Kinetic model of transesterification of diphenyl carbonate and 1,4-butyldiol

The transesterification of diphenyl carbonate (DPC) with 1,4-butyldiol (BD) was kinetically investigated in the presence of lithium acetate catalyst at 465 K.The reaction was followed by the measurement of the quantity of phenol which was distilled from the reactor.The experiments supported the assumption that the phenyl ester groups in DPC and phenyl hdroxybutyl carbonate (PHBH) had the same reactivity,and the transesterification obeyed first-order kinetics with respect to DPC and BD,and a rate equation was derived.The reaction rate was found to be first order with respect to the catalyst concentration as well.When those data were incorporated in the rate equation,excellent agreement between calculated values and the observed ones was recognized over a wide range.     

Kinetic model of transesterification of diphenyl carbonate and 1, 4-butyldiol

The transesterification of diphenyl carbonate(DPC)with 1,4-butyldiol(BD)was kinetically investigated in the presence of lithium acetate catalyst at 465K.The reaction was followed by the measurement of the quantity of phenol which was distilled from the reactor.The experiments supported the assumption that the phenyl ester groups in DPC and phenyl hdroxybutyl carbonate(PHBH)had the same reactivity,and the transesterification obeyed first-order kinetics with respect to DPC and BD,and a rate equation was derived.The reaction rate was found to be first order with respect to the catalyst concentration as well.When those data were incorporated in the rate equation,excellent agreement between calculated values and the observed ones was recognized over a wide range.     

Kinetics of vinylation of 4′-bromoacetophenone with n-butyl acrylate using palladacycle catalyst

The kinetics of vinylation of 4′-bromoacetophenone (4′-BAP) with n-butyl acrylate (n-BA) has been studied using palladacycle catalyst precursor 1, in the presence of sodium acetate (NaOAc) as a base and tetrabutylammonium bromide (TBAB) as a promoter in N-methyl-2-pyrrolidinone (NMP) solvent. The rate was found to be first order with respect to 4′-BAP, fractional order with the catalyst, and first order tending to zero order with NaOAc concentration. The rates passed through a maximum with variation of TBAB and n-butyl acrylate concentrations. The rate data have been analyzed to propose an empirical model, which is in good agreement with the mechanism already established for Heck reactions using palladacycle catalysts.     

New trends in the kinetics of hydroformylation of vinyl acetate using Rh complex catalysts

The kinetics of hydroformylation of vinyl acetate using [Rh(CO)₂Cl]₂ complex catalyst has been investigated at 80 °C. The trends are quite different from those observed for the HRh(CO)(PPh₃)₃-catalyzed systems. The dependence of the rate on P(H₂) and P(CO) was found to be linear, whereas the dependence of rate on vinyl acetate concentration was found to be first order, followed by substrate-inhibited kinetics at higher olefin concentrations. The rate dependence on the catalyst concentration was found to be fractional order. A rate equation has been proposed and kinetic parameters evaluated.     

Kinetics of formation and properties of aliphatic polyisocyanurates: Effect of monomer functionality

The kinetics of isothermal cyclotrimerization of bifunctional hexamethylene diisocyanate and trifunctional isocyanurate in the presence of hexabutyldistannyl oxide as a catalyst has been studied with differential scanning calorimetry and dielectric relaxation spectroscopy. It has been demonstrated that a rise in the glass transition temperature in the course of cure of the trifunctional monomer is satisfactorily described by the equilibrium first-order kinetics. The evolution of dielectric parameters is similar for both samples but is characterized by a shift along the time scale because of different specific concentrations of isocyanate groups in the parent monomers. Given the same catalyst concentration, the trimerization of hexamethylene diisocyanate proceeds at a higher rate than that of isocyanurate. For maximally cured systems, this effect manifests itself as a small increase in the glass transition temperature and the shear modulus in the rubbery state and a change in the temperature interval of α relaxation.     

Cyclotrimerization of aryl isocyanates catalyzed by alkoxyallenes through zwitterionic mechanism

Alkoxyallenes ( 1 ) are found to catalyze cyclotrimerization of aryl isocyanates ( 2 ) in dimethylformamide (DMF) to afford 1,3,5-triaryl-s-triazine-2,4,6-trione ( 3 : cyclic trimer of 2 ), although the reaction of 1 with 2 in bulk gave the corresponding copolymer. In order to speculate about the mechanism of the cyclotrimerization, macrozwitterion 4 , was prepared by copolymerization of 1 and 2 in bulk, and the catalytic activity of 4 was further studied. Cyclotrimerization of 2 was promoted by 4 and quenching of 4 with methanol completely destroyed the catalytic activity. Consequently, the alkoxyallene-catalyzed cyclotrimerization of 2 is assumed to take place through a zwitterion generated from 1 and 2 .     

