Preparation of high molecular weight poly(N‐vinylcarbazole) in high yield by low‐temperature precipitation polymerization of N‐vinylcarbazole

To produce high molecular weight poly(N‐vinylcarbazole) (PVCZ) with high conversion, N‐vinylcarbazole (VCZ) was heterogeneously polymerized in methanol at 30, 40 and 50 °C using a low temperature initiator, 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN), and the effects of polymerization temperature and concentration of initiator and solvent on the polymerization behaviour and molecular parameters of PVCZ investigated. Globally, experimental results correspond to predicted ones. Low polymerization temperature using ADMVN and a heterogeneous system using methanol proved to be successful in obtaining poly(N‐vinylcarbazole) (PVCZ) of high molecular weight and high conversion with small temperature rise during polymerization, although free radical polymerization by azoinitiator was used. The polymerization rate of VCZ in methanol at 30 °C is proportional to the 0.88th power of ADMVN concentration. The molecular weight is higher and the molecular weight distribution is narrower with PVCZ polymerized at lower temperatures. For PVCZ produced in methanol at 30 °C using an ADMVN concentration of 0.0001 mol/mol of VCZ, a weight average molecular weight of 1 750 000 g mol⁻¹ is obtained, with a polydispersity index of 1.82 © 2000 Society of Chemical Industry     

Single‐ and two‐step procedures of AGET emulsion ATRP of methyl methacrylate in a well‐mixed batch reactor

This study investigates the atom transfer radical emulsion polymerization of methyl methacrylate in a 2 L well‐mixed stirred batch reactor using activators generated by electron transfer as the initiation technique. The polymerization was carried out with ethyl‐2‐bromoisobutyrate as the initiator, copper bromide with 4,4′‐di‐5‐nonyl‐2,2′‐bipyridine as the catalyst system, Brij 98 as the surfactant, and ascorbic acid as the reducing agent. The reaction was carried out at constant temperature in the range of 50 to 70 °C under a blanket of nitrogen to minimize the presence of air in the system. Polymerizations were carried out according to single‐step and two‐step procedures. The coagulation was found to be a major problem, especially at high monomer conversion. However, adding more surfactant and lowering the reaction temperature weakened the effect of the coagulation but at the expense of the low monomer conversion. Measurement of molecular weight distribution and ? using gel permeation show that the two‐step techniques produced polymers with living features of atom transfer radical emulsion polymerization much better than those in the single‐step procedure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45308.     

Preparation of polyacrylamide aqueous dispersions using poly(sodium acrylic acid) as stabilizer

High‐solids, low‐viscosity, stable polyacrylamide (PAM) aqueous dispersions were prepared by dispersion polymerization of acrylamide in aqueous solution of ammonium sulfate (AS) using poly (sodium acrylic acid) (PAANa) as the stabilizer, ammonium persulfate (APS) or 2,2′‐Azobis (N,N′‐dimethyleneisobutyramidine) dihydrochloride (VA‐044) as the initiator. The molecular weight of the formed PAM, ranged from 710, 000 g/mol to 4,330,000 g/mol, was controlled by the addition of sodium formate as a conventional chain‐transfer agent. The progress of a typical AM dispersion polymerization was monitored with aqueous size exclusion chromatography. The influences of the AS concentration, the poly(sodium acrylic acid) concentration, the initiator type and concentration, the chain‐transfer agent concentration and temperature on the monomer conversion, the dispersion viscosity, the PAM molecular weight and distribution, the particle size and morphology were systematically investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Kinetic and molecular weight control for methyl methacrylate semi‐batch polymerization. I. Modelling

