乙烯基单体光聚合动力学与光固化流变行为

概述了光引发体系、光照强度、单体平均官能度、液晶含量、反应温度、助剂等对乙烯基单体/液晶混合物光聚合动力学及光固化流变行为的影响.在染料和胺组成的二元Ⅱ型(夺氢型)光引发体系中,引入适当的第三组分能显著提高反应速率和转化率;增加光照强度和升高温度也能显著提高反应速率和转化率.随着单体平均官能度的增加,体系的反应速率和转化率呈现先增加后降低的趋势.对于I型(裂解型)光引发剂,液晶含量增加,单体反应速率降低,但转化率基本不变;但对于Ⅱ型光引发剂,液晶含量增加能大幅提高单体反应速率和转化率.加入使体系黏度降低的助剂也能提高体系的反应速率和转化率.在体系相同、温度固定的条件下,反应速率越高,凝胶化时间越短;相同体系,温度升高,凝胶化时间提前;相同温度下,单体官能度愈高,体系凝胶时间亦愈短.     

2,2′-二邻甲氧基苯基-4,4′,5,5′-四苯基-1,2′-二咪唑复合光引发体系的光聚合动力学研究

本文研究了对2,2′-二邻甲氧基苯基-4,4′,5,5′-四苯基-1,2′-二咪唑(BMOIM)复合光引发体系引发聚合动力学过程.采用紫外光谱仪对引发剂、供氢体、增感剂在紫外区的吸收谱图进行了表征.利用实时红外光谱仪对复合光引发体系引发聚合动力学过程进行实时监测,考察了不同光强、引发剂浓度以及不同官能度单体对反应速率及最终双键转化率的影响.结果表明,在引发剂浓度为0.6%(质量分数)时,20s内双键转换率达到96%,随着引发剂浓度的提高,聚合速率增大.聚合速率以及最终双键转化率随着光强增大而增大;双官能团单体的最终双键转化率比三官能团单体的最终双键转化率要高.     

正离子聚合制备具有双峰分布丁基橡胶及其结构性能研究

通过活性负离子聚合法制备了具有不同微观结构的聚(苯乙烯-b-异戊二烯-b-苯乙烯)三嵌段共聚物(SIp S),并将其作为正离子聚合的大分子单体.采用2-氯-2,4,4-三甲基戊烷(TMPCl)/2,6-二叔丁基吡啶(Dt BP)/倍半乙基氯化铝(Al2Et3Cl3)的正离子聚合引发体系,引发异丁烯、异戊二烯以及SIp S结构中可反应的双键,合成了具有双峰分布的支化丁基橡胶.研究表明,SIp S中聚异戊二烯的3,4-结构有着更高的反应活性,更容易参与正离子聚合.随着SIp S中聚异戊二烯段含量的增加,支化丁基橡胶的产率增加,分子量也随之增加,聚合物溶液的特性黏数降低.通过体积排斥色谱(SEC)(多角激光光散射仪/示差监测器/在线黏度仪)及GPC-UV联用等仪器对支化丁基橡胶进行结构表征.证实了SIp S成功参与接枝反应,制备的丁基橡胶存在支化结构,而且产生的高分子区聚合物并不是由大分子单体物理混合所产生的.相较于线性丁基橡胶,支化丁基橡胶有着更快的应力松弛速率和更佳的物理机械性能.     

可聚合二苯甲酮类光引发剂的合成及其光聚合性能研究

以4-(2,3-环氧丙氧基)二苯甲酮(EBP)和丙烯酸为原料,通过开环反应合成了含有不饱和双键的可聚合光引发剂4-(丙烯酸-2-羟基丙酯-3-氧基)二苯甲酮(AEBP).采用红外光谱(FT-IR)、核磁共振氢谱(¹HNMR)对其结构进行表征,利用紫外吸收光谱对AEBP的紫外吸收波长进行表征,通过实时红外(RT-IR)研究了AEBP引发丙烯酸酯单体的光聚合动力学.采用萃取法对比了BP与AEBP引发固化体系后的迁移性.结果表明,随AEBP浓度增加,单体最终转化率增加;当助引发剂N,N-二甲氨基苯甲酸-乙酯(EDAB)浓度为1.2%时,单体最终双键转化率最高;AEBP对双官能度单体的引发效率较之三官能度单体的好;聚合速率随光照强度的增强而变快;固化后AEBP的迁移性比传统的BP大大降低.     

