Ultrasonically initiated emulsion polymerization of n‐butyl acrylate

Ultrasonically initiated emulsion polymerization of n‐butyl acrylate (BA) without added initiator has been studied. The experimental results show that high conversion of BA can be reached in a short time by employing an ultrasonic irradiation technique with a high purge rate of N₂. The viscosity average molecular weight of poly(n‐butyl acrylate) (PBA) obtained reaches 5.24 × 10⁶ g mol^?1. The ultrasonically initiated emulsion polymerization is dynamic and complicated, with polymerization of monomer and degradation of polymer occurring simultaneously. An increase in ultrasound intensity leads to an increase in polymerization rate in the range of cavitation threshold and cavitation peak values. Lower monomer concentration favours enhancement of the polymerization rate. ¹H NMR, ¹³C NMR and FTIR spectroscopies reveal that there are some branches and slight crosslinking, and also carboxyl groups in PBA. Ultrasonically initiated emulsion polymerization offers a new route for the preparation of nanosized latex particles; the particle size of PBA prepared is around 50–200 nm as measured by transmission electron microscopy. © 2001 Society of Chemical Industry     

Preparation and characterization of poly(styrene-co-butyl acrylate)-encapsulated single-walled carbon nanotubes under ultrasonic irradiation

Polymeric composite materials filled with single-walled carbon nanotubes (SWNTs) have attracted much attention, but successful applications of such composites require uniform dispersion of SWNTs in the polymeric matrix and the strong SWNTs-polymer interface interaction. In this paper, chemical modification combined with ultrasonically initiated in situ polymerization was successfully employed to prepare poly(styrene-co-butyl acrylate)/single-walled carbon nanotubes composites [P(St-BA)/SWNTs]. The whole procedure contained two steps: in the first step, 3-(trimethoxy)-propylmethacrylate-silane (silane-coupling agent, KH570), a kind of polymerizable vinyl monomer, was grafted onto the surface of SWNTs, forming KH570-g-SWNTs by reacting KH570 with hydroxyl groups on the surface of SWNTs, which was proved by combination of FTIR and XPS results. Due to the presence of polymerizable KH570 on the surface of SWNTs, this provides a basis for the next stage of polymerization to prepare polymer-encapsulated SWNTs composites. In the second step, an ultrasonically initiated in situ emulsion polymerization of monomer styrene (St) and n-butyl acrylate (BA) proceeded in the presence of KH570-g-SWNTs. Consequently, P(St-BA)/SWNTs composite emulsion was obtained. TEM confirmed that SWNTs were coated with the obtained polymer. FTIR and XPS further showed that even after 72 h of soxhlet extraction with boiling toluene, there were still unextracted polymers in P(St-BA)/SWNTs composite, indicating strong interaction between the polymer and carbon nanotubes. Finally, a mechanism for formation of polymer-encapsulated SWNTs through ultrasonically initiated in situ emulsion polymerization was proposed. This study could provide a new way to resolve the problems of the dispersion, stabilization, and compositing of SWNTs with polymer matrix and prepare polymer/SWNTs composites.     

可聚合乳化剂合成含氟丙烯酸酯无皂乳液及其性能

以甲基丙烯酸甲酯（MMA）、丙烯酸丁酯（BA）、甲基丙烯酸六氟丁酯（HFMA）等为主要原料,采用预乳化种子乳液聚合法合成了含氟丙烯酸酯无皂乳液,考察了可聚合乳化剂烯丙氧基壬基酚聚氧乙烯（10）醚硫酸铵（DNS-86）和HFMA的用量对无皂乳液的电解质稳定性和涂膜耐水性的影响。利用傅里叶红外光谱、差示量热扫描仪及热重分析对氟丙乳液涂膜进行了表征。结果表明：与传统乳液聚合得到的乳液及相应的涂膜相比,无皂乳液的耐电解质性能和涂膜的耐水性都有一定的提高,含氟单体有效地参与了聚合,涂膜的疏水性大大增强,耐热性显著提高。     

Miniemulsion copolymerization of styrene and butyl acrylate initiated by redox system at lower temperature: Reaction kinetics and evolution of particle‐size distribution

