Polymerization of methyl α-cyanoacrylate—II: Conditions for radical polymerization

The radical polymerization of methyl α-cyanoacrylate containing propane sultone at about 2 × 10^?2 mol dm^?3 can be initiated at 60° by azobisisobutyronitrile or by benzoyl peroxide; the amonic polymerization is not completely suppressed under these conditions but it is of minor importance. The polymer is not soluble in the monomer or in dioxan but polymerizations of the monomer in the bulk or dissolved in dioxan proceed at steady rates in their early stages and have the kinetics characteristic of free radical polymerization.     

Organocuprates as Initiators for Methyl Methacrylate Polymerization

Abstract

Polymerizations of methyl methacrylate initiated by organocuprates in tetrahydrofuran solution have been investigated. The heterocuprate lithium n-butylcyanocuprate was found to be an effective initiator at - 78°C, and lithium di-n-butylcuprate was confirmed as an effective initiator; both species give rapid polymerization to virtually complete conversion of monomer. Polydispersities (M_w/M_n ) are about 1.5. Polymerizations have an inherent termination reaction and a low initiator efficiency. Polymerization of methyl vinyl ketone is virtually uncontrollable, and polymerizations of methyl methacrylate are inhibited by styrene.     

Polymerizability of unsaturated monomers capable of forming stable radicals

Some unsaturated monomers bearing hindered phenol and arylamine groups capable of forming stable radicals were prepared. Radical polymerizations of vinyl monomers having such groups were investigated with the use of azobisisobutyronitrile, benzoyl peroxide, cumene hydroperoxide, and tetraethylthiuram disulfide as initiator. Polymerizations of these monomers went normally only when azobisisobutyronitrile was used as initiator. The other initiators inhibited polymerizations remarkably or completely. The results suggest that radicals resulting from benzoyl peroxide and cumene hydroperoxide or tetraethylthiuram disulfide abstract hydrogen of the phenol or the amine to produce the stable radicals, thereby inhibiting the polymerization. Meanwhile, carbon radicals resulting from azobisisobutyronitrile add selectively to the vinyl double bonds of the monomers to initiate the polymerizations. The vinyl derivatives as well as allyl derivatives and cinnamic acid derivatives copolymerize easily with conventional monomers such as styrene, maleic anhydride, and butadiene, again, only when azobisisobutyronitrile was used as initiator. Antioxidative properties for styrene copolymers and butadiene-styrene copolymers incorporating the hindered phenol monomers were investigated.     

Polycarbonate particles and dye‐labeled particles by miniemulsion polymerization

We describe the synthesis of several different polycarbonate particles by miniemulsion polymerization. The monomers were allylmethyl carbonate (AlMeC), di(ethylene glycol) bisallylcarbonate (DBAC), and 4‐vinyl‐1,3‐dioxan‐2‐one [vinyl ethylene carbonate (VEC)]. For these polymerizations, higher monomer conversions were obtained with oil‐soluble initiators (azobisisobutyronitrile and benzoyl peroxide) than with a water‐soluble initiator (potassium persulfate). Benzoyl peroxide was particularly effective in yielding particles with a narrow size distribution. Although increasing amounts of a surfactant (sodium dodecyl sulfate) led to smaller particles, the choice of the monomer was the major determinant. For example, in polymerization reactions carried out at 85 °C with benzoyl peroxide as the initiator and with otherwise identical recipes, we obtained particle sizes of 181 nm with AlMeC, 296 nm with VEC, and 203 nm with DBAC. Fluorescent particles were synthesized with comonomers based on the benzothioxanthene nucleus. Because the dyes had poor solubility in the monomers, it was necessary to include typically 20 wt % bromobenzene or dichlorobenzene based on the monomer in the miniemulsion reaction mixture. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1999–2009, 2004     

Chemically initiated graft copolymerization of acrylic acid onto acrylonitrile-butadiene-styrene (ABS) terpolymer and its constituent polymers

The graft copolymerization of acrylic acid onto acrylonitrile-butadiene-styrene terpolymer (ABS), has been initiated by the use of both benzoyl peroxide and azobisisobutyronitrile. Addition occurs in the butadiene region of the polymer, either by the loss of a vinylic hydrogen and subsequent radical formation and addition of monomer or by addition to the double bond. The amount of acrylic acid which may be added is dependent upon the time and temperature of the reaction and the concentration of monomer and initiator. Thermal analysis of the grafted samples show that the residue is less than that expected based upon the composition of the copolymer; similar results have been previously obtained for acrylic acid grafted by another technique. © 1996 John Wiley & Sons, Inc.     