二芳酮-可聚合胺紫外光引发1,6-己二醇二丙烯酸酯聚合的动力学研究

用Photo-DSC(光差热扫描)研究了一种可聚合胺助引发剂乙二醇-3-吗啡啉丙酸酯甲基丙烯酸酯(EGMPM)分别与二苯甲酮(BP)、4-(4-甲苯硫基苯基)苯基甲酮(BMS)、4-氯二苯甲酮(CBP)、4-氯甲基二苯甲酮(CMBP)、4-羟甲基二苯甲酮(HMBP)等二芳酮组成的光引发体系引发以1,6-己二醇二丙烯酸酯(HDDA)为单体的紫外光聚合动力学.考察二芳酮质量分数、聚合温度、光照强度对其光聚合动力学影响,并评价其引发效果;同时计算出了EGMPM/BP引发HDDA聚合体系的活化能.结果表明,二芳酮的质量分数增加时,反应达到最大反应速率的时间减少,单体的转化率也相应增加,单体聚合速率相应增大;相同质量分数(0.1%)的不同二芳酮,BMS体系达到最大反应速率的时间最短,单体转化率也最高;随着温度和光强的增加,单体最终转化率、最大反应速率增大,达到最大反应速率所需的时间减少.     

樟脑醌/乙二醇-3-吗啡啉基丙酸酯甲基丙烯酸酯引发牙科复合树脂的光聚合动力学研究

采用Photo-DSC研究了樟脑醌(CQ)/乙二醇-3-吗啡啉基丙酸酯甲基丙烯酸酯(EGMPM)可见光引发牙科复合树脂聚合的动力学过程.考察了CQ浓度、EGMPM浓度以及光强对牙科修复复合树脂光聚合动力学的影响.结果表明:增加引发体系的浓度和增加光强都可以增加反应速率和转化率;同时实验结果验证了Rp∝(I₀[CQ][EGMPM])^1/2的动力学关系.     

预辐射甲基丙烯酸甲酯形成过氧化物的结构及引发活性研究

乙烯类单体,在氧存在下经电离辐照形成具有强引发能力的过氧化物.离开辐射场,在一定条件下,过氧化物分解为自由基立即引发聚合进行.这一过程称为预辐射聚合.前人曾研究了预辐射聚合的反应机制和动力学过程.但对于辐照产生的过氧化物的组成、结构及其行为,只有推测,而无任何研究工作.本文报道以甲基丙烯酸甲酯(MMA)为单体,研究预辐照产物的结构和引发活性的初步结果.     

吡咯烷基-N-甲酸-丙烯酸乙二醇酯光聚合动力学的研究

采用实时红外技术对所合成的活性稀释剂吡咯烷基-N-甲酸-丙烯酸乙二醇酯的聚合动力学进行了测试.研究了光强、引发剂浓度及引发剂种类对其光聚合的影响.结果表明:光强越强、引发剂浓度越大,聚合速率越高,但是反应的最终双键转化率基本不变,均能达到100%左右.引发剂种类对其光聚合的最终双键转化率的影响不是特别明显,但对聚合速率有一定的影响.     

云点法研究丙烯腈共聚体系反应活性及其与热稳定性能的关联

采用滴定实验法分别测试了衣康酸(IA)、丙烯酰胺(AM)、丙烯酸甲酯(MA)与丙烯腈(AN)一系列单体组成比时的云点;采用红外光谱、示差扫描量热分析和热失重分析研究了共聚单体的选择对共聚物热稳定化反应的影响和机理及其与共聚体系反应活性的关联.结果显示,IA、AM或MA的引入有利于提高AN聚合体系的云点,不同共单体用量构成的云点迹线斜率可以比较共聚体系反应活性,并对AN共聚体系组成的优化选择具有普适性;而AN与IA较高的共聚反应活性使得P(AN/IA)聚合物热稳定性能好,氰基未环化指数、环化反应起始温度及表观活化能低,环化反应速率快,这可能由于IA分子结构含有2个羧基,引发活性点较多,可以在低温条件下引发氰基环化形成更多的梯形结构.     

