阳离子光引发剂芳茂铁六氟磷酸盐的制备

以二茂铁为原料制备了3种阳离子光引发剂芳茂铁六氟磷酸盐.考察了反应温度、反应时间和催化剂用量等因素对反应的影响.对产物进行了IR和UV光谱分析.     

乙烯基阳离子聚合引发剂的新进展

本文围绕着乙烯基阳离子聚合这一核心，简要地介绍了近年来在阳离子聚合引发剂方面取得的新进展，包括活性阳离子聚合和普通阳离子聚合引发剂两个部分。     

芳茂铁阳离子聚合光引发剂引发活性研究

研究了7种不同芳烃结构的芳茂铁四氟硼酸盐作为阳离子紫外光聚合和光固化引发剂在环氧体系中的光引发活性,其中[C₅H₅Fe₂,5-(CH₃)₂CO^-C₆H₃]BF₄(Ⅵ)和[CH₃CO^-C₅H₄Fe₂,4-(CH₃)₂-C₆H₄]BF₄(Ⅶ)为新物质.研究发现,这7个芳茂铁四氟硼酸盐在370和450nm附近均有较强吸收;芳环上引入共轭CC和共轭CO使吸收峰发生红移,且使摩尔消光系数和感光速度均有所提高,更适合于以高压汞灯为辐射光源的长波紫外固化;芳茂铁四氟硼酸盐可以引发环氧树脂、脂环族和脂肪族缩水甘油基环氧单分子,通过加热或使用有机过氧化物[如过氧化苯甲酰(BPO)]可明显提高环氧化合物的聚合速度.     

环氧有机硅阳离子型光敏预聚物的合成及其光敏性能的研究

合成了环氧有机硅光敏预聚物及阳离子光引发剂甲苯茂铁四氟硼酸盐 ,研究光引发剂种类、预聚物与单体配比、增感剂结构等因素对固化速度的影响 ,发现预聚物体系的感度较高 ,最小感度值为 1 65mJ/cm² ;并讨论了甲苯茂铁四氟硼酸盐的暗聚合能力     

{4-[4-（对硝基苯甲酰基）苯硫基]苯}苯基碘鎓六氟磷酸盐的合成与光引发性能测试

紫外光固化反应按机理分为自由基固化、阳离子固化以及自由基-阳离子混杂固化.自由基-阳离子混杂固化是指在同一体系里同时通过自由基聚合和阳离子聚合而发生的固化[1].混杂聚合结合了各个聚合反应的优点,表现出很好的协同效应.杂化光引发剂被设计成既能引发自由基聚合又能引发阳离子聚合的光引发剂.据报道,目前常见的杂化光引发剂主要有碘鎓盐类和苯基膦二苯甲酮类[2].     

控制/活性阳离子聚合的研究进展

从链引发、链增长两个方面对控制,活性阳离子聚合及其最新研究进展进行了综述.介绍了茂金属类、水溶性Lewis类和烷基铝等几类新型的引发体系,以及亲核试剂、沉淀平衡和"阳离子池"在控制链增长方面的应用.     

阳离子光引发剂敏化的研究进展

常用的阳离子光引发剂吸收波长在250-300 nm,与紫外光固化设备的辐射波长不匹配,光引发速率和效率低.本文介绍了阳离子光引发剂的种类、特点以及使引发剂体系吸收红移的研究,着重总结了阳离子光引发剂的敏化理论和技术.概述的敏化机理包括:能量转移、自由基氧化、激发态复合物和碎片加成.常用敏化方法有:添加光敏剂、扩大分子共轭使吸收红移和键合生色基团.文章还对新型阳离子光引发剂和光敏剂的设计和应用给予了展望.     

新型感可见光的光引发体系乙基曙红碘Weng盐的研究

合成并研究了新型感可见光的光引发体系乙基曙红碘Ｗｅｎｇ盐，结果表明，该引发剂的物理化学性质和光敏引发效率受其结构，介质性质和浓度等诸多因素影响。在可见光照射下，发生由乙基曙红阴离子向二苯基碘Ｗｅｎｇ阳离子的电子转移反应，产且具有引发活性的苯自由基和非活性的乙基曙红自由基。     

二茂铁四氟硼酸盐的阳离子光引发性能的研究

制备并研究了[CpFeCp]BF4作为阳离子光引发剂在高压汞灯下引发环氧类预聚物的光引发活性.发现其在紫外及可见光区均有较强吸收(λm=355nm、620nm);对环氧类预聚物,具有优良的光引发活性,感度值可达41.8mJ/cm2,优于其它的阳离子光引发剂;[CpFeCp]BF4的最佳使用浓度为3%(质量分数)左右,由于光照后仍有强后聚合活性,发现其在较低浓度(质量分数1%)引发后放置,仍可使聚合完全;同其它的阳离子光引发剂相比,[CpFeCp]BF4制备简单,非常有应用价值.     

