly as inhibitor for radical polymerization of styrene by benzoyl peroxide. Besides, the glass transition temperature (T_g) of the copolymers increases with increasing content of C₆₀. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2969–2975, 1999     

Chain transfer by addition–substitution–fragmentation mechanism. I. End–functional polymers by a single-step free radical transfer reaction: Use of a new allylic linear peroxyketal

A new chain transfer agent, ethyl 2-[1-(1-n-butoxyethylperoxy) ethyl] propenoate (EBEPEP) was used in the free radical polymerization of methyl methacrylate (MMA), styrene (St), and butyl acrylate (BA) to produce end-functional polymers by a radical addition–substitution–fragmentation mechanism. The chain transfer constants (C_tr) for EBEPEP in the three monomers polymerization at 60°C were determined from measurements of the degrees of polymerization. The C_tr were determined to be 0.086, 0.91, and 0.63 in MMA, St, and BA, respectively. EBEPEP behaves nearly as an “azeotropic” transfer agent for styrene at 60°C. The activation energy, E_atr, for the chain transfer reaction of EBEPEP with PMMA radicals was determined to be 29.5 kJ/mol. Thermal stability of peroxyketal EBEPEP in the polymerization medium was estimated from the DSC measurements of the activation energy, E_ath = 133.5 kJ/mol, and the rate constants, k_th, of the thermolysis to various temperature. © 1994 John Wiley & Sons, Inc.     

Kinetics and products derived from C<Subscript>60</Subscript> fullerene radiolysis in toluene

C₆₀ fullerene was radiolyzed in toluene solution both in presence of air and in vacuum at four different radiation doses 12, 24, 36, 48 and 96 kGy. Clear evidences of the addition of benzyl radicals to the fullerene cage derive from FT-IR and C¹³-NMR spectra of the reaction product. In presence of air the interference of oxygen is evident in the FT-IR spectra and from the elemental analysis. A detailed analysis of the kinetics of the multiple addition of benzyl radicals to the fullerene cage was made spectrophotometrically with the determination of the addition rate constants at the each addition step and the average number of benzyl groups added to the fullerene cage as function of the radiation dose.     

Methyl methacrylate polymerization in the presence of C60 (C70) and molecular characteristics of fullerene-containing poly(methyl methacrylate)

Kinetics was studied of bulk polymerization of methyl methacrylate initiated by dicyclohexyl peroxydicarbonate in the presence of tri-n-butylborane and fullerene C₆₀ (or C₇₀) at variable ratio initiator: fullerene. The deceleration of the polymerization in the first stage of the reaction (below 10% conversion) was established by dilatometric method that depended on the fullerene concentration and the mode of its addition to the monomer. It was shown that at similar ratios initiator: fullerene the C₆₀ inhibited the polymerization process considerably stronger than C₇₀. The gel-permeation chromatography revealed the widening of the molecular weight distribution of the poly(methyl methacrylates) containing C₆₀ or C₇₀ compared to its analog synthesized under the same conditions without fullerene. It was established that in the fullerene-containing poly(methyl methacrylates) all the framework nanospecies are linked by covalent bonds and are mostly accumulated in the low-molecular fractions. The effect of the covalently bound fullerene on the molecular characteristics of polymers were investigated by translational isothermal diffusion, high-speed sedimentation, and viscometry     

Anionic methods for synthesis of star polymers

Leading position among numerous methods for synthesis of star polymers is occupied, as regards their potential and diversity, by techniques based on the anionic polymerization. The review considers five basic approaches to application of the anionic polymerization mechanisms in relation to an agent used or procedure employed (methods with polyfunctional coupling agents, multifunctional initiators, polymerizing and nonpolymerizing divinyl agents; multistage methods, methods using C₆₀ fullerene). All groups of syntheses are illustrated by examples, and advantages of methods for synthesis of various homo- and heteroarm star structures are demonstrated. Particular attention is given to syntheses with C₆₀ fullerene. The potential of C₆₀ fullerene as a coupling agent for “living” polymer chains and methods for conversion of polymeric derivatives of C₆₀ (hexaadducts) to polyfunctional macroinitiators of anionic polymerization are described and techniques for functionalization of polymeric fullerene derivatives and their coupling into structures with a complex controllable architecture are presented.     

Effect of the medium on the reactivity of fullerene N60 with respect to the peroxide radicals RO2 ·. Chemiluminescence in the C60—AIBN—O2—C2H5Ph—PhH system

Chemiluminescence (CL), HLPC, and volumetry were used to demonstrate that fullerene N₆₀ exerts no inhibiting effect on the liquid-phase chain oxidation of hydrocarbons. Peroxide radicals RO₂ · do not add to N₆₀ in hydrocarbons with active C—H bond, because the reaction is suppressed by the competing addition of RO₂ · to the hydrocarbon. The addition of RO₂ · radicals to N₆₀ does occur in benzene (a solvent with strong C—H bonds) in the presence of low concentrations of the hydrocarbon oxidized. Fullerene N₆₀ is found to exhibit a new type of liquid_phase CL, which is presumably generated upon thermal decomposition of fullerene peroxides formed by adding peroxy radicals to fullerene in the C₆₀—AIBN—O₂—C₂H₅Ph—PhH system. The CL spectrum exhibits long-wavelength maxima at 645 and 685 nm. The supposed CL emitters are keto derivatives of fullerene N₆₀.     

A spectrophotometric,electron spin resonance,and calorimetric study of low-temperature postradiation living radical polymerization of vinyl monomers in the presence of C<Subscript>60</Subscript> fullerene

By means of UV-visible spectrophotometry, ESR spectroscopy, and calorimetry, it was shown that the low-temperature postradiation polymerization of vinyl monomers in the presence of C₆₀ fullerene (the yield of fullerene linking was above 90%) occurred via the radical mechanism in the living mode over the temperature range of 120–140 K.