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The thermal bulk polymerization of styrene is critically reviewed. There is still no generally accepted kinetic model for the thermal radical formation process, but ideal second‐ or third‐order models are widely used for modeling bulk systems. Since initiation and chain transfer reactions cannot be treated independently from one another as long as the same species is considered to be involved, it is concluded that non‐ideal kinetics, possibly in form of a (micro‐)viscosity dependency of the Mayo mechanism, are likely to be present. A mathematical model is presented that keeps the predictive capabilities of the Hui‐Hamielec model, but allows facile implementation of reaction specific modifications. Part 2 of this paper will focus on the effect of compartmentalization on the thermal polymerization of styrene.
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Lei Tian Panpan Zhao Xiangjie Li Shenqiang Wang Zafar Ali Baoliang Zhang Hepeng Zhang Qiuyu Zhang 《Macromolecular rapid communications》2016,37(1):47-52
Polymer microcavities with adjustable openings and surface roughness are fabricated on a large scale via single‐hole poly(glycidyl methacrylate) (PGMA) swelling seed particles. The size of openings of these microcavities can be adjusted by changing the amount of hydrophilic monomer, and the degree of surface roughness is easily regulated relying on the adjustment of the polarity of monomer. Furthermore, the morphology of PGMA/poly(styrene‐methacrylic acid) (PGMA/P(S‐MAA)) microparticles from microcavity to erythrocyte shape is controlled by the polarity of seed surface. From transmission electron microscopy images of PGMA/P(S‐MAA) microparticles, a fresh polymer particle appears in the cavity. To confirm this phenomenon, thermal annealing process in dioxane/water solution is carried out. Considering the flexibility of polymers, the openings and closing of the prepared microparticles are regulated following the increase in volume ratio of dioxane/water. Ball‐in‐bowl‐shaped PGMA/P(S‐MAA) microparticles are further presented, which proves secondary nucleation of monomer in the polymerization stage.
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Alessandro Butt Giuseppe Storti Massimo Morbidelli 《Macromolecular theory and simulations》2002,11(1):22-36
A method for the direct computation of the chain length distribution in a bulk polymerization is developed, based on the discretization procedure introduced by Kumar and Ramkrishna (Chem. Eng. Sci. 1996 , 51, 1311) in the context of particle size distribution. The overall distribution of chain lengths is partitioned into a finite number of classes which are supposed to be concentrated at some appropriate pivotal chain lengths. Several of the involved reactions lead to the formation of chain whose length differs from the pivotal values. Rules have been introduced in order to share chains between two contiguous classes, which have been designed so as to preserve two well‐defined properties of the distribution, such as, for example, two of its moments. The method has been applied to a polymerization system including propagation, bimolecular terminations and two different chain branching mechanisms: chain transfer to polymer and crosslinking. In addition, complex systems such as one with chain length‐dependent kinetic constants or a two‐dimensional distribution of chain length and number of branches have been considered. 相似文献
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考察了丙烯酸乙酯(EA)、甲基丙烯酸甲酯(MMA)、苯乙烯(St)和丙烯腈(AN)四种不同结构特征的乙烯基单体和桐油(TO)、蓖麻油(CO)两种生物质油在室温(25℃)下以氧化还原引发体系引发的本体均聚合和共聚合反应,以及环烷酸钴的配位效应对聚合的影响。结果表明,室温下取代基的供电性或共轭性越强的单取代烯烃逾难均聚合;苯乙烯不能均聚,也不能与丙烯酸乙酯共聚合;由于空间位阻的原因,桐油和蓖麻油的均聚合以及与其它单体的共聚合在常温下均不能进行;环烷酸钴的配位效应能够提高单体和自由基的活性,促进聚合反应进行。 相似文献
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Spin coating silica films were prepared from acid-catalyzed tetraethoxysilane (TEOS) solutions, and the magnitude of radiative striations formed on the surface of the resulting films was quantitatively evaluated by measuring surface roughness using a contact probe profilometer. Wave-like transverse profiles were obtained on the films prepared. Surface roughness parameters, Ra (arithmetical mean deviation), Rz (ten point height of irregularities) and S (mean spacing of local peaks), were determined. When the gel films were heated at higher temperatures (500°C), the film thickness decreased up to 22%, while none of Ra, Rz or S varied with heat-treatment temperature, indicating that the surface of the films is already densified at room temperature. Higher substrate rotation speeds caused decrease in Ra, Rz and S, revealing that the striations decreased both in amplitude and wavelength. Application of viscous sols aged for longer periods of time resulted in increased amplitude (Rz) of striations without change in wavelength (S). 相似文献