有机磺酰氯在自由基聚合中的应用进展

有机磺酰氯存在下的自由基聚合(Radical polymerization,RP)具有反应条件温和、体系组成简单、单体适用范围较广的优点。本文主要概述了有机磺酰氯在自由基聚合中的应用,主要包括原子转移自由基聚合(Atom transfer radical polymerization,ATRP)的引发剂、单电子转移活性自由基聚合(Single-electron transfer living radical polymerization,SET-LRP)的引发剂和普通自由基聚合的链转移剂。并分析了以上三种应用单体的适用范围、有机磺酰氯结构与聚合活性的关系以及有机磺酰氯(多官能团有机磺酰氯引发剂和链转移单体)在聚合物分子设计中的应用。     

Simultaneous determination of components released from dental composite resins in human saliva by liquid chromatography/multiple-stage ion trap mass spectrometry

Dental composite resins are widely used for fixing teeth; however, the monomers used in dental composite resins have been found to be cytotoxic and genotoxic, namely triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), and bisphenol A glycol dimethacrylate (Bis-GMA). In this study, we incubated dental composite resins with human saliva for demonstrating the released monomers and biodegradation products. A simple saliva sample dilution method without purification or derivatization was used for quantification. We found that liquid chromatography coupled with multiple-stage ion trap mass spectrometry (LC-MS(n) ) operated in selected reaction monitoring (SRM) mode was able to separate the three monomers within 10 min. The calibration curves were linear (R2 >0.996) over a wide range for each monomer in saliva: TEGDMA, 5-500 ppb; UDMA, 5-100 ppb, and Bis-GMA, 5-700 ppb. Furthermore, several biodegradation products were discovered with data-dependent MS/MS scan techniques. Although TEGMA degradation products have previously been reported, we identified two previously unknown UDMA degradation products. The LC-MS/MS method developed in this study was able to successfully quantify monomers and their principal biodegradation products from dental composite resins in human saliva.     

Chemorheology of photopolymerizable acrylates using a modified Boltzmann sigmoidal model

Experiments were conducted to evaluate the influence of ambient photoconversion on rheology for a range of photopolymerizable urethane dimethacrylate (UDMA) resins containing varying amounts of three comonomers including 1,6 hexane diol‐dimethacrylate (HDDMA), an alkoxylated cyclohexane dimethanol diacrylate monomer (CD‐582), and hydroxyethyl methacrylate (HEMA). Experiments were performed both as a function of composition and time‐dependent dose varying the intensity using a photorheometer. A semilog‐based sigmoidal model allowed the determination of four physical model parameters to define the relationship between reaction kinetics and its dynamic influence on viscosity. We have observed induction times and viscosity changes associated with the model that shows a trend in reaction kinetics in the following order from most to least reactive: UDMA > CD582 > HDDMA > HEMA. With increasing amounts of reactive diluent included in the formulation, the kinetics of reaction was more sluggish. The value of this sigmoidal model is that it could help define formulation and process conditions most likely to control crosslinking to maximize dimensional stability or other thermophysical properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2319–2325, 2008     

SWELLING AND WETTABILITY OF LIGHT-CURED METHACRYLATE-BASED DENTAL RESINS PREPARED FROM CHOLIC ACID

2 '-methacryloxy-3α, 7α 12α- trimethacryloyl cholic acid ethyl ester (CAGE4MA) has been prepared from cholic acid. Photo-polymeric resins were prepared from CAGE4MA. 2,2-bis[4-(2-hydroxy-3-methacrylyloxypropoxy)phenyl]propane (bis-GMA) was used for comparison, triethyleneglycol dimethacrylate (TEGDMA) was used as diluent. The polymerization was initiated by camphoroquinone (CQ)/N, N-dimethylaminoethyl methacrylate (DMAEMA) system. The conversion of CAGE4MA was 39% when the reaction time is 60s, which is lower than bis-GMA and TEGDMA.The swelling value of CAGE4MA resin was 0.41% in distilled water, which is much lower than those of bis-GMA resin (2.04%) and TEGDMA resin (4.77%) under the same conditions. Copolymers from CAGE4MA and TEGDMA have been prepared. With the increase of TEGDMA in mixture, the degree of conversion of CA GE4MA and swelling value increased. The swelling values of photocured resins in 0. 1mol/L HCl were also measured.     

