Synthesis of nanosized ethylene–propylene rubber latex via polyisoprene hydrogenation

Nanosized ethylene–propylene rubber (EPM) latex with a particle size of 47 nm was synthesized via an alternative route consisting of isoprene (IP) polymerization followed by hydrogenation. First, the IP monomer was polymerized by differential microemulsion polymerization to obtain polyisoprene (PIP) rubber latex with a particle size of 42 nm. The structure of synthetic PIP was hydrogenated at the carbon–carbon double bonds to produce an ethylene–propylene copolymer by diimide reduction in the presence of hydrazine and hydrogen peroxide using boric acid as promotor. The degree of hydrogenation was determined by proton nuclear magnetic resonance (¹H‐NMR) spectroscopy and the structure of the ethylene–propylene copolymer was identified by ¹³C‐NMR spectroscopy. In nanosized PIP hydrogenation, the hydrogenation level was found to be increased by boric acid addition. An EPM yield of 94% was achieved using a hydrogen peroxide : hydrazine ratio of 1.5 : 1. The EPM produced from PIP has high thermal stability with the maximum decomposition temperature of 510°C and a glass transition temperature of ‐42.4°C close to commercial ethylene–propylene diene rubber. Dynamic mechanical analysis indicated that EPM had a maximum storage modulus due to the saturated carbons domains of the ethylene segments in the polymer chains. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Comparison of styrene reversible addition–fragmentation chain‐transfer polymerization in a miniemulsion system stabilized by ammonlysis poly(styrene‐alt‐maleic anhydride) and sodium dodecyl sulfate

In this study, we conducted the reversible addition–fragmentation chain‐transfer (RAFT) polymerization of styrene (St) in a miniemulsion system stabilized by two different stabilizers, ammonlysis poly(styrene‐alt‐maleic anhydride) (SMA) and sodium dodecyl sulfate (SDS), with identical reaction conditions. The main objective was to compare the polymerization kinetics, living character, latex stability, and particle morphology. The macro‐RAFT agent used in both systems was SMA, which was obtained by RAFT solution polymerization mediated by 1‐phenylethyl phenyldithioacetate. The experimental results show that the St RAFT miniemulsion polymerization stabilized by SDS exhibited a better living character than that stabilized by ammonlysis SMA. The final latices were very stable in two systems, but different stabilizers had an obvious effect on the polymerization kinetics, living character, and particle morphology. All of the particles obtained by RAFT miniemulsion polymerization stabilized by SDS were solid, but an obvious core–shell structure was observed in the miniemulsion system stabilized by ammonlysis SMA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Ultrasonically initiated free radical‐catalyzed emulsion polymerization of methyl methacrylate (i)

The emulsion polymerization of methyl methacrylate initiated by ultrasound has been studied at ambient temperature using sodium lauryl sulfate as the surfactant. The investigation includes the: (1) nature and source of the free radical for the initiation process; (2) effects of different types of cavitation; and (3) dependence of the polymerization rate, polymer particle number generated, and the polymer molecular weight on acoustic intensity, argon gas flow rate, surfactant concentration, and initial monomer concentration. It was found that the polymerization could be initiated by ultrasound in the emulsion systems containing methyl methacrylate, water, and sodium lauryl sulfate at ambient temperature in the absence of a conventional initiator. The source of the free radical for the initiation process was found to come from the degradation of the sodium lauryl sulfate, presumably in the aqueous phase. The weight average molecular weight of the poly(methyl methacrylate) obtained varied from 2,500,000 to 3,500,000 g mol⁻¹, and the conversion for polymerization was up to 70%. Deviations from the Smith–Ewart kinetics were observed. The polymerization rate was found to be proportional to the acoustic intensity to the 0.98 power; to the argon gas flow rate to the 0.086 power; to the surfactant concentration to the 0.08 power, with the 0.035M–0.139M surfactant concentration range; and to the surfactant concentration to the 0.58 power, with the 0.139M–0.243M surfactant concentration range. The polymerization rate was found to increase with increasing initial monomer concentration up to a point where it became independent of initial monomer concentration. The polymer particle number generated per milliliter of water was found to be proportional to the acoustic intensity to the 1.23 power; to the argon gas flow rate to the 0.16 power; to the surfactant concentration to the 0.3 power, with the 0.035M–0.139M surfactant concentration range; and to the surfactant concentration to the 1.87 power, with the 0.139M–0.243M surfactant concentration range. The polymer weight average molecular weight was found to be proportional to the acoustic intensity to the 0.21 power, and to the argon gas flow rate to the 0.02 power. It was found to be inversely proportional to the surfactant concentration to the 0.12 and 0.34 power, with the 0.035M–0.139M and the 0.139M–0.243M surfactant concentration ranges, respectively. The polymer yield and polymerization rate were found to be much larger than those obtained from an ultrasonically initiated bulk polymerization method. The polymerization rates obtained at ambient temperature were found to be similar to or higher than those obtained from the conventional higher temperature thermal emulsion polymerization method. This investigation demonstrated the capability of ultrasound to both initiate and accelerate polymerization in the emulsion system, and to do this at a lower temperature that could offer substantial energy savings. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 797–825, 1999     

