Influences of hyperbranched polyethylenimine on the reactive compatibilization of polycarbonate/polyamide blends

The influences of hyperbranched polyethylenimine(h PEI), which possesses many reactive amino end-groups, on the blending properties of bisphenol-A polycarbonate(PC) and amorphous polyamide(a PA) were systematically investigated. Scanning electron microscopy(SEM) and differential scanning calorimetry(DSC) were used to observe the effect of h PEI on morphologies of PC and a PA phases in bulk blends. While the interfacial fracture toughness between planar PC and a PA layers with and without h PEI was studied by using augmented double cantilever beam(ADCB) method. Results show that the compatibility in PC/a PA blends can be significantly improved by adding a small amount of h PEI, mainly due to the interchange reactions between the polymers leading to the formation of block copolymers, cross-linked polymers and molecules with other constitutions. The augmented double cantilever beam experiments showed that the reactive process drastically reinforced the interfacial adhesion between planar layers of PC and a PA. However, degradation takes place during annealing at 180 °C, which was responsible for the production of small molar mass species of PC.     

紫甘蓝碳点的制备及其传感性能研究

以紫甘蓝为原料,硼氢化钠为还原剂,采用水热合成法制备了碳量子点ZGL-CQDs。该碳点的结构经XRD,TEM和FT-IR表征;光学性能研究表明:荧光量子产率可达6.20%,最大激发波长为360 nm,最大发射波长为446 nm;传感性能研究表明:该碳点在水溶液中对Cu~(2+)具有较好的选择性,对Cu~(2+)测定的线性范围为0.6×10~(-6)~2.60×10~(-6)mol/L,线性方程Y=-15.44958-2.05871x,R~2=0.9978,检出限为3.16×10~(-7)mol/L。     

受限状态聚合物熔体的分子动力学模拟

用粗粒化的分子动力学(MD)模拟方法从分子层次研究了受限于粗糙壁内的聚合物熔体的动力学性质. 结果表明, 对于链长较短的受限聚合物熔体体系, 随着膜厚的增加, 体系内部高分子链的松弛时间逐渐减少; 然而对于链长较长的受限体系, 聚合物链的松弛时间随着膜厚的增加先减少后增加. 推测这种由于链长的变化所引起的动力学性质的差异源自受限熔体内聚合物链聚集状态的改变, 并且通过考察交叠参数对这种改变进行了分析. 结果表明, 在膜厚增加的过程中, 决定受限状态高分子长链松弛机理的因素逐渐从受限效应转变成为链间的缠结效应.     

热历史对尼龙1212熔融行为的影响

利用DSC方法研究了不同热历史条件对尼龙1212熔融行为的影响.不同的热历史条件下,在DSC曲线上,观察到尼龙1212产生2个或3个熔融峰,依据聚合物结晶理论,对各峰的来源进行了分析.在160℃下不同温度退火120 min的尼龙1212样品DSC曲线上,低温结晶熔融峰主要由低温结晶形成的一些微晶体或者片晶熔融产生,其晶体完善程度较差,熔融峰值较低,峰面积较小;主熔融峰是由样品在淬火过程中形成的晶体和升温过程中低温结晶形成的晶体的熔融重结晶形成较为完善的晶体熔融所产生,熔融峰值较高,峰面积较大.在不同的升温速率条件下,熔融峰温度有所移动,表明不同升温速率条件下产生的熔融峰的结晶晶型是相同的.在不同结晶时间下结晶,延长结晶时间对较高完善程度晶体的生长有利.在不同温度下依次退火处理的样品,熔融产生两个附加峰,这两个附加峰的峰温都比它们相应的退火温度高,而峰高和峰面积随退火温度降低而减小.根据等温结晶结果,由Hoffman方法确定了尼龙1212的平衡熔融温度为202.8℃.     

Uniform to Accelerated Crystal Twisting Transition in Deuterate Polyethylene/Poly（ethylene-alt-propylene） Blend Films