Thermal degradation and isoconversional kinetic analysis of light-cured dimethacrylate copolymers

Thermal degradation kinetics of copolymers based on bis-phenol A ethoxylated dimethacrylate (Bis-EMA) with triethylene glycol dimethacrylate (TEGDMA), and urethane dimethacrylate (UDMA) with TEGDMA in wt/wt ratios 30/70, 50/50, or 70/30 were investigated using thermogravimetric analysis as a means to provide specific information regarding the internal structures of these resins. Thermogravimetric scans were taken at four different heating rates to perform an isoconversional analysis to determine the change of the effective activation energy as a function of conversion. A two-step degradation mechanism was found to occur in almost all copolymer compositions attributed to the existence of inhomogeneities in the macromolecular structure and the formation of weak links inside the polymeric network.     

Synthesis and photopolymerization of piperonylamine derivatives as a polymerizable cyclic acetals co‐initiator for light‐cured unfilled dental resins

The aim of this study was to synthesize and characterize N,N‐di(methacryly‐ethoxycarbonyl‐ethyl)‐N‐(1,3‐benzodioxole‐ 5‐methylene)(DMEBM) to replace both triethylene glycol dimethylacrylate(TEGDMA) as a dilute and the non‐polymerizable amine, which is added as a co‐initiator in dental resin mixtures. 2,2‐bis[4‐(2‐Hydroxy‐3‐methacryloxypropoxy) phenyl]‐propane (Bis‐GMA) and camphorquinone (CQ) were used as monomer and photoinitiator in these model dental resin systems, in contrast to ethyl 4‐dimethylaminobenzoate (EDMAB) which was usually used as a co‐initiator. DMEBM was synthesized via Michael‐Addition reaction and characterized using ¹H NMR spectroscopy. A mixture of Bis‐GMA/DMEBM/CQ was found to reach the double bond conversion of 67.5%, slightly higher than that of Bis‐GMA/TEGDMA/CQ/EDMAB (66.8%) and Bis‐GMA/TEGDMA/CQ/DMEBM (64.8%). In addition, the glass transition temperature of Bis‐GMA/TEGDMA/CQ/EDMAB (93.4°C) were higher than that of Bis‐GMA/TEGDMA/CQ/DMEBM (89.3 °C) and Bis‐GMA/DMEBM/CQ (80.4°C). The water sorption and solubility of Bis‐GMA/TEGDMA/CQ/DMEBM were higher than that of Bis‐GMA/TEGDMA/CQ/EDMAB and Bis‐GMA/DMEBM/CQ. However, the values were still within the range of the ISO 4049 standards. DMEBM could be used as a potential co‐initiator and diluent for dental composite. Copyright © 2009 John Wiley & Sons, Ltd.     

一种可聚合光引发体系及其性能研究

合成了一种可聚合双分子光引发体系——甲基丙烯酸-4-二苯酮甲酯(BPMM)光引发剂和甲基丙烯酸-3,4-亚甲基二氧基苯甲酯(MDBMM)助引发剂.采用含有水平样品支架的实时红外光谱仪(RTIR)监测光聚合动力学,动态力学分析仪(DMA)研究固化膜的机械性能.结果表明,聚合体系的聚合速率(Rp)和最终双键转化率(Pf)随MDBMM浓度的增加而增加,但是,随BPMM的浓度变化出现一最佳值(0.8%);相同的聚合条件下,与传统引发体系相比,BPMM/MDBMM虽然引发活性较差,但是其固化膜的Pf和玻璃化转变温度以及在37℃左右的储能模量与传统引发体系相近,并且MDBMM作为天然可食用植物化学成分衍生物的特点使其有可能适宜于在生物相容性要求较高的领域中应用.     

