磺化交联壳聚糖树脂固体酸催化剂的制备及表征

引言壳聚糖是自然界的第二大天然有机物甲壳素的脱乙酰产物,具有来源丰富、环境友好的优点。壳聚糖分子同时含有活泼的氨基和羟基,可通过烷基化、酯化、希夫碱等反应进行化学修饰生成具有各种不同新型结构和功能的衍生物[1]。近年来壳聚糖在催化领域的应用受到了越来越多的关注,功能化     

Production of biodegradable polyesters via enzymatic polymerization and solid state finishing

The synthesis of aliphatic polyesters (PEs) derived from diols (1,4‐butanediol and 1,8‐octanediol) and diacids or their derivatives (diethyl succinate, sebacic acid, 1,12‐dodecanedioic acid, and 1,14‐tetradecanedioic acid) was achieved in order to produce poly(butylene succinate) (PE 4.4), poly(octylene sebacate) (PE 8.10), poly(octylene dodecanate) (PE 8.12), and poly(octylene tetradecanate) (PE 8.14). The herein suggested procedure involved two stages, both sustainable and in accordance with the principles of “green” polymerization. The first comprised an enzymatic prepolymerization under vacuum, in the presence of diphenylether as solvent using Candida antarctica lipase B as biocatalyst, whereas a low‐temperature postpolymerization step [solid state polymerization (SSP)] followed in order to upgrade the PEs quality. In the enzymatically synthesized prepolymers, the range of number–average molecular weight attained was from 3700 to 8000 g/mol with yields reaching even 97%. Subsequently, SSP of PE 4.4 and 8.12 took place under vacuum or flowing nitrogen and lasted 10–48 h, at temperatures close to the prepolymer melting point (T_m ? T_SSP varied between 4°C and 14°C). The solid state finishing led to increase in the molecular weight depending on the prepolymer type, and it also contributed to improvement of the physical characteristics and the thermal properties of the enzymatically synthesized PEs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40820.     

反相悬浮聚合法制备水溶性固体聚丙烯酸

以环己烷为连续相,失水山梨醇单油酸酯(Span-80)为分散剂,K2S2O8为引发剂,采用反相悬浮聚合法合成了水溶性良好的固体聚丙烯酸(PAA),详细探讨了搅拌速度、分散剂用量、单体浓度、反应温度及反应时间等对聚合产物颗粒特性的影响。结果表明,较优的工艺条件是:搅拌速度500r/min、分散剂质量分数4%~8%(相对于单体质量)、单体质量分数50%、反应温度70℃、反应时间3.0h。     

强固体酸催化合成乙二胺的研究

研究了固体酸催化剂的制备工艺 ,采用NH4Cl离子交换后的MOR型分子筛作载体 ,并加入活性氧化铝制备成强固体酸催化剂。采用此催化剂 ,催化氨化单乙醇胺 ,可选择性的得到乙二胺 ,另外生成一定量的哌嗪。较佳的工艺条件为 :反应温度 340℃ ,NH3 /MEA摩尔比为 5 0、NH3 分压为 0 7MPa,单乙醇胺转化率大于 80 % ,乙二胺选择性为 4 8 1% ,哌嗪选择性为 31%     

Synthesis and properties of sulfonated aromatic fluoro‐polymers

Polycondensation of perfluorobiphenyl with α,α‐bis(4‐hydroxyphenyl)ethylbenzene and/or 9,9‐bis(4‐hydroxyphenyl)fluorene was investigated. The polycondensation of perfluorobiphenyl with α,α‐bis(4‐hydroxyphenyl)ethylbenzene and/or 9,9‐bis(4‐hydroxyphenyl)fluorene proceeded at low‐temperature to a give high‐molecular weight and thermal stable polymers. The ¹⁹F‐NMR spectra of the polymers indicate that the polymers consists of predominantly 1,4‐phenylene structure with respect to the perfluoro‐aromatic compound. The sulfonation of the polymers obtained from the polycondensation occurred at the phenyl groups and fluorenyl side chain. A tough and smooth film was prepared by a casting method from DMF solution of the sulfonated polymer. The films showed hydrolytic and oxidative stabilities, and a high‐proton conductivity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

