苯并噁嗪单体的分子设计及其合成研究进展

聚苯并噁嗪是近二三十年发展起来的一类新型热固性树脂.其重复单元是含氮、氧杂环结构的化合物,高温下可在无催化剂的情况下发生开环反应形成聚合物.聚苯并噁嗪具备熔体黏度低、易加工、成型收缩率接近零以及固化过程无挥发性物质产生等独特的优点,同时还保持了传统酚醛树脂优良的热稳定性、电绝缘性和机械性能.苯并噁嗪单体最大的优点在于其分子设计的灵活性,通过设计反应底物或者控制固化工艺可合成各种具有特定结构和性质的苯并噁嗪单体和树脂.主要从单官能度、双官能度、多官能度三方面概述了几种苯并噁嗪单体的类型及其合成方法.     

聚苯并噁嗪高性能化:分子设计、合金与纳米复合物

聚苯并噁嗪通过环状苯并噁嗪单体热诱导开环聚合得到,作为一种新型的酚醛树脂,不仅具有传统酚醛树脂的耐热、低吸水性等性质,还具有传统酚醛树脂不具备的性能,如分子设计的灵活性、固化反应没有小分子副产物产生、优异的尺寸稳定性以及良好的阻燃性能,在微电子、印刷电路板、电子封装以及航空航天等高技术领域具有广阔的应用前景.然而,聚苯并噁嗪缺点是固化温度高、固化材料脆性大.本文介绍了聚苯并噁嗪性能增强的各种方法,包括新型单体分子设计、引入可交联单元、高相对分子质量聚合物前体制备、聚合物合金化、纳米复合等.最近,石墨烯和笼型聚倍半硅氧烷(POSS)与聚苯并噁嗪复合材料因具有优异的热性能和电学性能,成为先进电子材料的潜力材料.     

含双螺环三聚磷腈单元的苯并噁嗪树脂的结构和热稳定性

以双螺环取代三聚磷腈基双苯甲酰氯和4-氨基(N-苯基)苯并噁嗪单体为原料合成了一种含双螺环取代三聚磷腈结构单元的苯并噁嗪树脂单体(HCP-5);采用傅立叶变换红外光谱仪(FT-IR)和核磁共振谱仪(1 H NMR,13 C NMR,31P NMR)表征了苯并噁嗪树脂单体的结构,基于FT-IR和示差扫描量热法研究了其固化行为,并利用热重分析和示差热重分析研究了HCP-5树脂单体、均聚物及其与双酚A型苯并噁嗪树脂(Bz)共聚物的热稳定性.结果表明,HCP-5均聚物具有很好的热稳定性和成炭性,其在317℃下的热失重为5%,在800℃下的残炭率为50%,可用于普通苯并噁嗪树脂改性.此外,HCP-5/Bz(1∶1;质量分数)共聚物在332℃下的热失重为5%,在800℃下的残炭率为48%.     

一种不含β-氢的苯并噁嗪的表征分析及催化固化研究

以邻烯丙基双酚A、多聚甲醛和烯丙基胺为原料，采用无溶剂的方法合成了一种不含β-氢的苯并噁嗪(2，2-二(3，8-二烯丙基-3，4-二氢-2H-1，3-苯并噁嗪)-丙烷(B—dbo)．GPC和元素分析结果表明，此噁嗪中间体主要是单量体和二聚体．用FTIR和^1H NMR对中间体结构进行了表征．结果表明，此苯并噁嗪的分子结构中存在三种反应官能团：噁嗪环、N-烯丙基、Ar-烯丙基．用DSC和FTIR研究三种反应基团在固化时的反应情况．将双酚A、邻烯丙基双酚A、TiCl4和PCl5作为催化剂按适量的比例加入B—dbo中，用DSC研究其固化行为，并对TiCl4催化试样在不同的固化温度下进行FTIR测试分析，提出在TiCl4催化下苯并噁嗪环副反应及开环固化机理．     

3-甲基邻苯二酚/糠胺型聚苯并噁嗪的制备与性能

通过分子设计合成了含有酚羟基的3-甲基邻苯二酚/糠胺型苯并噁嗪(M-f). 通过差示扫描量热法(DSC)测得M-f的放热峰值温度(T_p)为172 ℃, 而间甲酚/糠胺型苯并噁嗪(MC-f)的T_p为244 ℃, 表明酚羟基的引入有利于降低苯并噁嗪的开环固化温度. 通过非等温DSC法研究2种苯并噁嗪单体的固化动力学, Kissinger法和Ozawa法的计算结果均表明M-f的表观活化能低于MC-f. 此外, 通过拉伸剪切强度测试考察了聚苯并噁嗪对于金属基材的黏附性能, M-f聚合物对于铝和低碳钢基材的拉伸剪切强度分别为2.53 MPa和3.09 MPa, 均高于MC-f聚合物.     

