Investigation of polyacrylonitrile solution inhomogeneity by dynamic light scattering

Dynamic light scattering (DLS) has been used to quantify nanoscale heterogeneity in the industrially significant polyacrylonitrile (PAN) polymer solution. The heterogeneity in polymer solution, traced by the ratio of amplitudes of the slow to fast mode, is observed to be related to various parameters, such as molecular weight of the polymer, the type of co‐monomer, processing time, concentration of the solution, and the choice of the solvents. It has been identified that low molecular weight PAN homopolymer have the least heterogeneity issues. Amongst the chosen co‐polymers for this study, similar degree of heterogeneity was observed at concentration slightly above the critical concentration at which the polymer chains begin to overlap. Whereas, at higher concentration, PAN‐methacrylic acid (4 wt%) copolymer showed the least heterogeneity issue. The aggregate diffusion coefficient of PAN‐methacrylic acid (4 wt%) copolymer solution in dimethylformamide (DMF) and N,N‐dimethylacetamide (DMAc) are respectively determined to be ～1.6 × 10^?12 cm²/s and ～1.6 × 10^?13 cm²/s, which results in an estimated aggregate size of 9 nm and 90 nm. POLYM. ENG. SCI., 55:1403–1407, 2015. © 2015 Society of Plastics Engineers     

Polymerization of methyl methacrylate by metallocenes

Attempts at polymerizing methacrylate using metallocenes are reported. Polymerization is successful using ferrocene in a ketone solution, but not in benzene or without a solvent. Ketones are effective in the order: methyl ethyl ketone < cyclohexanone < cycloheptanone. Carbon tetrachloride has an accelerative effect on the polymerization in benzene and methyl ethyl ketone solutions, but no effect in cyclohexanone solution. Some binary systems, which consist of ferrocene and higher valence compounds such as cobalt trisacetylacetonate, are effective redox initiators. Cobaltocene polymerizes methyl methacrylate in the presence of carbon tetrachloride; zirconocene dichloride induces polymerization of methyl methacrylate in a cyclohexanone solution; whereas neither nickelocene nor titanocene dichloride are effective. Styrene and acrylonitrile were not polymerized by the metallocenes examined.     

甲基丙烯酸正丁酯共聚纤维的结构与性能

以甲基丙烯酸β-羟乙酯(HEMA)为第二单体,与甲基丙烯酸正丁酯(BMA)悬浮聚合制得BMA/HEMA二元共聚物,采用冻胶纺丝法制备BMA/HEMA共聚纤维,研究了加入HEMA的对纤维结构与性能的影响。结果表明:随着HEMA含量的增加,BMA/HEMA纤维分子间氢键作用和物理交联作用增强,纤维的玻璃化转变温度升高,但纤维表面变得粗糙,具有疏松多孔结构,其吸附性能提高。当HEMA质量分数为15%时,BMA/HEMA纤维对有机液体三氯乙烯的吸附量达18.5g/g。     

Scaling up the styrene butyl methacrylate copolymerisation reaction

The scale-up of benzoyl peroxide initiated copolymerisation of styrene and butyl methacrylate is studied here. The reaction is carried out in reactors of 3, 10 and 100 1 volume. Increasing the reactor size increase the weight average molecular weight and broadens the molecular weight distribution. Reducing the agitator diameter broadens the molecular weight distribution.     

A study of mass transport of linear polystyrene in polyethyl methacrylate gel by dynamic light scattering

Mass [i.e., linear polystyrene (PS) probe] transports in polyethyl methacrylate (PEMA) gels with ethylene dimethacrylate (EDMA) as crosslinker were studied by dynamic light scattering (DLS). For PEMA gels in toluene, we have established that it is a very well matched system, so that it is very convenient to study the mass transport of the PS macromolecule in such a system. Experiments show that the obstruction effects of PEMA gels for the mass transport of PS are obvious. Reasonably, the lower the gel obstruction for mass transport, the higher the diffusion coefficient D_t of PS in gel. Moreover, the larger the molecular weight of PS, the greater the obstruction effect of the gel. Furthermore, we traced quantitatively the evolution of D_t of PS during the crosslinking copolymerization of PEMA. The results show that, after the reaction, the obstacle for mass transport in the gel develops gradually. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2062–2066, 2002     

