Anionic Polymerization of Styrene in Binary Solvents

Experimental findings on the triple ion formation were examined by adopting more elaborate purification method for solvents. For polystyryllithium in dimethoxyethane (DME) and benzene mixtures, the overall rate constant of propagation (k_p) was confirmed to increase with increasing living end concentration under some conditions, in contrast with cases for polystyryllithium in tetrahydrofuran-benzene mixtures and for polystyryl sodium, potassium and cesium in DME-benzene mixtures. The propagation by the inter-molecular triple ions proposed earlier in order to elucidate the kinetic “anomaly” mentioned above was briefly discussed.     

Aluminate and Magnesiate Complexes as Propagating Species in the Anionic Polymerization of Styrene and Dienes

The influence of MgR₂ and AlR₃ additives on alkyllithium initiators in the anionic polymerization of butadiene has been investigated in non polar solvents. A strong decrease of the diene polymerization rate in the presence of the two Lewis acids was observed, similarly to that observed in the retarded anionic polymerisation of styrene. With n,s-Bu₂Mg, the percentage of 1,2 vinyl units increases with the [Mg]/[Li] ratio. This behavior is specific to magnesium derivatives bearing secondary alkyl groups and likely results from the additional complexation of lithium species by free dialkylmagnesium and/or a 1,4- to 1,2- chain end isomerization process during chain exchanges between polybutadienyl active chains and dormant ones attached to magnesium species. These reversible exchanges also lead to the formation of one supplementary chain by initial dialkyl magnesium which acts as reversible chain transfer agent. On the contrary with the R₃Al/RLi systems the number of chains is only determined by the concentration of initial alkyllithium and no modification of the polybutadiene microstructure compared to lithium initiators (1,4 units = 80%) is noticed. Dialkyl magnesiate complexes with alkali metal derivatives (i.e. alkoxide) are also able to influence the stereochemistry of the styrene insertion during the propagation reaction. Polystyrenes with different tacticities ranging from predominantly isotactic (85% triad iso) to syndiotactic (80% triad syndio) can be obtained with these initiators.     

Radical Copolymerization of Methyl Methacrylate with Styrene in Several Solvents

Radical copolymerization of styrene (M₁) with methyl methacrylate has been carried out in several solvents. The monomer reactivity ratio (r) was affected by the solvent. The values of log 1/r, Q₂, and e₂ were found to increase with the decreases of the V _C[dbnd]O and v _n[dbnd]c stretcning frequencies determined in the corresponding solvents.     

苯乙烯,丙烯腈在炭黑表面的阴离子接枝聚合

反应型炭黑;苯乙烯;丙烯腈在炭黑表面的阴离子接枝聚合     

Further Studies on the Anionic Copolymerization of Styrene and Glycidyl Methacrylate in Toluene

Sequential anionic copolymerization of styrene and glycidyl methacrylate (GMA) was performed with the protection of argon under normal pressure, where styrene, GMA, toluene, THF, n-butyllithium and a small amount of lithium chloride (LiCl) were used as first monomer, second monomer, solvent, polar reagent, initiator and additive, respectively. Polystyrene-b-poly(glycidyl methacrylate) diblock copolymers (PS-b-PGMA) with well-defined structure and narrow molecular weight distribution were prepared by the copolymerization reaction of poly(styryl)lithium with GMA under certain temperatures. The copolymers were characterized using gel permeation chromatography (GPC), ¹H-NMR, ¹³C-NMR, thin layer chromatography (TLC) and hydrochloric acid-dioxane argentimetric methods. The effects of additives, copolymerization temperature and THF dosage on the copolymerization were studied. No chain transfer reaction of anionic polymerization of styrene in toluene was observed. Slightly broader molecular weight distribution of PS-b-PGMA was observed with the increase the GMA repeat units. Using THF/toluene blend solvent could reduce the polydispersity index (M _w /M _n ) and dissolve the copolymer better than toluene alone. Lower temperature (< -40°C) and LiCl are required to prepare PS-b-PGMA with narrower molecular weight distribution.     

表面活性剂在非极性有机溶剂中的自组装

本文总结了表面活性剂在非极性有机溶剂中复杂反相聚集的研究进展。首先突破了表面活性剂在非极性溶剂(油)中溶解的难题,通过设计合成大头基的新表面活性剂,或引入合适添加剂使之与表面活性剂头基相互作用,由此增大头基有效尺寸,这些均能有效促进表面活性剂形成核-壳完整的聚集体,进而带动表面活性剂分散(溶解)在非极性溶剂中。基于聚集体带动溶解的思路,建立了制备表面活性剂/油均相溶液的直接溶解方法,讨论了制备方法的关键要素,它比文献常用的甲醇预溶解法方便且有效。列举了若干典型的表面活性剂/环己烷均相体系,以此评述了聚集体带动溶解的方法,也展现了丰富多样的反相聚集形貌,讨论了表面活性剂头基尺寸对聚集结构的影响。     

