高分子化学实验教学的探索

高分子化学实验是一门重要的基础实验课。针对传统化学实验课的诸多缺点和不足,文章介绍了厦门大学对高分子化学实验教学的探索和实践,主要在增加趣味性实验、注重应用性实验、穿插探索性实验以及提倡微型化实验方面进行探索。实践表明,高分子化学实验教学的探索在激发学生兴趣,提高学生的综合实验能力方面已经初见成效

Research Progress on SiCBased Composite Ceramic Prepared Through a SingleSourcePrecursor Route

在碳化硅(SiC)陶瓷中引入异质元素可赋予其更优异的性能,如良好的热稳定性和独特的电磁性能。采用单源聚合物先驱体法制备陶瓷,通过合成不同结构的单; 源聚合物先驱体,可在原子尺度设计、调控陶瓷的组成和微结构等方面,达到优化陶瓷性能的目的。根据近年来的研究成果,介绍了单源聚合物先驱体制备Si-B; -C、Si-M-C (M=Ti, Zr, Hf)和Si-M-C (M=Fe, Ni)复相陶瓷的研究动态,并展望了其今后的发展趋势。The introduction of heterogeneous elements into SiC ceramics can endow; the ceramics with more excellent performances, such as high temperature; stability and unique electromagnetic properties. When preparing ceramics; through a single-source-precursor route, the composition and; microstructure of ceramics can be designed and tailored by tuning the; architecture of single-source-precursors at the atomic scale for; optimizing the ceramic performance. The research trends on Si-B-C,; Si-M-C (M = Ti, Zr, Hf) and Si-M-C (M=Fe, Ni) ceramic composites derived; from a single-source-precursor route were elaborated according to the; research achievements in recent years, meanwhile, its development trend; in the future was discussed.福建省自然科学基金; 华侨大学2016年实验教学改革与建设课

Microwave-improved polymerization of ε-caprolactone initiated by carboxylic acids

The ring-opening polymerization of e-caprolactone (B-CL), initiated by carboxylic acids such as benzoic acid and chlorinated acetic acids under microwave irradiation, was investigated; with this method, no metal catalyst was necessary. The product was characterized as poly(epsilon-caprolactone) (PCL) by H-1 NMR spectroscopy, Fourier transform infrared spectroscopy, ultraviolet spectroscopy, and gel permeation chromatography. The polymerization was significantly improved under microwave irradiation. The weight-average molecular weight (M-w) of PCL reached 44,800 g/mol, with a polydispersity index [weight-average molecular weight/number-average molecular Weight (M-w/M-n)] of 1.6, when a mixture of epsilon-CL and benzoic acid (25/1 molar ratio) was irradiated at 680 W for 240 min, whereas PCL with M-w = 12,100 and M-w/M-n = 4.2 was obtained from the same mixture by a conventional heating method at 210 degreesC for 240 min. A degradation of the resultant PCL was observed during microwave polymerization with chlorinated acetic acids as initiators, and this induced a decrease in M-w of PCL. However, the degradation was hindered by benzoic acid at low concentrations. (C) 2002 Wiley Periodicals, Inc

固/液态聚碳硅烷共混制备碳化硅纤维的研究

以超支化液态聚碳硅烷(LPCS)与固态聚碳硅烷(纯PCS)的共混物作先驱体,熔融纺丝;所得原丝再在热空气气氛中氧化交联,在高温氮气气氛中热裂解,得到碳化硅纤维。研究表明,15%(质量分数)LPCS的加入,可使纯PCS先驱体的纺丝温度,从285℃降低到225℃;纺丝性能和纤维表面质量明显提高;还可以提高氧化交联的效率,降低交联温度,从而减少纤维部分融并、粘结的弊端;虽然纤维的室温力学强度有所降低,但抗氧化性能提高,1400℃氧化交联后,力学性能几乎不变;而纯PCS的力学性能却降为原来的50%

Single-source-precursor synthesis of high temperature stable SiC/C/Fe nanocomposites from a processable hyperbranched polyferrocenylcarbosilane with high ceramic yield

