Laccase/TEMPO-modified lignin improved soy-protein-based adhesives: Adhesion performance and properties

The aim of this study was to enhance the water resistance of soy protein (SP) adhesives using laccase/TEMPO-modified lignin. Kraft lignin was depolymerized by laccase enzyme in the presence of TEMPO to expand the oxidation reaction of both phenolic and non-phenolic compounds. This simplified process has the distinct advantage of enhancing lignin-protein interaction. Compared with SP adhesives, lignin-protein adhesives showed a stronger elastic modulus, higher thermal stability, and increased wet adhesion performance. Wet shear strength increased by 106% from 0.693 to 1.429 MPa, and partial wood failure was observed after the test. Better performance was also observed in the three-cycle soaking test. At the same time, the stronger interactions between -COO^- and -NH₂ groups of protein and lignin led to a decrease in flowability and spreadability.     

机械浆长纤维的TEMPO选择性催化氧化

采用TEMPO/NaBr/NaC10体系将机械浆长纤维精基单元中的伯羟基选择性氧化成羧基来提高纸浆纤维羧基的含量.研究了TEMPO、NaBr和NaC10的用量以及浆浓对纸浆纤维氧化的影响,同时研究了羧基含量对机械浆长纤维性能的影响.结果表明,在氧化过程中,随着TEMPO和NaBr用量的增加,反应速度提高,而氧化后的纸浆纤维羧基含量没有增加,随着NaC10用量的增加,纸浆纤维的羧基含量上升.随着纸浆纤维浓度的增加.羧基含量先上升后下降,浆浓在1.3%时,羧基含量达到最高值.随着纸浆纤维羧基含景的增多,浆料抄片的抗张指数和耐破指数上升,撕裂指数下降,氧化的纸浆纤维对细小纤维的留着率下降;浆料的保水值上升而游离度下降;浆纤维的卷曲和扭曲系数降低.研究还发现,低羧基含量的纤维能够吸附部分有机溶解物以及其他物质,使得白水中的有机溶解物和总有机碳的含量下降,这种吸附性能随着羧基含量的增加而下降.     

Nitroxide‐mediated polymerization of styrene initiated from the surface of montmorillonite clay platelets

Polymer‐grafted montmorillonite (MMT) hybrid composites which possess a hard backbone of MMT and a soft shell of brush‐like polystyrene (PSt) were prepared via “grafting from” strategy based on nitroxide‐mediated radical polymerization (NMRP) using 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) as mediator. Three steps were used to graft PSt chains to the surface of MMT: anchoring of methacrylatoethyl trimethyl ammonium chloride (DMC) onto the surface of MMT by ion exchange reaction first. And then, the surface alkoxyamine initiator was produced in a one‐step process by reacting simultaneously TEMPO, BPO, and DMC in the presence of MMT. Next, PSt chains with controlled molecular weights and polydispersities were grown from the alkoxyamine functionalized MMT surface. The prepared PSt‐g‐MMT hybrid particles have been extensively characterized by FTIR, XPS, XRD, TGA, TEM, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and reactivity of functionalized alkoxyamine initiators for nitroxide‐mediated radical polymerization of styrene

The synthesis and examination of different functionalized (2,2,6,6‐tetramethyl‐1‐piperidinyloxy free radical) TEMPO‐containing alkoxyamine initiators for nitroxide‐mediated radical polymerization of styrene are reported. Initiators with ester and carbonate functional groups were synthesized by a low‐temperature radical‐abstraction reaction of the functionalized ethylbenzene in the presence of TEMPO to introduce the functional groups onto the initiating chain‐end of polystyrene. An initiator with two alkoxyamine groups symmetrically located at each end of a carbonate bond was also synthesized and used for nitroxide‐mediated styrene polymerization. Styrene polymerization using these initiators followed first‐order kinetics up to approximately 60 min at 140 °C or 30% monomer conversion. Alkoxyamines bearing an acetoxy or tert‐butylcarbonate group at the p‐position of 1‐(2,2,6,6‐tetramethyl‐1‐piperidinyloxy)ethylbenzene behave in a similar way to the unfunctionalized initiator. With an initiator containing two alkoxyamine groups, the resulting polymer molecular weight was twice that of the polymer obtained from initiators with only one alkoxyamine group, as expected from propagation from both chain‐ends. Upon hydrolysis of the carbonate bond, it was revealed that equivalent polymer chain growth occurred from each alkoxyamine site in the difunctional initiator. Copyright © 2003 Society of Chemical Industry     