There are gel, glass, and cage effects in the methyl methacrylate (MMA) bulk polymerization. These effects will cause the propagation and termination rate constants and initiator efficiency change during the polymerization process, and make the kinetics and molecular weight more complex. A violent increase of conversion will bring a large amount of reaction heat evolved in a short time, and will promote temperature increase if the heat cannot be removed in time. Molecular weight of polymer will raise ten times at the same time. So, the temperature of polymerization system, kinetics of polymerization, and molecular weight and its distribution of polymer cannot be controlled. To control and unify them, the semibatch polymerization method is preferably selected. Furthermore, the kinetic and molecular weight models for MMA semibatch polymerization with the participation of chain transfer agent and new materials addition flow rate are presented. Using the presented models, the effects of temperature, initiator concentration and type, monomer or solvent concentration, and chain transfer agent concentration and type on the kinetics, and molecular weight and its distribution are simulated in this article. Experimental data of kinetics and molecular weight obtained from the published literature are compared with the simulation results to examine the presented models. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2838–2846, 2006     

Controlled radical copolymerization of vinyl acetate and dibutyl maleate by iodine transfer radical polymerization

Iodine transfer radical homo‐ and copolymerization of vinyl acetate (VAc) with dibutyl maleate (DBM) were carried out in the presence of ethyl iodoacetate (EtIAc) and 2,2′‐azobis(isobutyronitrile) (AIBN) as chain transfer agent and initiator, respectively, at 60 °C. Molecular weight and its distribution and (co)polymer structure (i.e. copolymer composition and chain end groups) were analysed using gel permeation chromatography and ¹H NMR spectroscopy, respectively. Homo‐ and copolymerization reactions proceed via a controlled characteristic with predetermined molecular weight and relatively narrow molecular weight distribution. The presence of DBM in the reaction mixture decreases the consumption rate of EtIAc as well as the polymerization rate. This is attributed to the effect of DBM on the transfer constant to the EtIAc and probably on the iodine exchange rate constant between the growing chains. The effect of the concentration of AIBN, EtIAc and overall monomers on the conversion, molecular weight and its distribution was studied. Simultaneously high conversion and molecular weight with a relatively narrow molecular weight distribution can be achieved only when equimolar and intermediate concentration of EtIAc and AIBN is used in the reaction mixture. End‐group analysis by ¹H NMR reveals that iodinated VAc end groups in the (co)polymer chains are unstable, resulting in aldehyde end groups. Thermogravimetric analysis shows that the thermal stability of the VAc‐based polymer increases on incorporating DBM units into the copolymer chains. © 2013 Society of Chemical Industry     

NaHSO_3-(NH_4)_2S_2O_8引发体系制备低相对分子质量聚丙烯酸钠

以丙烯酸和氢氧化钠为原料,NaHSO3-(NH4)2S2O8为氧化还原引发剂体系,NaHSO3为链转移剂合成低相对分子质量聚丙烯酸钠。研究了单体、引发剂及链转移剂的用量、反应温度和反应时间等对产物相对分子质量的影响。结果表明,反应温度为60℃、w(单体)=25%、w(引发剂)=0.6%、w(链转移剂)=2.0%、反应时间2h,可制得聚丙烯酸钠的粘均相对分子质量在2 000~3 000,单体转化率在98%以上。     

沉淀聚合制备低分子量聚丙烯酸及残液循环利用

以偶氮二异丁腈(AIBN)为自由基引发剂,石油醚为溶剂,异丙醇为链转移剂,通过沉淀聚合制备了低相对分子质量(简称分子量,下同)的聚丙烯酸。考察了引发剂用量、链转移剂用量、单体质量浓度对聚合收率的影响,确定最佳聚合条件为:AIBN用量为单体质量的10%,链转移剂用量为单体质量的100%,单体质量浓度100g/L,反应温度80℃,反应时间4 h。反应结束后产品在底部沉淀析出,溶剂可循环利用,在最佳聚合条件下,残液循环利用5次,单体的累计转化率达到92.6%。凝胶渗透色谱(GPC)分析表明,通过残液循环制备的产品重均分子量(Mw)变化不大,保持在1 000～1 300,多分散性(PDI)为1.92～3.38。     