Graft copolymerization of an itaconic acid/acrylamide monomer mixture onto poly(ethylene terephthalate) fibers with benzoyl peroxide

A mixture of acrylamide (AAm) and itaconic acid (IA) was grafted onto poly(ethylene terephthalate) (PET) fibers with benzoyl peroxide in aqueous media. The effects of polymerization conditions such as the temperature, polymerization time, initiator concentration, and monomer mixture ratio on grafting were investigated. The maximum graft yield was 76.1% with an AAm/IA mixture ratio of 90/10 (mol/mol). The graft yield was as low as 3% in the single grafting of IA, whereas the use of AAm as a comonomer increased the amount of IA that entered the fiber structure to 33.5%. An increase in the temperature from 65 to 85°C increased the grafting rate and saturation graft yield. However, an increase in the temperature above 85°C decreased the saturation graft yield. The graft yield increased up to an initiator concentration of 1.0 × 10^?2 M and decreased afterwards. The grafting rate was 0.65th‐ and 0.74th‐order with respect to the initiator and AAm concentrations, respectively. The densities, diameters, and moisture‐regain values of the AAm/IA‐grafted PET fibers increased with the graft yield. Similarly, there was an increase in the dyeability of the AAm/IA‐grafted fibers with acidic and basic dyes. The grafted fibers were characterized with Fourier transform infrared and thermogravimetric analysis, and their morphologies were examined with scanning electron microscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1795–1803, 2005     

Effect of graft copolymerization of 2-hydroxyethyl methacrylate on the properties of polyester fibers and fabric

Graft copolymerization of hydroxyethyl methacrylate (HEMA) onto poly(ethylene terephthalate) (PET) fibers using benzoyl peroxide (BP) as initiator was carried out in water and in water/organic solvent as a reaction medium. The effect of initiator concentration, reaction time, temperature, and reaction medium as well as addition of FeSO₄ to the polymerization medium was studied. Percent grafting was enhanced significantly by increasing BP concentration up to 0.016 mol/L and then decreased upon further increase in initiator concentration. Increasing the monomer (HEMA) concentration up to 0.48 mol/L improves significantly the graft yield. Raising the polymerization temperature up to 85°C causes a significant increase in grafting yield; further increase in temperature leads to decrease in graft yield. Incorporation of Fe⁺² ions in the polymerization system decrease the graft yield. The same situation is encountered when water/solvent mixture is used as reaction medium. Solvent employed were methanol, toluene, and benzene.     

