Styrene–butadiene–styrene/montmorillonite nanocomposites synthesized by anionic polymerization

We successfully synthesized an exfoliated styrene–butadiene–styrene triblock copolymer (SBS)/montmorillonite nanocomposite by anionic polymerization. Gel permeation chromatography showed that the introduction of organophilic montmorillonite (OMMT) resulted in a small high‐molecular‐weight fraction of SBS in the composites, leading to a slight increase in the weight‐average and number‐average molecular weights as well as the polydispersity index. The results from ¹H‐NMR revealed that the introduction of OMMT almost did not affect the microstructure of the copolymer when the OMMT concentration was lower than 4 wt %. Transmission electron microscopy and X‐ray diffraction showed a completely exfoliated nanocomposite, in which both polystyrene and polybutadiene blocks entered the OMMT galleries, leading to the dispersion of OMMT layers on a nanoscale. The exfoliated nanocomposite exhibited higher thermal stability, glass‐transition temperature, elongation at break, and storage modulus than pure SBS. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Modelling studies of the controlled anionic copolymerization of butadiene and styrene

The anionic polymerization of isoprene with n-butyl lithium and polar modifier such as TMEDA and tripiperdinophosphine oxide were studied and kinetic and reactor models are proposed for these systems. Reactor conversion, molecular weight distribution and polymer glass transition temperature had been calculated from the model and compared favorably to the actual data for various combinations of reactor systems and operating conditions. Simulations of the model can be used to design reactor systems and predict polymer properties of large-scale operations from results of small scale batch reactor runs.     

Anionic polymerization of dienes using oligobutadienyl-lithium as initiator

The aim of this work is to combine the microstructure of a radical-polymerized diene (butadiene and isoprene) with the functionality of an anionically prepared one, which could be used for polyurethane preparation after functionalization. A two-step anionic procedure was used in order to obtain a hydrocarbon-soluble lithium-based initiator. When compared with the related anionic polymers obtained under classical conditions, the vinyl content of the polydienes was three times greater. These findings are discussed on a mechanistic basis. © 1998 Society of Chemical Industry     

阴离子聚合反应中的极性调节剂

论述了阴离子聚合反应中所得的各类微观结构极性调节剂以及其发展方向,指出调节剂向高效、适于高温下使用方向发展,而从结构上是从对称结构向不对称结构方向发展。     

负离子溶液聚合法高苯乙烯橡胶的合成及其性能

以环己烷为溶剂、苯乙烯和丁二烯为单体、n-BuLi为引发剂、二乙二醇二甲醚(2 G)为结构调节剂,通过活性负离子溶液聚合合成了高苯乙烯橡胶,研究了引发剂种类、聚合温度、2 G/n-BuLi(摩尔比)、苯乙烯/丁二烯(质量比)、相对分子质量及其分布对共聚橡胶力学性能的影响。结果表明,当苯乙烯/丁二烯为60/40、2 G/n-BuLi为1.0时,在(65±2)℃下可聚合得到力学性能较好的高苯乙烯橡胶,其数均分子量为15×104~20×104、分子量分布为1.40左右。     

Living anionic polymerization of 4‐diphenylphosphino styrene for ABC triblock copolymers

Living anionic polymerization of 4‐diphenylphosphino styrene (DPPS ) achieved unprecedented poly(S‐b ‐I‐b ‐DPPS ) ABC triblock copolymers with predictable molecular weights and narrow polydispersities. In situ Fourier transform infrared spectroscopy probed the anionic polymerization, monitoring vinyl disappearance during sequential monomer addition for kinetic analysis. Varying the concentration of reinforcing, polystyrenic external blocks enabled diverse compositions with tunable thermomechanical properties and tailored morphology. Dynamic mechanical analysis confirmed the presence of microphase separation in the triblock copolymers and revealed a broad temperature range (ca 100 ^oC ) for a plateau region and onset of flow temperatures above 100 ^oC . Small‐angle X‐ray scattering and atomic force microscopy collectively revealed solid state morphologies of the triblock copolymers and probed phase separation at the nanoscale. Well‐defined poly(S‐b ‐I‐b ‐DPPS ) ABC triblock copolymers with tunable structure ? property relationships now permit phosphorus‐containing thermoplastic elastomers for emerging applications. © 2016 Society of Chemical Industry     