Synthesis of crosslinked poly(butyl methacrylate‐co‐pentaerythritol triacrylate) gel by single electron transfer‐living radical polymerization and its oil‐absorbing properties

A novel high oil‐absorbing crosslinked gel was synthesized by copolymerization of butyl methacrylate (BMA) with a small amount of pentaerythritol triacrylate (PETA) crosslinker using single electron transfer‐living radical polymerization (SET–LRP) initiated with carbon tetrachloride (CCl₄) and catalyzed by Cu(0)/hexamethylenetetramine (HMTA) in N, N‐dimethylformamide (DMF). The polymerization followed first‐order kinetics as indicated by linear increase of monomer concentration with reaction time. Effects of reaction temperature, crosslinker, initiator, and catalyst on the oil‐absorbing properties of the crosslinked gel were investigated in detail. The oil absorptions of the crosslinked gel to chloroform, toluene could reach 51.9, 34.5 g/g, respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

聚苯乙烯微球负载脲催化剂与碱协同催化环内酯的开环聚合

通过环己基异氰酸酯和4-三氟甲基苯异氰酸酯分别与氨基化聚苯乙烯反应, 构筑了聚苯乙烯(PS)负载的环己基脲(PS-U₁)和聚苯乙烯负载的4-三氟甲基苯基脲催化剂(PS-U₂). 利用PS-U/KOMe二元催化体系协同催化环内酯的开环聚合. 结果表明, PS-U/KOMe二元体系可高效催化ε-己内酯(ε-CL)、 δ-戊内酯(δ-VL)和L-丙交酯(L-LA)的开环聚合, 制备了低催化剂残留且环境友好的聚酯材料; 同时实现了PS-U的回收及循环利用.     

Cyclo-oligomerization of isocyanates with Na(PH2) or Na(OCP) as “P–” anion sources

We show that the 2-phosphaethynolate anion, OCP^–, is a simple and efficient catalyst for the cyclotrimerization of isocyanates. This process proceeds step-wise and involves five-membered heterocycles, namely 1,4,2-diazaphospholidine-3,5-dionide anions and spiro-phosphoranides as detectable intermediates, both of which were also found to be involved in the catalytic conversion. These species can be considered as adducts of a phosphide anion with two and four isocyanate molecules, respectively, demonstrating that the OCP^– anion acts as a formal “P^–” source. The interconversion between these anionic species was found to be reversible, allowing them to serve as reservoirs for unique phosphorus-based living-catalysts for isocyanate trimerization.     

Thermochromic and solvatochromic zinc biladienones: dynamic equilibria of a metal complex having a flexible framework sensitive to environment

Dehydration of zinc biladienone was catalyzed by zinc acetate, while the reverse reaction was catalyzed by triethylamine. The transformation can be performed thermally without catalyst, and the ratio of the hydrated form to the dehydrated form depended on the solvents: the dehydrated form is favored in CHCl₃ and CH₂Cl₂, while the hydrated form is favored in hexane, pyridine, and DMF. Kinetic studies on the thermal transformation of zinc biladienone from its hydrated blue form to the dehydrated yellow-brown form were performed in toluene and THF. The rate law was half order with respect to the zinc biladienone concentration in toluene, while first order in THF, leading to a slow transformation in concentrated solution in toluene.     

Fluoropolyethers end‐capped by polar functional groups. III. Kinetics of the reactions of hydroxy‐terminated fluoropolyethers and model fluorinated alcohols with cyclohexyl isocyanate catalyzed by organotin compounds

The kinetics of the dibutyltin dilaurate (DBTDL)‐catalyzed urethane formation reactions of cyclohexyl isocyanate (CHI) with model monofunctional fluorinated alcohols and fluoropolyether diol Z‐DOL H‐1000 of various molecular weights (100–1084 g mol^?1) in different solvents were studied. IR spectroscopy and chemical titration methods were used for measuring the rate of the total NCO disappearance at 30–60 °C. The effects of the reagents and DBTDL catalyst concentrations, the solvent and hydroxyl‐containing compound nature, and the temperature on the reaction rate and mechanism were investigated. Depending on the initial reagent concentration and solvent, the reactions could be well described by zero‐order, first‐order, second‐order, or more complex equations. The reaction mechanism, including the formation of intermediate ternary or binary complexes of reagents with the tin catalyst, could vary with the concentration and solvent and even during the reaction. The results were treated with a rate expression analogous to those used for enzymatic reactions. Under the explored conditions, the rate of the uncatalyzed reaction of fluorinated alcohols with CHI was negligible. Moreover, there was no allophanate formation, nor were there other side reactions, catalysis by urethane in the absence of DBTDL, or a synergetic effect in the presence of the tin catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3771–3795, 2002     