The kinetics of the miniemulsion copolymerization of styrene (St) and butyl acrylate (BA) initiated by redox initiators, (NH₄)₂S₂O₈/NaHSO₃, at lower temperature (45°C) was studied. The polymerization rate in miniemulsion copolymerization is lower than that of the corresponding conventional emulsion copolymerization. In regard to the rate of polymerization, the initiator concentration plays a more important role in miniemulsion copolymerization than in conventional emulsion polymerization, while the surfactant concentration has a more important role in conventional emulsion polymerization than in miniemulsion polymerization. These are attributed to their different nucleation mechanisms, which are the same as those found in the miniemulsion polymerization carried out at higher temperatures. While by eliminating nucleation via micelle and ensuring against homogeneous nucleation, miniemulsion polymerization can be carried out by the sole nucleation mechanism—monomer droplet nucleation—at lower temperature. Because of this, the particles become narrower during the polymerization and, finally, monodisperse polymer particles are obtained. The result of the particle numbers indicated that a continuous nucleation will cease at about 60% conversion. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 315–322, 1999     

高固含量丙烯酸酯无皂乳液的研制

以甲基丙烯酸甲酯(MMA)为硬单体、丙烯酸丁酯(BA)为软单体、丙烯酸(AA)为功能单体和过硫酸铵为引发剂,采用不同的反应性乳化剂合成了固含量为50%～60%的丙烯酸酯无皂乳液。讨论了反应性乳化剂的种类及用量对无皂乳液性能及粒径等影响。结果表明:当反应温度为80～85℃、反应性乳化剂为烯丙氧基壬基酚聚氧乙烯硫酸铵(DNS-86)且w(DNS-86)=4%～5%时,无皂乳液的固含量高达60%左右、凝胶率几乎为零且粒径相对较小。     

丙烯酸酯无皂乳液的合成

以过硫酸铵( APS)为引发剂,甲基丙烯酸甲酯( MMA)为硬单体,丙烯酸丁酯(BA)为软单体,丙烯酸(AA)为功能单体,可聚合乳化剂(WE-9)为乳化剂,采用预乳化法合成了一种聚丙烯酸酯无皂乳液.讨论了聚合温度,预乳化液滴加时间,乳化剂用量对乳液性能的影响.结果表明,当温度80 ℃,WE-9质量分数为1 5％,滴加时...     

氧化还原引发剂对丙烯酸酯乳液性能及聚合机制的影响

以过硫酸钾(KPS)和亚硫酸氢钠(NaHSO3)为自由基聚合体系的氧化-还原型引发剂,以十二烷基硫酸钠(SDS)和脂肪醇聚氧乙烯醚硫酸钠(AES)为阴/非离子型复合乳化剂,制备甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)和甲基丙烯酸(MAA)共聚物乳液。研究了引发剂种类及用量对该乳液性能及聚合过程等影响,探讨并提出了酸性条件下丙烯酸酯乳液体系的新型引发机制。结果表明:在其他条件保持不变的前提下,当m(KPS):m(NaHSO3)=1.00:0.45、w(KPS+NaHSO3)=0.6%时,乳液的单体转化率(98%)和黏度(5.900 Pa.s)相对最高,反应时间(2.0 h)相对较短且初始聚合温度(60℃)相对最低,此时乳液质量最稳定。     

丙烯酰胺改性丙烯酸酯乳液的合成及性能研究

通过预乳化半连续法制备了丙烯酰胺(AM)改性的丙烯酸酯乳液,探讨了功能单体AM用量对丙烯酸酯乳液和乳液胶膜性能的影响。结果表明:当AM用量为单体质量的1.0%时,乳液及乳液胶膜的综合性能最好。此时,功能单体AM改性的丙烯酸酯乳液聚合稳定性和转化率有所提高;乳液胶膜的力学性能有较大幅度的提高,吸水率有一定程度的降低。     

含氟丙烯酸酯共聚乳液的制备及表征

以甲基丙烯酸甲酯（MMA）、丙烯酸丁酯（BA）等为主要单体,丙烯酸全氟烷基酯（Zonyl TM）为含氟单体,甲基丙烯酸羟乙酯（HEMA）为交联单体,采用种子乳液聚合法制备了含氟丙烯酸酯共聚物乳液。研究了Zonyl TM、HEMA、引发齐（APS）用量、复合乳化剂（SDS/OP—10）、聚合温度、聚合时间和搅拌速度等因素对聚合反应最终转化率、耐水性和乳液稳定性的影响。制备的乳液单体总转化率高,乳液凝聚率低,聚合反应稳定,涂膜的综合性能优良。此外,含氟乳胶膜对水的接触角及TG分析结果表明,Zonyl TM有效参与了共聚反应,提高了涂膜的耐水性及耐热性。     