异戊二烯在二氧六环中的负离子聚合动力学

研究了以正丁基锂为引发剂 ,异戊二烯在二氧六环溶剂中负离子聚合的动力学。结果表明 ,增长反应对单体浓度和引发剂浓度皆为一级反应 ,活化能为45.22kJ/mol,频率因子为4.832×108L/(mol·min) ,并求出了生成1,4 -结构、1,2 -结构和3,4 -结构产物的速率常数分别为2.77×1012exp( -74760/RT) ,9.82×106exp( -39190/RT) ,8.02×107exp( -41180/RT)。     

异戊二烯在环己烷-二氧六环中的负离子聚合机理

推导了异戊二烯在环己烷－二氧六环混合剂中的负离子聚合机理,并通过实验进行了验证。研究表明,丁二烯聚合机理原则上同样适用于异戊二烯的负离子整合,推导出非1,4－结构产物含量与极性添加剂用量的关系式为1g[(a-b)/(xv-b)-1]=nlg[PA] lgK‘,求得了a,b,n,K′与温度的关系式,并指明了各自的物理意义。     

Effect of aluminum derivatives in the retarded styrene anionic polymerization

This paper reports on the influence of various aluminum derivatives, i.e. trialkyl aluminum, diisobutylaluminum hydride and diethylaluminum alkoxides, on the anionic polymerization of styrene in hydrocarbons at high temperature. The importance of the structure of the aluminum additives and of the ratio [Al]/[Li] on both the formation of ‘ate’ complexes, the retardation effect and the reactivity profile of the polymerization are investigated by UV-visible spectroscopy and polymerization studies. The presence of bulky alkyl groups and/or alkoxide ligands onto aluminum allows the retarded polymerization to proceed for [Al]/[Li] ratios higher than one. Some of these systems offers a broad polymerization window in which the rate of polymerization is strongly reduced and remains almost constant over a large range of [Al]/[Li] ratios. While for trialkylaluminum and diethylaluminum alkoxide the number of PS chains formed can be related directly to the initial amount of lithium initiator, for diisobutyl aluminum hydride and diisobutylpolystyryl aluminum, the hydride and polystyryl groups act as second chain carrier, thus yielding the formation of up to two polymer chains per ‘ate’ complex.     

Semibatch anionic ring‐opening polymerization of octamethylcyclotetrasiloxane in emulsions: effect of the amount of seed polymer particles

Semibatch anionic ring‐opening polymerization of octamethylcyclotetrasiloxane with the use of seed polymer particles in emulsions was studied. The concentration of the emulsifier was set above the critical micelle concentration. We investigated the effect of the amount of seed polymer particles on the chemical kinetics and the average particle size and distribution. During monomer starving conditions the polymerization rate strongly depended on the monomer feed rate and not on the amount of seed particles. Throughout the entire monomer feed period the average particle size increased. This increase depended on the number and the size of seed particles. In emulsions with higher particle sizes higher equilibrium conversions were obtained. In our opinion, a greater extent of backbiting reactions is responsible for lower equilibrium conversions during and at the end of the process. The seeded semibatch process seems a reasonable choice for designing emulsion products with high monomer conversion and desired particle size. © 2012 Society of Chemical Industry     