Study of the isothermal free radical polymerization of some higher <Emphasis Type="Italic">n</Emphasis>-alkyl methacrylates

The free radical polymerizations of higher n-alkyl methacrylates were not investigated in detail until now. In this work, the courses of the isothermal free radical bulk polymerization of dodecyl, quatrodecyl and hexadecyl methacrylates were investigated by differential scanning calorimetry. The effects of the polymerization temperature and the alkyl group length in the esters on the monomer conversions during polymerization were studied. It was found that the polymerization rate vs. time curves have two maxima. The free radical polymerizations of above-mentioned monomers proceed with slightly expressed gel effect at the temperatures below 90°C, at initiator concentration 1 mass% in monomer.     

Verdazyl-Mediated Polymerization of Styrene

Attempted controlled polymerizations of styrene, conducted in the presence of either 1,3,5-triphenyl-6-oxoverdazyl or 1,5-dimethyl-3-phenyl-6-oxoverdazyl radicals initiated with benzoyl peroxide or 1,1′-azobis(cyclohexanecarbonitrile) were universally unsuccessful regardless of the reaction temperature and the initiator/verdazyl molar ratio. No improvement was observed using a verdazyl-terminated styrene initiator adduct prepared by an exchange reaction between a styrene-TEMPO alkoxyamine and a 1,3,5-triphenyl-6-oxoverdazyl radical. However, controlled polymerizations of styrene were achieved at 125 °C using a styrene-verdazyl adduct containing the 1,5-dimethyl-3-phenyl-6-oxoverdazyl radical. Polydispersity indexes remained low throughout the polymerizations and plots of number average molecular weight ( ) versus time were linear. However, the actual values were considerably lower than theoretical, an unexpected result that is under investigation.     

Preparation of poly(methyl methacrylate) particles by dispersion polymerization with organic peroxide in the presence of trimethylsiloxy terminated poly(dimethylsiloxane) in supercritical carbon dioxide

Dispersion polymerizations of methyl methacrylate (MMA) were conducted with various types of organic peroxides as radical initiator in the presence of trimethylsiloxy terminated poly(dimethylsiloxane) in supercritical carbon dioxide. Micron-sized, relatively “monodisperse” poly(MMA) particles were prepared by using benzoyl peroxide.Part CCLII of the series “Studies on Suspension and Emulsion”     

硫氰基/有机铜锂体系引发MMA阴离子聚合研究

采用有机锂为引发剂,以甲基丙烯酸酯（MMA）类为单体进行阴离子聚合,其副反应较严重,因为在此类单体分子中存在卢碳和羰基碳两个亲核点,引发剂进攻羰基碳则会使链终止,在聚合过程中发生各种副反应,以碱金属（Li,Na,K）为反离子的有机碳负离子化合物,其亲核性较强,倾向于进攻羰基碳,因此甲基丙烯酸酯类单体的阴离子聚合除了采用较大立体阻碍引发剂外。     

Stable free radical polymerization of n-butyl acrylate in the presence of high-temperature initiators

Living radical polymerizations of acrylate are known to be difficult to achieve using TEMPO as a mediator. The stable free radical polymerization (SFRP) of acrylate tends to stop at low monomer conversion due to the accumulation of TEMPO in the medium as a result of unavoidable bimolecular termination. Rather than solving this problem by destroying the excess nitroxide using ascorbic acid or glyceraldehyde associated with pyridine as reported recently, high temperature initiators were used to slowly and continuously generate new radicals throughout the polymerization to consume the excess TEMPO molecules. Polymerizations of n-butyl acrylate initiated by the alkoxyamine unimer (1-benzoyloxy)-2-phenyl-2-(2′,2′,6′,6′-tetramethyl-1′-piperidinyloxy)ethane (BST) were performed between 130 °C and 134 °C in the presence of a series of high temperature peroxide and azo initiators. The best results in this study were obtained by the continuous addition of small amounts of di-tert-amyl peroxide throughout the polymerization. Under these conditions, the acrylate polymerizations fulfilled the criteria of a controlled polymerization process although the molecular weight distributions were slightly broad (M_w/M_n ∼ 1.5).     

