Preparation,characterization and selective reactions of novel [1,3]diazetidine‐2,4‐diones (uretdiones) — a new route to generate asymmetric substituted toluylenediisocyanate‐derivatives

The selective cyclodimerization of monomeric diisocyanates like IPDI 4 and TDI 5 yields [1,3]diazetidine‐2,4‐diones (uretdiones). On this basis, a new method for the selective transformation of the NCO‐groups of asymmetric substituted diisocyanates is described. The reaction with different nucleophiles yields carbamates and ureas such as 9 – 11 .     

Kinetics of transesterification of dimethyl terephthalate with poly(tetramethylene ether) glycol and 1,4-butanediol catalyzed by tetrabutyl titanate

The kinetics of tetrabutyl titanate catalyzed transesterification of dimethyl terephthalate with poly(tetramethylene ether) glycol of various molecular weight has been studied in the presence and absence of 1,4-butanediol. Detailed analysis of experimental data with a proposed kinetic model indicates that the equal reactivity hypothesis for functional groups is valid within a wide range of experimental conditions studied. It is also found that the reactivity of hydroxyl groups of macrodiols such as poly(tetramethylene ether) glycol is independent of the chain length of the polymer. Effect of various reaction parameters on the transesterification rate and the resulting product composition is also discussed.     

Kinetics of transesterification of dimethyl terephthalate with 1,4-butanediol catalyzed by tetrabutyl titanate

The kinetics of tetrabutyl titanate catalyzed transesterification of dimethyl terephthalate (DMT) with 1,4-butanediol (BD) is investigated. Detailed analysis of experimental data indicates that equal reactivity hypothesis for functional groups is valid for [BD]/[DMT] molar ratios greater than 2 up to 75% conversion. Effects of reaction temperature and catalyst concentration are also discussed.     

Experimental confirmation of extent of reaction at the gel point in a polyisocyanurate

Theoretical equations were developed to relate the extent of reaction at the gel point for a system where three functional groups trimerize to a ring structure during the polymerization reaction. Specific relationships were developed for a difunctional monomer where the two functional groups are of unequal reactivity and for a mixture of difunctional monomer where the two functional groups are of unequal reactivity and for a mixture of difunctional and monofunctional monomer where all three functional groups are of unequal reactivity. These two cases were tested experimentally by determining the extent of reaction at the gel point for the system isocyanate reacting to form isocyanurate. In the case of 4,4′-diisocyanatophenylmethane (MDI), the extent of reaction at gelation was determined experimentally to be 60%. When this data was analyzed according to the theory developed, a reactivity ratio of 2.38 was calculated for the rate of the first isocyanate group to react as compared to the second. Experiments were also performed with 2,4-toluene diisocyante, which gave a 72% conversion at the gel point. The extents of reaction at the gel point for mixtures of MDI and phenyl isocyanate were also determined experimentally. An analysis according to the theory developed further supported the idea that all three isocyanate groups in this system have different reactivities. Theoretical relationships also were developed for a trifunctional isocyanate reacting to form isocyanurate. Experimentally, a crude MDI was used, and approximate relationships were used to analyze the results.     

Radical homopolymerization and copolymerizations of ring-methoxy substituted α-cyanostyrenes

Radical homopolymerization and copolymerizations of ring-methoxy substituted α-cyanostyrenes were studied using benzoyl peroxide and dimethyl 2,2′-azobisisobutylate at 60°C. It was found that the cyanostyrenes containing 2-methoxy cyanostyrene gave homopolymer in moderate yield and they were also copolymerized with vinyl monomers such as styrene and vinyl acetate. The relative reactivity of the cyanostyrenes towards a polystyryl radical (1/r₂) in the copolymerization of cyanostyrenes (M₁) and styrene (M₂) was correlated with the Hammett and Taft substituent constants of the methoxy groups and the ¹³C NMR chemical shift of the β-carbon of the cyanostyrenes. The enhancement of the radical polymerization reactivity by introducing a nitrile group in the captodative α-position of styrene was considered to be due to the suppression of the termination reaction and the activation of the propagation reaction. In addition, thermal properties such as glass transition and degradation temperatures of the cyanostyrene polymers obtained were also examined.     