Synthesis of well-defined block copolymers of n-hexyl isocyanate with isoprene by living anionic polymerization

n-Hexyl isocyanate (HIC) was polymerized at different reaction temperatures and times, using alkali metal naphthalenide, via anionic polymerization in THF. To prevent the formation of trimers, the polymerization of HIC was also performed utilizing sodium tetraphenylborate (NaBPh₄) as a common ion salt. As the reaction temperature decreases, yield of the polymer increases due to stabilization of the active amidate anion at low temperature. In the absence of the additive, a quantitative yield was obtained at −98 °C. However, after most of the monomer was polymerized, further reaction led to trimerization. This was prevented in the presence of NaBPh₄ effectively and the living polymerization was performed successfully at −98 °C. The reaction rate retarded with increasing concentration of NaBPh₄, the optimum concentration of NaBPh₄ was 10 times the concentration of the initiator for the living polymerization of HIC. The living system led to the polymers of molecular weight (MW) as high as 50,000 g/mol. The observed MW was well in agreement with the calculated one. At the higher reaction temperature, −78 °C, the quantitative yield was obtained at 2 min of the reaction time, however the living character was not observed at longer reaction time. The study indicated that the amidate anion was stabilized using NaBPh₄ having bulky contact ion pair. The block copolymer of HIC with isoprene, poly(HIC-b-isoprene-b-HIC), was synthesized with help of the living character of polyisoprene and NaBPh₄. The morphology and composition of the block copolymers were investigated using TEM and ¹H NMR, respectively.     

Anionic polymerization of (meth)acrylic monomers: anionic polymerization of tert-butyl methacrylate in toluene

The anionic polymerization of tBMA initiated by an organolithium compound in toluene at low temperature (−78 °C and 0 °C) has been revisited. Under these experimental conditions, no ‘livingness’ is reported, consistently with formation of an important fraction of oligomers (M_n = 650). © 1999 Society of Chemical Industry     

Some light on the concept of unreactivity arising from active center association in anionic polymerizations

A long held assumption in hydrocarbon based anionic polymerization involving organolithiums is that the aggregated species are unreactive and thus serve only as reservoirs from which the active singlet species momentarily emerge to participate in the initiation or propagation events. This work demonstrates that contrary to the notion of aggregate dormancy such species can participate in monomer addition. The approach involved freeze-dried vitrified polystyryllithium which was found to be reactive toward butadiene and methanol vapors. The sub-glass transition state of the polystyryllithium eliminates the establishment of the aggregate: singlet equilibrium as a result of the inability of chains to undergo diffusion. Furthermore, it is shown that the lower bound gradient for the dependence of propagation rate on active center concentration, within experimental error, is about 1/5 for the majority of those diene systems where the active center concentration covers at least two decades. A computer evaluation of the propagation rate: active center data was done with the aim of testing and determining the equilibrium constants of these aggregated systems.     

Free radical polymerization of p-methyl styrene

An experimental investigation is reported of the free-radical synthesis kinetics of poly(p-methyl styrene) in cyclohexane at low monomer conversion in the temperature range 50°–70°C using AIBN initiator. The p-methyl styrene monomer contained greater than 97% paraisomer. Isothermal conversion/time curves were obtained using glass ampoule reactors and gravimetry and molecular weight distribution and weight-average molecular weights were measured by s.e.c. and low angle laser light scattering photometry (LALLSP). Transfer to small molecules (monomer, cyclohexane, —) was found to be small or negligible with virtually all of the polymer chains formed by termination by combination. Predicted and measured weight-average molecular weights are in good agreement for polymer synthesized at low conversions.     

Semibatch anionic ring-opening polymerization of octamethylcyclotetrasiloxane in emulsion

The semibatch anionic ring-opening polymerization of octamethylcyclotetrasiloxane in emulsion was studied under the condition of no seed particles used in polymerization system. Concentration of emulsifier was set above critical micelle concentration. Effect of monomer feed rate on the chemical kinetics, average particle size and distribution and on the polymer molar mass and distribution was investigated. During monomer addition, polymerization rate was constant and controlled by the monomer feed rate. According to the proposed mechanism for anionic polymerization in emulsion, it was assumed that also the number of active polymerization sites and monomer concentration at the particle surface, where propagation occurs, remain constant. A continuous increase of average particle size and absence of extensive condensation reactions at high conversion suggested that the freshly added monomer diffuses toward hydrophobic polymer particles, where it is consumed in propagation reaction and/or accumulated in the particle core.     

