Non-linear effect of 18-crown-6 in propylene oxide polymerization with potassium glycidoxide used as the inimer

A new initiating system containing potassium glycidoxide as the inimer and 18-crown-6 as the activator was used for propylene oxide polymerization. It was found that the rate of the reaction increased together with the crown ether concentration in a rather unexpected way. Two maxima of that parameter were found in the case of crown ether : inimer molar ratio equal to 3:1 and 6:1. On the other hand, the molecular weight of polymers showed two minima in those conditions. The heterogeneity of the reaction mixture and interactions between species present in the system could be responsible for the phenomena observed. The polydispersity of the polymers obtained was equal to about 1.2 and it was independent of the crown ether concentration.     

The effect of monomer structure on oxygen inhibition of (meth)acrylates photopolymerization

Oxygen inhibition during the free-radical photopolymerization of various monomers containing ether groups was investigated using photo-DSC and real-time FTIR (RTIR). Methacrylates and acrylates containing different number and types of ether groups were selected to determine the effects of ether group concentration and structure on oxygen inhibition. Also, the oxygen sensitivity of the free-radical polymerization of methacrylate and acrylate was compared. Compared to acrylates, methacrylates are much less sensitive to oxygen. Model poly(tetramethylene oxide) and poly(propylene glycol) system were evaluated to determine the effect of ether groups on polymerization kinetics in air. The polymerizations of the (meth)acrylates containing ether groups were found to be relatively insensitive to oxygen inhibition. The reduction of oxygen inhibition occurs by a series of chain transfer/oxygen scavenging reactions.     

Kinetics study of Ziegler-Natta catalyst based on TiCl3 modified by Lewis bases

Summary The kinetic in propylene polymerization of catalysts containing di-n-butyl ether (DBE) - Cat.A or di-n-butyl ether and ethyl benzoate (EB) - Cat. B used as internal electron-donor compounds was investigated. Comparing catalyst compositions with performances, one could conclude that the different kinetics observed were due to the different Lewis bases employed during catalyst synthesis. It seems that the electron-donors have modified the catalyst sites. It has found that added ethyl benzoate modified the structure of the active sites and increased the polymerization rate constant.     

Influence of the nature of monomers on the activity of supported titanium catalysts in the α-olefin polymerization

Summary Ethylene and propylene co-polymerization and sequential polymerization with high activity supported titanium catalysts were studied. Specific rate of homopolymerization and copolymerization constants for ethylene and propylene were determined by using the derived values of the solubility constants for monomers in nascent polymers. The reason of the increased rate of co-polymerization upon enriching the monomers mixture with propylene, the effect of activation of ethylene polymerization upon preliminary polymerization of propylene may be in the increasing number of active sites due to enlarged content of amorphous phase in the nascent polymer product.     

Radical polymerization of mono- and di-methacrylic esters containing bisphenol-S

Radical polymerizations of mono- and di-methacrylic esters containing bisphenol-S (BPS-M and BPS-DM) were studied in terms of polymerization rate, solvent effect, copolymerization and kinetic measurements of photocrosslinking. The solvents were found to affect significantly the polymerization rate. Polar solvents such as DMSO and acetonitrile were found to slow down the polymerization rate. Copolymerization of BPS-M(M₁) with MMA(M₂) was studied in acetone at 60°C. The monomer reactivity ratios were calculated to be r₁ = 3.72 ± 0.01 and r₂ = 0.80 ± 0.01 by the Fineman-Ross method. The high reactivity of BPS-M observed in this copolymerization system may be due to the “matrix effect”. Functional polymers containing methacrylate side-groups were successfully modified and photocrosslinked by irradiation in the presence of benzoin isopropyl ether. The photocrosslinking process is found to be of second order kinetics.     