Microemulsion polymerization of styrene using developed redox initiation system and study of rheological properties of obtained latices

Microemulsion polymerization of styrene was kinetically studied using a potassium persulfate (KPS)/P‐methyl benzaldehyde sodium bisulfite (MeBSBS) adduct as the developed redox pair initiation system. The rate of microemulsion polymerization of styrene was found to be dependent on the initiator, emulsifier, and monomer to the powers of 1.4, −0.77, and 0.83, respectively. The apparent Arrhenius activation energy (E_a) estimated for the microemulsion polymerization system was 6.5 × 10⁴ J/mol. Also, the morphological parameters were studied at different initiator concentrations. The rheological measurements for the prepared microemulsions were carried out to investigate the effect of the preparation parameters on the rheological behavior of the polystyrene microemulsions. The rheological flow curves of the polystyrene microemulsion latices prepared at different temperatures were carried out, and we found that the plastic viscosity and Bingham yield values of the flow curves increased with an increasing reaction temperature. That may be due to the cage effect of the prepared polymer particles, which trapped the medium molecules. The plastic viscosity increased with increasing emulsifier concentration while the Bingham yield value decreased. For the polystyrene microemulsion prepared in the presence of different initiator concentrations, the plastic viscosity and Bingham yield increased with increasing initiator concentration. This trend was found to be the same for the microemulsion latices prepared in the presence of different monomer concentrations. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1240–1249, 2000     

Laser-initiated homogeneously photocatalytic polymerization of phenylacetylene by W(CO)6-CH3I system

Summary The polymerization of phenylacetylene at room temperature by UV laser activated W(CO)₆ in CH₃I solvent was investigated. The weight-average molecular weight of the polymer is 10³, and the ¹H NMR spectra of polymers indicate that the polyphenylacetylene has a cis-transoidal structure. The experimental data show that not only laser wavelength, energy and irradiation time influence on the yield of polymer but also the laser energy influences the structure of polymer.     

Investigation of kinetics of 4‐methylpentene‐1 polymerization using Ziegler–Natta‐type catalysts

The kinetics of 4‐methylpentene‐1 (4MP1) polymerization by use of Ziegler–Natta‐type catalyst systems, M(acac)₃‐AlEt₃ (M = Cr, Mn, Fe, and Co), are investigated in benzene medium at 40°C. The effect of various parameters such as Al/M ratio, reaction time, aging time, temperature, catalyst, and monomer concentrations on the rate of polymerization and yield are examined. The rate of polymerization increased linearly with increasing monomer concentration with first‐order dependence, whereas the rate of polymerization with respect to catalyst concentration is found to be 0.5. For all cases, the polymer yield is maximum at an Al/M ratio of 2. The activation energies obtained from linear Arrhenius plots are in the range of 25.27–33.51 kJ mol^?1. It is found that the aging time to give maximum percentage yield of the polymer varies with the catalyst systems. Based on the experimental results, a plausible mechanism is proposed that envisages a free‐radical mechanism. Characterization of the resulting polymer product, for all the cases, through FTIR, ¹H‐NMR, and ¹³C‐NMR studies, showed isomerized polymeric structures with 1,4‐structure as dominant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2468–2477, 2003     

Kinetic study of the aqueous free‐radical polymerization of 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid via an online proton nuclear magnetic resonance technique

The free‐radical polymerization of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) in aqueous media and in the presence of potassium persulfate (KPS) as a thermal initiator was studied. The ¹H‐NMR method was applied to record the reaction data in online gain. The effects of the monomer and initiator concentrations and also the reaction temperature were studied. The order of reaction with respect to the monomer was much greater than unity (1.94). None of the three theories describing an order of reaction higher than unity could predict the AMPS polymerization mechanism in this study. So, a new mechanism is presented. It is suggested that initiation took place through the formation of a complex between the initiator and monomer, and termination occurred not only by a bimolecular reaction but also by a monomolecular reaction. The order with respect to KPS was 0.49; this was consistent with classical kinetic theory. The determined activation energy at the overall rate of reaction was 92.7 kJ mol^?1 K^?1. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