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表面光接枝原理,方法及应用前景 总被引:16,自引:0,他引:16
介绍了表面光接枝的原理,方法和应用前景,表面光接枝主要是用芳酮引发有机材料产生表面自由基,从而引发单体聚合生成表面接枝链。实施方法有气相法,液相法和连续液相法。表面光接枝应用领域广泛,可用于聚合材料的表面改性以及表面功能化。 相似文献
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This paper describes how the surface roughness and synthetic methods of Au nanorods affect the optical properties that are often associated with localized surface plasmon resonances. We synthesized Au nanorods with different aspect ratios and surface roughness by using two different synthetic strategies to observe surface plasmon resonance bands. One set of nanorods was prepared in high yield by using a seed‐mediated dropwise‐addition method with a growth‐directing surfactant in aqueous solution (Au nanorods in aqueous phase, GNRA). The other set of Au nanorods were synthesized by the electrochemical deposition of Au onto an anodized aluminum oxide (AAO) template (Au nanorods by AAO template, GNRT). The length of the nanorods was controlled by changing the total charge that was passed through the cell and their diameter was monitored by changing the diameter of the template channel. The as‐prepared Au nanorods were optimized to observe a quadrupole mode, which is one of the higher‐order surface plasmon bands. Our results showed differences between the optical properties of GNRA and GNRT. The roughness and crystal structure of the Au nanorods affected their optical properties. Smooth and single‐crystal surface on GNRA had larger and sharper peaks than GNRT. The discrete dipole approximation (DDA) method was used to calculate the optical properties of the Au nanorods and these results were in good agreement with our experimental results. 相似文献
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Franco Cataldo Ornella Ursini Pietro Ragni Valentina Lilla Giancarlo Angelini 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(1):16-24
Vinylidene chloride (VDC) or 1,1-dichloroethylene was polymerized with γ radiation in bulk or as inclusion complex in thiourea crystals (inclusion polymerization). The resulting poly(vinylidenechloride) (PVDC) samples obtained from the two different polymerization techniques were characterized by FT-IR and electronic absorption spectroscopies, by ozonolysis and by thermal analysis (TGA, DTG and DTA). It was found that two selective secondary reactions occur in the two PVDC samples, respectively obtained from bulk polymerization or from inclusion polymerization. In the former case, the main reaction is only a crosslinking reaction, while in the latter case, with the PVDC included into the thiourea channels, the crosslinking reaction is fully inhibited and instead a dehydrohalogenation reaction takes place producing the polyene structures. The presence of polyene structures in the PVDC synthesized by the inclusion polymerization was demonstrated by electronic absorption spectroscopy and by ozonolysis experiments. The presence of polyene segments in the PVDC causes a reduction in the thermal stability of the polymer, lowers its melting point and reduces its crystallinity. 相似文献
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In this paper we report on the treatment of industrial fibers and cords by means of plasma polymerization techniques. Coatings of plasma-polymerized pyrrole or acetylene were deposited on aramid fibers, aramid cords and polyester cords. The equipment was a custom-built semi-continuous reactor operated on a pulsed DC glow discharge. The fibers and cords were tested for adhesion to various polymers such as tire cord skim stock rubber compounds and epoxy adhesives. Standard industrial pull-out force adhesion measurement techniques were used. The deposition conditions of the plasma polymer films were varied within wide limits. It was found that, in general, films deposited under low-power and high-pressure conditions performed better than films prepared under high-power and low-pressure conditions. For some systems pulsing of the discharge power improved the performance further. For all systems studied, the optimized plasma polymer surface modification outperformed current industrial standards. The plasma-polymerized coatings were characterized by various techniques and the excellent performance results are explained in a tentative model based on the molecular structure of the films. This structure was found to be strongly dependent on the discharge conditions. 相似文献
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Yuzuo Ye Xingrong Zeng Hongqiang Li Pingxu Chen Chaoxian Ye Fuchun Zhao 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(1):42-46