MMA/BA共聚物改性的水性聚氨酯的合成与表征

以1, 4-丁二醇 (BDO)、二羟甲基丙酸 (DMPA) 和己二酸二酰肼 (ADH) 为扩链剂,以甲基丙烯酸甲酯 (MMA) 和丙烯酸丁酯 (BA) 改性聚氨酯 (PU),得聚氨酯-丙烯酸酯复合乳液 (PUA).研究了BA和二丙酮丙烯酰胺 (DAAM) 对乳液及膜性能和粘接性能的影响,并用傅立叶红外光谱 (FTIR)仪对PUA复合乳液进行了结构表征.实验结果表明当BA含量为4.0%～6.0%,DAAM含量为2.0%～3.0%时,乳液和膜性能较好,黏度性能较佳.用该乳液配制的胶黏剂对木材有很好的粘接性能.     

Polymerization of methyl methacrylate by copper-chelate of polyacrylic hydrazide

Copper-chelate of polyacrylic hydrazide was prepared, and its structure and properties were investigated. It was found that the chelate-polymer initiates radical polymerization of methyl methacrylate in aqueous dioxane at room temperature. The rate of polymerization initiated by the chelate-polymer was much higher than that by monomeric model-chelate of such as acethydrazide. The catalytic activity found in the copper-chelate of polyacrylic hydrazide is perhaps caused by the polyelectrolyte-behaviour of the polymer. The influences of the concentration of copper ion, molecular weight of polymer-ligand, ionic strength, hydrogen ion concentration and composition of solvent on the polymerization were investigated. It was considered that the polymerization is affected not only by stability but also by conformation of the chelate-polymer. The tacticity of the polymethyl methacrylate obtained is also discussed.     

Synthesis and characterization of butyl acrylate/methyl methacrylate/glycidyl methacrylate latexes

The butyl acrylate (BA)/methyl methacrylate (MMA), and glycidyl methacrylate (GMA) composite copolymer latex was synthesized by seeded emulsion polymerization technique taking poly(methyl methacrylate) (PMMA) latex as the seed. Four series of experiments were carried out by varying the ratio of BA : MMA (w/w) (i.e. 3.1 : 1, 2.3 : 1, 1.8 : 1, and 1.5 : 1) and in each series GMA content was varied from 1 to 5% (w/w). The structural properties of the copolymer were analyzed by FTIR, ¹H‐, and ¹³C‐NMR. Morphological characterization was carried out using transmission electron microscopy (TEM). In all the experiments, monomer conversion was ～99% and final copolymer composition was similar to that of feed composition. The incorporation of GMA into the copolymer chain was confirmed by ¹³C‐NMR. The glass transition temperature (T_g) of the copolymer latex obtained from the differential scanning calorimetry (DSC) curve was comparable to the values calculated theoretically. With increase in GMA content, particles having core‐shell morphology were obtained, and there was a decrease in the particle size as we go from 2–5% (w/w) of GMA. The adhesive strength of the latexes was found to be dependent on the monomer composition. With increase in BA : MMA ratio, the tackiness of the film increased while with its decrease the hardness of the film increased. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Reaction catalyzed by montmorillonite: Polymerization of methyl methacrylate

The polymerization of methyl methacrylate (MMA) was carried out in aqueous media having various concentrations of potassium persulfate as initiator in the presence or the absence of montmorillonite (Texas) at various temperatures. The rate of polymerization increased with increasing initiator concentration. Thermal stabilities of the resulting composite materials were studied and the activation energies of polymerization and degradation were determined. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 367–372, 1997     

Grafting of butyl acrylate and methyl methacrylate on butyl rubber using electron beam radiation