Study on the effective process parameters influencing styrene and acrylonitrile grafting onto seeded polybutadiene latex

A series of experiments were designed and conducted to determine the significance of process parameters in the grafting of styrene and acrylonitrile onto polybutadiene seeds in a semicontinuous emulsion copolymerization system. The significances of the parameters were obtained by comparing the variance ratios, or F values, with F‐distributions. The significance level of each test (α‐value) was obtained by variance analysis. The important process parameters in industrial polymerization processes are usually monomer‐to‐polymer ratio, initiator type and concentration, chain‐transfer agent, and reaction temperature. The target responses were final monomer conversion, grafting degree, grafting efficiency, gel percent, and viscosity‐average molecular weight of free styrene‐acrylonitrile (SAN). The analysis of variance indicated that cumene hydroperoxide as the initiator and reaction temperature had strong effects on the graft structure. Moreover, free SAN molecular weight was significantly affected by the monomer/polymer ratio and cumene hydroperoxide and n‐dodecyl mercaptan as chain‐transfer agents. The raspberry‐like morphology of grafted acrylonitrile‐butadiene‐styrene (ABS) particles and phase separation within the particles were confirmed by transmission electron microscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

低相对分子质量聚丙烯酸钠的合成研究

以过硫酸铵-亚硫酸氢钠为氧化还原引发体系、亚硫酸氢钠同时作链转移剂合成低相对分子质量的聚丙烯酸钠。研究了单体、引发剂及连转移剂的用量、反应温度和反应时间等对产物相对分子质量的影响。结果表明反应温度为75℃、单体用量25%～30%(质量分数,下同)、引发剂用量0.40%～0.60%、链转移剂用量4.0%～5.0%、反应时间6.0h时,可制得聚丙烯酸钠的粘均相对分子质量在2000～3000之间,单体转化率为95%以上。     

Poly(dimethylsiloxane‐b‐styrene) diblock copolymers prepared by reversible addition‐fragmentation chain transfer polymerization: Kinetic model

Well‐defined polydimethylsiloxane‐block‐polystyrene (PDMS‐b‐PS) diblock copolymers were prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization using a functional PDMS‐macro RAFT agent. The RAFT polymerization kinetics was simulated by a mathematical model for the RAFT polymerization in a batch reactor based on the method of moments. The model described molecular weight, monomer conversion, and polydispersity index as a function of polymerization time. Good agreements in the polymerization kinetics were achieved for fitting the kinetic profiles with the developed model. In addition, the model was used to predict the effects of initiator concentration, chain transfer agent concentration, and monomer concentration on the RAFT polymerization kinetics. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Experimental Study of a Tetrafunctional Peroxide Initiator: Bulk Free Radical Polymerization of Butyl Acrylate and Vinyl Acetate

Summary This investigation examines the use of a tetrafunctional peroxide initiator in the bulk free radical homopolymerization of butyl acrylate and vinyl acetate. Rate of polymerization, molecular weights and in certain cases, gel fraction data were collected for selective experiments and compared to the results obtained with a monofunctional counterpart. In order to avoid the formation of insoluble gel material, further experiments were completed with varying concentrations of a chain transfer agent. Experimental results showed that when used at identical concentrations, the tetrafunctional initiator produced a faster rate in the polymerization of both butyl acrylate and vinyl acetate compared to the monofunctional initiator. Without the use of a chain transfer agent, runs with butyl acrylate produced significant amounts of gel material isolated by Soxhlet extraction. For a particular reaction time, the tetrafunctional initiator produced higher levels of gel compared to its monofunctional counterpart. When a chain transfer agent was used, the molecular weights were determined by its concentration and in turn, initiator functionality did not have an impact. In the polymerization of vinyl acetate, similar observations were made and no discernable difference could be seen between the molecular weight results of samples produced with either initiator.     