稀土Schiff碱配合物催化烷基异氰酸酯室温聚合

利用Schiff碱稀土配合物Ln（H2Salen）2Cl3·2C2H5OH与AI（i—Bu）3组成的催化体系催化烷基异氰酸酯室温聚合,详细考察了催化剂组成以及聚合条件等对烷基异氰酸酯聚合的影响,并研究了己基异氰酸酯的聚合动力学．以La、Nd、Sm和Gd四种稀土元素为代表,合成了相应的Schiff碱配合物,结果表明轻稀土体系比重稀土体系好,La的聚合活性最高．在-40℃-40℃很宽的聚合温度范围内,可以得到分子量分布窄（MWD=1．50～2．40）的高分子量聚异氰酸酯,20℃为最佳的聚合温度．己基异氰酸酯的最佳聚合条件为：[AI]／[La]=30（摩尔比）,[n-HexNCO]／[La]=100,[n—HexNCO]=3．43mol／L,甲苯溶液中20℃聚合12h,聚合物收率74．0％,聚合物黏均分子量高达73．5×10^4,数均分子量40．2×10^4,MWD=1．79．聚合动力学研究表明己基异氰酸酯聚合反应对单体浓度和催化剂浓度都是一级关系,聚合反应活化能为43．64kJ／mol．     

Effect of polar aprotic solvents on the trimerization of phenyl isocyanate by organometallic catalysts

Studies of the trimerization of phenyl isocyanate by organometallic catalysts in the presence of various solvents have shown that dipolar aprotic solvents, such as DMSO and DMF, even in small amounts enhance greatly the rate of reaction. In accordance with their mode of action and of the effect of DMSO or DMF, the catalysts could be divided into three groups. Group I comprises tributyltin oxide, Ti(OBu)₄ and Zr(OBu)₄, which give a fast addition to the isocyanate. Maximum increase in rate was observed at DMSO:PhNCO = 1:1 due to the formation of a 1:1 charge transfer complex between them. Group 2 comprises naphthenates of Pb.Zr and Co which form complexes with the isocyanate, the reaction being much faster with the C.T. complex of DMSO and PhNCO: maximum increase in rate was observed at low DMSO concentrations, about the same as that of the catalyst. Group 3 comprises nucleophiles such as the amine catalysts, where the enhancement in rate was not great, due to the same mode of nucleophilic interaction of the catalyst and DMSO or DMF with the isocyanate.     

Nd(naph)3-Al(i-Bu)3体系催化丙烯酸乙酯及丙烯酸亚丁酯聚合

丙烯酸酯类极性单体的聚合反应通常采用自由基型引发剂。过渡金属化合物与烷酸铝所组成的配位催化剂对这类极性单体的催化聚合迄今仍处于研究阶段。我们在稀土催化环氧烷烃聚合的基础上曾研究了稀土钕的磷酸盐体系催化甲基丙烯酸甲酯、正丁酯的聚合。本文研究了环烷酸钕体系催化丙烯酸乙酯及丙烯酸正丁酯的聚合特征。     

Novel synthesis of rod‐coil block copolymers by combination of coordination polymerization and ATRP

Combination of coordination polymerization and atom transfer radical polymerization (ATRP) was applied to a novel synthesis of rod‐coil block copolymers. The procedure included the following steps: (1) monoesterification reaction of ethylene glycol with 2‐bromoisobutyryl bromide yielded a α‐bromo, ω‐hydroxy bifunctional initiator, (2) CpTiCl₃ (bifunctional initiator) catalyst was prepared from a mixture of trichlorocyclopentadienyl titanium (CpTiCl₃) and bifunctional initiator. Coordination polymerization of n‐butyl isocyanate initiated by such catalyst provided a well‐defined macroinitiator, poly(n‐butyl isocyanate)‐Br (PBIC‐Br), and (3) ATRP method of vinyl monomers using PBIC‐Br provided rod (PBIC)‐coil block copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4037–4042, 2007     

Synthesis of poly(methyl methacrylate) via ARGET ATRP and study of the effect of solvents and temperatures on its polymerization kinetics

This investigation reports the synthesis of poly(methyl methacrylate) via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) and studies the effect of solvents and temperature on its polymerization kinetics. ARGET ATRP of methyl methacrylate (MMA) was carried out in different solvents and at different temperatures using CuBr₂ as catalyst in combination with N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a ligand. Methyl 2‐chloro propionate was used as ATRP initiator and ascorbic acid was used as a reducing agent in the ARGET ATRP of MMA. The conversion was measured gravimetrically. The semilogarithmic plot of monomer conversion versus time was found to be linear, indicating that the polymerization follows first‐order kinetics. The linear polymerization kinetic plot also indicates the controlled nature of the polymerization. N,N‐Dimethylformamide (DMF), tetrahydrofuran (THF), toluene, and methyl ethyl ketone were used as solvents to study the effect on the polymerization kinetics. The effect of temperature on the kinetics of the polymerization was also studied at various temperatures. It has been observed that polymerization followed first‐order kinetics in every case. The rate of polymerization was found to be highest (k_app = 6.94 × 10⁻³ min⁻¹) at a fixed temperature when DMF was used as solvent. Activation energies for ARGET ATRP of MMA were also calculated using the Arrhenius equation.     

