水溶性封闭异氰酸酯单体的解封动力学

采用热失重分析(TGA)法研究了水溶性封闭型异佛尔酮二异氰酸酯(IPDI)的热分解过程, 利用傅里叶变换红外光谱法(FTIR)考察了谱图中40 与140 ℃两种温度下的异氰酸酯特征峰. TGA与FTIR的结果表明失重阶段即对应封闭异氰酸酯的解封闭反应. 用Friedman-Reich-Levi (FRL)和Flynn-Wall-Ozawa (FWO)两种动力学模型研究了解封反应的表观活化能E, 所得平均表观活化能分别为125.0和124.5 kJ·mol-1. 采用双等双步法对解封过程进行表观机理函数判断, 结果符合Jander方程, 反应机理为三维扩散, 结合FWO方程确定了反应级数n和指前因子对数lnA的范围.     

Synthesis and Properties of Imidazole-Blocked Toluene Diisocyanates

Abstract

Imidazole-, 2-methyl imidazole-, and benzimidazole-blocked toluene diisocyanates (TDI) were prepared and characterized by elemental analysis, IR, and NMR spectroscopy. Simultaneous TGA/DTA results showed that the thermal stability of the adduct decreases in the following order: imidazole-TDI > 2-methylimidazole-TDI > benzimidazole-TDI. Gelation test involving imidazole-blocked adducts and hydroxyl-terminated polybutadiene were also carried out. The cure rate of the adduct increases from the imidazole- to the 2-methylimidazole- and to the benzimidazole-blocked adduct. It is also found that the benzimidazole-blocked adduct shows better solubility in the polyols.     

Research on the Blocking Reaction Kinetics and Mechanism of Aqueous Polyurethane Micelles Blocked by 2,4,6-Trichlorophenol

The blocked terminal-isocyanate (NCO) aqueous polyurethane micelles were prepared by using the 2,6-hexamethylene diisocyanate (HDI), polyethylene glycol (PEG), dimethylol propionic acid (DMPA), and 2,4,6-trichlorophenol (TCP) as blocking agent. This paper was focused on the kinetics research of the TCP blocking terminal-NCO of pre-polymer, which occurred during the preparation process of TCP blocked aqueous polyurethane micelles. The kinetics parameters were obtained in the absence and presence of dibutyl tin dilaurate (DBTDL) as catalyst, respectively. Furthermore, the mechanism for TCP blocking terminal-NCO of pre-polymer was explored. The results showed that the blocking reaction was second order reaction, and the reaction activation energy was 43.890 KJ/mol without catalyst. In the presence of DBTDL, the blocking reaction activation energy was reduced to 34.412 KJ/mol, and the reaction rate was improved significantly. In addition, TCP blocking terminal-NCO of pre-polymer could be ascribed to the nucleophilic addition between nucleophilic phenolic hydroxyl of TCP and the carbon atom of -NCO group.     

Facile Synthesis of Polyhydroxylated Polybutadiene Derived from Hydroxyl-Terminated Polybutadiene via Thiol-Ene Click Reaction

Polyhydroxylated polybutadiene (PHPB) was synthesized via a thiol-ene click reaction between hydroxyl-terminated polybutadiene (HTPB) and 2-mercaptoethanol (ME) with 2,2’-azoisobutyronitrile (AIBN) as initiator. Effects of AIBN content, reaction time and temperature on the click reaction were investigated by determining hydroxyl value of the PHPB. The PHPB was characterized by FT-IR, ¹H-NMR, ¹³C-NMR and GPC. Relative reactivity of three types of C?C double bonds (1,2-vinyl, 1,4-cis and 1,4-trans units) in the HTPB reacting with the ME was discussed. The results showed that the optimal reaction conditions were that the AIBN content, reaction time and temperature were 2.0 wt%, 180 min and 70°C, respectively. Under these conditions, the hydroxyl value of the PHPB was 3.12 mmol·g^?1 when the HTPB/ME mass ratio was 10:2. All three types of C?C double bonds in the HTPB could react with the ME and the reactivity order was: 1,2-vinyl unit > 1,4-cis unit > 1,4-trans unit.     

甲基紫精对三乙胺与C60反应的催化作用

采用ESR技术对甲基紫精(MV2 )在三乙胺与C60的电子转移反应中的催化作用进行了研究.反应体系无MV2 存在时,三乙胺与C60并不发生电子转移反应,得不到电荷的分离态;在MV2 存在的条件下,由三乙胺向C60分子的电子转移得以实现,并检测到活泼中间体MV ·及电荷分离态C-·60,MV2 　实质上起到催化剂的作用.     

