一种自引发自交联苯并口恶嗪的合成及热性能分析

苯并口恶嗪树脂(Bz)是一类耐热性很好和残炭率较高的酚醛树脂。结合光聚合技术,通过分子设计合成出具有新型功能的苯并口恶嗪单体,使用核磁氢谱和傅里叶变换红外光谱对其结构进行表征和确认。利用实时红外研究其光聚合行为,透射红外研究其热固化行为;萃取法和热重分析分别测其凝胶含量以及热稳定性。实验结果表明,合成出的新型苯并口恶嗪(BZOA)具有自引发自交联功能,双键转化率最大可达99.96%。热聚合过程中先碳碳双键反应而后开环固化,热固化产物的凝胶含量达到91.36%。随着BZOA量的增加,BZOA共聚物的残炭率(Yc)从0.48%升高到29.03%,耐热性能显著提高。     

苯并口恶嗪/环氧树脂/酚醛树脂共混体系的催化固化行为研究进展

苯并口恶嗪/环氧树脂/酚醛树脂三元共混体系在一定程度上克服了苯并口恶嗪树脂固化温度高、固化时间长这一缺点,且具有优异的耐热性、介电性能、尺寸稳定性和低吸湿性等综合性能。基于苯并口恶嗪的一元、二元催化固化体系是研究其三元共混体系的理论基础,文中除了重点讲述苯并口恶嗪/环氧树脂/酚醛树脂三元共混体系的催化与固化行为,还对苯并口恶嗪及其与环氧树脂、酚醛树脂的二元共混体系的催化固化行为进行了简要的概述。     

低介电苯并口恶嗪树脂的研究进展

苯并口恶嗪树脂作为一种新型的酚醛树脂,具有分子设计性强,固化过程无小分子释放,热稳定性和力学性能优异,残炭率高等优点,使其成为电子通讯行业的重要基体材料。为满足高频、高速通信技术对低介电高分子树脂的应用需要,苯并口恶嗪树脂的低介电改性对于信号的高频、高速传播具有重要意义,这引起了材料研究者的广泛关注。文中综述了近年来对苯并口恶嗪树脂进行低介电改性的一系列研究工作,包括新单体合成,无机-有机杂化,与其它树脂共聚等,并对低介电苯并口恶嗪树脂的研究趋势进行了概述。     

静电纺丝技术制备聚苯并口恶嗪基复合纤维及热性能

苯并口恶嗪树脂(Bz)是一类具有耐热性好和残炭率高的酚醛树脂。文中以聚氧化乙烯(PEO)为基体,与合成的主链型聚苯并口恶嗪(PBA-AD6)共混,利用静电纺丝技术制备了聚苯并口恶嗪基复合纤维。通过核磁共振和红外光谱验证了PBA-AD6的化学结构,扫描电子显微镜和热重分析仪对复合纤维的形态和直径及热稳定性进行了分析。实验结果表明,m(PBA-AD6)/m(PEO)=7/3时,纤维具有一定的柔韧性且无串珠结构,并随着PEO量的增加,纤维直径分布趋于均一。在热处理过程中,苯并口恶嗪发生热开环聚合反应。当m(PBA-AD6)/m(PEO)=9/1其热稳定性最好。     

DOPO对苯并口恶嗪树脂的阻燃改性

采用9,10-二氢-9-氧杂-10-磷菲-10-氧化物(DOPO)与二苯甲烷二胺型苯并口恶嗪(BOZ-M)混合,制备了固化浇铸体。采用差示量热扫描(DSC)、动态机械分析(DMA)、垂直燃烧试验、热失重分析(TGA)及扫描电镜(SEM)对浇铸体性能进行了分析和研究。结果表明,DOPO可以和苯并口恶嗪树脂发生开环加成反应,进而将DOPO分子结合到聚苯并口恶嗪树脂的网络结构中;当DOPO的含量大于5%,即可以使聚苯并口恶嗪树脂的阻燃性达到UL-94V0级;DOPO的加入,降低了聚苯并口恶嗪树脂的交联密度和玻璃化转变温度,但提高了它的高温残炭量。     

