二茂铁疏水改性支化聚乙烯亚胺水溶液的聚集结构与流变行为

通过将二茂铁接枝在大分子链上制备了疏水改性支化聚乙烯亚胺(Fc-BPEI),用动态光散射、透射电镜及旋转流变仪研究了其水溶液中大分子的聚集态结构与流变行为. 考察了剪切作用、浓度、温度对溶液中大分子结构和形态及流变行为的影响. 研究结果表明,二茂铁改性的聚乙烯亚胺分子尺寸明显增大,且随浓度增大体系中大分子逐渐从分子内疏水缔合为主向分子间疏水缔合为主转变,形成分子间缔合体. 上述原因使得Fc-BPEI溶液黏度显著增大,但是该体系却呈现典型的牛顿流体特征. 对样品进行连续升-降温循环热处理,发现经过升降温处理后的Fc-BPEI体系黏度明显增大,且增幅随热循环次数增加而逐渐减小. 动态流变测试结果表明,这种现象缘于热处理使得大分子链缔合方式和形态发生变化,体系中出现穿插于多个分子间缔合体的PEI大分子,产生了类似网络结构的大分子聚集结构. 经热处理的Fc-BPEI溶液呈现显著的剪切变稀现象,高浓度溶液的抗剪切能力显著提高.     

Influence of shearing on impact polypropylene copolymer: Phase morphology,thermal and rheological behavior

The influences of shearing conducted by a Brabender rheometer on phase morphology,thermal and rheological behavior of a commercial impact polypropylene copolymer(IPC) were studied.The crystallization and melting traces show that short-time annealing at 210°C is unable to completely erase the influence of shearing on the samples.When the samples which were treated at a rotation speed of 80 r/min crystallize at a cooling rate of 10 K/min,their 7_cs and corresponding T_ms obviously rise with the increase of shearing time.Furthermore,the POM results reveal that the shearing can lead to the formation of shish-kebab and the shish-kebab amount is proportional to shearing time.The rheological measurement results show that the treated samples exhibit different G’~ωdependences.The ’second plateau’ appears when the sample is treated at a rotation speed of 60 r/min or 80 r/min for 10 min,and linear G’~ωdependence is observed at other rotation speeds.In addition,it is found that the appearance of the ’second plateau’ depends on the shearing time when the rotation speed is fixed. According to SEM observations,it is proposed that the ’second plateau’ of IPC samples should be ascribed to the aggregation of dispersion particles.     

In situ controllable synthesis platinum nanocrystals on TiO(2) by novel polyol-process combined with light induced photocatalysis oxidation

Clean Pt/TiO(2) with highly dispersed controlled Pt nanocrystals was prepared by a novel approach combining an in situ polyol process with light induced photocatalysis oxidation. The interaction between TiO(2) and Pt under the assistance of surfactants hinders the agglomeration. The preference to form three dimensional clusters as the cluster size increases enables the formation of controlled Pt nanocrystals.     

The multiple effects of Al-doping on the structure and electrochemical performance of LiNi<Subscript>0.5</Subscript>Mn<Subscript>0.5</Subscript>O<Subscript>2</Subscript> as cathode material at high voltage

The application of LiNi_0.5Mn_0.5O₂ as a high-voltage cathode material for lithium-ion batteries is limited by its poor cycle performance. Therefore, we attempt to improve the cyclability of this material at high voltage by using a doping method and propose a detailed mechanism for the effect of the doping amount on the structure and electrochemical performance. In this work, LiNi_0.5-zAl_zMn_0.5O₂ (z?=?0.00, 0.03, 0.05, 0.08) electrodes were prepared via a simple co-precipitation followed by a solid-state method. X-ray diffraction and Rietveld refinement revealed that a suitable amount of Al doping into LiNi_0.5Mn_0.5O₂ can stabilize the structure and lower the Li/Ni cation mixing, but an excessive doping would lead to Al-ion doping in the lithium layer, which can block lithium diffusion and affect the rate property. Specifically, LiNi_0.47Al_0.03Mn_0.5O₂ shows a much higher capacity retention compared to LiNi_0.5Mn_0.5O₂ both at 25 °C (78.5 vs. 68.8% at 0.2 C) and 60 °C (70.8 vs. 69.0% at 0.2 C). Moreover, Al-doping can retard the voltage drop during the discharge-charge state, with the discharge voltage for LiNi_0.5-zAl_zMn_0.5O₂ (z?=?0.00, 0.03, 0.05, 0.08) decreasing slowly with increasing Al content.     