对炔丙氧基苯基噁唑啉的合成及改性苯并噁嗪树脂的研究

通过四步法合成了对炔丙氧基苯基噁唑啉(p-propynyloxyphenyl-2-oxazoline简称POPO),采用核磁共振氢谱(1H-NMR)、傅立叶红外光谱(FTIR)、气相色谱质谱联用仪(GC-MS)和元素分析证实了其分子结构,以示差扫描量热仪(DSC)和热重分析(TGA)揭示了其固化行为和热分解性质,该化合物熔点为120℃,起始固化温度为200℃,固化峰值温度为280℃,自固化产物5 wt%热失重温度为321℃.在此基础上,通过溶液共混法制备了双酚A型苯并噁嗪(BZ)/对炔丙氧基苯基噁唑啉(POPO)共聚树脂,且对其固化机理、固化产物的热分解性质和动态力学性能进行考察.结果表明,该噁唑啉作为交联剂,与苯并噁嗪发生开环聚合和自身炔基发生三聚成环反应,使固化产物的交联密度增加,DSC、TG和动态热机械分析(DMA)表明噁唑啉的引入提高了固化树脂的热性能和动态力学性能.且在噁唑啉含量为10 wt%时,固化树脂的综合性能较优,较之纯的双酚A型苯并噁嗪树脂,起始固化温度从215℃降低至180℃,残碳率从28%提高至44%,玻璃化转变温度从166℃提高至186℃.     

新型生物基苯并嗪的合成及性能

以生物基糠胺、 酚酞和多聚甲醛为原料, 制备了一种新型生物基苯并噁嗪树脂——酚酞糠胺型苯并噁嗪树脂(PPTL-F-BOZ), 采用FTIR, ¹H NMR和 ¹³C NMR等手段对其单体PTL-F-BOZ的结构进行了表征, 并对其固化反应、 耐热和阻燃性能进行分析. 结果表明, 与传统的化石基双酚型苯并噁嗪——双酚A苯胺型苯并噁嗪(BPA-A-BOZ)相比, PTL-F-BOZ显示出较低的固化反应温度, 且糠胺中呋喃环的存在会增加聚合物的交联密度, 并减缓苯氧结构向苯酚结构的重排反应, 致使其在DSC曲线中出现了2个固化峰. PPTL-F-BOZ树脂具有较高的T_5%(质量损失5%的温度)和800 ℃的残炭率, 其极限氧指数(LOI)高达36.2%, 在垂直燃烧中达到V-0等级, 表现出优异的热稳定性和阻燃性能.     

聚苯并噁嗪/POSS杂化材料

苯并噁嗪是一类新型的热固性树脂,它以良好的机械性能、热稳定性、可加工性、分子可设计性以及固化无小分子释放等优点而备受关注。然而,苯并噁嗪树脂存在的脆性大、韧性差等不足也是其研究改进的焦点。本文概述了近年苯并噁嗪树脂的研究进展,着重介绍了课题组在聚苯并噁嗪/POSS杂化材料方面的研究思路和具体实例。聚苯并噁嗪/POSS杂化材料研究结果表明,杂化结构的引入能明显改善苯并噁嗪树脂的综合性能,这对苯并噁嗪树脂及其复合材料以及其它热固性树脂体系的研究具有一定的指导意义。     

双酚芴双胺型苯并嗯嗪树脂的合成、结构及热性能

以9-芴酮、苯酚为原料,以质量分数为98%的浓硫酸为催化剂,2-巯基丙酸为助催化剂,合成了双酚芴[9,9-双(4-羟苯基)芴],再用其与乙二胺和多聚甲醛反应,合成了线性双酚芴双胺型苯并噁嗪树脂(BF-eda树脂).采用FTIR,'H NME和<'13>C NMR等分析手段对双酚芴和BF-eda树脂的化学结构进行了表征;...     