Being nonpolar in nature, butyl rubber (IIR) has poor compatibility toward polar polymers and fillers. It can be improved by grafting polar substrates on the butyl elastomer. Radiation‐induced polymer processing is getting increasing interest, as it leads to new and improved polymers with desirable and interesting properties. In this investigation, electron beam radiation has been used to graft methyl methacrylate (MMA) and butyl acrylate (BA) on IIR. This process has several advantages over conventional grafting processes such as cationic polymerization (which needs very low temperature and stringent reaction conditions) and solution radical polymerization (which often needs solvent removal and recycling). The grafted polymers were characterized by using ¹H NMR, IR, TGA, and SEM analysis. The degree of grafting increases with a decrease in irradiation dose as well as with an increase in monomer concentration. It was observed that there was a decrease in intrinsic viscosity in irradiated IIR samples, indicating the chain scission. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1340–1346, 2006     

Semibatch emulsion copolymerization of methyl methacrylate and butyl acrylate

The concentration of sodium lauryl sulfate (SLS) in the initial reactor charge is the most important parameter in determining the particle size of a semibatch emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA). The number of particles formed is proportional to the concentration of SLS to the 0.5–1.2 power and it is proportional to the concentration of the nonyl phenol–40 mol ethylene oxide adduct to the 0.014–0.72 power. The number of particles is almost independent of the concentration of the initiator. The solubility of monomer in water has an important effect on the nucleation mechanism according to the literature. However, the ratio of MMA to BA does not show any significant effect on the latex particle size in our laboratory. The particle size also increases with increasing ionic strength or agitation speed. Experimental data of particle-size distribution and molecular weight distribution support the coagulative nucleation mechanism when the concentration of SLS is way below its critical micelle concentration (CMC). © 1995 John Wiley & Sons, Inc.     

Study of mechanical damage in rubber-toughened poly(methyl methacrylate) by single and multiple scattering of light

As glassy polymers are usually somewhat brittle, several blending techniques are used to toughen these materials and to increase their impact strength. The microstructures of toughened polymers are complicated, as are their mechanical damage mechanisms. Moreover, these materials are mostly opalescent or even opaque, which renders difficult any optical investigation of the damage process. The scale of the damage generally ranges from nanometers to several micrometers, thus requiring a large panel of experimental techniques to investigate its microstructural evolution. When illuminated with a light beam, any non-perfectly transparent body will scatter light with a scattering pattern depending on the size, shape, and location of the microscopic light scatterers it contains. If the body is highly opaque, an incident light beam, if not absorbed, is scattered successively by several scatterers before emerging again at the front surface of the body. It has recently been shown that there is a coherent interference enhancement of the randomly multiple scattered light in a small angle range around the exact reverse direction of the incident light. This so-called coherent backscattering cone can be analyzed in terms of the size, shape and density of the scatterers. In this work, this technique is applied to a rubber-toughened PMMA containing core-shell (hard core) particles, an initially transparent material that becomes progressively opaque during mechanical damage under stress. The damage mechanism within the rubber particles is compared with the size and shape of the light scatterers inferred from coherent backscattering and light transmission measurements.     

甲基丙烯酸甲酯与丙烯酸正丁酯乳液聚合的研究

以甲基丙烯酸甲酯与丙烯酸正丁酯为主要原料,过硫酸铵为引发剂,OP-10、十二烷基硫酸钠(K12)为乳化剂,用乳液聚合法合成了聚丙烯酸酯类共聚乳液,考察了聚合条件对乳液聚合的影响。实验结果表明,在单体、引发剂、水用量一定时,合适的反应条件为乳化剂(OP-10∶K12=1∶1)2%,单体滴加时间以60~90min,80℃反应2h左右。     

Organotin polymers. IV. Binary and ternary copolymerizations of tributyltin acrylate and methacrylate with styrene,allyl methacrylate,butyl methacrylate,butyl acrylate,and acrylonitrile