CO气相偶联合成草酸二甲酯催化剂的研制

考察助剂、制备方法和还原介质对CO气相偶联合成草酸二甲酯催化剂性能的影响。结果表明,以贵金属Pd为活性组分,非贵金属C为助剂,以α-Al_2O_3为载体,采用分步等体积浸渍法制备的催化剂,在水合肼还原后,具有良好的反应活性和稳定性。在反应温度130℃,空速3 000 h^(-1)时,产物中草酸二甲酯含量90%以上,时空收率平均可达813 g·(L·h)^(-1)。催化剂PC-3反应500 h后,物理性能和反应活性变化不大。     

On the Role of Tin Catalysts in Step-Growth Polymerization Reactions

Organotin compounds have been used to catalyze the condensation of various α,ω-dihydroxyl terminated organosiloxane diols. This tin catalyzed reaction extends the length of siloxane chains and it also produces narrow molar mass distribution polyorganodisilanols (M_w/M_n = 1.4). The reaction occurs between a variety of siloxanes that are terminated with hydroxyl groups and it does not depend on the organic side groups connected to silicon for the systems studied here. These systems include silicon atoms bearing dimethyl, methylphenyl or methyl 1,1,1 trifluoropropyl substituents. The organotin catalyst in the reaction facilitates the organosilanol condensation releasing water as a byproduct. However it does not appear to facilitate the opening of siloxane bonds nor the redistribution of siloxane bonds under the conditions employed here. Copolymerization of linear oligomeric dimethylsiloxane diol and linear oligomeric methylphenylsiloxanediol was found to give a relatively equal reactivity of homo polymerization and hetro polymerization in the condensation and randomly alternating segmented block copolymers that were formed. The reaction kinetics of the polymerization was used to experimentally verify the fact that there is a chain length dependence of the reacting silanol end-groups. The molar mass values during the polymerizations were determined using gel permeation chromatography. The chromatography, viscosity and FTIR results demonstrate that the reactivity of the hydroxyl end-groups in the polycondensation reaction decreases upon increasing the chain length of the siloxane. It therefore appears that these tin catalyzed siloxane systems deviate from the widely demonstrated hypothesis of Paul Flory on the “equal reactivity of functional groups” for step-growth polymerizations.     

Linseed Oil‐Based Thermosets by Aza‐Michael Polymerization

Aza‐Michael addition on acrylated linseed oil (AELO) is performed to synthetize biobased bulk thermosets without any catalyst. First, acrylation of epoxidized linseed oil (ELO) allows to obtain acrylate functions with vicinal hydroxyl groups which enhance the reactivity of acrylates. The autocatalytic effect of hydroxyl groups on acrylate monomers is highlighted by kinetic studies monitored by NMR and FTIR analyses on model molecules. Then, Priamine 1071, amine terminated poly(propyleneoxide) (PPO) and meta‐xylylenediamine (MXDA) are used as cross‐linkers with AELO. Curing kinetics are studied by DSC analyses to compare the reactivity of these structures. Priamine 1071 shows the highest reactivity; curing at room temperature is performed and high conversion is reached. Two enthalpies are observed with MXDA and only one at high temperature for PPO‐based materials. Thermosets with a large range of mechanical properties are finally obtained from soft materials with PPO‐diamine to hard materials with MXDA. Practical Applications: Thermosets are obtained by curing AELO with various diamines via aza‐Michael reaction. Model reaction allows to demonstrate catalytic effect of hydroxyl groups on Aza‐Michael reaction of acrylated oil with amines. Hence, linseed oil is a promising resource in terms of sustainable development in polymer science.     

Copolymerization of Benzylidene malononitrile with methyl methacrylate and spectroscopic studies before and after irradiation with gamma rays of the obtained copolymer

Benzylidene malononitrile (BMN) monomer was prepared from the condensation of benezaldehyde with malononitrile in absolute ethanol as a reaction medium using few drops of piperidine as a catalyst at the reflux temperature for one hour. This monomer (BMN) was copolymerized with methyl methacrylate (MMA) by solution polymerization technique in the presence of benzoyl peroxide as a free radical initiator using dimethyl formamide as a reaction medium in a sealed tube under a nitrogen atmosphere at 65°C. The Kelen-Tudös and Fineman-Ross were used to determine the copolymerization parameters of MMA (M 1 ) and BMN (M 2 ) monomers. It was found that, the reactivity ratios r 1 and r 2 for MMA and BMN are equal to 2.45, 0.12 - 0.05 respectively. Alfrey Price (Q) and (e) values were calculated and the obtained data indicated that the copolymer structure is a block system. Also, infrared, 1 H-NMR and UV-visible spectroscopic studies for the obtained copolymer were performed. Further UV-visible studies of the PMMA film blended with 1% by weight of the prepared MMA-BMN copolymer were carried out before and after irradiation with different gamma doses in the range from 0-100 KGy.     