基于酚醛三元聚合体系的固化行为及性能EI北大核心

以环氧豆油(ESO)醚化接枝改性酚醛树脂,而后以剩余酚羟基为酚源在树脂结构中引入苯并口恶嗪环,合成了一种具有优异韧性和热稳定性的环氧大豆油、苯并口恶嗪及酚醛三元共聚树脂(ESO-PA-PF)。采用红外光谱(FT-IR)表征了改性树脂的分子结构,以差示扫描量热法(DSC)对改性树脂的固化行为进行了分析,阐述了各组分对树脂固化行为的影响机理。热重分析法(TG)对热稳定性的分析表明,改性树脂的热稳定性较酚醛树脂及环氧豆油改性酚醛树脂有很大程度提高。共聚改性树脂具有较高的冲击韧性及弯曲强度,用扫描电镜(SEM)观察了改性酚醛树脂样品冲击断面的微观形貌,并对树脂的增韧机理进行了探讨。     

基于酚醛三元聚合体系的固化行为及性能

以环氧豆油(ESO)醚化接枝改性酚醛树脂,而后以剩余酚羟基为酚源在树脂结构中引入苯并口恶嗪环,合成了一种具有优异韧性和热稳定性的环氧大豆油、苯并口恶嗪及酚醛三元共聚树脂(ESO-PA-PF)。采用红外光谱(FT-IR)表征了改性树脂的分子结构,以差示扫描量热法(DSC)对改性树脂的固化行为进行了分析,阐述了各组分对树脂固化行为的影响机理。热重分析法(TG)对热稳定性的分析表明,改性树脂的热稳定性较酚醛树脂及环氧豆油改性酚醛树脂有很大程度提高。共聚改性树脂具有较高的冲击韧性及弯曲强度,用扫描电镜(SEM)观察了改性酚醛树脂样品冲击断面的微观形貌,并对树脂的增韧机理进行了探讨。     

含双螺环取代三聚磷腈结构苯并口恶嗪树脂的合成与性能

以六氯环三聚磷腈,1,1′-二羟基联苯,对羟基苯甲酸乙酯和含活泼官能团的苯并口恶嗪单体为原料合成了含双螺环取代三聚磷腈结构的苯并口恶嗪单体(HCP)。采用FT-IR,1 H-NMR,13 C-NMR,和31P-NMR进行了表征,并研究了其固化行为以及HCP均聚物和HCP与双酚A苯并口恶嗪树脂(Bz)共聚物的热性能。结果表明,HCP均聚物在氮气氛下的起始热分解温度为333℃,800℃时残炭42%。HCP/Bz共聚物的起始热分解温度为367℃,800℃残炭率达52%,具有比HCP和Bz均聚物更好的热稳定性和成炭性能。     

La_2O_3对双酚A和对氯苯酚型聚苯并口恶嗪热稳定性的影响

为了研究La2O3对不同酚类结构聚苯并口恶嗪热稳定性的影响,将La2O3分别引入双酚A/苯胺型苯并口恶嗪和对氯苯酚/苯胺型苯并口恶嗪中间体中,制备了La2O3/苯并口恶嗪固化物。通过红外光谱、热重分析、热重分析-红外光谱联用分别研究了La2O3对聚苯并口恶嗪化学结构、热稳定性和热降解历程的影响。结果表明,La2O3并不影响2种聚苯并口恶嗪的化学结构;La2O3与氮原子间的配位作用锚固了不稳定的"悬挂"苯胺结构,抑制了双酚A/苯胺型苯并口恶嗪热降解过程中胺类降解产物的挥发,使得其固化物的5%热失重温度推迟了21℃,800℃残炭率提高了11%;氯原子的引入导致苯胺的对位在固化过程中参与了反应,使得对氯苯酚/苯胺型聚苯并口恶嗪固化物中的苯胺结构主要存在于较稳定的化学交联结构中;La2O3与其氮原子中的配位作用几乎不影响胺类降解产物的挥发,La2O3仅仅使其固化物初始热分解温度有所提高,而几乎不影响其800℃残炭率。     