Graft polymerization of propylene sulfide on crosslinked polystyrene

Sulfur containing graft polymers that may be of interest as polymeric transfer agents were synthesized. Graft polymerization of propylene sulfide on crosslinked polystyrene beads was investigated; both crosslinked polystyrene and its chloromethylated derivative were grafted. Crosslinked polystyrene was metallated by BuLi–TMEDA and was used to initiate anionic graft polymerization of propylene sulfide. Graft polymers of high polypropylene sulfide content corresponding to 10 mmol s/g were obtained. The grafted polypropylene sulfide was evenly distributed across the bead cross section. No change in bead surface characteristics was observed. Grafting on chloromethylated polystyrene beads was achieved by reaction between the chloromethylene groups with sulfide groups of performed polypropylene sulfide, and with terminal sodium thiolate groups of living polypropylene sulfide.     

孪链聚醚的合成及其在办公废纸脱墨中的应用

以辛醇、环氧乙烷、环氧丙烷、乙二醇二缩水甘油醚、三氯氧磷为原料,在KOH、BF3-乙醚溶液的催化作用下合成了不同聚合度的孪链磷酸酯聚醚.研究了聚醚聚合度对办公废纸脱墨性能的影响,结果表明,该类聚醚在聚合度较低时(n＜7)具有良好的脱墨效果.     

Polyurethanes with long fluorinated side chains

Copolymer triols were prepared from propylene oxide and glycidyl (α,α,ω-trihydrododecafluoroheptyl) ether or pentadecafluoroheptylepoxyethane. Cationic polymerization was used and block copolymers were obtained in the molecular weight range of 1,000 to 3,000. These copolymer triols were reacted with an 80/20 mixture of 2,4-/2,6-tolylene diisocyanate, giving polyurethanes with the same polymer backbone as the conventional polyurethanes based on polyoxypropylene triols and tolylene diisocyanate. It was found that these polyurethanes, containing between 0% and 45% fluorine, showed increasing adhesion to anodized aluminum with increasing urea bond content of the polymer. However, the fluorine content did not show the expected effect on adhesion. Isothermal gravimetric analysis showed that the heat stability of the fluorourethanes was lower than for conventional urethanes on a weight basis, only because the segments split off in heat degradation were heavier for the fluorourethane. This phenomenon might possibly also apply to urethanes with a fluorinated backbone. On a mole basis fluorourethanes might be as stable as nonfluorourethanes. It was also found that the thermostability, as measured by weight loss, increased with an increasing degree of crosslink density in the polymers.     

Heat-resistant thermosetting polyimide matrix resins containing keto,ether, hexafluoroisopropylidene linkages and maleimido- and nadimido- end capped groups

Various heat-resistant thermosetting polyimides containing hexafluoroisopropylidene and keto and ether groups suitable for fiber-reinforced composites development have been synthesised by thermal polymerization of maleimido and nadimido end capped polymer precursors. Thermal polymerization involving addition reactions was performed at 225°C for 1.5 h and post-curing at 290°C for 0.5 h. Tough polymers XVIII to XXIII were obtained. The thermal polymerization was monitored using infrared spectroscopy. The polymer precursors were characterized by IR, ¹H-NMR, and elemental analysis. The synthesized polymers were evaluated for thermal stability using dynamic thermogravimetric analysis (TGA). All the polymers showed thermal decomposition temperatures in the range of 430–435°C in nitrogen and in air. The char yield of the polymers was in the range of 60–67% in nitrogen at 800°C. This study indicated that thermally synthesized polymers from hexafluoroisopropylidene, keto, and ether containing polymides are potential candidates for the development of advanced materials for aerospace and high-tech applications. © 1993 John Wiley & Sons, Inc.     

锌/钴双金属氰化络合物催化环氧丙烷聚合机理

用以二乙二醇二乙醚为有机配体的锌／钴双金属氰化络合物进行了环氧丙烷的聚合，并用扩展X射线精细结构分析方法研究了催化剂激活和环氧丙烷聚合过程中锌离子和钴离子的区域结构变化。结果表明，锌／钴双金属氰化络合物催化环氧丙烷的聚合是一个活性聚合体系。在环氧丙烷聚合过程中锌离子由与3．0个氧原子配位转变为与5．7个氧原子配位，表明聚合活性中心为5．0个氧原子配位的螯合锌离子。     

Novel aromatic macrocyclic oligomers: intermediates for the preparation of high-performance polymers

