Laser-initiated polymerization of epoxies in the presence of maleic anhydride

Laser-initiated polymerization of cyclohexene oxide in the presence of maleic anhydride was investigated. The influences of solvents laser irradiation time and the monomer feed ratio on the polymer yield and composition were evaluated. The rate of polymerization increased with an increase in the molar concentration of maleic anhydride in the monomer feed. Short irradiation times of 1–3 min duration gave very high yield of epoxy polymer (>80% conversion). Infrared spectral studies of the polymer product indicated the formation of polyether linkage at lower levels of conversion and an adduct of polyether and maleic anhydride at higher polymer conversions. The quantitative chemical analyses results also showed similar results. The results indicated that the polymerization was initiated by the excited charge transfer complex between the electron donor, cyclohexane oxide, and the electron acceptor–maleic anhydride. In the initial stages of polymerization, cyclohexene oxide undergoes a cationic polymerization in the presence of the radical anion of maleic anhydride. Laser-initiated polymerization of cyclohexene oxide/maleic anhydride is several hundred times more efficient than UV-initiated polymerization, as measured by the energy absorbed by the polymer system.     

Laser-initiated polymerization of charge-transfer monomer systems

The laser-initiated polymerization of charge-transfer monomer complexes was investigated with a pulsed nitrogen laser and an argon laser. Several donor-acceptor monomer charge-transfer systems were screened for polymerization in different solvents. Polymerization by laser initiation was achieved in two of these systems; that is, 2-vinylnaphthalene/fumaronitrile and 9-vinylanthracene/fumaronitrile. The best polymer yields were obtained with the 2-vinylnaphthalene/fumaronitrile system in sulfolane solvent. The influences on the polymer yield and composition of solvents, varying focal path length, glass conditioning, initiation sources, environment, and monomer feed ratios were evaluated. Infrared (IR) spectral studies, gel permeation chromatography (GPC), and chemical analyses were performed to characterize the polymer products arising from the polymerization of 2-vinylnaphthalene/fumaronitrile in sulfolane. The polymer contained a high percentage of sulfolane (ca. 1/3 mol fraction), presumably arising from solvent transfer to the growing polymer chains during the propagation phase of the polymerization.     

Laser-Initiated copolymerization of N-vinylpyrrolidone with maleic anhydride and maleimide

This article describes the laser-initiated copolymerization of N-vinylpyrrolidone with maleic anhydride and maleimide via charge transfer complexes. The dependence of copolymer yield on the molar ratios of the monomers in the feed and on the irradiation time is described. Based on the ultraviolet and infrared spectroscopy, and chemical analysis results, a tentative mechanism of polymerization is suggested. The rates of polymerization of several monomer systems are compared. The N-vinylpyrrolidone and maleimide system shows the highest rate of polymerization.     

电荷转移聚合研究——苯肼及其衍生物引发丙烯腈聚合

研究了苯肼(PHZ)及其衍生物引发丙烯腈(AN)聚合以及苯肼作为电子给体与醌作为电子受体形成的电荷转移复合物(CTC)对丙烯腈的引发聚合作用。测定了光聚合时的引发剂、单体指数和聚合活化能分别为0.66、2.1和33.4千焦耳/摩尔。光聚合机理认为是PHZ与AN在光照下形成激基复合物(exciplex),它分解产生自由基引发单体聚合。而暗聚合的机理认为是PHZ与醌形成CTC,CTC再分解引发单体聚合。exciplex与CTC分别已由荧光光谱和紫外吸收光谱检出。     

Cyclopolymerization. XI. Polyelectrolytes and Polyampholytes from N-Alkyl-N,N-diallylamines and Methacrylamide

The preparation and properties of some poly[RN(CH₂CH[dbnd]CH₂)₂hydrochlorides], where R may be methyl, n-propyl, n-hexyl, benzyl, and allyl, are discussed. Water-soluble polydiallyl-amine hydrochlorides have been prepared in high yields both by γ-irradiation and by chemical initiation. The polymers were characterized by solubility measurements, IR spectra, NMR spectra, and molecular weight determinations. Polydiallyl-amines as their free bases were found to gel both in solution and in the solid state; the factors influencing gelation were investigated. The polymerization of a mixture of methacrylamide and either methyl-or n-propyldiallylamine hydrochloride by chemical initiation and γ-irradiation in water, dioxane, and dimethylformamide was studied, and evidence is presented for and against the formation of a true copolymer. In all polymerizations, substantial quantities of either amine monomer or amine homopolymer were isolated. Although the amount of amine incorporated into the “copolymer” increased with an increased amine: Mam ratio in the monomer feed, the yield of “copolymer” decreased at a greater rate.     