一氯二乙基铝／氯苄／吡啶引发体系引发的异丁烯阳离子聚合

活性聚合是控制聚合物的分子量、分子量分布、结构和端基的最有效和简单的方法之一。就异丁烯单体(IB)而言,自Kennedy首次报道其活性阳离子聚合以来,陆续报道了一些新的活性引发聚合体系,这些体系主要有两类:一类是叔丁基的酯、醚、醇与路易斯酸构成的引发体系;另一类是特丁基氯与路易斯酸加电子给予体(如DMSO、DMA等),其中以     

Synthesis and activity of aryl benzyl methyl sulfonium salts as cationic initiators: Effect of substituent on aryl group

Benzyl o-, m-, and p-substituted phenyl methyl sulfonium salts ( 2b – 2g ) were synthesized and their activities as cationic initiators were evaluated in the bulk polymerization of phenyl glycidyl ether (PGE). Especially, their activities were estimated with respect to the effect of substituents on the aryl groups. In the polymerizations of PGE with a series of benzyl p-substituted phenyl methyl sulfonium salts, the order of their activities was found to be 2c (CH₃OCOO) > 2b (CH₃COO) > 2d (CH₃O) ～ 2a (HO). In particular, 2c was the most active initiator of all, capable of initiating the polymerization of PGE even at room temperature. In the polymerizations with 2a, 2e (m-Cl), 2f (o-CH₃), and 2g (m-CH₃), the activity of 2e was the highest of all while those of 2a, 2f , and 2g were almost the same. These results strongly suggested that the electron-withdrawing group placed on the aryl group undoubtedly enhanced the activity of the sulfonium salts as the cationic initiators.     

Redox initiated cationic polymerization: Silane‐N‐aryl heteroaromatic onium salt redox couples

In this article, a new route for the synthesis of N‐aryl heteroaromatic onium salts by the direct copper catalyzed arylation of pyridine, substituted pyridines, isoquinoline, and acridine with diaryliodonium salts is described. It was demonstrated that these N‐aryl heteroaromatic onium salts undergo facile platinum or rhodium‐catalyzed reduction by silanes bearing Si? H groups. The reduction of N‐aryl heteroaromatic onium salts generates Brønsted acids. When this redox reaction was carried out in situ in the presence of an appropriate monomer, cationic polymerization was observed. Using this approach, the cationic polymerizations of epoxides, oxetanes, 1,3,5‐trioxane, styrene, and vinyl ethers were carried out. The use of optical pyrometry to monitor the redox initiated cationic polymerizations of some representative multifunctional monomers is described. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Application of S‐alkylsulfonium salts of aromatic sulfides as new thermal latent cationic initiators

The cationic initiation activity of derivatives of S‐methylsulfonium salts of dibenzothiophene ( 3a ), diphenyl sulfide ( 4a ), thioanisole ( 4d ), and tetrahydrothiophene ( 5 ) was evaluated in the polymerization of glycidyl phenyl ether ( 1 ). These initiators were soluble in 1 and capable of initiating the cationic polymerization of 1 on heating, with the exception of methyltetrahydrothiophenium tetrafluoroborate ( 5 ; in the range of room temperature to 160 °C). Among them, methyldiphenylsulfonium tetrafluoroborate ( 4a ) showed a moderate thermal latency that brought about the polymerization of 1 efficiently at 160 °C but not below 80 °C. S‐Alkylsulfonium salts of aromatic sulfides such as phenoxathiin ( 6a ) and thianthrene ( 6b ) also were evaluated for their activity in the cationic polymerization of 1 , from which the thermal latent behavior of these salts also was confirmed (i.e., there was no reaction at 60 °C for 3 h, but there was a high enough conversion at 140 °C). Furthermore, the catalytic activity of S‐alkylsulfonium derivatives was controllable by both the property of the substituents on the aromatic rings and the character of the alkyl groups on the sulfur atom. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 18–27, 2000     

Structure and reactivity of addition fragmentation agents in photochemically and thermally induced cationic polymerization

Specially designed allylic onium salts with different hetero‐atoms and various substituent patterns at the allylic double bond have been shown to be very efficient initiators for cationic polymerization. They can be used alone or in conjunction with radical initiators. The mechanism of initiation involves radical formation, radical addition and fragmentation. In some cases, oxidation reactions were found to contribute to the formation of initiating species. In this work, the role of structural parameters onto reactivity is discussed.     

Dithiadiazolium salts as initiators for the cationic ring-opening polymerization of tetrahydrofuran

Mono-, bis- and tris-(1,3,2,4-dithiadiazolium) salts [R-(CNSNS ⁺)_n]_n+[AsF^-₆]_n (R = aryl, n = 1, 2, 3) were found to initiate the cationic ring-opening polymerization of tetrahydrofuran (THF) at room temperature to give clear gels from which the pure polymer was precipitated. 1,3,2,4-Dithiadiazolium cations associated with the hard [AsF₆]^- anion thus constitute a new class of cationic polymerization initiators. The poly(THF) formed by initiation with 1,3,2,4-dithiadiazolium cation was characterized by gel permeation chromatography, infrared spectrophotometry, and ¹³C-NMR spectroscopy. Number-average molecular weights of 198 700 g mol^-1 (polydispersity 1.96) and 190 000 g mol^-1 (polydispersity 1.61) were obtained using [PhCNSNS ] [AsF₆] and [C₆H₃-1,3,5-(CNSNS )₃][AsF₆]₃, respectively, as initiators. The use of multifunctional dithiadiazolium salts as initiators suggests that they may be useful in the preparation of starburst and dendritic polymers. © 1992 John Wiley & Sons, Inc.     