A uniform to accelerated crystal twisting transition is observed in deuterate polyethylene/poly（ethylene-alt- propylene） （d-PE/PEP） blend films. And the band period is a function of initial d-PE concentration, quench depth and annealing time of phase separation. As Keith and Padden suggested, twisting of lamella is due to the unbalanced stress on its both sides, which can supply a satisfying explanation to banded spherulites formed in homogeneous systems. When it comes to d-PE/PEP blend system, in homogeneous 99% d-PE/PEP （weight fraction of d-PE） blend film, the formation of banded spherulite is observed as a result of uniform twisting of ribbon like d-PE lamellae along the radial direction. With the amorphous PEP piling up, it transfers into accelerated edge-on to fiat-on twisting due to crystallization assisted phase separation. The mechanism can be interpreted as following： d-PE molecules must inter-diffuse to the twisting growth front to continue the secondary nucleation and growth process. Meanwhile, the amorphous PEP molecules are rejected and accumulated at the twisting growth front. Once the d-PE lamella begins to twist because of unbalanced stress on both sides, the accumulated rubber phase at the growth front strengthens the unbalance and accelerates the edge-on to flat-on twisting. The concentration wave propagates further away with constant speed, and leads to concentric ring pattern with periodic nonuniform twisting along the radial direction. Since this is a kinetic effect, the band period can be controlled through initial d-PE concentration, quench depth and annealing time of phase separation. Our result shows that crystallization assisted phase separation can modify lamella growth kinetic pathway, thereby assisting concentric ring pattern formation.     

纤维增强树脂基复合材料中的横穿结晶研究

在以结晶性聚合物为基体树脂的纤维或织物增强复合材料中,经常出现横穿结晶(横晶)界面相。本文综述了近年来对纤维增强树脂基复合材料中横穿结晶的研究,内容包括横晶的概念,纤维表面诱导成核的机理,纤维诱导成核的能力和条件,横晶的生长和终止以及横晶的力学效应等。在不同的树脂/纤维复合材料体系中,由于其横穿结晶本身和本体球晶在尺寸和数目比例等方面呈现各不相同的复杂局面,横晶对复合材料性能的影响显得复杂。通过各种手段调控横晶的形态、尺寸及数量,使横晶的存在有利于复合材料整体性能的提高,是进行纤维增强结晶性聚合物基复合材料设计时应该遵循的一个基本原则。     

固化剂对环氧树脂/聚砜共混物层状结构形成的影响

不同含量的聚砜(PSF)对环氧树脂(EP)/PSF共混物相结构有重要影响,通过对反应分相后的样品进行断面观察,发现一定PSF含量时,体系形成了层状结构.这种层状结构通常为3层,包括上下2个外层、由聚砜和环氧树脂的颗粒-基体结构组成,以及1个双连续结构形成的中间层.研究表明,这种层状结构由反应诱导相分离开始之初形成的双连续结构发展而来,由于反应和相分离的进一步发展热塑性树脂富集相的体积分数逐渐减小、以及组分间的动力学不对称而最终形成的.在一定PSF浓度范围内,不同温度固化样品时均得到了这种层状结构.改变固化剂类型,层状结构的形貌受到影响,当固化剂活性较高时,外层变薄中间层增厚.当组分间的相容性较好时,双连续结构甚至不能演化发展到层状结构.     

高分子链相关函数与液体小分子速度/应力-时间相关函数的可类比性

通过标度关系,给出了良溶剂和熔体或θ溶剂中真实高分子链相关函数的幂率衰减关系.这一问题的物理背景,与液体中小分子速度和应力的时间相关函数的长时间拖尾现象,具有可类比的物理图像,但是由于高分子系统的复杂性,高分子的链相关函数表现出更复杂和丰富的可能形式.     

吴茱萸内酯的NMR研究

从吴茱萸Evodia Rutaecarpa (Juss.) Benth.中分离得到并鉴定了化合物吴茱萸内酯, 我们应用二维核磁技术首次对化合物吴茱萸内酯的核磁信号进行了准确归属, 并纠正了文献中部分氢信号归属的错误。     

激光光散射测量荧光/磷光体系溶液结构的原理和方法

通过对商业化激光光散射谱仪改造升级,以4种不同波长的激光785、632.8、532和457 nm作为独立光源,可以根据不同的荧光体系选择不同的入射激光,有效避免荧光、磷光对散射光信号的干扰,从而使激光光散射谱仪能用于荧光/磷光等吸光材料溶液结构的测定.非荧光和荧光聚苯乙烯小球标准样品的测定都验证了改造后仪器测量结果的准确性和精确性.实验结果表明,当荧光体系对入射光有吸收时,动态光散射的相关函数与静态光散射得到的均方回转半径都不能反映荧光样品的真实溶液结构,此时的结果只能作为定性参考,只有选择样品无吸收的入射光波长,符合(准)弹性散射时,所测结果才能反映样品的真实结构.单分子荧光谱仪的对照实验证实了改造光散射谱仪的正确性与必要性.