环氧丁羟型聚氨酯弹性体的制备与性能

以间氯过氧苯甲酸(mCPBA)为氧化剂对降解法制备的端羟基聚丁二烯(DHTPB)中的部分双键进行环氧化改性,通过控制mCPBA和双键的比例制得具有不同环氧率的环氧化端羟基聚丁二烯(EHTPB),经1H-NMR分析测试表明EHTPB的环氧率分别为5%、10%和15%,与设计值基本一致.进一步以EHTPB为多元醇、4,4'-二苯基甲烷二异氰酸酯(MDI)为异氰酸酯、1,4-丁二醇为扩链剂制备了环氧丁羟型聚氨酯弹性体(EPU),并对其性能进行了测试,研究结果表明:丁羟胶的环氧化改性对聚氨酯弹性体的力学性有着一定的提升作用,其杨氏模量和拉伸强度随环氧率的上升而提高,而断裂伸长率则随环氧率的上升有所下降;环氧丁羟型聚氨酯弹性具有优异的弹性恢复能力;环氧化改性后,聚氨酯弹性体的热稳定性有一定程度的提高;聚氨酯弹性体的玻璃化转变温度随环氧率的上升而升高.     

端羟基聚丁二烯/增塑剂共混物相容性的分子动力学模拟

固体推进剂和炸药的力学性能在很大程度上依赖于配方中高分子粘结剂与增塑剂的相容性. 本文对相容和非相容两种体系进行了分子动力学(MD)模拟, 以考察分子模拟方法的实用性. 为预测固体推进剂中端羟基聚丁二烯(HTPB)与增塑剂癸二酸二辛酯(DOS)、硝化甘油(NG)的相容性, 采用MD模拟方法在COMPASS力场下, 对HTPB、DOS、NG和共混物HTPB/DOS、HTPB/NG的密度、内聚能密度及溶度参数等进行了模拟计算. 通过比较溶度参数差值(△δ)的大小、分子间径向分布函数和模拟前后体系密度变化情况均可以预测HTPB/DOS属于相容体系,而HTPB/NG属于不相容体系, 与实验结果一致. 径向分布函数分析同时揭示了HTPB/增塑剂组分之间的相互作用及本质. 本文的模拟方法可以作为预测聚合物与增塑剂相容性的有利工具, 也可以为固体推进剂和炸药的配方设计提供理论指导.     

聚丁二烯聚氨酯(脲)

综述了聚丁二烯聚氨酯（脲）的结构与性能，影响性能的因素和改性方法，并简要介绍了其应用。     

A catalyst system for the formation of amides by reaction of carboxylic acids with blocked isocyanates

A catalyst for the reaction of blocked isocyanates (blocking agent diisopropylamine and dimethyl pyrazole) and carboxylic acids was identified. Magnesium and in some instances calcium salts proved to be highly active as catalyst. This reaction gives amides in quantitative yield and excellent selectivity and is suitable for coating and general chemical purposes.     

Base-Mediated Biginelli-Like Reaction Ignited by Aromatic Isocyanate: A Facile One-Pot Synthesis of N 4-Aryl-5-carboxyl-6-methyl Cytimidine Derivatives

The new three-component Biginelli reaction of aromatic isocyanate, ethyl acetoacetate, and substituted urea (or thiourea as well as guanidine) is described for the first time. In this reaction, N ⁴-aryl-5-carboxyl-6-methyl cytimidine derivatives were obtained in moderate to excellent yields by employing DBU as a highly effective catalyst. This methodology provides several advantages such as good functional group tolerance, excellent yields, atom efficiency, and experimental simplicity.     

Metal-Containing Initiator Systems. 30. Vinyl Polymerization Initiated with Bis(ethyl acetoacetato)copper(II) and Maleimide

Some electron-accepting compounds such as maleimide (MIm), maleic anhydride (MAn), and tetracyanoquinodimethane were found to show pronounced accelerating effects on vinyl polymerization initiated with metal chelates. The polymerization of methyl methacrylate (MMA) initiated with bis(ethyl acetoacetato)-copper(II) (Cu(eacac)₂) and MIm was studied kinetically in benzene. The overall activation energy of the polymerization was calculated to be 11.5 kcal/mol. This value was much lower than that (17.6 kcal/mol) for the polymerization of MMA with Cu(eacac)₂ alone. The polymerization rate (R_p) was expressed as R_p =k[MIm]^1/2 [Cu(eacac)₂]^1/2 [MMA] The first-order dependence of R_p on the monomer concentration indicated that the monomer had no participation in the initiation step, in contrast with polymerization in the absence of MIm (where a monomer concentration dependence of 1.4th order was observed). Electronic spectroscopic study revealed that a complex between MIm and Cu(eacac)₂ had been formed. The ligand radical, an acetylcarboethoxymethyl radical, was trapped by 2-methyl-2-nitrosopropane in the reactions of Cu(eacac)₂ with MIm and with MAn in benzene. From these results the mechanism of the initiation of polymerization is discussed.     