Catalytic and inhibiting effects of ferrocene on the bulk radical–coordination polymerization of methyl methacrylate from the standpoint of formal kinetics

The kinetic curves and rates of bulk radical–coordination polymerization of methyl methacrylate initiated by the benzoyl peroxide–ferrocene system at 293–373 K, initial benzoyl peroxide concentrations of 10^–4–10^–1 mol/L, and a constant initial ferrocene concentration of 10^–3 mol/L have been calculated using a mathematical model in which the process is considered from the standpoint of formal kinetics. The calculations have demonstrated that, at low methyl methacrylate conversions, ferrocene catalyzes the process at any benzoyl peroxide concentration; at medium and high methyl methacrylate conversions, deficient amounts of ferrocene with respect to benzoyl catalyze the process as well, while excess ferrocene inhibits the process. The observed effect is explained by the specific ferrocene–benzoyl peroxide interaction, which, depending on the ferrocene: benzoyl peroxide ratio, either increases or decreases the concentration of radicals in the reaction mass.     

Prediction and Experimental Characterization of the Molecular Architecture of FRP and ATRP Synthesized Polyacrylate Networks

Summary: This work reports experimental and modeling studies concerning the conventional (FRP) and atom transfer radical polymerization (ATRP) of acrylate/diacrylate monomers. In the framework of a recently developed general approach, kinetic models including crosslinking reactions and branching by chain transfer to polymer are discussed for FRP and ATRP polymerization systems. Besides molecular weight distribution (MWD), fairly good predictions of the z-average radius of gyration could be obtained for these non-linear polymers. A set of experiments was performed at 1 L scale in a batch reactor using n-butyl acrylate (BA) or methyl acrylate (MA) as monovinyl monomers and 1,6-Hexanediol diacrylate (HDDA) or bisphenol A ethoxylate diacrylate (BEDA) as crosslinkers. In FRP experiments, AIBN was used as initiator and ATRP polymerizations were initiated by ethyl 2-bromopropionate (EBrP) and mediated by CuBr using PMDETA (N,N,N′,N″,N″-pentamethyldiethylenetriamine) as ligant. Polymerizations were carried out in solution at 60 °C with different dilutions using toluene and DMF as solvents. Products formed at different polymerization times were analyzed by SEC/RI/MALLS yielding average MW, MWD, z-average radius of gyration and monomer conversion. Important differences in the molecular architecture of the synthesized FRP and ATRP highly branched polyacrylates have been identified. Comparisons of experimental results with predictions have put into evidence the important effect of intramolecular cyclizations at all dilutions, even with ATRP polymerizations.     

Polymerisations effectuees en milieux non reguliers. Hypothese des zones de surconcentration locale appliquee aux polymerisations radicalaires amorcees par l'eau oxygenee—1 Aspect qualitatif

Radical polymerizations in alcohols, with aqueous hydrogen peroxide cleaved by heat or u.v., give one or several products, according to monomer structure and experimental conditions. Results lead to a hypothesis of local overconcentrations, some with high concentration of monomer and low concentration of hydrogen peroxide and others rich in initiator but weak in monomer.     

Non-ideal kinetics in vinyl polymerization: Note on primary radical termination in benzoyl peroxide initiated polymerization of vinyl chloride in dichloroethane

The kinetics of vinyl chloride polymerization initiated by benzoyl peroxide doubly labelled with ¹⁴C and 'H were studied in 1,2-dichloroethane solution at 60°. The importance of primary radical termination in the polymerization is examined by kinetic analysis and by analysis of polymers for combined initiator fragments.     