Synthesis of asymmetric H-shaped block copolymer by the combination of atom transfer radical polymerization and living anionic polymerization

A new asymmetric H-shaped block copolymer (PS)₂-PEO-(PMMA)₂ has been designed and successfully synthesized by the combination of atom transfer radical polymerization and living anionic polymerization. The synthesized 2,2-dichloro acetate-ethylene glycol (DCAG) was used to initiate the polymerization of styrene by ATRP to yield a symmetric homopolymer (Cl-PS)₂-CHCOOCH₂CH₂OH with an active hydroxyl group. The chlorine was removed to yield the (PS)₂-CHCOOCH₂CH₂OH ((PS)₂-OH). The hydroxyl group of the (PS)₂-OH, which is an active species of the living anionic polymerization, was used to initiate ethylene oxide by living anionic polymerization via DPMK to yield (PS)₂-PEO-OH. The (PS)₂-PEO-OH was reacted with the 2,2-dichloro acetyl chloride to yield (PS)₂-PEO-OCCHCl₂ ((PS)₂-PEO-DCA). The asymmetric H-shaped block polymer (PS)₂-PEO-(PMMA)₂ was prepared via ATRP of MMA at 130 °C using (PS)₂-PEO-DCA as initiator and CuCl/bPy as the catalyst system. The architectures of the asymmetric H-shaped block copolymers, (PS)₂-PEO-(PMMA)₂, were confirmed by ¹H NMR, GPC and FT-IR.     

Synthesis of low molecular weight-hydroxy polycaprolactone macromonomers by coordinated anionic polymerization in protic conditions

This article reports the development of a new catalytic process that takes advantage of the exchange reaction between aluminium alkoxides and alcohols to obtain functionalized low molecular weight oligomers by anionic ring-opening polymerization. The aluminium alkoxides can be used in homogeneous medium or grafted on a porous support to make possible a heterogeneous process. ω-Hydroxy oligo polycaprolactones macromonomers with 2-hydroxyethylmethacrylate or hydroxymethylstyrene as polymerizable end groups have been synthesized and characterized by NMR and SEC. Mass spectrometry (LSIMS) has been used in an attempt to determine the MWD. These macromonomers have been engaged in copolymerization with styrene and the reactivity ratios have been approached. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2357–2372, 1997     

桥硫结构MTAE的活性阴离子共聚合

合成了一种新型1,1-二苯基乙烯(DPE)类衍生物——9-亚甲基-9H-噻吨(MTAE),其两个苯环通过桥硫结构相连形成三并环,并研究了MTAE的活性阴离子聚合特性。以苯为溶剂,仲丁基锂为引发剂,将MTAE分别与苯乙烯(St),1,4-二乙烯基苯(1,4-DVB),异戊二烯(Ip)进行二元以及三元共聚合。结果表明:在室温条件下和苯溶剂中,MTAE不能与St共聚,可与1,4-DVB共聚,形成线型交替共聚物。基于这一特性合成了特殊结构的MTAE-DVB-St三元交替共聚物。此外,MTAE在相同条件下与Ip共聚时表现出很高的反应活性,合成了MTAE-Ip交替共聚物,交替结构中Ip单元呈高反式-1,4结构。MTAE独特的桥硫结构以及共聚合特性为新型功能化聚合物拓展了全新的前景。     

阴离子淤浆聚合尼龙6的性能研究

通过阴离子淤浆聚合方法,以氢氧化钠为催化剂、异氰酸酯作活化剂,以惰性脂肪烃为分散剂,在不同的反应时间和140～150℃温度下,制得了不同相对分子质量的尼龙6,最高相对粘度17．5。通过熔融纺丝,获得了可纺性良好的纤维,其断裂强度5．0～6．9 cN／dtex。X衍射测试分析表明,同阴离子本体聚合尼龙6(MC尼龙6)和高粘度尼龙6比较,阴离子淤浆聚合尼龙6在二次成型中更易于生成轫性较好的γ晶型,具有更高的冲击强度。