Effect of ultraviolet irradiation on terpolymerization of sulfur dioxide with two unsaturated compounds

The terpolymerization of sulfur dioxide, butene-1 and acrylonitrile affords terpolymers containing equimolar amounts of sulfur dioxide and butene-1 with various acrylonitrile contents. Ultraviolet irradiation was found to accelerate the polymerization and decrease the acrylonitrile content in the polymer. This fact is interpreted by a mechanism through a copolymerization of sulfur dioxide–butene-1 complex and acrylonitrile, whereby the polymerizability of sulfur dioxide–butene-1 complexed monomer may be accelerated by ultraviolet light. In fact, a binary system of sulfur dioxide and butene-1 was found to be accelerated by ultraviolet irradiation, and it affords a maximum rate at a 1:1 composition of feed monomer. Ultraviolet light of 250–300 mμ wavelength is effective for the initiation and the propagation. This may be ascribed to the ultraviolet absorption of the sulfur dioxide–butene-1 complex. The temperature coefficient was measured in both dark and ultraviolet irradiation reactions. The ultraviolet irradiation enhances the reactivity of sulfur dioxide–butene-1 complexed monomer at low temperature. In the terpolymerization with sulfur dioxide, isoprene, and butadiene, the ratio of isoprene and butadiene in the terpolymer was not altered by ultraviolet irradiation because both monomers from complexes with sulfur dioxide, perhaps having the same temperature coefficient for the polymerization.     

Radical polymerization of metal-coordinated monomers with ligands of pyrrole-containing schiff bases

The copper complexes and the cobalt complex with the ligand of 3-(2-pyrrolylmethyl-enimino)propene-1 (PIP) or p-(2-pyrrolylmethylenimino)styrene (PIS) were synthesized and homopolymerizations and the copolymerization with styrene, acrylonitrile, methyl methacrylate and acrylic acid studied. In the polymerization of chelate monomers, inhibition of radical polymerization by the central metal ion was observed, but the chelate polymer could be obtained only if the initiator was present in higher concentrations in the feed. It is considered that the strength of inhibition depends on the electronic configuration of d-orbitals of the central metal ion. The initiation mechanism of the cupric chelate monomer may be reduction of the metal ion by the redox reaction with a primary radical via the intramolecular electron transfer through the π-conjugated system of the ligand prior to the propagation step. This mechanism was verified by studying the redox reaction of various copper complexes with DPPH. In the system of the copper complex containing PIS and acylic acid the alternating copolymer could be obtained at any mole fraction of monomer mixture in feed.     

Ring-opening isomerization polymerization of 2-methyl-2-oxazoline initiated by charge transfer complexes

The possibility of opening cyclic iminoethers and forming linear polymers or copolymers under the action of charge transfer complexes has been studied. The polymerization of 2-methyl-2-oxazoline, acting as donor, proceeds in the presence of various organic electron-acceptors such as tetracyanoethylene 7,7,8,8-tetracyanoquinodimethane and 2,4,7-trinitrofluorenone. Initiation takes place by charge transfer complexes formed between the monomer and the acceptor. With acceptors which possess polymerizable bonds, i.e. tetracyanoethylene and tetracyanoquinodimethane, copolymers are obtained.     

Polymerization of 1,P-Epoxides Initiated by Tetraalkyl Aluminates. I. Polymerization of Ethylene Oxide in the Presence of Sodium Tetrabutyl Aluminate

The polymerization of ethylene oxide (EO) initiated by NaA1Bu₄ is shown to proceed upon initial complex formation between monomer and initiator. In polymerization in toluene a high order of the kinetic equation with respect to initiator was found, indicating that chain propagation proceeds on dimers and trimers of the active center. An induction time of polymerization in THF is observed. It is necessary to reach a specific concentration of the NaAIBu₄.EO complexes which take part in the polymerization process. The wide molecular weight distribution, the high effectivity coefficient (initiation efficiency), and the polymerization rate increase with polymer yield are evidence of a polycentric polymerization mechanism.     

Kinetic study of the alternating copolymerization of butadiene and methyl methacrylate

A kinetic investigation of the alternating copolymerization of butadiene and methyl methacrylate with the use of a system of ethylaluminum dichloride and vanadyl chloride as a catalyst was undertaken. The relation between the polymer yield and the molar fraction of methyl methacrylate in the feed was examined by continuous variation of butadiene and methyl methacrylate, the concentrations of total monomer, ethylaluminum dichloride, and vanadyl chloride being kept constant. This continuous variation method revealed that the polymer yield attains its maximum value with a monomer feed containing less than the 0.5 molar fraction of methyl methacrylate. This value of the molar fraction of methyl methacrylate affording the maximum polymer yield decreased on increasing the total monomer concentration but was not changed on varying the concentration of ethylaluminum dichloride. The number of active species estimated from the relation between yield and molecular weight of the polymer was almost constant, regardless of the molar fraction of methyl methacrylate in the feed. Consequently, it can be said that the maximum polymer yield depends mainly on the propagation reaction, not on the initiation reaction or the termination reaction. Three types of the mechanism have been discussed for this alternating copolymerization: polymerization via alternating addition of butadiene and methyl methacrylate complexed with ethylaluminum dichloride by the Lewis-Mayo scheme; polymerization via the ternary intermediate of butadiene, methyl methacrylate, and ethylaluminum dichloride; polymerization via the complex formation of butadiene and methyl methacrylate complexed with ethylaluminum dichloride occurring only at the growing polymer radical. From the kinetic results obtained, it was shown that the first and third schemes are excluded, and polymerization by way of the ternary intermediate is compatible with the data.     