苯并噁嗪/环氧树脂/4,4′-二氨基二苯砜三元共混体系玻璃化转变温度的研究

采用动态热机械分析(DMA)研究了苯并噁嗪/环氧树脂/4,4′-二氨基二苯砜(DDS)三元共混体系玻璃化转变温度(Tg)与固化剂DDS含量的关系.随着DDS含量的增加,三元体系的交联密度呈现先增加后降低的变化趋势,介于聚苯并噁嗪和苯并噁嗪/环氧树脂体系之间;但是三元体系的Tg却逐渐降低,当DDS的含量超过20 mol%时,低于聚苯并噁嗪的Tg.差示扫描量热法(DSC)的结果表明,DDS对苯并噁嗪和环氧树脂都有很强的固化效果.通过测定体系的凝胶化时间,借助Arrhenius方程,判断三元体系的初始反应过程,推测了固化体系可能的网络化学结构.对各体系DMA曲线中损耗模量,储能模量和力学损耗因子的变化情况分析,结果表明体系最终Tg受氢键相互作用、交联密度和网络规整性以及链段的刚性等因素综合影响,其中氢键的类型和相互作用的强弱对Tg的影响最大.     

Synthesis, curing kinetics and thermal properties of novel difunctional chiral and achiral benzoxazines with double chiral centers

Novel difunctional chiral and achiral benzoxazine monomers were synthesized from the reaction of bisphenol A with paraformaldehyde and primary amines, including S-(+)-3-methyl-2-butylamine and rac-(±)-3-methyl-2-butylamine, by solventless method. The chemical structures of chiral and achiral benzoxazines were identified by fourier transform infrared, nuclear magnetic resonance (¹H NMR and ¹³C NMR). The curing behavior and non-isothermal curing kinetics of chiral and achiral benzoxazine monomers were investigated by differential scanning calorimeter (DSC). Isoconversional methods based on Friedman and Kissinger–Akahira–Sunose were applied to analyze the curing process of chiral and achiral benzoxazines. The thermal properties of cured polymers were characterized by DSC and thermogravimetry. The results suggested that the optical purity and stereo-configuration for chiral and achiral benzoxazines have definite influence on curing behavior and thermal properties despite the same chemical structure. Chiral benzoxazine displayed typical characteristics of difunctional benzoxazines. Achiral benzoxazine showed distinctly double peaks in DSC exotherms due to the presence of racemic and mesomeric isomers. The thermal properties of achiral polybenzoxazine were slightly higher than those of chiral polybenzoxazine, and were much higher than those of other bisphenol A-C₃–C₈ linear aliphatic amine-based polybenzoxazines because of tight packing, low free volume, and abundant intramolecular and intermolecular hydrogen bonds in network structure of polymers.     

Synthesis, curing behavior and thermal properties of fluorene containing benzoxazines

A series of difunctional fluorene-based benzoxazine monomers were synthesized from the reaction of 9,9-bis-(4-hydroxyphenyl)-fluorene with formaldehyde and primary amines including aniline, o-toluidine, n-butylamine, and n-octylamine. Their chemical structures were confirmed by FT-IR, ¹H and ¹³C NMR analyses. The curing behaviors of the precursors were monitored by differential scanning calorimetry (DSC) and FT-IR. The thermal properties of cured polymers were evaluated with DSC and thermogravimetric analysis (TGA). The fluorene-based polybenzoxazines show the typical curing characteristic of oxazine ring-opening for difunctional benzoxazines centred at 231-250 °C, and remarkably higher glass transition temperature and better thermal stability ascribed to the high rigidity, high aromatic content, and intermolecular and intramolecular hydrogen bonding. The thermal decomposition temperature and char yield of aromatic amine-fluorene-based polybenzoxazines are much higher than those of aliphatic amine-based polybenzoxazines.     