缩短氯乙烯悬浮聚合时间的动力学研究

研究了有机过氧化物引发剂引发氯乙烯悬浮聚合的过程和影响因素，给出了不同温度、不同引发体系的聚合动力学试验数据和聚合时间-转化率、聚合时间-转化速率曲线．讨论了不同引发体系对PVC树脂质量的影响。试验结果表明：采用适宜的复合有机过氧化物引发剂可缩短聚合时间1h，提高聚合釜的生产能力。     

氯化聚氯乙烯复合纳滤膜的制备及其在模拟RB5染料废水处理中的应用

以氯化聚氯乙烯（CPVC）超滤膜为基膜,采用单宁酸（TA）和哌嗪（PIP）在CPVC膜表面共沉积后与交联剂均苯三甲酰氯（TMC）进行界面聚合得到PA/TA/CPVC复合纳滤膜,采用扫描电镜（SEM）、原子力显微镜（AFM）、红外光谱及接触角对PA/TA/CPVC复合纳滤膜进行了表征,并探讨了干燥时间、TA/PIP浓度比、TA+PIP总浓度、TMC浓度对PA/TA/CPVC复合纳滤膜微观结构与性能的影响。结果表明,TA/PIP浓度比最佳为7/3,TA/PIP层的最佳干燥时间为20min,PA/TA/CPVC复合纳滤膜的纯水通量随着TA+PIP总浓度的增加和TMC浓度的增加而减少,对PEG1000的截留率均在90%以上。PA/TA/CPVC复合纳滤膜纯水通量最大值为4.5L/(m² · h · bar),此时PEG1000的截留率达到95.8%。对模拟RB5染料废水的最大通量为4.3L/(m² · h · bar),此时RB5的截留率为95.4%,对模拟RB5染料废水的稳定性较好。     

Pressure effects on polymerization of syndiotactic polystyrene

Polymerization pressure has a direct effect on the synthesis of syndiotactic polystyrene (s-PS) with metallocene as a catalyst. The polymerization rate, yield rate, and average molecular weight show a linear relationship with pressure, that is, they all increase with increased polymerization pressure. However, under 1000 psi, the yield of s-PS increases with polymerization duration while the yield rate decreases. As a whole, this syndiotactic polymerization proceeds relatively fast in comparison with ordinary vinyl polymerization. Optimal conditions (pressure, temperature, and duration) for the synthesis of s-PS have been explored. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1747–1752, 1998     

Thermal and strain rate sensitive compressive behavior of polycarbonate polymer - experimental and constitutive analysis

The mechanical behavior of polycarbonate (PC) polymer was investigated under the effect of various temperatures and strain rates. Characterization of polymer was carried out through uniaxial compression tests and split Hopkinson pressure bar (SHPB) dynamic tests for low and high strain rates respectively. The experiments were performed for strain rates varying from 10 ^?3 to 10³ and temperature range of 213 to 393 K. By conducting these experiments, the true stress–strain (SS) curves were obtained at different temperatures and strain rates. The results from experiments reveal that the stress–strain behavior of polycarbonates is different at lower and higher strain rates. At higher strain rate, the polymer yields at higher yield stress compared to that at low strain rate. At lower strain rate, the yield stress of the polymer increases with the increase in strain rate while it decreases significantly with the increase of temperature. Likewise, initial elastic modulus, yield and flow stress increase with the increase in strain rate while decreases with the increase in temperature. The yield stress increases significantly for low temperature and higher strain rates. On the basis of experimental findings, a phenomenological constitutive model was employed to capture the mechanical behavior of polymer under temperature and loading rate variations. The model predicted the yield stress of polymer at varying strain rate and temperature also it successfully predicted the compressive behavior of polymer under entire range of deformation.     

