硅橡胶包覆十八烷/聚(St-MMA)储能微胶囊复合材料制备及热性能

以十八烷/聚(苯乙烯-甲基丙烯酸甲酯)(P(St-MMA))微胶囊为相变材料,硅橡胶作为载体,制备了十八烷/P(St-MMA)/硅橡胶复合材料。研究了微胶囊的加入方式及加入量,硅橡胶包覆方法。通过红外光谱(IR)和扫描电镜(SEM)研究复合材料的结构和形貌。通过力学性能测试如拉伸强度、扯断伸长率,确定最佳的加工方法。通过热重分析法(TG)、差示扫描量热法(DSC)和储热性能对复合材料的热性能进行研究。结果表明,十八烷制成微胶囊加入到硅橡胶中,且微胶囊加入量是2份时,十八烷/P(St-MMA)微胶囊/硅橡胶的热稳定性热稳定性及力学性能较好。室温硅橡胶包覆微胶囊掺混固化法制备的复合材料的力学性能优于直接共混后热固化法和混炼涂抹后热固化法。十八烷/P(MMA-St)/硅橡胶复合材料的焓值为67.6J/g,储能效果好。     

石墨烯/正十八烷微胶囊的制备与及其热性能研究

以石墨烯/正十八烷为芯材,三聚氰胺-尿素-甲醛树脂(MUF)为壁材,苯乙烯马来酸酐共聚物(SMA)为乳化剂,采用乳液聚合法制备相变微胶囊.系统研究了石墨烯对于正十八烷微胶囊性能的影响.采用场发射扫描电子显微镜(FE-SEM)、傅里叶变换红外光谱分析仪(FTIR)、拉曼光谱仪、X射线衍射仪(XRD)、Hot Disk热常数分析仪、示差扫描量热仪(DSC)和热重分析仪(TGA)对相变微胶囊的外貌形态、晶型结构和热性能进行表征和分析.结果表明,微胶囊呈圆球形且光滑,粒径约为1~30μm.当石墨烯添加量为0.1 g时,微胶囊的形貌无明显变化.当加入过量石墨烯时,微胶囊出现了明显的团聚现象.XRD测试表明,包覆于微胶囊中的石墨烯没有使微胶囊的结晶峰位置发生明显的偏移,这对于微胶囊的实际应用是有利的.微胶囊的相变热焓和包覆率随着石墨烯的加入而不断减小,但芯材的过冷现象得到了明显的改善.石墨烯对于微胶囊传热性能的提升有着显著的效果.当石墨烯的添加量为0.2 g时,微胶囊的导热系数为0.092 W·m-1·K-1,与纯微胶囊相比提高了约51%,这说明石墨烯改善了传统相变微胶囊的传热性能,提升了相变微胶囊的应用性能.     

正十六烷聚脲微胶囊化相变材料

用界面聚合法，合成了直径大约2.5 μm可用于热能储存含相变材料的聚脲包覆微胶囊.在含乳化剂的水溶液中，将溶有芯材正十六烷的有机相乳化成微米级油性液滴，随后加入的水溶性单体二胺与甲苯2,4-二异氰酸酯在胶束界面相互反应形成囊壁.分别用乙烯二胺，1,6-己二胺和它们的混合物作为水溶性单体进行了研究.并用红外光谱和热分析分别考察了不同胺类对微胶囊化学结构和热性质的影响.红外谱图显示合成了聚脲微胶囊，热重曲线表明含正十六烷的聚脲微胶囊能够耐受大约300 ℃高温，差示扫描量热测试表明所有样品均具有合适的相转变热，冷热循环实验揭示微胶囊能够维持储热容量不衰减.研究表明微胶囊化的正十六烷作为相变储热材料具有良好的应用前景.     

辣素微胶囊的原位聚合法制备与热降解动力学

在乳液体系中,以尿醛为壁材,以原位聚合法制备了辣素同系物———N-香草基壬酰胺微胶囊。红外光谱证实了尿醛的形成,X-射线衍射显示了同样作为半晶高分子囊壁,尿醛包裹囊心前后出现的结构晶型差异。根据吸附等温曲线假设微胶囊为紧密堆积形式,对于尿醛单体颗粒和尿醛微胶囊的TGA,采用Achar-B rind ley-Sharp-W endworth方法,对两者进行热重数据的处理,以作图法求得了动力学参数,确定了热降解动力学模式函数,回归系数良好。TGA求解的活化能数据证明由于晶型差异,导致单体与微胶囊热稳定性不同,从而与XRD结论一致。     

脲醛树脂微胶囊的改性

为了提高脲醛树脂微胶囊的稳定性,选择化学结构不同的聚乙烯醇、苯酚、三聚氰胺对脲醛树脂进行了改性.通过优化反应条件,得到了具有良好耐热、耐水性的脲醛树脂微胶囊.采用光学显微镜观测了微胶囊的形貌;用FT-IR表征了微胶囊的化学结构;用TGA分析了微胶囊的热性能.研究结果表明:3种改性后的微胶囊的热稳定性均有所提高,其中苯酚改性的微胶囊热稳定性最好;聚乙烯醇改性微胶囊的疏水性下降,苯酚和三聚氰胺改性的微胶囊的疏水性都有所增强.     