Synthesis and properties of flame‐retardant benzoxazines by three approaches

We propose three approaches to obtain flame‐retardant benzoxazines. In the first approach, we synthesize a novel benzoxazine (dopot‐m) from a phosphorus‐containing triphenol (dopotriol), formaldehyde, and methyl amine. Dopot‐m is copolymerized with a commercial benzoxazine [6′,6‐bis(3‐phenyl‐3,4‐dihydro‐2H‐1,3‐benzoxazineyl)methane (F‐a)] or diglycidyl ether of bisphenol A (DGEBA). The thermal properties and flame retardancy of the F‐a/dopot‐m copolymers increase with the content of dopot‐m. As for the dopot‐m/DGEBA curing system, the glass‐transition temperature of the dopot‐m/DGEBA copolymer is 252 °C, which is higher than that of poly(dopot‐m). The 5% decomposition temperature of the dopot‐m/DGEBA copolymer increases from 323 to 351 °C because of the higher crosslinking density caused by the reaction of phenolic OH and epoxy. In the second approach, we incorporate the element phosphorus into benzoxazine via the curing reaction of dopotriol and F‐a. After the curing, the thermal properties of the F‐a/dopotriol copolymers are almost the same as those of neat poly(F‐a), and this implies that we can incorporate the flame‐retardant element phosphorus into the polybenzoxazine without sacrificing any thermal properties. In the third approach, we react dopo with electron‐deficient benzoxazine to incorporate the element phosphorus. After the curing, the glass‐transition temperatures of polybenzoxazines decrease slightly with the content of dopo, mainly because of the smaller crosslinking density of the resultant polybenzoxazines. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3454–3468, 2006     

Recent advancement on polybenzoxazine—A newly developed high performance thermoset

Polybenzoxazine is a newly developed addition polymerized phenolic system, having a wide range of interesting features and the capability to overcome several shortcomings of conventional novolac and resole type phenolic resins. They exhibit (i) near zero volumetric change upon curing, (ii) low water absorption, (iii) for some polybenzoxazines T_g much higher than cure temperature, (iv) high char yield, (v) no strong acid catalysts required for curing, (vi) release of no byproduct during curing and also possess thermal and flame retarding properties of phenolics along with the mechanical performance. Though benzoxazine based materials possess several advantages, they have not yet became very attractive to the industries. To improve the mechanical properties and processibility several strategies have been reported including (i) synthesis of benzoxazine monomers with additional functionality, (ii) incorporation of benzoxazine in polymer chain, and (iii) benzoxazine based composites or alloys. In this article, we have discussed about the recent development of benzoxazine chemistry. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5565–5576, 2009     

Synthesis, curing kinetics and thermal properties of bisphenol-AP-based benzoxazine

A novel bisphenol-AP-aniline-based benzoxazine monomer (B-AP-a) was synthesized from the reaction of 4,4′-(1-phenylethylidene) bisphenol (bisphenol-AP) with formaldehyde and aniline. The chemical structures were identified by FT-IR, ¹H and ¹³C NMR analyses. The polymerization behavior of the monomer and the types of hydrogen bonding species were monitored by differential scanning calorimetry (DSC) and FT-IR. The curing kinetics was studied by isothermal DSC and the isothermal kinetic parameters were determined. The thermal properties of cured benzoxazine were measured by DSC and thermogravimetric analysis (TGA). The bisphenol-AP-aniline-based polybenzoxazine (poly(B-AP-a)) exhibited higher glass transition temperature (T_g) and better thermal stability than corresponding bisphenol A-aniline-based polybenzoxazines (poly(BA-a)). The T_g value of poly(B-AP-a) is 171 °C. The temperatures corresponding to 5% and 10% weight loss is 317 and 347 °C, respectively, and the char yield is 42.2% at 800 °C. The isothermal curing behavior of B-AP-a displayed autocatalysis and diffusion control characteristics. The modified autocatalytic model showed good agreement with experimental results.     

Synthesis and properties of new polybenzoxazines containing (substituted) cyclohexyl moieties

A series of new polybenzoxazines were synthesized based on diphenols containing (substituted) cyclohexyl moiety and were characterized by FT‐IR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. These new benzoxazine monomers exhibited better processability with lower peak cure temperature and a wide cure controllable window (CCW) as manifested in differential scanning calorimetric analysis. The cure analysis was performed by FT‐IR spectroscopy. Glass transition temperature of new polybenzoxazines varied from 170 to 205°C. The cyclohexyl bridge groups facilitated ring opening, resulting in polymer with improved thermal stability in comparison to bisphenol A‐based benzoxazine as assessed by the various thermal analyses. The water contact angles of polybenzoxazines containing (substituted) cyclohexyl moieties were higher than that of bisphenol A‐based polybenzoxazine, implying their higher hydrophobicity. Copyright © 2009 John Wiley & Sons, Ltd.     