Miniemulsion polymerization of styrene using the oil-soluble initiator AMBN

The Mettler RC1 calorimeter was used to measure the rate of polymerization of conventional emulsion, homogenized emulsion, and miniemulsion polymerizations of styrene initiated with 2,2′-azobis(2-methylbutyronitrile). It was noted that the rate of polymerization significantly increased as the surface area of the monomer droplets increased. This was taken as strong evidence that in the miniemulsion and homogenized emulsion polymerizations, the fraction of the initiator soluble in the oil phase was responsible for single radical generation. The partitioning of AMBN at 70 °C was measured by high-pressure liquid chromatography to be 134 parts in the oil : 1 part in the water. Predissolving polystyrene in the miniemulsion prior to homogenization resulted in an enhancement in the rate of polymerization, although to a lesser extent than what has been previously noted for parallel miniemulsion polymerizations initiated with potassium persulfate. It was also noted that the method of addition of the oil-soluble initiator (either predissolved in the monomer prior to homogenization or dissolved in a small separate phase of monomer and added directly to the reactor) has a measurable effect on the kinetics in the miniemulsion polymerization of styrene. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4449–4457, 1999     

Polymerization of N-vinylcarbazole. II. Kinetic studies on polymerizations involving azoisobutyronitrile and benzoyl peroxide

The polymerization of N-vinylcarbazole at 60°C in benzene has been initiated with azoisobutyronitrile, benzoyl peroxide, and their mixtures. The kinetics indicate that the azonitrile and the peroxide promote polymerizations of fundamentally different types. The resulting polymers have been examined by gel-permeation chromatography. The polymer produced with benzoyl peroxide contains a small amount of a high molecular weight fraction which, from the point of view of end groups, resembles the polymer made by use of the azonitrile. It is concluded that benzoyl peroxide in this system gives rise to two types of polymerization which occur simultaneously.     

Nitroxide mediated living radical polymerization in miniemulsion

The introduction of the aqueous phase into a living radical polymerization increases the complexity of the kinetics by creating the possibility of species partitioning between the aqueous and organic phases, and introducing aqueous phase reactions which could play a significant role particularly in chain initiation and/or particle nucleation. We have conducted a series of styrene miniemulsion polymerizations in which the solubility of initiator and nitroxide have been systematically varied. Experiments were run using either water-soluble (potassium persulphate) or oil-soluble (benzoyl peroxide) initiator, and either TEMPO or 4-hydroxy-TEMPO. These two nitroxides vary considerably in their water solubility. The effects of initiator and nitroxide solubility in water on conversion-time behaviour, molecular weight and initiator efficiency are presented.     

苯氧铜/正丁基锂体系引发MMA负离子聚合及其活性特征的研究

采用苯氧铜/正丁基锂(PhOCu/n-BuLi)体系引发MMA聚合, 通过GPC, ¹H NMR对聚合物进行了表征. 实验结果表明, 该体系聚合反应速度较快, 温度、引发体系组成是影响聚合物分子量及其分布、单体转化率、引发剂引发效率、聚合物的立构规整性的主要因素; －40 ℃时分子量分布比较窄, 但引发效率也比较低(大约15%). 低引发效率、宽分子量分布与引发剂的聚集状态有关. 分子量与单体浓度、引发剂浓度的关系说明, 该体系具有一定程度的活性聚合特点.     

Radical polymerization of di-n-butyl itaconate in the presence of Lewis acids

Intramolecular chain-transfer reaction takes place in polymerizations of itaconates at high temperatures and/or at low monomer concentrations. Polymerizations of di-n-butyl itaconate (DBI) were carried out at 60 °C in the presence of Lewis acids such as scandium trifluoromethansulfonate. Lewis acids hardly influenced the intramolecular chain-transfer reaction in bulk polymerizations. Polymerizations in methanol accompanied transesterification reaction catalyzed by Lewis acids. In polymerizations in toluene, catalytic amounts of Lewis acids were found to be effective in suppressing the intramolecular chain-transfer reaction. Lewis acids showed no significant influences on stereospecificity of polymerization, though isotactic-specificity increase in polymerizations of other acrylate monomers such as methyl methacrylate.     

SYNTHESIS AND POLYMERIZATION OF 2-OXO-3-METHYLENE-1,4-DIOXANES

A new kind of monomers was successfully synthesized by the reaction between 2-chloro methyl cycloketal and trimethylsilyl cyanide, followed by ring closure and dehaiogenation. Polymerizations of the monomers were carried out in benzene solution at 80℃with benzoyl peroxide as initiator. Both the structures of monomers and polymers were characterized by IR, ~1H NMR, ~(13)C NMR and elemental analysis.