碳酸二甲酯甲基化反应催化剂和反应机理研究进展

碳酸二甲酯(DMC)作为一种绿色化学试剂,因其分子中含有多种活泼的官能团,可取代卤代甲烷、硫酸二甲酯等甲基化试剂被广泛应用于有机合成中。综述了近年来DMC作为甲基化试剂与相应化合物发生甲基化反应的研究进展,重点对甲基化反应的催化剂、可能的反应机理等进行了介绍和分析。基于目前的研究现状,提出了DMC作为甲基化试剂今后研究和发展的主要方向。     

The polyurea structure and the role of Amine-Terminated Polyethers and Polyesters in Polyurethanes

The Reaction Injection Molding (RIM) technology has made it possible to master the fast reaction of di- and polyamines with di- and polyisocyanates, leading to the preferred polyurea structure. Telechelics with amino end groups are gaining increased interest for the manufacture of polyurethane-polyurea materials by this technology. They make it possible to substitute all urethane groups in the elastomers with urea groups. The telechelics which are considered are amine-terminated polyethers (ATPE) and polyesters based on the typical soft-segment forming polycondensation polymers which are widely used in polyurethane chemistry. Isocyanate-terminated prepolymers of toluene diisocyanate and polyether polyols can be hydrolyzed in aqueous alkaline media via the carbamate intermediate to the amineterminated prepolymers. The reactivity of these aromatic ATPEs was ideally fit for the RIM process. ATPEs by the hydrolysis process are somewhat limited if products with low viscosities are required. In the reaction of chloro-nitrobenzenes with polyether polyols followed by the hydrogenation of the nitro groups of the terminal phenoxy moieties, we found a path for the synthesis of low viscosity aromatic ATPEs. Capping of polyether polyols with acetoacetate groups and subsequent reaction of the acetoacetylated polyethers with amines, leads to polyethers with terminal imine or enamine groups, which are derivates of aminocrotonic acid. We determined that this approach is a universal method for the synthesis of a large variety of aromatic as well as aliphatic ATPEs with low viscosities. Trifluoroacetic acid turned out to be the ideal catalyst for the reaction of the acetoacetylated polyethers with aromatic diamines, one amino group forming the imine link, the second one remaining intact and providing the desired reactivity towards isocyanates. Aliphatic diamines do not require a catalyst for this reaction. They lead to aminocrotonates with aliphatic amino groups that have high reactivity towards isocyanates, which is to be expected from aliphatic amines. The reaction of the chloroformates of polyether polyols with diamines can also be used to synthesize a variety of ATPEs. We recently developed an approach to low viscosity ATPEs having secondary amino end groups. The hydroxyl groups of the polyether polyols are converted to chloride or methanesulfonyl. The polyethers terminated with these leaving-groups are reacted with primary aliphatic or aromatic amines to give the secondary ATPEs in very good yields.     

Monomer apparent reactivity ratios for acrylonitrile/methyl vinyl ketone copolymerization system

Methyl vinyl ketone was firstly used to successfully copolymerize with acrylonitrile. This was achieved by using azobisisobutyronitrile as the initiator, and dimethyl sulfoxide as the solvent. Effect of copolymerization systems on monomer apparent reactivity ratios for copolymer of acrylonitrile with methyl vinyl ketone was studied for contrast. Values of monomer apparent reactivity ratios were calculated by Kelen–Tudos method. It has been found that the apparent reactivity ratios in aqueous suspension polymerization system were similar to those in solution polymerization system at polymerization conversion less than 20%. Beyond 50% of conversion, the changes of monomer apparent reactivity ratios become less prominent. In water‐rich reaction medium [(H₂O/dimethylsulfoxide (DMSO)>80/20), monomer apparent reactivity ratios were approximately equivalent to those in aqueous suspension polymerization system. In DMSO‐rich reaction medium (DMSO/H₂O > 80/20), apparent reactivity ratios were similar to those in solution polymerization system. Values of apparent reaction ratios both decreased when AN/MVK copolymer was synthesized in DMF and DMAc. The values of apparent reaction ratios gradually tend to 1 with increasing the copolymerization temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4045–4048, 2006     