Recent studies aimed at the development of macrocyclic oligomers as the intermediates for the preparation of high-performance polymers are reviewed. Efficient methods for the preparation of a range of cyclic oligomers, such as aryl ether ketones, aryl ether phthalazines, aryl ether isoquinolines, aryl ether phthalazinones, and arylene sulfides, have been developed. Cyclization was achieved via a nucleophilic aromatic substitution reaction under high-dilution conditions. The cyclic aryl ether oligomers undergo a facile ring-opening polymerization to form high molecular weight polymer. Cyclic oligomers containing an aromatic sulfide linkage also undergo a facile free-radical ring-opening polymerization to form high molecular weight polymers which can be amorphous or crystalline. Due to their low molecular weights, these cyclic oligomers have very low melt viscosities which makes them attractive intermediates for a variety of applications for which the conventionally prepared high molecular weight polymers would not be suitable.     

Polymerization of propylene with TiCl3–AlEt2Cl–trilauryltrithiophosphite catalyst

AlEt₃Cl was modified with TLTTP (trilauryltrithiophosphite) in the catalyst system consisting of TiCl₃ and AlEt₂Cl. The effects of TLTTP on the polymerization of propylene were studied in comparison with those of alkyl homologues of TLTTP. The catalytic behavior of the TiCl₃–AlEt₂Cl-TLTTP catalyst system in the polymerization of propylene was also studied in comparison with that of the TiCl₃–AlEt₂Cl catalyst system. In the study of the effect of various alkylthiophosphites added, it is found that the bulkiness of the alkyl group affects the rate of propylene polymerization and the stereoregularity of the resultant polymers. The TiCl₃–AlEt₂Cl–TLTTP catalyst system gave different catalytic behavior in the propylene polymerization from that of the unmodified conventional catalyst system (TiCl₃–AlEt₂Cl). These effects of TLTTP were considered to be due to the bulkiness of the alkyl groups attached to the phosphorous atom and the higher reactivity to TiCl₃ of the modified AlEt₂Cl than of the unmodified AlEt₂Cl.     

Polyaramides containing arylene sulfone ether linkages

Polyamides containing arylene sulfone ether linkages were synthesized from 4,4′[sulfonybis (p-phenyleneoxy)] dibenzoyl chloride (SPCI), 3,3′-[sulfonylbis (p-phenyleneoxy)] dibenzoyl chloride (SMCl) and various aromatic diamines (ARD), by solution and interfacial polymerization techniques. In solution polymerization, the effect of various acid acceptors such as propylene oxide (PO), lithium hydroxide (LiOH) in the presence of lithium chloride (LiCl), and triethylamine (TEA) on teh molecular weight of the olyamides was studied. The effect of structure of studied. The effect of structur of various aromatic diamine sof molecular weight and thermal properties of polyamides was also studied. The polyamides prepared were characterized by solution viscosity, elemental analysis thermo-gravimetric analysis, differential scanning calorimetry, and x-ray diffraction. Physical and thermal properties of polyamides prepared from SPcl and Ard were compared with the polyamides prepared from SMCl and ARD.     

Radical polymerization of new functional monomers: Mono- and dimethacryloyl isocyanate containing bisphenol-A and its derivatives

New functional monomers mono-and dimethacryloyl isocyanate containing bisphenol-A were prepared on reaction of methacryloyl isocyanate (MAI) with bisphenol-A (BPA) and its derivatives at low temperature. The monomers thus obtained were characterized with IR, UV, and ¹H- and ¹³C-NMR spectra. Radical polymerization of mono-and dimethacryloyl isocyanate containing bisphenol-A and its derivatives was studied in terms of the rate of polymerization, solvent effect, copolymerization, thermal properties, and kinetic measurements of photocrosslinking. Polar solvents such as DMSO and NMP were found to slow the polymerization. Copolymerization of BPA-MAI (M₁) with MMA (M₂) in DMF was studied at 90°C. The monomer reactivity ratio was calculated to be r₁ = 0.17 and r₂ = 1.34 according to the method of Fineman–Ross. Functional polymers containing the allyl group were successfully modified and photocrosslinked on irradiation in the presence of benzoin isopropyl ether. The photocrosslinking process follows second-order kinetics. © 1996 John Wiley & Sons, Inc.     