乙烯基硅氧烷改性丙烯酸酯乳液聚合的动力学及成核机理分析

用种子乳液聚合法研究了硅氧烷改性丙烯酸酯的乳液聚合,对影响种子乳液聚合动力学的因素进行讨论,并分析了乳液聚合的成核机理.实验结果表明：反应温度、引发剂浓度、乳化剂浓度和有机硅氧烷用量对有机硅改性丙烯酸酯乳液聚合动力学有较大的影响.反应温度越高,引发剂浓度越高、乳化剂浓度越高、有机硅氧烷用量相对较小,乳液聚合反应的转化率越高;此外,体系的pH值在6～8之间时也有利于反应的进行.种子乳液聚合中R_P∝［E］^0.72,R_P∝［I］^0.56,表观活化能E_a为143.92 kJ•mol^-1.种子乳液聚合初期,反应主要是单体液滴成核;进入壳层反应时,反应成核主要是以胶束成核为主.     

Statistical experimental strategies approach to emulsion copolymerization of styrene and n-butyl acrylate

A batch emulsion copolymerization for the preparation of styrene-n-butylacrylate (St/BA) copolymer latexes is investigated. A series of n-butylacrylate-styrene copolymer latexes were obtained by emulsion copolymerization in the presence of K₂S₂O₈ (KPS) as initiator and with/without emulsifier (sodium lauryl sulfate). The effect of such preparation conditions as initiator concentration, the St/BA ratio, reaction temperature, agitation rate, and emulsifier concentration on the polymerization rate, particle size of copolymer latex, and molecular weight distribution of the resulting copolymer (∼ 80% conversion), respectively, is systematically studied using fractional factorial design methodology. Fractional factorial analysis indicates that the effects of the St/BA ratio, reaction temperature, emulsifier concentration, as well as the two-factor interaction of temperature and emulsifier concentration, are the key variables influencing the polymerization rate. At ∼ 80% monomer conversion, statistical analysis clearly isolates emulsifier concentration as the dominant factor affecting average particle size of copolymer latex; results also indicate that the effects of the St/BA ratio, reaction temperature, and emulsifier concentration are major effects influencing the polydispersity of polymer molecular-weight distribution. For 7.30 g KPS/100 g monomer and 500 rpm agitation rate, the conditions for minimizing molecular-weight distribution (∼ 80% conversion) occur for a reaction temperature, St/BA ratio, and surfactant concentration of 70°C, ∼ 3.59/1, and ∼ 2.08 g/100 g monomer, respectively, generating a minimum molecular-weight polydispersity of ∼ 3.0. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 551–563, 1998     

Poly(methyl acrylate) and copolymer of acrylic acid and butyl acrylate prepared by γ‐irradiation in the presence of 1,1‐diphenylethene: Synthesis and application in emulsion polymerization

Poly(methyl acrylate) and amphiphilic copolymer of butyl acrylate and acrylic acid were prepared in the presence of 1,1‐diphenylethene (DPE) by γ‐irradiation‐induced polymerization. The influences of polymerization time, amounts of DPE in system on conversion, molecular weight (MW), and its distribution (M_w/M_n) were studied. The results indicate that the polymerization in the presence of DPE and initiated by γ‐irradiation shows the character of controlled radical reaction. The prepared copolymer was used as the polymeric emulsifier in the emulsion polymerizations of butyl acrylate (BA) and styrene (St), respectively, to assess the possibility of making monodisperse latices of relatively high solids content (～ 35–45%) in an one‐step batch process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Kinetic investigations of acrylic–polyurethane composite latex

The effect of various reaction parameters on the rate of polymerization, R_p, and on the particle size and morphology of aqueous acrylic–polyurethane hybrid dispersions, prepared by semibatch emulsion polymerization, was investigated. The particles of polyurethane dispersion were used as seeds during the polymerization of acrylic component: methyl methacrylate (MMA), butyl acrylate (BA), and a mixture of MMA and BA with the ratio of 1:1. These emulsions were found to form structured polymer particles in aqueous media using scanning electron microscopy. The kinetics of the emulsion polymerization was studied on the basis of Wessling's model. The influence of emulsifier and initiator concentrations, including the monomer feed rates, R_m, on the rates of polymerization and on the properties of the resulting dispersions were studied. The number of particles and the particle size were also measured during the polymerization process. The final values were found to be independent of the concentration of the emulsifier, initiator and the monomer feed rate in monomer starved conditions. In the steady‐state conditions, during the seeded semibatch hybrid emulsion polymerization, the rate of polymerization and the monomer feed rate followed the Wessling relationship 1/R_p = 1/K + 1/R_m. The dispersions MMA/PU, BA/PU, and MMA/BA/PU have K values of 0.0441, 0.0419 and 0.0436 mol/min, respectively. The seeded BA/PU hybrid polymerization proceeded according to Smith‐Ewart Case I kinetics, while the MMA/PU hybrid emulsions demonstrate Case II of the Smith‐Ewart kinetic model. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2639–2649, 2002     