Studies of reactions with polymers. III. Syntheses and properties of poly(vinyl alcohol) graft terpolymers

A condensation-coupling reaction through esterification is performed between the hydroxy groups of poly(vinyl alcohol) (PVA) and the anhydride groups of methyl methacrylate (MMA)-co-maleic anhydride (MA) copolymer to produce the PVA-g-MMA/MA graft terpolymer. The MMA-co-MA copolymer was obtained by copolymerization of MA and MMA in dimethyl sulfoxide by using azobisisobutyronitrile as initiator. The structure of reaction products was confirmed by infrared analysis, and the dependence of composition, viscosity, and yield of the graft terpolymer on the MA content in MMA-co-MA as well as the concentration of the reactants fed were investigated. Mechanical properties, water content, and gel content of the membranes of terpolymers were measured over a wide range of compositions. PVA-g-MMA/N-ethylol maleimide was also synthesized by reacting the residual anhydride groups on PVA-g-MMA/MA with ethanol amine, this reaction proceeds through the PVA-g-MMA/N-ethylol maleamic acid intermediate.     

Thermal and swelling studies of hydrophobically modified polyacrylamide hydrogels

Hydrophobically modified polyacrylamide hydrogels were prepared by polymerizing acrylamide, using n‐butyl acrylate and 2‐ethyl hexyl acrylate as comonomers and dimethyl formamide as a solvent. We report here for the first time that the Alfred Q‐e reactivity ratios are matching with the experimental value (elemental analysis result) for the terpolymer hydrogel systems. Differential scanning calorimetry (DSC) thermograms of the hydrogel samples revealed two endothermic transitions, one near 0°C, corresponding to the melting transition of ice and another above ambient temperature. This high temperature transition is due to the rearrangement of water molecules engaged in hydrophobic hydration surrounding the hydrophobic groups (alkyl side chains). This depends on the type of hydrophobic groups and the gel compositions. Swelling and deswelling studies of the gels were performed using various solvents such as water and isopropyl alcohol. An abnormally high swelling and deswelling behavior was observed in the homopolymer gels and the gels with low amount of hydrophobic comonomers. This could be attributed to the more intramolecular cross‐linked structure formed during synthesis in organic solvent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Monomer apparent reactivity ratios for acrylonitrile/ammonium itaconate radical copolymerization systems

Ammonium itaconate was first used to copolymerize with acrylonitrile. This was achieved by using azobisisobutyronitrile as the initiator and dimethyl sulfoxide as the solvent. Effects of copolymerization systems on monomer apparent reactivity ratios for acrylonitrile/ammonium itaconate copolymers were studied. The values of monomer apparent reactivity ratios were calculated by Kelen‐Tudos method. The apparent reactivity ratios in the aqueous suspension polymerization system are similar to those in the solution polymerization system at polymerization conversions of less than 18% [reactivity ratio of acrylonitrile (r_AN) = 0.47 ± 0.01, reactivity ratio of ammonium itaconate (r_AIA) = 3.08 ± 0.01]. At conversions of more than 50%, the changes of monomer apparent reactivity ratios become less prominent (r_AN = 0.68 ± 0.01, r_AIA = 2.47 ± 0.01). In water‐rich reaction medium [(H₂O/dimethylsulfoxide (DMSO) > 80/20)], the monomer apparent reactivity ratios are approximately equivalent to those in the aqueous suspension polymerization system. In DMSO‐rich reaction medium (DMSO/H₂O > 80/20), the apparent reactivity ratios are similar to those in the solution polymerization system. With an increase in the polarity of the solvent, the values of apparent reaction ratios both decrease. The values of apparent reaction ratios gradually tend to 1 with increasing the copolymerization temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3920–3923, 2007     