Copolymerization of Styrene and Methyl Methacrylate with Lithium as Initiator

Copolymers of styrene and methyl methacrylate prepared with lithium dispersion as initiator do not contain random sequences of both monomers. Fractionation of the copolymers with acetonitrile and the NMR spectra of the insoluble fractions show that these are block copolymers which consist of a polystyrene portion and a poly(methyl methacrylate) portion. When the copolymerization is stopped at low conversion the copolymer has a high styrene content, which sometimes exceeds the value expected for radical copolymerization. This fact would indicate that styrene is preferentially polymerized at the early stages of chain propagation. When the copolymerization is carried to high conversion some crosslinked polymer is formed which contains more styrene than the soluble part of the same experiment. When a piece of metallic lithium is used as initiator, it is found that the crosslinked polymer is formed on the surface of the metal. The addition of lithium phenoxide or β-naphthoxide to the system eliminates the formation of crosslinked polymer. A possible mechanism is proposed.     

Estimation of Kinetic Parameters for the Polar-Modified Anionic Solution Copolymerization of 1,3-Butadiene and Styrene

Summary : The application of the terminal copolymerization model to polar modified anionic initiated 1,3-butadiene/styrene systems in hydrocarbon solvent requires the determination of twelve kinetic model parameters. These include frequency factors (k_xY,∞), activation energies (E_xY) and live chain end association numbers (n_xY) for all four possible combinations of live chain end termini and free monomer. The individual determination of all twelve parameters requires an enormous numerical effort and a large number of experiments. A method for estimating parameters with a minimum number of kinetic batch experiments in an industrial environment will be demonstrated.     

Kinetics Approximation Considering Different Reactivities of the Structural Units Formed by the Anionic Copolymerization of 1,3‐Butadiene and Styrene Using Al/Li/Ba as Initiator

The copolymerization reaction of butadiene and styrene copolymers prepared by anionic living polymerization using an initiator composed of alkyl aluminum, n‐butyl lithium, and barium alkoxide is studied using a kinetic model that considers the reactivity of active sites to be different; this assumption is justified by the varying geometric configurations. With the first‐order Markov model, the expressions for the fraction of active sites and dyad distribution are obtained. The rate constants are determined by fitting to the conversion and Bernoulli dyad data using the nonlinear least squares method. The conversion and dyad sequence distribution are correctly predicted, and the experimental results indicate that the microstructure and sequence distribution do not change with the conversion and temperature.

     

Radiation-Induced Copolymerization of Trioxane with Styrene Oxide

Copolymerization of trioxane (TOX) and styrene oxide (STO) induced by gamma radiation was studied under varying operating conditions to see the effects of radiation dose, STO concentration, postpolymerization temperature, and duration on the polymer yield. Charging 5% STO with TOX STO conversion was 65% but yield was only 23% compared with 62% for the homopolymer. Molecular weight, melting point, density, and thermal stability of the copolymer samples were determined.     

Photochemical Copolymerization of Styrene with Methyl Methacrylate

The photochemical copolymerization of styrene with methyl methacrylate were investigated under various conditions. The reactivity ratio and the ? values were evaluated.     

Structure of the Li + Ion Close Environment in Various Solvents

The literature data on various methods for studying structural characteristics of the Li+ ion close environment in a number of oxygen-containing solvents were generalized. The coordination numbers of the Li+ cation, interparticle distances, and types of ionic association were discussed. The number of coordinated solvent molecules and the Li+–O distance in the first coordination shell are independent of the nature of the considered solvents.     

苯乙烯和叔丁氧羰氧苯乙烯的分散共聚合

苯乙烯和叔丁氧羰氧苯乙烯在有机溶剂中分散共聚得到１．３～６．６μｍ均一尺寸聚合物粒子。考察了溶剂的溶度参数、反应温度、单体比和分散剂对生成粒子的影响，溶剂和生成的共聚物粒子的极性（溶度参数）相差越大导致位于尺寸减小；反应温度较低时，得到的粒子尺寸亦较小。     

Copolymerization and Copolymers of Styrene N-(2,4,6-Tribromophenyl) Maleimide with Styrene

Kinetic studies of the free radical copolymerization of N-(2,4,6- tribromophenyl) maleimide (TBPMI) with styrene in solution were carried out. The thermal and flammability characteristics of the resulting polymers were also investigated. The monomer reactivity ratios were found to be r ₁ = 0.006 ± 0.0026 (TBPMI) and r ₂ = 0.086 ± 0.0023, and the activation energy of the copolymerization reaction was E_a = 73.6 kJ/mol. The resulting copolymers showed an alternating structure regardless to the monomer feed composition. The molecular weights of the copolymers obtained are relatively high and gradually increase by increasing the TBPMI fraction in the feed, whereas the T_g's showed similar values (540 K) for the equimolar ratio of the comonomers. The course of copolymerization up to high conversion was followed by microcalorimetry and is characterized by a remarkable increase of the initial reaction rate as the fraction of TBPMI was increased; it is also higher at higher total monomer concentrations. However, the overall conversion decreases when the fraction of TBPMI is higher than the equimolar ratio. The thermal stability of the alternating copolymers is higher than that of polystyrene, and their mixture showed appreciable flame-retardant properties, as demonstrated by a limiting oxygen index measurement.     