The monomer reactivity ratios for the copolymerization of tributyltin acrylate with styrene and allyl methacrylate have been found to be r₁ = 0.213, r₂ = 1.910 and r₁ = 0.195, r₂ = 2.257, respectively. Also, the copolymerization parameters of tributyltin methacrylate with styrene and allyl methacrylate were as follows: r₁ = 0.256, r₂ = 1.104 and r₁ = 2.306, r₂ = 1.013. Copolymerization reactions were carried out in solution at 70°C using 1 mole % AIBN, and the copolymer compositions were determined by tin analysis. Ternary copolymerization of the three systems butyl methacrylate–tributyltin methacrylate–acrylonitrile, butyl acrylate–tributyltin methacrylate–acrylonitrile, and styrene–tributyltin acrylate–acrylonitrile have been studied, and the terpolymer composition of each system was determined through tin and nitrogen analyses. The variation of instantaneous and average terpolymer composition with conversion fit satisfactorily the experimental results over a wide range of conversion.     

Copolymerization of bromophenylmaleimide with ethyl or butyl methacrylate

N‐p‐Bromophenylmaleimide (BrPMI) does not polymerize in solution by conventional free radical mechanism. However, it readily polymerized in bulk when mixed with a free radical initiator and heated in a microwave oven for 7–8 min. Copolymerization of ethyl methacrylate or butyl methacrylate with BrPMI was conducted in dioxane. The copolymers were characterized by IR and ¹H NMR spectroscopy and gel permeation chromatography. The monomer reactivity ratios were calculated by a non‐linear least‐square analysis. Thermal analysis indicated a great improvement in thermal stability of the copolymers compared with the methacrylate homopolymers. BrPMI was also polymerized in bulk in the DSC pan, which allowed the calculation of the activation energy of its polymerization. Copyright © 2003 Society of Chemical Industry     

Radical polymerization of n‐butyl methacrylate initiated by stibonium ylide

1,2,3,4‐Tetraphenylcyclopentadiene triphenyl stibonium ylide initiated radical polymerization of n‐butyl methacrylate (n‐BMA) in dioxane at (60 ± 0.2)°C for 90 min under nitrogen atmosphere has been carried out. The system follows nonideal kinetics, i.e., R_p α [ylide]^0.2 [n‐BMA]^1.8. The value of k/k_t and overall energy of activation have been computed as 0.133 × 10^?2 L mol^?1 s^?1, 33 kJ/mol, respectively. The FTIR spectrum shows a band at 1745 cm^?1 due to acrylate group of n‐BMA. The ¹H NMR spectrum shows a peak of two magnetically equivalent protons of methylene group at 2.1 δ ppm. The DSC curve shows glass transition temperature (T_g) as 41°C. The presence of six hyperfine lines in ESR spectrum indicates that the system follows free radical polymerization and the initiation is brought about by phenyl radical. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2457–2463, 2007     

Chemical and mechanical properties of butyl methacrylate grafted wool fiber

Because polymer‐grafted wool fibers had been reported to have better functional performance, a K₂S₂O₈–NaHSO₃ redox system was used as the initiator for the grafting copolymerization of butyl methacrylate (BMA) onto wool fibers. Grafted samples of wool‐g‐BMA with different grafting percentages (5.2–25.86) were obtained through variations in the monomer concentration in the reaction system. The evidence for grafting was provided by scanning electron microscopy and infrared spectroscopy. After the grafting, the moisture retention of the wool‐g‐BMA fibers decreased slightly. Optical measurements showed that the birefringence decreased, indicating a lower degree of molecular orientation of the wool‐g‐BMA fibers. The tensile strength increased as the grafting percentage increased. Beyond an 18–25% grafting percentage, the elongation at break decreased, and this indicated a reduction of the elastic deformation, which meant that the flexibility of the modified fibers may have deteriorated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3813–3817, 2004     

Soapless emulsion polymerization of butyl methacrylate through microwave heating

Soapless emulsion polymerization of n‐butyl methacrylate (BMA) was carried out through microwave heating with potassium persulfate (KPS) as an initiator at 73 ± 2°C. The influence of the monomer amount, the initiator amount, and the addition of ethanol on the monomer conversion, the particle size, and its distribution were studied. The results indicate that microwave polymerization had a much higher rate and produced smaller particles with a slightly broader size distribution compared with normal polymerization. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2455–2459, 2001