Polymer/carbon nanotube composite emulsion prepared through ultrasonically assisted in situ emulsion polymerization

In this study, ultrasonic irradiation and in situ emulsion polymerization were combined to prepare stable poly(methyl methacrylate‐co‐n‐butyl acrylate) (P(MMA‐BA))/carbon nanotubes (CNTs) composite emulsion, which solves the dispersion problem of CNTs in the latex. Two stages were adopted. In Stage I, ultrasonically initiated in situ emulsion polymerization was conducted to disperse CNTs and prepare the seed emulsion containing polymer coated CNTs. In Stage II, conventional in situ emulsion polymerization was conducted to further enhance the monomer conversion and solid content. The dispersion behavior of MWCNTs in aqueous solution under ultrasonic irradiation was investigated by spectrophotometry. The effects of CNTs content on the emulsion stability and mechanical properties of composite film were studied. The results suggest that in the composite emulsion the long CNTs with a diameter of 20–40 nm are separated and dispersed by the formed polymer latex nanoparticles with a size of 20–40 nm. The spherical polymer latex nanoparticles adhere to the wall of CNTs to form a structure like “grapes on the twig.” The smooth, uniform, and flexible polymer/CNTs composite films were prepared from the composite emulsion. The CNTs can be individually dispersed in P(MMA‐BA)/CNTs composite film. Tensile tests suggest that with the increase in the CNTs content, the Young's modulus and the yield strength of the film increase. Only at 1 wt % CNTs, the Young's modulus increases from 124 to 289 MPa, and the yield strength is improved about ～14%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3123–3130, 2006     

Structure and mechanical properties of the hybrid films of well dispersed SiO2 nanoparticle in polyimide (PI/SiO2) prepared by sol–gel process

Methyl methacrylate-butyl acrylate structural latexes were synthesized by two-stage seeded emulsion polymerization using 1,1-diphenylethylene (DPE) as a control reagent. In the first stage, the seed latex particles with the precursor poly (methyl methacrylate-DPE) (P(MMA-DPE)) were prepared, and then the second monomer n-butyl acrylate (nBA) was swollen into the seed latex particles under stirring at room temperature. In the second stage, the polymerization of nBA was thermally initiated at 80 °C, and the latex particles composed of block copolymer were synthesized. The size and morphology of the latex particles were investigated by light scattering and TEM. The contact angles of different latex films were also measured. The block copolymer was characterized by size exclusion chromatography, nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. Microphase separation of the block copolymer was examined using atomic force microscopy.     

Polymer–leather composites. II. Kinetics of the deposition of selected acrylate monomers by polymerization into chrome-tanned cattlehide

Limited kinetic information on a convenient process for depositing polymer in 5-oz cattlehide is presented in this article. The work includes a systematic study of the total polymerization rate and of the derived rates of deposition into the fibrous matrix, of bound polymer formation, and of polymer production in the external aqueous phase (the float) for three acrylic monomers. The monomers used, with a persulfate–bisulfite redox initiating system at 27°C, were methyl methacrylate (MMA), n-butyl acrylate (BA) and a fixed mixture of n-butyl acrylate and methyl methacrylate (BA + MMA). The effects of the reaction variables on rate, as measured by their intensity exponents, were not in agreement with a rate expression proposed to describe grafting in homogeneous polymerization, nor were they wholly compatible with classical and modified Smith–Ewart theories for heterogeneous emulsion polymerization. The experimental behavior, however, was in harmony with self-nucleation in the aqueous phase. Exponential orders of dependence were initiator > 0.5 (MMA, 0.72; BA + MMA, 0.66); monomer, zero; surfactant, ～0.5. The approximately 0.6 order dependence (MMA, 0.9) on leather amount was shown to be largely apparent and to decline as total polymerization proceeded. Thus a dominant grafting reaction was not supported. In support of this conclusion, simple impregnation of the matrix with preformed emulsion polymer yielded the same amount of bound polymer as that formed in situ. It was concluded that monomer is initiated largely from active centers formed initially near fibers or fibrils to form embryo polymer particles, which join penetrating swollen polymer particles and become unstable. These nucleate a polymer front, containing occluded radicals, which grows by diffusion regulated transport of monomer to complete deposition.     