Synthesis and properties of natural rubber modified with stearyl methacrylate and divinylbenzene by graft polymerization

The graft polymerizations of stearyl methacrylate (SMA) and divinylbenzene (DVB) onto natural rubber (NR) were carried out in a solution process using benzoyl peroxide (BPO) as an initiator in toluene or chloroform. The main products of the grafted NR include an uncrosslinked (sol) part [sol(SMA–NR–DVB): s‐SNRD] and a crosslinked (gel) part [gel(SMA–NR–DVB), g‐SNRD]. s‐SNRD was obtained by extraction using tetrahydrofuran. It was identified by IR and ¹H‐NMR spectroscopies. The glass transition temperature (T_g) and thermal properties of s‐SNRD and g‐SNRD were studied by DSC and TGA. The glass transition temperature and thermal decomposition temperature of s‐SNRD and g‐SNRD were higher than were those of NR. The light resistance and weatherability of s‐SNRD were measured with a Weather‐o‐Meter. The light resistance and weatherability of s‐SNRD are better than are those of NR. The effects of the initiator concentration, mol ratio of SMA to DVB, reaction time, temperature on grafting ratio, and crosslinking ratio were investigated. The highest grafting ratio and crosslinking ratio in the graft polymerization of SMA and DVB onto NR were obtained when the mol ratio of SMA to DVB and BPO were 4.0 and 2 wt %, at 80°C for 48 h, respectively. Following several studies on oil‐absorptive polymers in our laboratory, 9 the oil absorptivity of g‐SNRD was examined using crude oil. The oil absorptivity of g‐SNRD was 600% when the immersion time was 10 min. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2464–2470, 2001     

Photopolymerization behavior and phase separation effects in novel polymer dispersed liquid crystal mixture based on urethane trimethacrylate monomer

Polymer dispersed liquid crystals (PDLCs) are often formed by polymer induced phase separation, based on photopolymerization of multifunctional acrylate monomers. The emerged morphology is controlled by the interplay between polymerization rate and phase separation dynamics, which depends on different parameters such as monomer structure and functionality. In this work, a new PDLC formulation containing urethane trimethacrylate (UTMA) monomer is introduced, which has different molecular weight evolution, polymer gel point, and polymerization kinetics in comparison with some common ester acrylate (such as TMPTA and DPHPA) based PDLC compositions. UTMA is synthesized and characterized by Fourier transform infrared, ¹H‐NMR, and ¹³C‐NMR spectroscopic techniques. Simultaneous examination of polymer evolution and LC phase separation by real‐time infrared spectroscopy shows that the UTMA based PDLC, which contains trifunctional urethane acrylate monomer, has greater amount of bond conversion, polymerization rate, and liquid crystal (LC) phase separation in comparison with TMPTA based PDLC. In spite of the acrylate monomers, which show gel point conversions as low as 1.83–5.72%, UTMA reaches to its maximum rate at 19.5% conversion, which causes higher phase separation and therefore greater LC domain size. The experimental results are explained more precisely by means of SEM and optical microscopy analyses. The results are confirmed by electro‐optics measurements. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Co γ-irradiation-initiated RAFT polymerization of VAc at room temperature

In this work, the reversible addition-fragmentation chain transfer (RAFT) polymerization of vinyl acetate (VAc) was successfully performed at room temperature using ⁶⁰Co γ-irradiation as the initiation source. Under the dose rate of 10 Gy/min irradiation, the polymerization proceeded smoothly and converted approximately 90% of the monomer within 7 h. The molecular weight distribution (M_w/M_n) remained narrow (M_w/M_n < 1.35) up to 90% conversion. Compared to AIBN-initiated RAFT polymerization at 60 °C, ⁶⁰Co γ-irradiation-initiated RAFT polymerization is a technique that can better control the molecular weight, especially at high conversion. The ¹H NMR spectra and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry confirmed that most of the chain ends of poly(VAc) (PVAc) from γ-irradiated RAFT polymerization were living and can be reactivated for chain-extension reactions. The microstructures of PVAc from ⁶⁰Co γ-irradiated RAFT polymerization (almost head-to-tail addition) and AIBN-initiated RAFT polymerization (5% tail-to-tail addition) were different, as revealed by the ¹³C NMR spectra. For the first time, ⁶⁰Co γ-irradiation was used as an initiation source for RAFT polymerization of VAc at room temperature.     