电化学催化下的多氟烷基化反应研究进展

氟化学已经在各行各业受到广泛应用,氟化学和有机化学的结合也遍地生花.由于将氟原子或氟基团引入到药物中具有重要意义,因此寻求一种有效的氟烷基化途径至关重要.随着电化学的发展,人们将电化学和氟烷基化反应进行了巧妙地结合.进而得到了更加安全、经济、环保并且高效的氟烷基化途径.在电化学指导下的氟烷基化反应途径,不仅在反应方式方...     

Preparation of a blocked isocyanate compound and its grafting onto styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer

The ε-caprolactam was used to block the isocyanate group to enhance the storage stability of allyl (3-isocyanate-4-tolyl) carbamate. The spectra of FTIR and NMR showed that blocked allyl (3-isocyanate-4-tolyl) carbamate (BTAI) possesses two chemical functions, an 1-olefin double bond and a blocked isocyanate group. The FTIR spectrum showed BTAI could regenerate isocyanate group at elevated temperature. DSC and TG/DTA indicated the minimal dissociation temperature was about 135 °C and the maximal dissociation rate appeared at 226 °C. Then the styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer (SEBS) was functionalized by BTAI via melt free radical grafting. The effect of temperature, monomer and initiator concentrations on the grafting degree and grafting efficiency was evaluated. The highest grafting degree was obtained at 200 °C. The grafting degree and grafting efficiency increased with the enhanced concentration of BTAI or initiator. The weight-average molecular weight (M_w) increased greatly at higher initiator concentration and lower ratio of the monomer/initiator. And the molecule weight distribution (MWD) of the modified SEBS became wider than that of pure SEBS. It is obvious that shearing thinning behavior of grafted SEBS is more profound than pure SEBS.     

CURE CHARACTERISTICS OF HYDROXYL TERMINATED POLYBUTADIENE PREPOLYMER WITH BLOCKED TOLUENE DIISOCYANATE-Ⅱ

Cure characteristics of hydroxyl terminated polybutadiene (HTPB) prepolymer with avariety of blocked toluene diisocyanate (TDI) in the presence of triethylamine (TEA) andchloroacetic acid catalyst are reported. Phenol, thiophenol, p-chloropheno1, p-nitrophenol,p-cresol, resorcinol, naphthols, caprolactam and butylated-hydroxytoluene were used as blockingagents. Viscosity measurements have been carried out using a mixture of HTPB and blocked TDIin cyclohexanone in the presence of the catalysts at 50℃ and 60℃ using Haake rotational vis-cometer. Viscosity measurements have also been carried out with 50% solids such as ammonium sulphate along with HTPB and TDI adduct.     

Acidic Media Impedes Tandem Catalysis Reaction Pathways in Electrochemical CO2 Reduction

Electrochemical CO₂ reduction (CO₂R) in acidic media with Cu-based catalysts tends to suffer from lowered selectivity towards multicarbon products. This could in principle be mitigated using tandem catalysis, whereby the *CO coverage on Cu is increased by introducing a CO generating catalyst (e.g. Ag) in close proximity. Although this has seen significant success in neutral/alkaline media, here we report that such a strategy becomes impeded in acidic electrolyte. This was investigated through the co-reduction of ¹³CO₂/¹²CO mixtures using a series of Cu and CuAg catalysts. These experiments provide strong evidence for the occurrence of tandem catalysis in neutral media and its curtailment under acidic conditions. Density functional theory simulations suggest that the presence of H₃O⁺ weakens the *CO binding energy of Cu, preventing effective utilization of tandem-supplied CO. Our findings also provide other unanticipated insights into the tandem catalysis reaction pathway and important design considerations for effective CO₂R in acidic media.     

