Dielectric and dynamic mechanical relaxation studies on poly(aryl ether ketone)s

The relaxation behavior of four amorphous poly(aryl ether ketone)s was investigated using dielectric relaxation spectroscopy and dynamic mechanical analysis. The temperature dependence of the relaxation times of the glass transition process and the cooperative nature of this process were unaffected by changes in polymer structure. The temperature location of the loss peaks for all polymers progressed smoothly between the low frequency of the mechanical measurements and the higher frequencies of the dielectric probe. Differences were observed in mechanical activation energy and dielectric relaxation strength for one polymer which contained a significant concentration of meta linkages, compared with the para-linked polymers, while relaxation broadness was generally greater in the dynamic mechanical mode. Changes in chemical structure had little effect on the shape, intensity, and location of the β-relaxation peak, the main observation being that the Arrhenius activation energy measured by dynamic mechanical analysis was significantly higher than that calculated from the dielectric data. The dielectric β-relaxation was sensitive to absorbed moisture. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 851–859, 1998     

Phenylated poly(P-phenylene vinylenes) prepared via the chlorine precursor route (CPR)

The synthesis of several highly phenylated PPV derivatives by a chlorine precursor route (CPR) was investigated in order to understand its scope. Three 1,4-bis(chloromethyl)benzene monomers were prepared via a robust and versatile synthetic procedure involving the Diels-Alder reaction. The monomers were then polymerized to the corresponding precursor polymers with about 1.0 equivalent of potassium t-butoxide in THF. Only one monomer gave a soluble precursor polymer while the other two gave insoluble precursor polymers. The soluble precursor polymer was deposited as thin films and then converted to the corresponding PPV derivative, which showed green photoluminesence and electroluminesence.     

若丹明B荧光增强二硫化碳高阶受激喇曼散射

 利用若丹明B乙醇溶液的荧光改变了二硫化碳的一至三阶Stokes喇曼谱线的强度分布,选择性地增强了三阶Stokes喇曼谱线。在泵浦功率密度为~560MW^.cm^-2时,对染料摩尔浓度分别为~10^-5、cm^-5散射池和~10^-4、1cm散射池进行实验,观察到二硫化碳的三阶Stokes喇曼谱线与染料激光形成的共振增强现象及、二阶Stokes喇曼谱线的部分或完全耗尽。     

铝球弹丸高速正撞击薄铝板穿孔研究

 低地球轨道上的航天器易受到微流星体及空间碎片的超高速撞击，导致其严重的损伤甚至灾难性的失效。撞击损伤特性研究是航天器防护设计的一个重要问题。通过铝球弹丸超高速正撞击薄铝板的实验研究和数值模拟，证明了AUTODYN-2D软件数值模拟预测薄铝板超高速撞击穿孔直径的有效性。通过对弹丸直径、弹丸撞击速度和薄铝板厚度影响薄铝板超高速撞击穿孔直径的数值模拟，以及利用实验结果和数值模拟结果拟合的曲线，得到了铝球弹丸超高速撞击薄铝板的穿孔规律以及影响薄铝板超高速撞击穿孔直径的主要因素。     

苯乙烯/马来酸酐和苯乙烯/甲基丙烯酸二甲氨基乙酯二元体系在聚四氟乙烯多孔膜上的γ辐射接枝

在氮气的氛围下用γ辐照的方法在聚四氟乙烯多孔膜上接枝苯乙烯 马来酸酐、苯乙烯 甲基丙烯酸二甲氨基乙酯二元单体 .并且研究了剂量、剂量率、溶液中单体的浓度和二元单体的摩尔比等条件对接枝率的影响 .探讨了两种单体的竞聚率对接枝率、接枝膜的组成及性能的影响 .结果表明 ,苯乙烯 马来酸酐二元体系对接枝率有协同效应 ,苯乙烯 甲基丙烯酸二甲氨基乙脂二元体系对接枝率表现为加合效应 .制备的二元接枝的聚四氟乙烯多孔膜可以进一步磺化来制备用于质子交换膜燃料电池的质子交换膜 .     