微生物调驱模拟实验研究

为了研究微生物调剖及提高采收率效果,通过细胞融合技术构建了两株用于采油的生物工程菌株STP-1和STP-5,该菌株能在50℃下繁殖并代谢生物多糖和气体。调剖物理模拟实验结果表明,微生物注入培养后能够显著降低岩心的渗透率,降低率分别为82.67%和58.24%,说明两株菌具有很好的调剖作用。驱油模拟实验结果表明,STP-1和STP-5提高采收率分别达到21.92%和13.49%,具有良好的提高采收率效果。本研究表明该两株菌在调剖和提高原油采收率方面具有良好的应用潜力。     

婴儿共同注意与社会能力发展的关系

共同注意作为婴儿早期发展的里程碑,对后期的社会发展有重要的影响．文章简要回顾了共同注意、社会能力的概念和测量方式,重点解释了共同注意预测社会能力的理论基础,并归纳了现有关于二者关系的研究,总结了此类研究中的不足．为未来的研究提供了可能的方向．     

简论普通物理教学的近似方法

结合普通物理教学中的典型例子，简要论述了近似方法在处理物理问题时的必要性和实用性。     

氧化铝基催化剂上二硫化碳水解反应性的研究

本文通过等体积浸渍法制备了三种氧化铝基催化剂，在实验室固定床上考察ＣＳ２浓度、空速和反应温度等因素对水解反应的影响。研究结果表明：Ｋ２Ｏ和Ｐｔ的负载都可以提高氧化铝上ＣＳ２的催化水解转化率，催化剂表面碱性是ＣＳ２水解反应活性中心在３０００ｈ＾－１和４０－１４０℃范围内，ＣＳ２在三种催化剂上反应活化能力为３５．３７－５５．５３ｋＪ／ｍｏｌ；通过二硫化碳催化水解反应类型的数学分析，进行实验值与计算值之     

Synthesis, characterization and degradability of the comb-type poly(4-hydroxyl-ε-caprolactone-co-ε-caprolactone)-g-poly(l-lactide)

The novel comb-type biodegradable graft copolymers based on ε-caprolactone and l-lactide were synthesized. Firstly, 2-oxepane-1,5-dione (OPD) was synthesized by the Baeyer-Villiger oxidation of 1,4-cyclohexanedione, and was subsequently copolymerized with ε-caprolactone (CL) to produce poly(2-oxepane-1,5-dione-co-ε-caprolactone) (POCL) catalyzed by stannous(II) 2-ethylhexanoate in toluene. Then, POCL was converted into poly(4-hydroxyl-ε-caprolactone-co-ε-caprolactone) (PHCL) using sodium borohydride as reductant. Finally, poly(4-hydroxyl-ε-caprolactone-co-ε-caprolactone)-g-poly(l-lactide) (PHCL-g-PLLA) were prepared successfully by bulk ring-opening polymerization of l-lactide using PHCL as a macro-initiator. All the copolymers have been characterized by ¹H and ¹³C NMR, DSC, and GPC. Compared with the random copolymer of poly(CL-co-LA), the elongation is highly increased. And the thermal analysis showed that the crystallization rate of the PCL backbone in the graft copolymers was greatly reduced compared to the PCL homopolymer. The hydrolytic degradation of the copolymer was much faster in a phosphate buffer (pH = 7.4) at 37 °C, which is confirmed by the weight loss and change of intrinsic viscosity.