Molgewichtsverteilung und Langkettenverzweigung bei der anionischen Polymerisation von Butadien

The copolymerization of butadien with small amounts of divinyl benzene (DVB) has been investigated. The polymerization has been carried out with a lithiumamide as initiator in n-hexane as solvent under addition of tetrahydrofuran (THF) to govern the content of vinyl groups. By gel permeation chromatography coupled with a viscometer the molecular weight distribution (MWD) and long chain branching as a function of the conversion and of the molecular weight have been determined. Using a differential refractometer and a UV-photometer as detectors the distribution of the branching agent DVB vs. molecular weight has been studied. With our example long chain branching decreases with increasing conversion. The insertion of DVB occurs mainly in the first phase of the reaction. With increasing conversion the MWD becomes broader. At very high degrees of conversion the molecular weight increases considerably by coupling reactions.     

双硫酯作为链转移剂的苯乙烯本体聚合研究

研究了二硫代苯甲酸苄基酯（BDB）、二硫代苯甲酸苯乙基酯（PEDB）及二硫代苯甲酸异丙苯基酯（CDB）三种RAFT试剂作为链转移剂的苯乙烯本体聚合。动力学研究表明,当BDB及PEDB浓度和偶氮二异丁腈（AIBN）浓度同时增大时,AIBN浓度提高所导致的聚合反应速率提高起主导作用：当CDB和AIBN浓度同时提高时,CDB浓度提高所导致的聚合速率降低作用影响更显著。对CDB体系,随转化率提高分子量分布变宽。对BDB体系,当其浓度较高时,随转化率提高分子量分布变窄;当其浓度较低时,不利于实现可控,活性聚合,反应后期分子量分布变宽。动力学和GPC分析均表明以BDB为链转移剂时苯乙烯本体聚合的可控性最好。在同时考虑链转移剂和引发剂作用的基础上,提出了修正的聚合物分子量预测模型,该模型可有效预测以双硫酯为链转移剂的苯乙烯RAFT聚合体系的分子量。     

可控分子质量丙烯酰胺溶液聚合研究

研究了含有链控剂的丙烯酰胺的水溶液聚合。对在链控剂甲酸钠存在下,反应温度、单体质量分数,引发剂质量分数、引发剂中氧化剂与还原剂配比以及溶液pH值对聚合物分子质量的影响进行了系统研究。结果表明,控制单体质量分数为10%,引发剂质量分数为单体的0.13%(m(氧化剂)∶m(还原剂)=3∶2),体系pH值=6.0,当链控剂甲酸钠的加入量在0.8%~2.5%时,可以合成分子质量在(37~100)×104之间的低分子质量聚丙烯酰胺。     

New dinitroxide for stable free radical polymerization of styrene

A new dinitroxide (1,4‐di (1‐oxy‐2,2,6,6‐tetramethyl‐1‐piperidin‐4‐yl)‐xylene) (DTPX) was synthesized and successfully used in stable free radical polymerization of styrene. The results of the polymerizations showed that the DTPX was a suitable mediating agent for stable free radical polymerization of styrene. However, it was found that the dinitroxide mediating process resulted in a higher level of decomposition of the internal bisalkoxyamine linkage in the polymer chain, which resulted in polymers possessing a terminal alkoxyamine and an adjacent hydroxylamine, and the decomposition became more obvious at high conversion through monitoring the change of molecular weights with the conversion by gel permeation chromatography and the polymer structure by ¹H‐NMR. The reaction temperature showed obvious effects on the polymerization, and the polymerization of styrene at 110°C led to a better controlled polymerization than that at 125°C with narrower molecular weight distributions and slight decomposition of the nitroxide up to monomer conversions of 76.7%, however, the rate of the polymerization was decreased and an induction period appeared at 110°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1137–1145,2006     

On the gel effect in the presence of a chain transfer agent in methyl methacrylate polymerization and its copolymerization with various acrylates