含改性松香的丁二醇二缩水甘油醚固化反应动力学研究

设计了含改性松香无苯环的环氧固化体系和无松香的对照体系,分别是无松香体系Ⅰ：丁二醇二缩水甘油醚（BDGE）和甲基六氢苯酐（MeHHPA）;无规体系Ⅱ：丙烯酸松香（AR）、BDGE和MeHHPA;有规体系Ⅲ：丙烯酸松香基环氧树脂（ARE,由AR和BDGE预聚而来）和MeHHPA。对三体系的固化反应应用动态示差扫描量热仪（DSC）进行了研究,利用KAS法求得不同转化率下的表观活化能,通过整个反应过程反应活化能的变化,得到了三体系反应的内在机理,结果发现松香基的引入及引入顺序都对固化反应产生影响。     

In situ SIMS analysis and reactions of surfaces prepared by soft landing of mass-selected cations and anions using an ion trap mass spectrometer

Mass-selected polyatomic cations and anions, produced by electrosonic spray ionization (ESSI), were deposited onto polycrystalline Au or fluorinated self-assembled monolayer (FSAM) surfaces by soft landing (SL), using a rectilinear ion trap (RIT) mass spectrometer. Protonated and deprotonated molecules, as well as intact cations and anions generated from such molecules as peptides, inorganic catalysts, and fluorescent dyes, were soft-landed onto the surfaces. Analysis of the modified surfaces was performed in situ by Cs⁺ secondary ion mass spectrometry (SIMS) using the same RIT mass analyzer to characterize the sputtered ions as that used to mass select the primary ions for SL. Soft-landing times as short as 30 s provided surfaces that yielded good quality SIMS spectra. Chemical reactions of the surfaces modified by SL were generated in an attached reaction chamber into which the surface was transferred under vacuum. For example, a surface on which protonated triethanolamine had been soft landed was silylated using vapor-phase chlorotrimethylsilane before being returned still under vacuum to the preparation chamber where SIMS analysis revealed the silyloxy functionalization. SL and vapor-phase reactions are complementary methods of surface modification and in situ surface analysis by SIMS is a simple way to characterize the products produced by either technique.     

Orbits of parabolic subgroups on metabelian ideals

Let k be an algebraically closed field, t∈Z?1, and let B be the Borel subgroup of GLt(k) consisting of upper-triangular matrices. Let Q be a parabolic subgroup of GLt(k) that contains B and such that the Lie algebra qu of the unipotent radical of Q is metabelian, i.e. the derived subalgebra of qu is abelian. For a dimension vector with , we obtain a parabolic subgroup P(d) of GLn(k) from B by taking upper-triangular block matrices with (i,j) block of size di×dj. In a similar manner we obtain a parabolic subgroup Q(d) of GLn(k) from Q. We determine all instances when P(d) acts on qu(d) with a finite number of orbits for all dimension vectors d. Our methods use a translation of the problem into the representation theory of certain quasi-hereditary algebras. In the finite cases, we use Auslander-Reiten theory to explicitly determine the P(d)-orbits; this also allows us to determine the degenerations of P(d)-orbits.     

氮气中空心阴极放电条纹的发光特性

利用发射光谱法,在氮气环境下研究了圆柱型空心阴极放电条纹的特性。测量得到了气压为20 Pa,放电电流为1.3 mA时条纹区的发射光谱,结果表明发射光谱主要为氮分子的第一正带系(B3П_g →A3П_u)和 第二正带系(C3П_u→B3П_g )。利用双原子光谱发射理论,计算得到了氮分子振动温度的空间分布特性。结果表明光谱线强度呈周期性分布,明纹中心处的谱线强度高于暗纹中心处的谱线强度。明纹中心处的N₂分子振动温度为3 500～4 400 K,并且从阴极到阳极,明纹中心处光谱线强度和分子振动温度逐渐下降。同时测量得到了放电电流为1.0和1.5 mA时的发光条纹特性,研究了放电电流对条纹特性的影响。随着放电电流的增加,明纹中心处的分子振动温度升高,条纹间距增加。另外,利用测量得到的发光条纹,计算得到了条纹区的平均约化电场强度为44～49 m-1·Pa-1,并且由阴极向阳极逐渐降低。对于揭示气体放电中发光条纹的形成机理和促进空心阴极放电的稳定性有重要的参考价值。     

丙三醇溶液声致发光中的黑体辐射谱

利用U型管圆锥泡声致发光装置,测量到了丙三醇溶液中圆锥泡声致发光的光谱和光脉冲。结果表明,测量得到的发光光谱为光滑的连续谱,且与理论模拟得到的黑体辐射谱相吻合,拟合温度分布于2 600～3 500 K范围内。文章从空间和时间两方面分析了圆锥泡空化发光中存在黑体辐射的原因：较大的气泡体积(气泡塌缩半径为1.4 cm)与较长的发光时间(几十微秒)。另外,实验研究表明随着发光波长的增长,光脉冲宽度变宽,从而进一步证明了圆锥泡声致发光中的黑体辐射机制。最后,利用测量得到的发光光谱和脉冲计算得到了发光光强为0.18 J,远远高于其他方式得到的声致发光光强。