NSFC [50802079, 51072169]; Natural Science Foundation of Fujian Province of China [2011J01330]Hydrosilylation of vinyl ferrocene with allylhydridopolycarbosilane was used to synthesize a processable hyperbranched polyferrocenylcarbosilane (HBPFCS), which was characterized by combination of gel permeation chromatography, Fourier transform infrared (FT-IR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. The polymer-to-ceramic transformation of the HBPFCSs was then investigated by FT-IR and C-13 MAS NMR spectroscopy as well as by thermal gravimetric analysis (TGA). A self-catalytic effect of ferrocenyl units in the HBPFCS skeleton on dehydrocoupling was found during a curing process at 170 degrees C resulting in a high ceramic yield of ca. 80% at 1200 degrees C in Ar. Finally, microstructures and magnetic properties of the final ceramics were studied by techniques such as X-ray diffraction, energy dispersive spectroscopy, Raman spectroscopy, transmission electron microscopy and vibrating sample magnetometry. The final ceramic (pyrolysis temperature >= 900 degrees C) is characterized by a microstructure comprised of a SiC/C/Fe nanocomposite. Turbostratic carbon layers located at the segregated alpha-Fe crystal boundary avoid interdiffusion and explain the exclusive existence of alpha-Fe in a SiC/C matrix even at 1300 degrees C. Variations of the iron content in the HBPFCSs and of the pyrolysis conditions facilitate the control of the composition and ceramic micro/nanostructure, influencing in particular magnetic properties of the final SiC/C/Fe nanocomposite ceramic

低氧含量液态超支化聚碳硅烷的合成与陶瓷化研究

以甲醇对氯甲基三氯硅烷(Cl3SiCH2Cl)进行烷氧化反应,然后经过格氏偶联反应和还原反应,制备了低氧含量液态超支化聚碳硅烷(HBPCS)。通过凝胶渗透色谱法(GPC)、核磁共振(NMR)以及元素分析对由此制备的HBPCS进行表征。结果表明,提高烷氧化比例,可以有效抑制溶剂四氢呋喃开环的副反应,降低先驱体氧含量。通过热失重分析(TGA)和X射线衍射(XRD)分别对HBPCS的热性能及相应陶瓷在高温下的结晶行为进行研究

偶氮二异丁腈引发液态聚碳硅烷的交联研究

在偶氮二异丁腈(2,2′–azobisisobutyronitrile,AIBN)引发下,研究液态超支化聚碳硅烷(hyperbranched polycarbosilane,HBPCS)的无氧热交联,考察交联温度、AIBN用量以及时间对交联反应及陶瓷产率的影响。结果表明:较高的温度可促进交联;AIBN用量越多越有利于交联,陶瓷产率先增加而后稳定,其最佳用量为1.0%～2.0%(质量分数,下同);随着交联时间延长,HBPCS的交联程度和陶瓷产率先增加而后保持不变。对于AIBN用量1.5%的体系,HBPCS经80℃交联6h后,其1000℃下的陶瓷产率高达75%以上。此外,对最终陶瓷相组成进行表征,发现AIBN的引入能够有效抑制β-SiC的结晶

液态超支化聚碳硅烷的研究进展

液态超支化聚碳硅烷(HBPCS)因具良好的流动性和可自交联性,适用于制备SiC陶瓷基复合材料而倍受青睐。对它的合成、交联、陶瓷化和应用探索等方面的研究动态进行了综述,并展望了其今后的发展趋势

过氧化苯甲酰在液态聚碳硅烷交联中的应用

聚碳硅烷热解前的交联对于提高其最终陶瓷产率至关重要。研究了过氧化苯甲酰(BPO)引发液态超支化聚碳硅烷(HBPCS)的交联反应对于陶瓷产率的影响。FT-IR和GPC证实,添加为0.5%～2.0%(质量分数,下同)的BPO,即可在80～140℃下引发HBPCS交联;在考察的实验条件下,提高交联温度、延长反应时间或增加BPO用量,均可提高HBPCS交联程度。BPO用量为2.0%时,HBPCS交联样品在1000℃下的陶瓷产率高达65%,比未加BPO的提高25%

Microsphere Pattern Prepared by a "Reverse" Breath Figure Method

通讯作者地址: Xiong, XP (通讯作者), Xiamen Univ, Coll Mat, Dept Mat Sci & Engn, Xiamen 361005, Peoples R China 地址: 1. Xiamen Univ, Coll Mat, Dept Mat Sci & Engn, Xiamen 361005, Peoples R China 电子邮件地址: [email protected] have reported all interesting method, named reverse breath figure, for the preparation of polymeric microsphere patterns. By the same procedure as breath figure, instead of under a humid atmosphere, linear and star-shaped poly(styrene-block-butadiene) copolymers dissolved in solvents such as toluene, trichloroform, and dichloromethane were cast onto the surface of a glass substrate in methanol or ethanol vapor. After the complete evaporation of the solvent, microspheres with the diameters ranging from hundreds of nanometers to several micrometers were prepared. The microsphere patterns are the reverse of the honeycomb porous structure of breath Figure. The mechanism of the microsphere formation has been studied to show that when the surface tension of the polymer solution is 1.5 mN/m higher than that of the condensed liquid, microsphere patterns call be prepared, whereas a honeycomb porous film of breath Figure call be obtained when the Surface tension of the polymer solution is lower than that of the condensed liquid. The viscosity of the polymer solution is also an important factor to influence the fabrication of the microsphere patterns.National Natural Science Foundation of China 2084400