多壁碳纳米管对苯并口恶嗪树脂固化反应的影响

苯并口恶嗪树脂作为新的热固性材料需要较高的温度进行凝胶和固化。碳纳米管可以催化苯并口恶嗪树脂的固化反应。文中采用差示扫描量热仪(DSC)通过动态DSC分析及恒温DSC分析研究了不同质量分数的碳纳米管对苯并口恶嗪树脂固化的催化效果。结果表明,加入过量的纳米管会导致反应活化能和指前因子增加,这意味着其阻碍了固化反应。2%的碳纳米管对苯并口恶嗪树脂固化有最好的催化效果,表现为固化的活化能由275.83 kJ/mol降至51.97 kJ/mol。     

A cellular automaton simulation of the degradation of porous polylactide scaffold: I. Effect of porosity

A cellular automaton method that includes a fabricating model for solvent casting/porogen leaching and a multiple-particle random walk model for oligomer molecular diffusion was used to simulate degradation behaviors and their dependence on the initial porosities (80%, 90% and 95%) of porous polylactide (PLA) scaffolds. Changes in the mass loss, molecular weight, numbers of PLA chains and ester groups, oligomer molecules release and average degradation rate with degradation time were investigated. The results show that during degradation, higher initial porosity resulted in greater molecular weight and a higher average number of ester groups and less mass loss, a lower number of oligomer molecules being released and a lower ratio of oligomer molecules remaining in the scaffold to those in the whole model. The average degradation rate and average number of PLA chains initially changed in direct proportion to the initial porosity, but there was an inverse change later in the degradation. In addition, no hollow structures were found in any of the scaffolds during the degradation, which indicates there was no dramatic autocatalytic phenomenon such as that seen for massive solid structures such as a plate in the porous PLA scaffold. The above simulated results are consistent with recent experimental reports, suggesting our simulating method has potential application in studying the degradation behaviors of porous scaffolds for tissue engineering.     

吡啶硼烷改性对沥青性能及组成的影响

以吡啶硼烷为添加剂对煤焦油沥青进行改性,考察了工艺条件（硼添加量,反应温度,反应时间）对改性沥青软化点、残炭值及其族组成的影响,发现吡啶硼烷参与并促进了沥青分子的反应,其结果是随着硼添加量的增加,改性沥青的软化点、残炭值提高,TS组份的含量降低,而PI组份的含量增加,在同一反应条件下,体系有无吡啶硼烷,所得结果有显著差别,吡啶硼烷改性系列的软化点、残炭值及PI组分的含量均明显高于纯沥青系列。     

Electronic transmission across a metal /conjugated-oligomer/metal structure: role of intrinsic disorder

We have studied electronic transmission across metal/conjugated-oligomer/metal structures: (a) one oligomer chain, and (b) two oligomer chains sandwiched between metal contacts, in the presence of lattice fluctuations. The lattice fluctuations are approximated by static white noise disorder. Resonant transmission occurs when the energy of an incoming electron coincides with a discrete electronic level of the oligomer. Because of disorder there is an enhancement of electronic transmission for energies that lie within the electronic gap of the oligomer. If fluctuations are sufficiently strong, a transmission peak within the gap is found at the midgap energy E = 0 for degenerate conjugated oligomers. For the two-chain case the spatial mirror symmetry is broken and coherence between the wavefunctions of two chains is partly lost when fluctuations are introduced.     

聚合物中小分子扩散的分子动力学模拟

采用分子动力学(MD)方法,以研究低聚体在聚甲基丙烯酸甲酯中的扩散为例,通过分析高分子链长、低聚体含量、聚合度和温度对扩散系数的影响,揭示小分子在聚合物中扩散过程.通过比较扩散系数的模拟值与实验值,发现两者比值在4左右.为获得小分子在聚合物中的扩散系数提供了一种较好的方法.     

Preparation of carbon microparticle assemblies from phenolic resin using an inverse opal templating method

Three-dimensionally (3D) well-ordered carbon microparticle assemblies with different particle morphologies were fabricated by infiltration of phenolic resin solution into SiO₂ inverse opal structures and subsequent carbonization. The effect of the phenolic resin solution concentration and the carbonization temperature on the morphology of the fabricated carbon microparticles was investigated. At a carbonization temperature of 1000 °C, carbon microparticles with interlocked bridges were obtained when the concentration of phenolic resin solution is 40 wt% and hollow carbon microparticles with opened window channels were obtained at a concentration of 30–35 wt%. When the carbonization temperature was decreased to 500 °C, carbon microparticles with interlocked bridges also were observed, even when the phenolic resin concentration was 30 wt%. The structures and properties of the carbon microparticles and their assemblies were characterized using SEM, XRD, and N₂ adsorption.     