On the acidity of liquid and solid acid catalysts. Part 3. Esterification of benzoic and mesitoic acids

Methyl esters of benzoic and mesitoic acid have been prepared with high yields (>98 wt%) from the corresponding carboxylic acids + methanol in aprotic solvents over samples of H₂SO₄/SiO₂ at 60°C. The results show a high catalytic efficiency of the solids but also suggest an acid strength comparable to that observed in concentrated aqueous H₂SO₄ (range >90 wt%) when the acid requirements for the esterification of analogous compounds in aqueous acid solutions are taken into account. Indeed, different reacting species, i.e., ArC(OH) ₂ ⁺ from benzoic acid and 2,4,6‐triMe‐ArC=O⁺ from mesitoic acid are involved in the esterification, but the mesitoyl cation can be formed and esterified in the acidity ranges between 92 and 98 wt% H₂SO₄. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and catalytic activity of the thermoresponsive polymers having pyrrolidine side chains as base functionalities

Optically active polymers having chiral 2‐aminomethylpyrrolidine side chains have been newly synthesized by a radical homopolymerization of the corresponding protected acrylamide monomer and copolymerization with N‐isopropylacrylamide followed by deprotection. The resulting polymers were found to be thermoresponsive showing lower critical solution temperatures (LCSTs) at 27–65°C in their aqueous solutions. The pyrrolidine side chains of the resulting thermoresponsive polymer promoted aldol reaction between cyclohexanone and p‐nitrobenzaldehyde in water, and the reaction proceeded most smoothly at its LCST. Moreover, the diastereomeric ratio (syn : anti) of the aldol adducts obtained at the reaction at 40°C was 22 : 78, whereas the diastereomeric ratio (syn : anti) was 55 : 45 at 20°C. These results indicate that the pyrrolidine side chains catalyze the aldol reactions in the relatively hydrophobic field generated by the thermoresponsive polymer at its LCST. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of polyaniline/vermiculite clay nanocomposites by in situ chemical oxidative grafting polymerization

BACKGROUND: Recently, conducting polymers have attracted much attention, since they have interesting physical properties and many potential applications, such as in conductive coating charge storage. Hence the synthesis of conducting polymer nanocomposites is also an area of increasing research activity. RESULTS: Vermiculites (VMTs) were successfully delaminated using an acid treatment. Polyaniline (PANI)/VMT nanocomposites were prepared by in situ chemical oxidative grafting polymerization. CONCLUSION: The chemical grafting of PANI/VMTs was confirmed by Fourier transform infrared and UV‐visible spectroscopy. The percentage of grafted PANI was 142.7 wt% as a mass ratio of the grafting PANI and charged nano‐VMTs, investigated using thermogravimetric analysis. In addition, characteristic agglomerate morphology of PANI was observed in the composites using scanning electron microscopy. Thermal analyses indicated that the introduction of VMT nanosheets had a beneficial effect on the thermal stability of PANI. The electrical conductivity of the nanocomposites was 3.9 × 10^?3 S cm^?1, a value typical for semiconductors. Copyright © 2009 Society of Chemical Industry     

Synthesis of conductive PSt-g-PANi/TiO2 nanocomposites by metal catalyzed and chemical oxidative polymerization

Well-defined polymer-TiO₂ nanocomposites of core–shell structure were prepared by two-steps, surface-initiated atom transfer radical polymerization (ATRP) of styrene and in situ chemical oxidative polymerization of aniline monomers from the surfaces of the TiO₂ nanoparticles. The methods used include the following: initially, the ATRP initiator was covalently attached to the surface of TiO₂ nanoparticles by esterification of 2-bromo-2-methyl propionic acid with hydroxyl group. The metal-catalyzed radical polymerization of styrene with modified TiO₂ nanoparticles was performed using a copper catalyst system to give the TiO₂-based core hybrids linking PSt segments (TiO₂-PSt hybrids). Next, the TiO₂-PSt reacted with HNO₃/H₂SO₄ to produce a nitro group containing polystyrene to form TiO₂-PSt-NO₂, and obtained TiO₂-PSt-NO₂ was treated with hydrochloric acid/SnCl₂, and converted to an amine group containing polystyrene (TiO₂–PSt-NH₂). Finally, surface oxidative graft copolymerization of aniline, using the –NH₂ moieties of TiO₂/PSt-NH₂ as the anchoring sites. Characterization of these well-defined nanocomposites included FTIR, thermogravimetric analysis, transmission electron microscopy, and X-ray diffraction.     