Development of a DOPO-containing benzoxazine and its high-performance flame retardant copolybenzoxazines

A DOPO-containing benzoxazine, which could not be prepared by the traditional approaches, was successfully prepared from phenol, aniline and DOPO by a three-step procedure. The first step is the condensation of 2-hydroxybenzaldehyde with aniline, forming an intermediate imine. The second step is the addition of DOPO to the imine resulting a secondary amine. The third step is the ring closure condensation leading to DOPO-containing benzoxazine. All these structures were confirmed by 1D and 2D NMR spectra. The curing of mixtures of DOPO-containing benzoxazine and benzoxazine of bisphenol A has been studied. In the samples the molar ratio of benzoxazine monomers was varied to achieve different phosphorus content. The phosphorus-containing polybenzoxazines have been characterized by dynamic mechanical thermal analysis and thermogravimetric analysis. Limiting oxygen index values indicates good flame retardant properties.     

Synthesis and characterization of fluid 1,3‐benzoxazine monomers and their thermally activated curing

Novel mono‐ and difunctional aliphatic oxyalcohol‐based benzoxazines have been synthesized and characterized in detail. Molecular structures of the monomers were investigated by spectral analysis. The obtained benzoxazine monomers exhibit fluidic behavior, which makes them particularly useful for many applications compared to other traditional benzoxazines. Differential scanning calorimetry was used to monitor the thermal crosslinking behavior of synthesized monomers. Mono‐ and bifunctional benzoxazine monomers exhibited low curing exhothermic peak with the onset around 173 and 180 °C, respectively. Relatively, low ring‐opening polymerization temperature was due to the hydroxyl groups present in the structure of the monomers. The hydrogen bonding of hydroxyl groups may cause alignment of the monomers in the liquid state. Thermal stabilty of the polybenzoxazines was studied by thermogravimetric analysis. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Synthesis and curing of amino‐containing benzoxazine as a novel hardener for diglycidyl ether of bisphenol‐A

Benzoxazines containing various additional functional groups have been extensively reported to improve the properties of polybenzoxazines. In this work, a novel amino‐containing benzoxazine (PDETDA‐NH₂) was conveniently synthesized from diethyltoluenediamine (DETDA), 2‐hydroxybenzaldehyde, and paraformaldehyde and was used as a hardener for diglycidyl ether of bisphenol‐A (DGEBA). The curing behaviors of PDETDA‐NH₂ and PDETDA‐NH₂/DGEBA systems were studied by DSC, FT‐IR, and ¹H NMR. When curing, PDETDA‐NH₂ was firstly polymerized to N,O‐acetal‐type polymer and then rearranged to Mannich‐type polymer at elevated temperature, while the addition reaction between amino and benzoxazine was discouraged because of the steric hindrance of alkyl substituents. During PDETDA‐NH₂/DGEBA curing, it was found that the reactions happened in the order of addition polymerization of amino and epoxide, ring‐opening polymerization of benzoxazine, etherification between phenolic hydroxyl of the polymerized benzoxazine, and epoxide. Compared with DETDA cured DGEBA, PDETDA‐NH₂ cured DGEBA showed higher modulus, higher char yield, and much lower water uptake.     

Synthesis,characterization, and polymerization of brominated benzoxazine monomers and thermal stability/flame retardance of the polymers generated

Novel monofunctional brominated benzoxazine 3‐(2,4,6‐tribromophenyl)‐3,4‐dihydro‐2H‐1,3‐benzoxazine (P‐bra) and bifunctional brominated benzoxazine 6,6′‐bis(3‐(2,4,6‐tribromophenyl)‐3,4‐dihydro‐2H‐1,3‐benzoxazinyl) isopropane (B‐bra) were prepared and highly thermally stable polybenzoxazines were obtained by the thermal cure of the corresponding benzoxazines monomers. The chemical structures of these novel monomers were confirmed by FITR, ¹H‐NMR and elemental analysis. FTIR spectra and differential scanning calorimetry (DSC) suggested that the polymerization was thermally initiated and occurred via ring‐opening of the monomer in each case. Thermogravimetric analysis (TGA) indicated that brominatation could have a profound effect on increasing char yield and on thermal degradation temperatures. The results of UL‐94 burn test showed that the polybenzoxazines prepared from P‐bra and B‐bra had good flame retardance. Copyright © 2009 John Wiley & Sons, Ltd.