The kinetics of methyl methacrylate (MMA) polymerization, and of its copolymerization with various acrylates, at high conversions in the presence of a chain transfer agent, are investigated with a dilatometer over the entire course of reaction. The displacement to higher conversions of the onset of the gel effect in the MMA homopolymerization, in the presence of a chain transfer agent, was determined. Similar information is also provided for the MMA-acrylate copolymerization systems. An increase in polymerization temperature slightly delays the onset of the gel effect in the MMA-acrylate copolymerization, but considerably increases the final conversion. The final conversion in copolymerization for a constant concentration of the chain transfer agent is independent of the initiator concentration, but is a function of the polymerization temperature. The reaction time for reaching the limiting conversion in copolymerization is increased with an increasing amount of the second monomer, as well as with an increasing number of carbon atoms in the acrylate used as the second monomer. © 1993 John Wiley & Sons, Inc.     

低分子量AN/AA共聚物的制备

以过硫酸钾—亚硫酸氢钠的氧化还原体系为引发剂,采用水相沉淀聚合法制备了AN/AA共聚物,用不同链转移剂控制共聚物的分子量。研究了反应时间、引发剂含量、链转移剂含量对聚合物转化率以及聚合物分子量的影响。结果表明,选用N,N-二乙基羟胺为链转移剂,其用量为5%,反应时间为2 h时,共聚物分子量最小,控制在15000左右。     

Free‐radical terpolymerization of n‐butyl acrylate/butyl methacrylate/d‐limonene

d ‐Limonene (Lim) is a renewable monoterpene derived from citrus fruit peels. We investigated it for use as part of a more sustainable polymer formulation. The bulk free‐radical terpolymerization of n‐butyl acrylate (BA)/butyl methacrylate (BMA)/Lim was carried out at 80°C with benzoyl peroxide as the initiator. The terpolymerization was studied at various initial BA/BMA/Lim molar ratios, and the products were characterized for conversion, terpolymer composition, molecular weight, and glass‐transition temperature. Lim was observed to undergo a significant degradative chain‐transfer reaction, which greatly influenced the polymerization kinetics. The rate of polymerization, final conversion, and polymer molecular weight were all significantly reduced because of the presence of Lim. Nonetheless, polymers with relatively high weight‐average molecular weights (20,000–120,000 Da) were produced. The terpolymer composition was well predicted with the reactivity ratios estimated for each of the three copolymer subsystems. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42821.     

丙烯腈与丙烯酸乙酯乳液共聚合及其表征

用氧化还原引发体系在低温下研究了丙烯腈与丙烯酸乙酯的乳液共聚合。考察了聚合温度、乳化剂浓度和分子量调节剂浓度对聚合的影响 ,结果表明 ,随温度升高 ,乳化剂浓度增大 ,单体转化率和分子量增大 ,乳液更稳定 ;链转移剂十二烷基硫醇浓度增加 ,分子量显著降低 ,转化率有所降低 ,表明十二烷基硫醇在调节分子量的同时也起着缓聚剂的作用。用激光粒径分析仪考察了 2 0℃时聚合过程中乳胶粒子大小的变化 ,发现聚合过程的成核和增长均在胶束中进行的。用凝胶渗透色谱法研究了十二烷基硫醇对聚合物分子量的影响 ,发现聚合时加入分子量调节剂 ,活性链寿命较短并呈单峰分布 :聚合时不加入分子量调节剂 ,活性链寿命较长并呈双峰分布。 DSC结果表明 ,随聚合体系中软单体含量增加 ,共聚物的玻璃化温度降低。     

低分子量聚丙烯酸钠的合成

采用自由基溶液聚合方法制备了低分子量聚丙烯酸钠,研究了链转移剂用量、单体浓度、温度、反应时间及引发剂用量、加料方式等因素对聚丙烯酸钠分子量的影响。实验结果表明,合成了低分子量(500-10000)聚丙烯酸钠。