Oligomer Dynamics of LL-37 Truncated Fragments Probed by α-Hemolysin Pore and Molecular Simulations

Oligomerization of antimicrobial peptides (AMPs) is critical in their effects on pathogens. LL-37 and its truncated fragments are widely investigated regarding their structures, antimicrobial activities, and application, such as developing new antibiotics. Due to the small size and weak intermolecular interactions of LL-37 fragments, it is still elusive to establish the relationship between oligomeric states and antimicrobial activities. Here, an α-hemolysin nanopore, mass spectrometry (MS), and molecular dynamic (MD) simulations are used to characterize the oligomeric states of two LL-37 fragments. Nanopore studies provide evidence of trapping events related to the oligomer formation and provide further details on their stabilities, which are confirmed by MS and MD simulations. Furthermore, simulation results reveal the molecular basis of oligomer dynamics and states of LL-37 fragments. This work provides unique insights into the relationship between the oligomer dynamics of AMPs and their antimicrobial activities at the single-molecule level. The study demonstrates how integrating methods allows deciphering single molecule level understanding from nanopore sensing approaches.     

用液态含环氧基丙烯酸酯低聚物改性环氧树脂

采用溶液聚合法合成了以丙烯酸丁酯为主链的液态含环氧基丙烯酸酯低聚物,并用其对环氧树脂进行增韧改性.讨论甲基丙烯酸环氧丙酯以及低聚物用量对改性环氧树脂力学性能的影响,并研究了改性环氧树脂的微观形态和耐热性能.结果表明:当低聚物用量为10%(质量分数),丙烯酸丁酯和甲基丙烯酸环氧丙酯的质量比为80∶20时,改性环氧树脂的拉伸强度和冲击强度比纯环氧树脂提高6.7%和219.1%,同时体系的耐热性能基本不下降;改性环氧树脂呈两相结构,随低聚物用量增加橡胶粒子粒径尺寸增大;且Tg先升高后降低.     

KOH活化法制备气体分离用炭分子筛膜

选用KOH为活化剂,利用化学活化法制备炭分子筛膜,考察在热塑性酚醛树脂(PFNR)涂膜液中添加不同质量分数的KOH对炭分子筛膜的影响.结果表明,在炭化过程中,KOH的加入可促进炭分子筛膜孔径的均匀分布,使炭分子筛膜具有发达的孔隙结构.当KOH在PFNR中的添加量从0％增加到4％时,H2的渗透速率由23.68×10-10 mol·m-2·s-1·pa-1提高到28.6×10-10 mol·m-2·s-1·Pa-1;但H2/N2和H2/CH4的分离系数明显下降,分别从471.3下降到147.5、540下降到270.CO2/CH4和O2/N2的分离系数只有轻微下降.     

Schiff碱化合物的合成及跃迁偶极矩的测定

通过芳0胺醛综合反应合成了6种具有非线性光学活性的给体一受体型Schiff碱化合物,测定了化合物的熔点,用元素分析、红外光谱、紫外光谱进行了表征。测定了化合物的跃迁偶极矩,并研究了化合物的溶致变色效应。     

Ambipolar field effect transistors with heterojunction of organic semiconductors

Ambipolar operations in organic field effect transistors (OFETs) with heterojunction structures have been demonstrated. We have selected a biphenyl capped thiophene oligomer (BP2T) as p-type and fullerene (C₆₀) as n-type materials in the active layer of the OFETs. To investigate their intrinsic behaviors we measured the OFET characteristics in vacuum without breaking vacuum after device fabrication. Their electric characteristics depended on the heterostructure configurations. The OFET prepared with a co-deposited thin film of BP2T/C₆₀ showed high carrier transport performance and both carriers were efficiently injected into the channel of the active layer. In the bi-layered device, ambipolar characteristics were only observed when the n-type C₆₀ molecules penetrated deeply into the BP2T layer.