Novel Surfactant for the Reduction of CO2/Brine Interfacial Tension

The synthesis of novel CO₂ philic surfactant using maleic anhydride and dipropylene tertiary butyl alcohol is reported. The synthesis involved the esterification of maleic anhydride to produce bis(2-(2-(tert-butoxy)propoxy)propyl) maleate and subsequent sulfonation of the esterified product. Para toluene sulfonic acid was employed as catalyst for the esterification reaction. The esterification reaction was optimized for the maximum yield of 98% of bis(2-(2-(tert-butoxy)propoxy)propyl) maleate. The esterification reaction kinetics employing heterogeneous catalyst were also studied. Although this is a bimolecular reaction, a first order reaction kinetics with respect to acid has been observed. The activation energy was found to be 58.71 kJ/mol. The diester was followed by the sulfonation process and a yield of 85% of surfactant was achieved. The synthesized surfactant successfully lowered down the IFT between CO_2/brine to 1.93 mN/m. This surfactant has a great potential to be used for CO₂-EOR applications.     

Kinetics and mechanistic aspects on electron‐transfer process for permanganate oxidation of poly(ethylene glycol) in aqueous acidic solutions in the presence and absence of Ru(III) catalyst

The kinetics and mechanism of oxidation of poly(ethylene glycol) (PEG) by the permanganate ion as a multiequivalent oxidant in aqueous perchlorate solutions at an ionic strength of 2.0 mol dm⁻³ has been investigated spectrophotometrically. The reaction kinetics was found to be of complex in nature. The pseudo–first‐order plots showed curves of inverted S‐shape, consisting of two distinct stages throughout the entire course of reaction. The first stage was relatively slow, followed by a fast reaction rate at longer time periods. The first‐order dependence in [MnO₄⁻], fractional first‐order dependence in [H⁺], and fractional first‐order kinetics in the PEG concentration for the first stage have been revealed in the absence of the Ru(III) catalyst. The influence of the Ru(III) catalyst on the oxidation kinetics has been examined. The oxidation was found to be catalyzed by the added Ru(III) catalyst. The First‐order dependence on the catalyst and zero order with respect to the oxidant concentrations have been observed. The kinetic parameters have been evaluated, and a tentative reaction mechanism consistent with the kinetic results is suggested and discussed.     

Studies of relationship between polymer structure and hydration environment in amphiphilic polytartaramides

The relationships between the chemical structures and hydration environment of the polymers can provide significant insight into the water‐amphiphilic polymer interactions. Here, the hydrophobicity of amphiphilic block copolymers poly(ethylene tartaramide‐b‐alkyl isocyanate) is gradually tuned by using of a series of pendant alkyl (isopropyl, n‐butyl, cyclopentyl, and cyclohexyl) groups. Dynamics of hydration probed by low‐field NMR relaxometry exhibits a heterogeneous environment of water molecules, corresponding to tightly bound water with slow re‐orientational mobility and loosely bound water with fast re‐orientational mobility. Progressively larger amounts of bound water are present in the copolymers, ongoing from pendant isopropyl, n‐butyl, cyclopentyl, and finally to cyclohexyl group. Water in the copolymer bearing the cyclohexyl group has a significantly high partial specific heat capacity. Therefore, hydrophobic interaction between the polymer and water is enhanced when the hydrophobicity of the polymer is increased, resulting in considerable hydrophobic hydration with decreased mobility of the bound water. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 138–145     

Development of high‐performance networked polymers consisting of isocyanurate structures based on selective cyclotrimerization of isocyanates

Selective and quantitative cyclotrimerization of p‐tolylisocyanate proceeded by using sodium p‐toluenesulfinate as a catalyst and 1,3‐dimethylimidazolidinone as a solvent. Exploitation of this system to the cyclotrimerization of methylene diphenyl 4,4′‐diisocyanate (MDI) permitted formation of the corresponding networked polymer, which was selectively consisted of isocyanurate moiety and thus exhibited excellent thermal stability. Utilization of phenyl isocyanate (PhNCO) as a comonomer with varying feed ratio [MDI]₀/[PhNCO]₀ allowed successful control of flexibility of the networked polymers, while retaining its high thermal stability. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011