Cure study of addition-cure-type and condensation-addition-type phenolic resins

By the incorporation of propargyl and methylol groups on to novolac backbone, a series of addition-curable phenolic resins and condensation-addition dual-cure type phenolic resins (novolac modified by propargyl groups referred as PN, and novolac modified by propargyl and methylol groups simultaneously referred as MPN) were synthesized. The processing characteristics, thermal cure and catalytic cure behavior for both resins were investigated mainly by means of viscosity measurement and non-isothermal differential scanning calorimetry (DSC) techniques. The effect of propargyl and methylol content of PN and MPN, the molecular weight and the configuration of the parent novolac, on the processing and cure behavior was studied in details. Processing parameters and curing kinetic parameters were obtained. Both resins exhibit excellent processing properties. Thermal cure of PN resins possessed one cure mechanism and that of MPN resins possessed two cure mechanisms according to DSC analysis. The dual-cure-type mechanism made MPN resins superior to PN resins in terms of a mild and controllable cure process. Compared with thermal cure, catalytic cure of PN resins showed lower initiation temperature and cure temperature by about 60 °C. These novel resins have a bright prospect of application as matrix for thermal-structural composite materials.     

Turning Points in Catalysis

This personal journey through the enlarging landscape of heterogeneous catalysis, pure and applied, starts with the discovery in 1823 of a dramatic example of the synthesis of water that was to serve as the basis of the first commercial exploitation of catalysis, Dobereiners lighter (tinder box). The quickening pace of successive industrial innovations and of academic insight during the intervening 170 years are summarized and the turning points, both major and minor, identified. Although new concepts and new ideas emerged in relative profusion, few exhibited the longevity predicted for them at birth by their proponents. Some concepts, like broken milestones on a vanished road, have ceased to retain their significance. Some have survived, even flourished. But in catalysis, as in most other branches of natural science, new tools and new techniques, rather than new concepts, tend to hold sway. And just as experimental advances in enzymology and immunology have led to the design of remarkable new biocatalysts so also, but not yet at the same level of delicate control, have the tools and techniques of solid-state chemistry (including novel preparative and computational procedures), generated many powerful rationally designed inorganic catalysts.     

Effects of SEBS-g-BTAI on the morphology, structure and mechanical properties of PA6/SEBS blends

Styrene-b-(ethylene-co-1-butene)-b-styrene (SEBS) triblock copolymer functionalized with ε-caprolactam blocked allyl (3-isocyanate-4-tolyl) carbamate (SEBS-g-BTAI) was used to toughen polyamide 6 (PA6) via reactive blending. Compared to the PA6/SEBS blends, mechanical properties such as tensile strength, Young’s modulus, especially Izod notched strength of PA6/SEBS-g-BTAI blends were improved distinctly. Both rheological and FTIR results indicated a new copolymer formed by the reaction of end groups of PA6 and isocyanate group regenerated in the backbone of SEBS-g-BTAI. Smaller dispersed particle sizes with narrower distribution were found in PA6/SEBS-g-BTAI blends, via field emitted scanning electron microscopy (FESEM). The core-shell structures with PS core and PEB shell were also observed in the PA6/SEBS-g-BTAI blends via transmission electron microscopy (TEM), which might improve the toughening ability of the rubber particles.     

傅克烷基化反应在超高交联聚合物中的应用

超高交联聚合物主要是通过傅克烷基化反应来制备的,具有合成简单、多孔、无毒、结构稳定、质轻等特点。本文介绍了傅克烷基化反应的条件和机理,展示了超高交联聚合物的合成方法及这些材料在气体储存/分离、水处理、催化、传感等领域中的应用,并对傅克烷基化反应与超高交联聚合物的进一步结合做出了展望。     

NMR Analysis of Hydroxyl-Terminated Polybutadiene End Groups and Reactivity Differences with Monoisocyanates

Nuclear magnetic resonance (NMR) spectroscopy was employed to investigate both the end group microstructure of R-45HTLO hydroxyl-terminated polybutadiene (HTPB) and reactivity rate differences among the different types of end groups. There is some conflict in the literature about the exact nature of the end groups and which resonance frequencies represent the three main types of methylene-hydroxyl end groups (cis, trans, or vinyl) and other possible branch point end groups (geraniol). NMR spectral analysis of small molecule model compounds supports the cis, trans, and vinyl end groups model. A model reaction scheme is proposed that produces branch points without the requirement of any “geraniol” structures. The reaction, with and without catalyst, of the various HTPB end groups with three different monoisocyanates (2-fluorophenyl isocyanate, phenyl isocyanate, and tert-butyl isocyanate) monitored by NMR spectroscopy, revealed different reactivity rates that are correlated with the assigned structures. In both the catalyzed and uncatalyzed reactions, the vinyl end groups reacted slower than the cis or trans end groups. As expected, the bulky isocyanates were the slowest to react, while the isocyanate group with electron withdrawing groups reacted the fastest. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2665–2671