芳香叔胺引发烯类单体聚合研究——单体结构与聚合的关系

不同烯类单体在芳香叔胺存在下的聚合机构不一样。甲基丙烯酸甲酯等有α-甲基的烯类单体在不照光的条件下即可被芳香叔胺引发聚合,其聚合机构认为是首先α—甲基被胺-氧复合物氧化,生成单体过氧化物。再与胺形成氧化还原体系,分解产生自由基。 丙烯酸酯,丙烯腈等没有α-甲基的单体,只有光照时才被芳香叔胺氧化聚合,不光照时完全不聚合。这是因为这些单体不被胺-氧复合物氧化。光照下聚合的机构认为是因光的激发,这些单体与芳香叔胺形成电子转移激发络合物,再分解产生自由基。 研究了单体结构,胺结构对光聚合速度的影响。不同单体的活性次序是: AN>MA>VA>St 不同芳香叔胺的活性次序是: DMT>DMA>DMB>DNA 表明单体双键电子云密度越小,芳香叔胺氮原子上电子云密度越大,越容易形成激发态电子转移络合物,从而越容易聚合。     

Preparation and structural characterization of poly(4-vinylphenylacetate-co-maleic anhydride)

Poly(4-vinylphenylacetate-co-maleic anhydride) was synthesized by free-radical initiation to yield a 1:1 copolymer over a 0.2-0.8 mole fraction range of monomer feed in maleic anhydride. Evidence of 1:1 charge transfer complex between 4-vinylphenylacetate and maleic anhydride was obtained in the UV region at 355 nm. The ¹³C NMR chemical shifts and ¹H NMR integration data indicate that poly(4-vinylphenylacetate-co-maleic anhydride) has an alternating and stereoregular structure. The molecular weight of poly(4-vinylphenylacetate-co-maleic anhydride) was controlled by using specific solvents and initiator concentrations.     

N,N-二乙基硫代氨基甲酰硫基团(S_2CNEt_2)为假卤原子转移的原子转移自由基聚合新体系

综述了原子转移自由基聚合 (ATRP)中 ,以N ,N 二乙基硫代氨基甲酰硫基团 (S2 CNEt2 )转移实现活性聚合、控制聚合物结构的 4种新方法 :非卤化物 ,N ,N 二乙基二硫代氨基甲酸亚铜 [Cu(S2 CNEt2 ) ]催化甲基丙烯酸甲酯 (MMA)的正向ATRP ;2 ,2′ 联吡啶存在的条件下 ,过氧化苯甲酰 (BPO)与Cu(S2 CNEt2 )的氧化还原反应控制MMA的本体反向ATRP;同时含可转移卤原子、基团的氯化二乙基二硫代氨基甲酸铜 [Cu(S2 CNEt2 ) Cl]成功地用于偶氮二异丁腈或BPO引发的乙烯类单体反向ATRP.假卤原子S2 CNEt2 转移的ATRP得到窄分布的精确结构聚合物分子链ω 端含有光敏基团S2 CNEt2 ,可引发乙烯类单体的常温光聚合 ,实现ATRP与光聚合相结合制备嵌段共聚物     

Preparation and characterization of star ABC triblock copolymer of ethylene oxide,styrene and methyl methacrylate

A universally significant method,which combines the anionic polymerization with photoinduced charge transfer polymerization,for preparation of soluble star ABC triblock copolymer of ethylene oxide,styrene and methyl methacrylate,was described.The poly(ethylene oxide) (PEO) block was formed by initiation of phenoxy an-ions using p-aminophenol protected by Schiff's base as the parent compound Then the charge transfer system composed of PEO chains with deprotected-amino end groups and benzophenone initiated the polymerization of styrene and methyl metnacrylate sequentially under UV irradiation.The formed star triblock copolymer of styrene,ethylene oxide and methyl methacrylate could be purified by thin-layer chromatography (TLC) and characterized by IR,1H NMR,GPC (gel permeation chromatogrphy) and PGC (pyrolysis gas chromatography).     