Syntheses of biodegradable polymer networks based on polycaprolactone and glutamic acid

Biodegradable trifunctional oligomer was synthesized from polycaprolactone and glutamic acid and characterized by Fourier‐transform infrared (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectroscopies. Injectable and in situ crosslinkable polymer networks were fabricated by the copolymerization of oligomer with triethylene glycol dimethacrylate (TEGDMA) and used to evaluate the initial compressive strengths, viscosities, shrinkages, thermal stabilities, and biodegradabilities in the forms of polymer network neat resin and their composites with β‐tricalcium phosphate. The initial compressive strengths (CS) values of neat resins ranged from 9.54 to 187.6 MPa. Both neat resins and composites had polymerization shrinkage ranging from 0% to 11.7%, which increased with increasing of TEGDMA contents in resin. Moreover, in polymer composite resins, shrinkage values decreased with increasing filler level from 0% to 4.6%, and exothermic evolution values decreased from 33.5°C to 29.7°C as increasing filler level. The composite with the formulation of (polycaprolactone)‐glutamate triacrylate (PCLGTA)/TEGDMA (25/75) and powder/liquid (P/L) ratio of 1.0 exhibited the highest exothermal and lowest shrinkage values. The increase of oligomer in the formulation led to an increase in viscosity.     

樟脑酮/过氧化物复合体系引发丙烯酸酯可见光聚合反应

采用差热扫描方法（ＤＳＣ）研究了樟脑酮（ＣＱ）／过氧化物（ＰＯ）复合体系引发三缩乙二醇双甲基丙烯酸酯（ＴＥＧＤＭ）的可见光聚合．与ＣＱ单一引发体系相比,ＣＱ和ＰＯ组成的复合体系更为有效．实验结果指出,加入过氧化物,如ＤＣＰＯ和ＤＢＰＯ,使聚合速率显著增加,最大速率到达时间明显缩短,然而它们对应的过氧化氢化合物,如ＴＢＨＰ、ＣＭＨＰ却效果不佳,复合体系的增效作用表明,激发态ＣＱ通过能量传递机制,使过氧化物发生有效的光解生成活性自由基,同时发现在含氧的条件下聚合反应速率得到增加．     

含硅丙烯酸酯化合物光固化性能的研究

本文主要研究含硅丙烯酸酯预聚物ANS的感光性能及光敏剂种类、活性稀释剂丙烯酸 β 羟乙酯 (HEA)用量、预聚体ANS本身结构对ANS感光体系感光性能的影响.发现ANS具有很高光敏性,其紫外响应峰在 334mm处.安息香双甲醚 (651)作为ANS的光引发剂,引发效果最好.活性稀释剂HEA可以降低体系的粘度,提高光固化膜透光率,调解光固化物的性能.预聚体结构不同,其感光性能有着很大差别.     

Characterization of dimethacrylate polymeric networks: a study of the crosslinked structure formed by monomers used in dental composites

The resin phase of dental composites is mainly composed of combinations of dimethacrylate comonomers, with final polymeric network structure defined by monomer type/reactivity and degree of conversion. This fundamental study evaluates how increasing concentrations of the flexible triethylene glycol dimethacrylate (TEGDMA) influences void formation in bisphenol A diglycidyl dimethacrylate (BisGMA) co-polymerizations and correlates this aspect of network structure with reaction kinetic parameters and macroscopic volumetric shrinkage. Photopolymerization kinetics was followed in real-time by a near-infrared (NIR) spectroscopic technique, viscosity was assessed with a viscometer, volumetric shrinkage was followed with a linometer, free volume formation was determined by positron annihilation lifetime spectroscopy (PALS) and the sol–gel composition was determined by extraction with dichloromethane followed by ¹H NMR analysis. Results show that, as expected, volumetric shrinkage increases with TEGDMA concentration and monomer conversion. Extraction/¹H NMR studies show increasing participation of the more flexible TEGDMA towards the limiting stages of conversion/crosslinking development. As the conversion progresses, either based on longer irradiation times or greater TEGDMA concentrations, the network becomes more dense, which is evidenced by the decrease in free volume and weight loss after extraction in these situations. For the same composition (BisGMA/TEGDMA 60–40 mol%) light-cured for increasing periods of time (from 10 to 600 s), free volume decreased and volumetric shrinkage increased, in a linear relationship with conversion. However, the correlation between free volume and macroscopic volumetric shrinkage was shown to be rather complex for variable compositions exposed for the same time (600 s). The addition of TEGDMA decreases free-volume up to 40 mol% (due to increased conversion), but above that concentration, in spite of the increase in conversion/crosslinking, free volume pore size increases due to the high concentration of the more flexible monomer. In those cases, the increase in volumetric shrinkage was due to higher functional group concentration, in spite of the greater free volume. Therefore, through the application of the PALS model, this study elucidates the network formation in dimethacrylates commonly used in dental materials.