丙烯醇聚醚的合成及烷基醚化封端

将起始小相对分子质量的丙烯醇聚醚在碱性条件下进行烷基醚化封端反应,考察起始剂种类、起始剂相对分子质量、起始剂品质等因素对聚合的影响;考察聚醚的结构、双金属氰化物(DMC)催化剂的质量分数对封端聚醚的影响.结果表明:起始剂的种类对聚醚聚合影响不大,但起始剂的相对分子质量对聚合的影响较大,当相对分子质量>700时,聚醚相对分子质量的理论值与实际值的差值会随着起始剂相对分子质量的变大而变大;K+、Na+质量分数<5×10-5、水质量分数<0.1%、酸羟值<0.1 mg/g时,不会引起DMC中毒;聚醚结构不同,封端率不同,封端率最大而羟值最低时DMC的质量分数为6×10-5.     

Polymerization of tetrahydrofuran initiated by heteropolyacid in the presence of substituted oxirane

Both propylene oxide and epichlorohydrin could effectively promote the polymerization of tetrahydrofuran initiated with a heteropolyacid, H₃PW₁₂O₄₀, in low concentration. Water or butylene glycol was used to control the molecular weight of the product in the range of 1000–3000. The promotion activity of propylene oxide was similar to that of ethylene oxide and better than that of epichlorohydrin, especially when water was introduced. The polymerization started upon addition of propylene oxide or epichlorohydrin. After the polymerization stopped, it could be reinitiated with the addition of a new portion of propylene oxide or epichlorohydrin. The products were found to be copolyether glycol with hydroxyl groups at both ends. The melting point of the polymer obtained by using propylene oxide promoter was about 20°C lower than that of polytetramethylene ether glycol having the same molecular weight. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3239–3246, 2000     

Methylaluminoxane: only a cocatalyst or something more?

Summary Methylaluminoxane (MAO) was used as a catalyst for the polymerization of several vinyl monomers. Polymer yields were found to decrease in the order styrene > isobutyl vinyl ether > methyl methacrylate ≈ acrylonitrile > α-methylstyrene > vinyl acetate = 0. The polymers exhibit low to moderate molar mass with broad distributions. NMR analysis were used to determine the polymers steric microstructure and the end groups. MAO was also able to produce styrene-methyl methacrylate, styrene-isobutyl vinyl ether and methyl methacrylate-isobutyl vinyl ether copolymers. Experimental evidences are against ionic polymerization mechanisms, whereas proofs for a radical mechanism are more controversial, but altogether against of it.     

新型聚芳醚砜共聚物的制备及其性能

以4,4’-二氯二苯砜、4,4’-二羟基二苯砜和2,4-二羟基二苯砜为单体,通过缩聚合成一系列主链含异构体醚键单元的聚芳醚砜共聚物,利用核磁共振碳谱(13C NMR)、差示扫描量热分析(DSC)和高压毛细管流变仪对产物进行了测试和分析。对比不同产物的熔体黏度、玻璃化转变温度和力学性能,发现随着共聚单元含量的增加,聚芳醚砜共聚物的流动性逐渐提高,玻璃化转变温度逐渐降低,并且屈服点伸长率和缺口冲击强度均逐渐提高。这一结果对实际应用中提高聚芳醚砜树脂流动性和韧性、降低热加工温度等具有重要的指导意义。     

含异氰脲酸酯结构聚醚多元醇的合成

以1,3,5-三羟乙基异氰脲酸酯(THEIC)为引发剂、三氟化硼乙醚络合物为催化剂,环氧化合物为环单体,进行了阳离子开环聚合反应的研究.发现THEIC与环氧单体可在非均相体系中平稳地进行阳离子开环聚合反应.在THEIC体系,就链引发而言,环氧氯丙烷的大于环氧丙烷、丁基醚环氧乙烷.调整环单体加料次序就可以获得嵌段共聚醚多元醇.