丙烯酸共聚物囊壁的正十八烷微胶囊的制备和性能表征

以二丙烯酸1,4-丁二醇酯为交联剂, 成功制备了甲基丙烯酸甲酯-甲基丙烯酸共聚物为壁材, 正十八烷为囊芯的相变材料微胶囊. 采用扫描电子显微镜(SEM)、差示扫描量热仪(DSC)和热重分析仪(TG)分别考察了单体与芯材投料比、单体浓度和交联剂的含量对微胶囊形貌、相变热性能、热稳定性能的影响. 实验结果表明: 随着单体与芯材投料比或单体浓度的增加, 微胶囊表面均变得致密, 壁厚增加; 随着交联剂含量的增加, 微胶囊的表面变得更加致密光滑, 热稳定性显著增强; 随着单体与芯材投料比的增大, 微胶囊热焓值减小, 被包裹的囊芯含量减少.     

一种致密的相变储能微胶囊的制备与表征

制备了以聚脲为第一壁材、苯乙烯-二乙烯苯为第二壁材,以相变点在16℃左右的石蜡为芯材的相变储能微胶囊。采用红外光谱、差示扫描量热分析、热重分析测试技术表征了制备的相变储能微胶囊的结构组成以及热性能;采用溶剂淋洗法研究了影响包覆率的因素。结果表明,相变储热微胶囊是复合相变材料,微胶囊的热稳定性好,致密性优良;通过对水油比、乳化剂及苯乙烯-二乙烯苯用量等各因素对微胶囊包覆率影响的讨论,得出在水与油质量比3.2,乳化剂相对于水的质量分数为2%时,加入苯乙烯与二乙烯苯质量比为10∶1混合液的质量分数为6.0%时,其包覆率达81.14%;制备的微胶囊能耐较高温度,在150℃以下无质量损失,且微胶囊储热能力高达80J/g。同时发现,储热能力与芯壁比有关,比值越大储热潜能越高。     

纳米二氧化硅改性石蜡微胶囊相变储能材料的研究

以石蜡为芯材,甲基丙烯酸甲酯-丙烯酸共聚物为壁材,纳米SiO2为改性剂,采用原位聚合法制备了石蜡微胶囊相变储能材料,系统研究了添加纳米SiO2对石蜡微胶囊相变材料性能的影响;采用傅里叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)、示差扫描量热法(DSC)和热重分析(TGA)等对石蜡微胶囊相变材料的化学结构、表面形貌和热性能进行了表征.研究表明,纳米SiO2能够有效提高微胶囊壁材的热稳定性,当丙烯酸酯壁材中添加3％改性纳米SiO2时,微胶囊呈球形且表面光滑,尺寸250 ～ 300 nm,具有良好的储热能力,相变潜热高达134.79 J/g,分解温度比未添加改性纳米SiO2的石蜡微胶囊提高了40 K,经过1000次热循环测试,石蜡渗漏率仅2.96％.     

乳化工艺对微胶囊型硬脂酸相变材料热性质的影响

以硬脂酸为芯材, 碳酸钙为壁材, 采用原位聚合法制备了微胶囊型相变材料; 通过扫描电子显微镜、 红外光谱及差热-热重分析对其表面形貌和热性质进行了表征; 通过改变乳化剂的种类及用量, 研究了乳化工艺对微胶囊型相变材料表面形貌、 相变温度和包覆率的影响. 实验结果表明, 在选用的3种乳化剂十二烷基苯磺酸钠、 十六烷基三甲基溴化铵和曲拉通X-100中, 十二烷基苯磺酸钠相对效果最好, 乳化剂与芯材最佳质量比为0.5%, 相变温度为112.24 ℃时, 封装率达到92.1%.     

微胶囊碳酸氢钠合成工艺及热分解特性的研究

利用环氧树脂(EP)对碳酸氢钠(SB)进行包覆合成微胶囊碳酸氢钠,通过红外光谱仪(FTIR)、扫描电子显微镜(SEM)、差示扫描量热计(DSC)和热重分析仪(TG)等表征手段,分析了合成反应温度、环氧树脂与碳酸氢钠的质量比对微胶囊碳酸氢钠的结构、表面形貌特征以及热分解特性的影响。结果表明:当反应温度为70℃,环氧树脂与碳酸氢钠的质量比为1∶5时,碳酸氢钠的改性效果较理想,表面形貌比较规整,起始分解温度由118℃提高至154.9℃,分解温度区间从46.3℃缩短到24.8℃;使用微胶囊碳酸氢钠制备的微发泡聚丙烯材料,发泡质量较理想。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Highly efficient and stereoselective cycloaddition of nitrones to indolyl- and pyrrolylacrylates

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.     

Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources

A transition metal-free method for the direct amination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.     

l-Proline-catalyzed five-component domino reaction leading to multifunctionalized 1,2,3,4-tetrahydropyridines

Multifunctionalized 1,2,3,4-tetrahydropyridines are concisely synthesized in good yields via l-proline-catalyzed or l-proline/FeCl₃-cocatalyzed one-pot multicomponent reactions (MCRs). The MCRs involve a domino hydroamination/prins reaction/Mannich-type reaction/intramolecular dehydration-cyclization process. The molecular structure of 5baa, one of multifunctionalized 1,2,3,4-tetrahydropyridines, was confirmed by single-crystal X-ray diffraction.     

Exploring the scope of the Gewald reaction: Expansion to a four-component process

An efficient four-component reaction was developed to take advantage of the reactivity of the 2-aminothiophene-3-carbonitrile functionality, which is obtained during the classical three-component Gewald reaction. Various α-methylene bearing ketones were reacted with malononitrile, elemental sulfur, and aryl/heteroarylnitrile derivatives in t-BuOH/NaOH to afford 2-arylthieno[2,3-d]pyrimidin-4-amines in high yields. Preliminary studies revealed the photophysical properties of the products and their potential for use as metal sensors.