Cationic polymerization behavior of isobutyl vinyl ether with arenesulfonates as non‐salt‐type latent thermal initiators

Substituted and unsubstituted benzenesulfonic acid cyclohexyl esters (1–7) were synthesized, and their possibility as latent thermal initiators in the cationic polymerization of isobutyl vinyl ether (IBVE) was examined to develop novel non‐salt type latent cationic initiators. Thermal decomposition of cyclohexyl p‐nitrobenzenesulfonate (2) in C₆D₆ at 80°C proceeded to exclusively afford cyclohexene as well as p‐nitrobenzenesulfonic acid. Cationic polymerization of IBVE with 1 mol % of an arenesulfonate (1–6) in bulk was carried out at 40–100°C for 12 h. No polymerization took place below 50°C, while the consumption of IBVE depending on both the polymerization temperature and the structure of the arenesulfonates was observed above 60°C. The obtained polyIBVEs showed bimodal GPC curves in several cases, revealing the intervention of two independent propagation species in the polymerization. The cationic polymerization of IBVE with cyclohexyl 2,4,6‐triisopropylbenzenesulfonate (7) at 80°C confirmed the acceleration effect of bulkiness on the polymerization rate. It was concluded that the polymerization was largely dependent on both electronic and steric factors of the aryl groups of the initiators which were directly related to the stability of the sulfonate anions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 293–301, 1999     

Developments in the theory of cationic polymerization-VII [1a,b]: Theoretical attempts at improving initiators for cationic polymerization of alkenes

The initiation of the cationic polymerisation of alkenes is examined in detail by means of simple thermodynamic concepts. From a consideration of the kinetic requirements it is shown that the ideal initiator will yield a stable, singly charged anion and a cation with a high reactivity towards the monomer by simple, well defined reactions. It must also be adequately soluble in the solvent of choice and for the experimental method to be used. The calculations are applied to carbocation salts as initiators and a method of predicting their relative solubilities is described. From established and predicted data for a variety of carbocation salts the position of their ion:molecule equilibria and their reactivity towards alkenes are examined by means of Born-Haber cycles. This treatment established the relative stabilities of a number of anions and the reason for dityl, but not trityl salts initiating the polymerisation of isobutene.The outcome of our treatment is a general method for selecting theoretically promising new initiators.     

Cationic polymerization of glycidyl phenyl ether initiated by various arylsulfonium salts as new thermal latent cationic initiators

The cationic initiation activity of derivatives of S-methylsulfonium salts has been evaluated in the cationic polymerization of glycidyl phenyl ether ( 1 ). These initiators are soluble in 1 and capable of initiating the cationic polymerization of 1 on heating, except for methyltetrahydrothiophenium tetrafluoroborate ( 6 ) (r.t. −160°C). Among them, methyldiphenylsulfonium tetrafluoroborate ( 4 ) shows moderate thermal latency, that is the polymerization of 1 occurs efficiently at 160°C but not below 80°C.     

New High‐Power LEDs Open Photochemistry for Near‐Infrared‐Sensitized Radical and Cationic Photopolymerization

Cyanines derived from heptamethines were investigated in combination with iodonium salts as initiators of the radical polymerization of tripropylene glycol diacrylate and epoxides derived from bisphenol‐A‐diglycidylether. A new near‐infrared (NIR) LED prototype emitting at 805 nm with an exposure intensity of 1.2 W cm^?2 facilitated initiation of both radical and cationic polymerization using sensitizers derived from cyanines. This new light‐emitting device has brought new insight into the photochemistry of cyanines with the general structure 1 because a combination of photonic and thermal processes strongly influences reaction pathways. In particular, cationic cyanines comprising a cyclopentene moiety and diphenylamino group in the center initiated the cationic polymerization of epoxides. Selective oxidation of this unit explains why specifically these derivatives may function as initiators for cationic polymerization. In contrast, when the diphenylamino group was replaced by a barbital group at the meso‐position cationic polymerization of epoxides was not initiated.     

Light- and Manganese-Initiated Borylation of Aryl Diazonium Salts: Mechanistic Insight on the Ultrafast Time-Scale Revealed by Time-Resolved Spectroscopic Analysis

Manganese-mediated borylation of aryl/heteroaryl diazonium salts emerges as a general and versatile synthetic methodology for the synthesis of the corresponding boronate esters. The reaction proved an ideal testing ground for delineating the Mn species responsible for the photochemical reaction processes, that is, involving either Mn radical or Mn cationic species, which is dependent on the presence of a suitably strong oxidant. Our findings are important for a plethora of processes employing Mn-containing carbonyl species as initiators and/or catalysts, which have considerable potential in synthetic applications.