固体超强酸催化合成乙酸异戊酯

用固体超强酸SO42-/Fe2O3-Al2O3作催化剂,以冰乙酸和异戊醇为原料合成乙酸异戊酯,考察了醇酸摩尔配比、反应时间、反应温度对反应收率的影响,得出反应的最佳条件为：反应时间30 min,原料异戊醇与冰乙酸的摩尔配比为2.0∶1.0,催化剂用量为乙酸用量的3%,固体超强酸SO24-/Fe2 O3-Al2 O3作催...     

Hydrolysis of sugars catalyzed by water-tolerant sulfonated mesoporous silicas

Mesoporous silicas are modified with sulfonic acid groups either by one-pot or by grafting method. In the hydrolysis of sucrose and starch, the sulfonated mesoporous silicas work as water-tolerant recyclable solid acid catalysts, showing higher conversion and turnover frequency than conventional Amberlyst-15, Nafion-silica and HZSM-5 catalysts.     

磺化石墨烯固体酸催化剂的制备及活性评价

石墨烯是由碳原子以sp₂杂化连接的单原子层构成的新型二维碳原子晶体,由于含有众多具有反应活性的碳碳双键,石墨烯纳米片表面很容易进行化学修饰键合有机官能团而改变其性质。采用改良Hummers法制备氧化石墨烯,通过磺化反应制备磺化石墨烯固体酸催化剂,通过FT-IR、元素分析和XPS等对其结构进行表征。将制备的氧化石墨烯和磺化石墨烯应用于催化纤维二糖的水解反应,以纤维二糖糖苷键的水解反应为模型考察其酸催化性能。结果表明,氧化石墨烯和磺化石墨烯中含有-COOH、-OH和-SO₃H等官能团,磺酸根密度分别为1.0 mmol·g^-1和2.2 mmol·g^-1,氧化石墨烯和磺化石墨烯具有与H₂SO₄相比拟的酸催化活性,尽管酸性强度和密度较低,但催化活性与H₂SO₄相当。     

Ni0.5 Fe2.5 O4/ZrO2磁性纳米固体酸的合成与表征

将磁性基质Ni0.5Fe5O4／ZrO2和ZrO2进行组装制备出磁性固体酸催化剂，采用TEM、DTA、XRD等手段对Ni0.5Fe5O4／ZrO2磁性固体酸催化剂的结构和性能进行表征，结果表明磁性基质的引入延迟了ZrO2的晶化以及ZrO2(t)相向ZrO2(m)相的转变，使ZrO2更加稳定．     

乳液聚合法合成水杨酸分子印迹聚合物微球

以水杨酸为模板分子,乙二醇二甲基丙烯酸酯为交联剂,采用乳液聚合法制备了水杨酸分子印迹聚合物微球（SMIP）,采用紫外差示光谱分析了模板分子与功能单体的相互作用,以荧光分光光度计为检测手段,讨论了不同功能单体、模板分子与功能单体的摩尔比、交联剂用量、洗脱液类型等对SMIP吸附性能的影响,并进一步考察了SMIP的形貌和粒径分布。研究结果表明,以丙烯酰胺为功能单体合成的SMIP表现出较好的吸附性能,印迹因子可达1.61,而且微球呈单分散性,平均粒径约60 nm。     

Synthesis of polypyrrole nanoparticles in natural rubber–polystyrene blend via emulsion polymerization