Grafting of polystyrene branches to polyethylene and polypropylene

Polyethylene (PE) and polypropylene (PP) were reacted with benzoyl peroxide (BPO) and 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) to prepare PE‐TEMPO and PP‐TEMPO macroinitiators, respectively. Molecular weight of PP decreased, whereas that of PE increased during the reaction with the BPO/TEMPO system. Polystyrene (PS) branches were grafted to PE and PP backbone chains as a result of bulk polymerization of styrene with the PE‐TEMPO and PP‐TEMPO macroinitiators. A significant amount of PS homopolymer was produced as a byproduct. Weight of the resulting PE‐g‐PS and PP‐g‐PS increased with the polymerization time up to 20 h and then leveled off. Melting point of PE and PP domains in PE‐g‐PS and PP‐g‐PS, respectively, lowered as the content of PS in the copolymers increased. However, glass transition of the copolymers was almost identical with that of PS homopolymer, indicating that the constituents in the copolymers were all phase‐separated from each other. In scanning electron microscopy of the incompatible PE/PS, PP/PS, and PE/PP/PS compounded with PE‐g‐PS and PP‐g‐PS, any clear indication of enhanced adhesion between the phases was not observed. However, phase domains in the blends were, nevertheless, reduced significantly to raise mechanical properties such as maximum stress and elongation at break by 20–75%. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1103–1111, 2002     

聚苯乙烯负载TEMPO催化醇的选择性氧化

将4-羟基-TEMPO通过醚键负载于聚苯乙烯氯球上制得负载TEMPO氯球(TEMPO-PS),考察了TEMPO-PS/CuCl体系催化苄醇选择性氧气氧化的性能。结果表明,在离子液体[bmi m][PF6]中,TEMPO-PS/CuCl体系对各种苄醇均有较好的催化活性。催化体系经3次循环使用活性无明显降低。     

TEMPO催化醇氧化反应的最新研究进展

有机小分子催化剂2,2,6,6-四甲基哌啶-1-氧自由基（TEMPO）催化醇的氧化,反应条件温和,具有高活性和高选择性,成为醇选择氧化的一个重要方法。综述了近几年TEMPO催化醇氧化反应的发展过程及其固定化方法的研究进展。     

氧化甲壳素的合成

在TEMPO（2，2，6，6-四甲基哌啶氮氧自由基）和NaBr的催化作用下用NaClO溶液氧化甲壳素得到氧化甲壳素；产品纯化后，经^13C-NMR和红外分析鉴定出糖基C6位羧基的存在；同时对原料的选择和反应的工艺备件作了初步的探索，得到了合适的反应温度（0-5℃）和pH值（10-11），产率迭到45％左右。     

Iron Chloride/4‐Acetamido‐TEMPO/Sodium Nitrite‐Catalyzed Aerobic Oxidation of Primary Alcohols to the Aldehydes

A variety of 4‐substituted 2,2,6,6‐tetramethylpiperidyl‐1‐oxy (TEMPO) derivatives has been screened for their ability in the oxidation of primary alcohols to the aldehydes with dioxygen under mild conditions. An evaluation of the efficiency of these 4‐substituted TEMPO derivatives in the alcohol oxidation may allow an insight into the effect of the structural variations of TEMPO on the oxidation of alcohols, which should facilitate catalyst design and screening efforts. Based on the screening results of 4‐substituted TEMPO derivatives, the catalyst comprised of 4‐acetamido‐TEMPO, iron chloride and sodium nitrite, has been developed for the highly efficient oxidation of a wide range of primary alcohols including primary aliphatic alcohols to the corresponding aldehydes under mild conditions.     

The electrochemistry of TEMPO-mediated oxidation of alcohols in ionic liquid

The detailed electrochemistry of TEMPO-mediated oxidation of alcohols to carbonyl compounds in ionic liquid medium is presented. It is shown that TEMPO diffusion currents are suppressed in IL medium, relative to acetonitrile solvent, due to the high viscosity of the IL medium; however, the presence of substrate and base reagent significantly reduces IL viscosity, improving performances significantly. Cyclic voltametry shows that the kinetics of the reaction between electrooxidized TEMPO and the alcohol are similar in both media. It was also observed that in the case where the oxidation product is non-enolizable, electrolyses (diaphragm cell) with catalytic quantities of TEMPO, and in the presence of base (2,6-lutidine), results in close to 100% Faradaic and 100% chemical efficiencies. In contrast, prolonged electrolysis of alcohols yielding enolizable products results in catalyst deactivation due to the irreversible reaction between the active form of the catalyst and the product, which ultimately leads to low product yields and catalyst loss. Under these circumstances, reasonable Faradaic and chemical selectivities can only be obtained with partial electrolyses (to ≤1F/mol).