Unusually highly efficient,singlet state,visible light photoinitiators based on styrylbenzimidazolium phenyltributylborate photoredox pairs for vinyl monomers free radical polymerization

In this article, hemicyanine dye–borate complexes, for example, 1,3‐dimethyl‐2‐[4‐(N,N‐dialkylamino)styryl]benzimidazolium phenyl‐tri‐n‐butylborates, were employed as the novel, very effective photoinitiators operating in the visible light region. The influence of the sensitizers and electron donor structure on the photopolymerization kinetics of multiacrylate monomer was investigated by photo‐DSC. The maximum photopolymerization quantum yield measured for 2‐ethyl‐2‐(hydroxymethyl)‐1,3‐propanediol triacrylate (TMPTA) was about 67 for sample of thickness of about 1 mm under 100 mW/cm² laser irradiation. It was found that the polymerization rate and the final conversion degree were depended on the dye structure. Moreover, the photoinitiating systems described gave a double bond conversion higher than the photoinitiator possessing as chromophore RBAX (Rose Bengal derivative), the common triplet state initiator. Additionally, the rate of photopolymerization depends on ΔG_el of electron transfer between borate anion and styrylbenzimidazolium cation. This latter value was estimated for a series of styrylbenzimidazolium borate salts. The relationship between the rate of polymerization and the free energy of activation for electron transfer reaction gives the dependence predicted by the classical theory of electron transfer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4119–4129, 2009     

甲基丙烯酸甲酯聚合动力学和分子量及分布的开放控制

在甲基丙烯酸甲酯聚合过程中 ,凝胶效应会导致转化率在短时间内出现突变 ,这对工业反应器非常危险 ,同时也导致分子量剧增、分子量分布加宽 .为了使聚合反应速度、分子量及分布同时得到控制 ,提出 3个控制目标 ,即热荷分布指数、预定分子量及变化、分子量分布指数 .在甲基丙烯酸甲酯半间歇聚合动力学和分子量模型的基础上 ,通过单体、溶剂和链转移剂 3种物料的流量和加料方式的仿真计算 ,对动力学、分子量及分布进行开放控制 ,并进行优化 ,得到热荷分布指数和分子量分布指数分别小于 2 0和 2 2的控制策略 ,且分子量达到预定要求 .选择两种优化策略进行实验验证 ,结果与开放控制仿真结果一致     

碘鎓盐/胺光引发聚合体系的初级反应研究

碘鎓盐/胺复合体系,用作自由基光敏聚合的引发剂具有良好的效果^[1],但是关于碘鎓盐和胺相互作用产生有引发活性的自由基的光化学反应机制尚不清楚。     

Anionic synthesis of well-defined polymer blends by controlled chain-transfer reactions

The scope and limitations of controlled chain transfer reactions in living anionic polymerization have been investigated. In contrast to the random nature of normal chain transfer reactions, this procedure first effects controlled living anionic polymerization followed by addition of a stoichiometric amount of suitable chain transfer agent when the monomer has been completely consumed. The resulting anionic species is then used to initiated polymerization of a second monomer charge with the same monomer or with a different monomer. A variety of hydrocarbon acids and amine compounds with pKa values in the range of 30–40 have been evaluated as chain transfer agents in the presence and absence of coordinating ligands. Efficient chain transfer to poly(styryl)lithium has been observed using 1,1-diphenylpropane. Reinitiation efficiency to both styrene and butadiene monomer was quantitative and controlled blends of different molecular weight polystyrenes or blends of polystyrene with polybutadiene have been prepared. The use of these chain transfer reactions to prepare functionalized polymers has also been investigated.     

Electroinitiated cationic polymerization of styrene in the presence of ferric chloride

The electroinitiated polymerization of styrene has been studied in acetone with ferric chloride as the electrolyte. At a fixed monomer concentration, the polymer yield depends on the current strength as well as the concentration of ferric chloride. The molecular weight of the polymer lies in the range of 1000–3000. Addition of zinc chloride to the system or replacement of the solvent by DMF (partly or fully) or methanol retards the polymerization. The current exponent of polymerization is unity with a reaction rate constant of 4.416 × 10^?2 reaction percent per hour. The locus of polymerization is the anode compartment. A cationic mechanism has been proposed for the polymerization, the initiating step consisting of an electron transfer from an adsorbed charge transfer complex of styrene and ferric chloride.     

Polymerization photoinitiated by carbonyl compounds. VI. Mechanism of benzil photoinitiation

The mechanism of the photoinitiation of the vinyl polymerization sensitized by benzil and 4,4′-dimethoxybenzil was studied. The monomers considered were methacrylic acid esters and styrene derivatives. All these monomers are efficient quenchers of the excited triplet benzil. However, the initiation efficiency of the benzil is important only when styrene derivatives are employed as monomers. The main polymerization process follows a simple free radical mechanism. The initiation step is a consequence of the interaction (triplet benzil–monomer double bond) through a charge transfer complex.