Synthesis and nitrosation of processible copolymers from pyrrole and ethylaniline

A series of copolymers were prepared by an oxidative polymerization of pyrrole (PY) and 2-ethylaniline (EA) in HCl. The polymerization process was followed by tracking open-circuit potential and temperature of the reaction solutions. The fine particles of the PY/EA copolymers obtained in situ were further N-nitrosated for the first time in order to improve their solubility. The size, structure, and properties of the fine particles and their N-nitroso products were systematically characterized by laser particle size analyzer, FTIR, UV-vis, GPC, solution casting, and TG techniques. It is found that both the open-circuit potential and temperature of the solutions exhibit a maximum during the copolymerization, while the particle size of the copolymers will decrease monotonically with prolongating polymerization time or doping. Both the polymerization yield and molecular weight of the copolymers exhibit a minimum with PY/EA ratio, indicating a mutual retarding effect between the PY and EA monomers. The top potential and top temperature of the copolymerization as well as the particle size and its distribution, solubility, film-forming ability, electroconductivity, and thermostability of the copolymers all depend significantly on the PY/EA ratio. The PY/EA copolymers have good solubility in the solvents with the solubility parameter from 23 to 27 J^1/2/cm^3/2, dielectric constant greater than 12 and polarity index from 6.4 to 7.4 and their solubility becomes further better with increasing EA content. The N-nitrosation of copolymers can also improve their solubility in polar solvents furthermore. The copolymers with PY content of less than 30 mol% in NMP and THF exhibit good thin-film formability. The copolymer films become smoother and tougher with increasing EA content and by N-nitrosation. With increasing PY content, the decomposition temperature, maximum decomposition rate, char yield at 500 °C, and activation energy all decrease but decomposition order increases. The temperature at the maximum weight-loss rate of the copolymers has a maximum at the PY/EA molar ratio of 30/70. These results suggest that the polymer obtained is a real copolymer containing two comonomer units.     

Synthesis and characterization of poly(dihalophenylene oxide)s by solid-state thermal-decomposition of manganese phenolate complexes with tetramethylethylenediamine

The characterization of poly(dihalophenylene oxide)s synthesized by solid-state thermal decomposition of manganese phenolate complexes with tetramethylethylenediamine (TMEN) ligand is reported. The complexes prepared with 2,4,6-trichlorophenol (TCP) and 2,4,6-tribromophenol (TBP) have been characterized by FTIR spectroscopy, elemental analysis, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The dependence of the polymerization yield on temperature and decomposition time of the complexes has been investigated. Maximum polymerization yield is obtained at 220°C and 48 h. The polymers synthesized from the complexes have been characterized by ¹H-NMR and FTIR spectroscopy, DSC, and viscometric measurements. All polymers have a branched structure, a high T_g and low intrinsic viscosity. © 1999 Society of Chemical Industry     

Ring‐opening polymerization of cyclohexene oxide by recyclable scandium triflate in room temperature ionic liquid

In this article, we provide a concept of a two‐phase polymerization system consisting of immiscible monomer and room temperature ionic liquid (IL). The catalyst is immobilized in the IL phase where polymerization takes place. The produced polymer is extracted by the monomer, and the remaining IL phase is catalytically active for more polymerizations. Thus, common volatile organic solvents are no longer needed. Ring‐opening polymerization of cyclohexene oxide (CHO) in 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate IL ([bmim][BF₄]) using scandium triflate [Sc(OTf)₃] catalyst serves as a realistic example of such concept. The yield of polyCHO in [bmim][BF₄] is higher than that in bulk. IL containing Sc(OTf)₃ can be used for at least three times. A circulatory polymerization process is carried out with added catalyst to keep a relatively high yield in following circulation processes. The assignments of proton signals of polyCHO in ¹H NMR are discussed in detail. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012