Organic nano-silica was firstly synthesized by sol-gel method with methyl methacrylate (MMA) and butyl acrylate (BA) in the micelles as dispersing media, tetraethoxysilicate (TEOS) as precursor, hydrochloric acid as catalyst and methacryloylpropyl trimethoxysilane (A174) as modifier. Subsequently, the nano-silica/polyacrylate composite emulsions were directly prepared by in-situ emulsion polymerization under the action of the initiator. The structure and properties were characterized by Fourier transform infrared spectroscopy (FTIR), dynamic light-scattering (DSL), thermogracvimetry (TG) and transmission electron microscopy (TEM). The results showed that A174-modified nano-silica was successfully synthesized in the acrylate-based emulsions by the sol-gel method. The nano-silica was encapsulated by polyacrylate, and the composite latex particles exhibited an apparent core-shell structure. The A174 could improve the lipophilicity of nano-silica and increase the grafting efficiency of polyacrylate on nano-silica particles. The nano-silica/polyacrylate composite latex film had better thermal stability, and the composite latex particles had greater average size and broader size distribution in contrast to those of pure polyacrylate emulsions. 相似文献
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Junfeng Zhang Koichi Kato Yoshikimi Uyama Yoshito Ikada 《Journal of polymer science. Part A, Polymer chemistry》1995,33(15):2629-2638
Surface graft polymerization of glycidyl methacrylate (GMA) was carried out onto a high- density polyethylene (PE) sheet pretreated with corona to introduce peroxides onto the PE surface. Graft polymerization of GMA was effected by UV irradiation of the coronatreated PE in the presence of monomer solution without the use of any photosensitizer. The graft layer was found by staining the PE cross section to localize in the surface region of PE. The physical change in the PE surface was characterized by scanning electron microscopy, while the chemical changes due to the GMA graft polymerization were assessed by the dynamic contact angle, FT-IR, and x-ray photoelectron spectroscopy (XPS) measurement. The peroxide formation by corona exposure was confirmed by the XPS measurement after derivatization with SO2. The epoxy groups introduced onto the PE surface by the GMA graft polymerization were reactive with water (in the presence of HCI) and amines. The adhesion between the GMA-grafted PE and an epoxy resin was studied by means of a shear strength test method. The GMA-grafted PE exhibited strong interfacial adhesion with the epoxy resin, compared to the original and corona-treated PE. The adhesion strength of the GMA-grafted PE was nearly two times higher than that of the corona-treated PE. This strongly suggests that the enhanced adhesion between the surface-grafted PE and the epoxy resin is ascribed to covalent bonding of the epoxy groups on the GMA-grafted surface to the amines in the epoxy resin. © 1995 John Wiley & Sons, Inc. 相似文献
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Shihai Yang Adam Seyfarth Samuel P. Bateman Ras B. Pandey 《Macromolecular theory and simulations》2006,15(3):263-271
Summary: A computer simulation model is proposed to study film growth and surface roughness in aqueous (A) solution of hydrophobic (H) and hydrophilic (P) groups on a simple three dimensional lattice of size with an adsorbing substrate. Each group is represented by a particle with appropriate characteristics occupying a unit cube (i.e., eight sites). The Metropolis algorithm is used to move each particle stochastically. The aqueous constituents are allowed to evaporate while the concentration of H and P is constant. Reactions proceed from the substrate and bonded particles can hop within a fluctuating bond length. The film thickness ( ) and its interface width ( ) are examined for hardcore and interacting particles for a range of temperature ( ). Simulation data show a rapid increase in and followed by its non‐monotonic growth and decay before reaching steady‐state and near equilibrium ( ) in asymptotic time step limit. The growth can be described by power laws, e.g., with a typical value of in initial time regime followed by at . For hardcore system, the equilibrium film thickness ( ) and surface roughness ( ) seem to scale linearly with the temperature, i.e., at low and at higher . For interacting functional groups in contrast, the long time (unsaturated) film thickness and surface roughness, and decay rapidly followed by a slow increase on raising the temperature.
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环单体的合成,聚合及与环氧树脂的固化反应 总被引:1,自引:0,他引:1
合成了新螺环原碳酸酯单体:3,9-二(对甲氧基苄基)-1,5,7,11-四氧杂螺环[5,5]十一烷。以BF3·OEt2为催化剂,实现了其阳离子聚合。聚合产物的^1H NMR、^13C NMR、IR及元素分析均表明发生了双开环聚合反应。探讨了其聚合历程。用DSC和IR跟踪环氧树脂及其与螺环单体混合后的固化反应过程,研究了固化剂、反应条件对固化反应的影响。 相似文献