甲醇为原料联合制备碳酸二甲酯、甲缩醛和二甲醚反应体系热力学计算及节能分析

围绕碳酸二甲酯的高效、绿色、安全、节能合成目标,构建了联合生产碳酸二甲酯、甲缩醛和二甲醚反应体系及节能工艺。借助Aspen Plus软件对独立反应及复杂体系进行了热力学分析。由结果可知,升高反应压力或降低温度可明显提高碳酸二甲酯的平衡组成;与甲缩醛和二甲醚合成工艺相耦合后,可大幅提升甲醇平衡转化率,由0.5%~5.9%提高到91.7%~96.3%。根据热力学计算结果和动力学因素,提出顺序生产碳酸二甲酯、甲缩醛和二甲醚的串联催化反应器工艺。甲缩醛和二甲醚的分离采用简单精馏方式,碳酸二甲酯和水共沸物的分离采用变压精馏,3种产品的质量浓度均可达到99%以上。可有效解决单独生产碳酸二甲酯和甲缩醛生产中原料循环量大、能耗高和易爆炸等缺陷。     

Kinetics of esterification of cycloaliphatic epoxies with methacrylic acid

The esterification of cycloaliphatic epoxy resins CER I and CER II containing glycidyl and cyclohexane epoxy groups, respectively, as their reactive units was carried out using a 1 : 0.9 stoichiometric ratio of resin and methacrylic acid in the presence of triphenylphosphine. The reaction was performed at 80, 85, 90, 95, and 100°C and it followed second‐order kinetics. The specific rate constants, calculated by regression analysis, were found to obey an Arrhenius expression. Kinetic and thermodynamic parameters, activation energy, frequency factor, entropy, enthalpy, and free energy of the reaction, revealed that the reaction was spontaneous and irreversible and produced a highly ordered activated complex. The reactivity of CER II was found to be higher than that of CER I. The difference in the reactivity of the cycloaliphatic epoxies was explained by proposing a reaction mechanism. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3197–3204, 2002     

固体碱碱性位对3-戊酮和碳酸二甲酯反应的影响

考察了固体碱碱性位对3-戊酮和碳酸二甲酯反应的影响,并推测了反应在不同碱性位上的反应机理.实验结果表明,由表面羟基引起的弱碱位有利于3-戊酮自身缩合反应(4-甲基-5-乙基-4-庚烯-3-酮)的进行;Lewis酸碱离子对有利于碳酸二甲酯的甲基化反应的发生,主产物为2-甲基-3-戊酮和3-甲氧基-2-戊烯;而由固体碱表面...     

Direct Synthesis of a Fluidizable SAPO-34 Catalyst for a Fluidized Dimethyl Ether-to-Olefins Process

The dimethyl ether to olefins process is very important for converting coal to chemicals. A SAPO-34 molecular sieve with a particle size up to 50 μm has been synthesized with morpholine as the template. The cold model fluidization experiment indicates that the SAPO-34 catalyst with average size of 45–50 μm is of good fluidization properties. After high temperature steam treatment at 1073 K for 8 h, this large fluidizable catalyst showed good reactivity and selectivity for the dimethyl ether to olefins (DTO) reaction in a micro-reactor. X-ray diffraction characterization showed that the structure of the catalyst was maintained well. A fluidized reactor of 50 mm inner diameter was used to carry out the DTO reaction, which showed that the fluidizable SAPO-34 is a selective catalyst for light olefin production.     

Selective hydroxyalkoxylation of epoxidized methyl oleate by an amphiphilic ionic liquid catalyst

Oleic acid is an attractive biobased platform chemical. Precursors for biobased materials can be accessed by epoxidation and subsequent hydroxyalkoxylation of oleic acid. The hydroxyalkoxylation step is conventionally performed with sulfuric acid or a metal catalyst. Due to their high polarity, many ionic liquid catalysts are ineffective for hydroxyalkoxylation of fatty acid derivatives with non-polar alcohols. In this work, we utilized an amphiphilic ionic liquid catalyst to perform hydroxyalkoxylations of epoxidized methyl oleate. An ionic liquid catalyst based on dimethyl lauryl amine was synthesized and evaluated for this reaction due to its long alkyl group. The amphiphilic nature of the ionic liquid allowed for better miscibility and reactivity compared to other ionic liquids. Several alcohols were used with high yields (≥80%) and selectivity (≥92%), including nonpolar alcohols with longer alkyl chains such as octanol and dodecanol. The high selectivity of these conditions could be advantageous for applications in lubricants, biofuels, or polyol preparation. This work demonstrates a greener alternative to conventional hydroxyalkoxylation catalysts.