Semi-continuous emulsion copolymerization of vinyl acetate and butyl acrylate in presence of AMPS

The emulsifier-free emulsion polymerization of vinyl acetate (VAc) and butyl acrylate (BA) in the presence of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) was carried out by a semi-continuous process. AMPS was a reactive surfactant in the aqueous emulsion, due to its amphiphilic structure and the unsaturated double bonds. Potassium persulfate (KPS) was used as initiator. The following factors were mainly examined: quantity of AMPS, BA and KPS concentrations, which could significantly affect the particle size and its distribution, conversion, gel content, minimum film-forming temperature, etc. The particle size and its distribution were characterized by dynamic laser particle size analyzer, and morphology of the latex particles was characterized by transmission electron microscopy (TEM). Fourier transform infrared spectroscopy was used to characterize chemical structure of copolymers. The results indicated that AMPS was successfully reacted onto the resulted copolymer of vinyl acetate and butyl acrylate. A hydrophilic sulfonic acid group in the molecular structure of AMPS tended to be distributed in particles surface after polymerization. As a result, an electrostatic repulsion between the particles was produced in order to maintain stability of the system. Thermogravimetric analysis curves suggested that as BA content increased, thermal stability of the polymer increased accordingly. The conversion-time plots with varying AMPS and initiator contents were obtained, which illustrated that the initiator concentration could greatly influence the polymerization rate and the final conversion. The TEM micrographs of the final emulsifier-free latex particles for P(VAc/BA/AMPS) system revealed small particle size in monodisperse polymer latex. The particles of the latex were measured as about 150 nm.     

Effect of carboxylic acid monomer and butadiene on particle growth in the emulsifier-free emulsion copolymerization of styrene-butadiene-carboxylic acid monomer

Carboxylated styrene-butadiene rubber (XSBR) latexes were prepared by emulsifier-free batch emulsion copolymerization of styrene and butadiene with different types of carboxylic acid monomers (AA, MAA, IA). It was found that the particle growth is dependent on the hydrophilic nature of carboxylic acid monomers. SEM studies showed that N_p is almost constant in the particle growth stage (conversion above 10%). Through some calculations by data obtained from DLS technique, average diameter of monomer swollen polymer particles of all the XSBR latexes at the same conversion of 0.4 was obtained to be 368.91, 174.17 and 437.15 nm for AA, MAA and IA, respectively. Several kinetic parameters related to the particle growth stage such as the average number of growing chain per particle were calculated to be 0.474, 0.370 and 1.685 for AA, MAA and IA, respectively. It was observed that these kinetic parameters increase with increasing average diameter of monomer swollen polymer particles, which is consistent with the emulsion polymerization kinetics. Moreover, results indicated that the polymerization rate per particle or equivalently the average number of the growing chain per particle (particle growth stage) decreases by replacing a part of styrene with butadiene in the emulsion copolymerization recipe of styrene-carboxylic acid monomer.     

阳离子型全氟丙烯酸酯无皂乳液的合成及性能

以全氟烷基乙基丙烯酸酯(FEA)为含氟单体,以甲基丙烯酰氧乙基三甲基氯化铵(DMC)为阳离子单体,采用无皂乳液聚合方法合成了阳离子型全氟丙烯酸酯共聚物乳液.分析了FEA含量对涂膜性能的影响,讨论了DMC用量对聚合转化率、涂膜吸水率以及乳胶粒粒径大小的影响;利用FT-IR和X-射线衍射分析(XRD)对共聚物乳液进行了表征,结果表明,当FEA和DMC质量分数分别为7.1%和12%时,涂膜的吸水率最小,仅为3.75%,乳胶粒平均粒径为65 nm.随着FEA量的增加,共聚物膜的硬度减小,拉伸强度增加,断裂伸长率降低;XRD分析显示全氟丙烯酸酯无皂乳液具有好的结晶性.     

VAc／BA／AA乳液共聚反应动力学研究

用丙烯酸丁酯（BA）和丙烯酸（AA）对醋酸乙烯酯（VAc）进行共聚改性,制备了稳定的VAc／BA／AA共聚乳液。研究了该聚合体系的动力学特征,讨论了乳化剂浓度（CE）、引发剂浓度（C1）和反应温度（T）对聚合速率和单体转化率的影响。实验结果表明,乳液聚合速率随着CE、C1和T的增加而增大;单体转化率随着CE和C1的增加而增大,在75℃时转化率有最大值;得到该共聚乳液体系的表观活化能Ea=64．4kJ·mol^-1;聚合反应速率Rp^∝CE^0.45C1^0．76该式与经典的乳液聚合动力学模型有较大偏差。