Nanoparticles of polypyrrole (PPy) in 40/60 wt % natural rubber (NR)–polystyrene (PS) blends were synthesized by emulsion polymerization using ferric sulfate [Fe₂ (SO₄)₃], sodium dodecyl sulfate (SDS), and n‐amyl alcohol as the oxidant, surfactant, and cosurfactant, respectively. The NR/PS/PPy blends were characterized by Fourier transform infrared spectroscopy (FTIR), elemental analysis, thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM). FESEM micrographs showed that NR/PS/PPy blends were homogeneous, and PPy nanoparticles were well distributed throughout the binary matrix of NR/PS. The size of PPy particles in the blends was in the range of 26–80 nm. The electrical conductivities of the pellets prepared from NR/PS/PPy blends increased as the composition of PPy nanoparticles was increased, which were in the range of 8.9 × 10^?8 – 2.89 × 10^?4 S/cm. Thermal stability of the blends increased as the content of PPy was increased, as shown by TGA thermograms. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Broadband dielectric spectroscopy of Nafion‐117, sulfonated polysulfone (sPSF) and sulfonated polyether ketone (sPEK) membranes

Nafion^®‐117, sulfonated polysulfone (sPSF) and sulfonated polyetherketone (sPEK) are characterized using broadband dielectric spectroscopy in the frequency range of 10 MHz–100 mHz. Overall, there are 4–5 relaxation processes in these sulfonated membranes and a comparison of their spectral features allows assigning the relaxation processes. At an optimum amplitude of ～100 mV_rms, all the relaxations are clearly defined as the electrode polarization is minimized. At low temperatures (?130 °C), these membranes show a broad relaxation peak in the mid‐frequency region, which quickly shifts towards the high‐frequency region as the temperature is increased to ?90 °C. This peak is observed in proton exchange membranes for the first time due to the use of low ac amplitude, and it is assigned to the relaxation of the confined water in the micro‐pores. With all the membranes, the peak associated with ? SO₃H group relaxation is observed in the same frequency range at a temperature of ～?80 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44790.     

直接熔融聚合聚乙醇酸的合成与表征

以乙醇酸为原料,在催化剂氯化亚锡质量分数0.5％,反应温度165℃,反应压力70 Pa,反应时间10 h的条件下进行熔融聚合,直接合成了生物降解的医用纤维材料聚乙醇酸(PGA),用IR,DSC,X射线衍射等进行了表征,并与乙交酯开环聚合二步法合成PGA进行了比较。直接熔融聚合PGA的结晶度和微晶尺寸高于二步法,其合成工艺流程短、简单易行、耗时少,有利于降低医用纤维材料PGA的开发成本。     

炭基固体磺酸催化剂的制备及其催化活性研究

以竹材为原料,硫酸为磺化剂,通过炭化-磺化法制得竹炭基固体磺酸催化剂,并用于癸二酸和正丁醇的酯化反应,考察了制备条件对催化剂活性的影响.采用傅里叶红外光谱（FTIR）、X射线衍射（XRD）、扫描电子显微镜仪（SEM）及热失重分析（TGA）等手段对催化剂进行表征.结果表明,在炭化温度325℃下炭化1h,磺化温度125℃下磺化1h制得的催化剂,其含酸量可达到1.4 mmol/g,在催化癸二酸和正丁醇的酯化反应中,转化率高达99％,此时催化剂的催化活性最高,且催化剂可循环多次利用.此竹炭基固体磺酸催化剂具有无定形炭结构,热稳定性可达230℃.     

固体超强酸催化合成乙酸正丁酯

分别用固体超强酸S₂O₈^2-/ZrO₂ 和SO₄^2-/ZrO₂作催化剂,以冰乙酸和正丁醇为原料合成了乙酸正丁酯,考察醇与酸物质的量比、反应时间、反应温度、催化剂用量和催化剂焙烧温度等因素对酯化率的影响。得出反应的最佳条件为：n（正丁醇）∶n（冰乙酸）=1.3∶1.0 ,催化剂用量为冰乙酸质量的3%,反应温度115 ℃左右,反应时间30 min,固体超强酸S₂O₈^2-/ZrO₂ 和SO₄^2-/ZrO₂作催化剂时,乙酸正丁酯的收率分别为96.5%和90.5%。