苯乙烯与N-对位取代苯基马来酰亚胺的乳液共聚

合成了苯乙烯(St)与 N-对位取代基马来酰亚胺的3种二元共聚物乳液.在苯乙烯与N-对位取代苯基马来酰亚胺(N-p-RPhMI)的最大共聚比内,通过种子滴加乳液聚合制得高稳定性、高固含量(40%)、低粘度的共聚物乳液.研究了 N-p-RPhMI 苯环对位上取代基团对共聚物乳液的性能以及共聚物热性能影响.结果表明:N-p-RPhMI 的加入提高了乳液的产率,并且随着取代基团极性的增强,乳液产率提高,乳胶粒的平均粒径增大,乳液的表观粘度降低;共聚物的热分解温度随着取代基团极性的增加而提高,但取代基极性对共聚物的玻璃化转变温度(Tg)的影响明显.同时,St/N-对甲氧基马来酰亚胺(N-p-MOPhMI)体系中助溶剂的加入对共聚物乳液性能影响很大,使共聚物的热起始分解温度升高,但对共聚物的 Tg 基本无影响.     

Reactivities of Dialkyl Citraconates in Radical Copolymerization with Styrene

The radical copolymerization of dialkyl citraconate (DRC, R[dbnd]CH₃, C₂H₅, n-C₃H₇, i-C₃H₇, n-C₄H₉, i-C₄H₉, s-C₄H₉, C₆H₁₁, C₆H₅CH₂) (M₁) with styrene (ST, M₂) was performed at 60°C, using azobisisobutyronitrile as the initiator in tetrahydrofuran in order to clarify the polymerization behavior of DRC and the substituent effects on copolymerization. The monomer reactivity ratios r₁ and r₂ and the Q₁ and e₁ values were determined from the results obtained. It was found that the relative reactivities 1/r₂ of DRC toward an attack by a polystyryl radical could be correlated not by the steric-substituent constant E_S of the alkyl group in DRC, but by the polar-substituent constants σ? in Taft' equation: log (1/r₂) = ρσ + δE_S. It was also observed that the e₁ values are associated with Taft' σ constant. It was found that the weight-average molecular weights of the copolymers are between 8.5 × 10³ and 1.4 × 10⁴.     

苯乙烯-甲基丙烯酸羟乙酯无皂乳液聚合过程

苯乙烯-甲基丙烯酸羟乙酯无皂乳液聚合过程;成核机理     

Studies of the Mechanism of Copolymerization of Electron-Donor Dienes and Acrylonitrile

In the copolymerizations of acrylonitrile with l-ethoxy-1,3-butadiene and l-diethylamino-1,3-butadiene, the resulting copolymers were found to have a highly alternating structure. Their monomer reactivity ratios were determined by the Fineman-Ross and Kelen-Tüdos methods. A mechanism for this alternating copolymerization system is suggested on the basis of chemical shift differences between the head-to-tail and head-to-head monomer sequence distributions.     

New Catalyst for the Copolymerization of Styrene with Carbon Monoxide

Carbonmonoxide(CO)witholefinscanbec0p0lymerizedwithfreeradicalinitiatorsorn0bletransitionmetalc0mpoundcatalystS.Thefreeradicalinitiatedcopolymerizationunderhighgaspressure(upt0l(X)Mpa)andl2O-l65oC',whereasthemostusednobletransitionmetalcompoundsf0rthec0polymerizati0nofcarbonmonoxidewitholefinsarepalladiumorrhodiumcompounds"'.In0urw0rk,theneodymiumcomp0undcatalystsystemswerefoundt0beactiveforthecopolymerizationofstyreneandcarbonm0noxide.Thecopolymerizationofstyreneandcarbonm0n0xidewascAned0u…     

超临界二氧化碳中丙烯酸与苯乙烯共聚

以超临界二氧化碳为介质, 进行丙烯酸与苯乙烯共聚反应, 合成出具有疏水链段结构的改性丙烯酸聚合物. 研究了压力和投料比对聚合反应的影响. 用红外光谱、紫外光谱和核磁共振谱分析其结构及组成. 采用粘度计测定其水溶液粘度随pH值的变化. 研究结果表明, 该聚合物水溶液具有明显的疏水缔合作用.