罗英武
博士 教授 博士生导师
浙江大学 化学工程与生物化工系
活性自由基(细)乳液聚合,大分子工程与纳米结构聚合物,热塑性弹性体,功能与智能高分子新材料,聚合物多孔材料
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- 姓名:罗英武
- 目前身份:在职研究人员
- 担任导师情况:博士生导师
- 学位:博士
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学术头衔:
博士生导师, 国家杰出青年科学基金获得者
- 职称:高级-教授
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学科领域:
化学
- 研究兴趣:活性自由基(细)乳液聚合,大分子工程与纳米结构聚合物,热塑性弹性体,功能与智能高分子新材料,聚合物多孔材料
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2919
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730
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成果数
12
罗英武, Zegui Yan, , Yingwu Luo, Yulin Deng, Joseph Schork
Journal of Applied Polymer Science, Vol. 91, 347-353(2004),-0001,():
-1年11月30日
In our previous work, we reported that cationic water-soluble pressure-sensitive adhesives (PSAs) could be synthesized in ethanol or methanol. These cationic water-soluble adhesives would not cause a stickies problem during paper recycling and can be easily removed from the papermaking system by adsorbing on wood fibers. In this study we report the synthesis and application of waterbased cationic PSAs using miniemulsion polymerization. A redox initiator system of cumene ydroperoxide/tetraethylenepentamine was used to force interfacial polymerization. The end-use properties of the PSAs were evaluated, and the repulpability of the PSAs in paper recycling was studied. It was found that the cationic PSA from miniemulsion polymerization itself was insoluble and nondispersible in water during the paper recycling process. However, if this waterinsoluble cationic PSA from miniemulsion was formulated with a water-soluble cationic PSA made from ethanol, the solubility or dispensability of the former PSA in water was improved. The molecular weight and degree of crosslinking of the PSA polymer have significant effects on the properties and dispersability of PSA.
addition polymerization, copolymerization, emulsion polymerization, adhesives, recycling
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【期刊论文】Grafting Mechanisms in Hybrid Miniemulsion Polymerization
罗英武, John G. Tsavalas, Yingwu Luo, * F.Joseph Schork
Journal of Applied Polymer Science, Vol. 87, 1825-1836(2003),-0001,():
-1年11月30日
The ultimate objective of hybrid miniemulsion polymerization is to produce a water-based crosslinkable coating through in situ grafting of a free radical growing acrylic polymer with an unsaturated resin. Certain authors have reported low grafting while others have reported higher. This article explores the factors that influence the grafting tendencies of these systems. Methacrylates such as methyl methacrylate (MMA) have a sterically hindered radical center that lowers its reactivity toward unsaturated resin. This steric hindrance from the methyl group forces grafting of this type of monomer to occur by abstraction of a hydrogen allylic to a resinous double bond. This chain transfer produces a relatively inactive radical on the resin that reduces the grafting efficiency. The transfer process also inherently produces some degree of terminated PMMA polymer within the particle. Grafting occurs in this type of system through termination of living PMMA chains with that radical produced on the resin. For relatively watersoluble monomers such as MMA, grafting efficiency is further lessened by homogeneous nucleation resulting from the monomer hydrophilicity. These newly created particles cannot contain alkyd due to its hydrophobicity and thus inability to transport across the aqueous phase, and hence cannot produce grafted polymer. Nonetheless, degree of grafting of nearly 50% was observed in these systems. For hybrid systems involving an acrylate monomer such as butyl acrylate (BA), virtually complete grafting with alkyd was observed. This is due to the uninhibited BA radical center allowing the molecule to add directly through a resin double bond. This process offers the possibility for complete grafting. Homogeneous nucleation is not involved in this system due to the insolubility of BA in the aqueous phase. Resin double bond content and degree of conjugation also play an integral role in the grafting process.
miniemulsion, alkyd, hybrid, acrylic, graft
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罗英武, YINGWU LUO, ZHIXUE WENG, ZHIMING HUANG, ZUREN PAN
,-0001,():
-1年11月30日
Based on our previous general model of the gel/sol partition, a model of the gel fraction of polymer is developed in the VC heterogeneously crosslinking suspension polymerization, where the kinetic factors such as two-phase polymerization mechanism, distinction of the gel and sol radicals, and the effects of the gel on kinetics are taken into account. The model is applied to the VC/diallyl phthalate (DAP) suspension copolymerization. The model parameters are obtained by fitting the experimental data with the model. The model turns out to be successful to predict the development of the gel fraction with conversion. It is inferred that the intermolecular crosslinking reaction is affected by diffusion. In addition, the crosslinks prove to be nonrandomly distributed in the VC/DAP suspension copolymerization.
crosslinking copolymerization, free radical, gel fraction, vinyl chloride
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罗英武, YINGWU LUO, F. JOSEPH SCHORK
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 39, 2696-2709(2001),-0001,():
-1年11月30日
The polymerization kinetics of butyl acrylate/[2-(methacryloyoxy)ethyl]trimethyl ammonium chloride (BA/MAETAC) macroemulsion and miniemulsion copolymerizations was investigated with cumene hydroperoxide/tetraethylenepentamine as aredox initiator system. The postulate of an interfacial copolymerization with the twocomponent redox initiator system (one hydrophobic and the other hydrophilic) was confirmed. Adding MAETAC had a complex effect on the polymerization kinetics of BA. The influence was ascribed to variations in the nucleation mechanism, which were dependent on the level of MAETAC, and the polymerization method (macroemulsion vs miniemulsion). It was proposed that at the beginning of a macroemulsion copolymerization with high MAETAC composition the micellar copolymerization occurred, which controlled the nucleation process. The hydration properties of the latex were used to characterize the copolymer composition. The composition of the copolymer from the interfacial polymerization was very heterogeneous. The copolymer composition was lower in BA when there was an increase in BA conversion or the particle size. Adding salt increased the MAETAC content and decreased the BA content in the copolymer.
butyl acrylate, cationic monomer, emulsion polymerization, miniemulsion polymerization, interfacial polymerization
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罗英武, YINGWU LUO, , F.JOSEPH SCHORK
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 40, 3200-3211(2002),-0001,():
-1年11月30日
Butyl acrylate conventional emulsion (macroemulsion) and miniemulsion polymerizations were carried out with an oil-soluble initiator (azobisisobutyronitrile) in the presence or absence of an aqueous-phase radical scavenger. For macroemulsion polymerization, in the presence of an aqueous-phase radical scavenger, no particle nucleation occurred, whereas in the absence of an aqueous-phase radical scavenger, particle nucleation proceeded as expected. For miniemulsion polymerization, the rate of polymerization was much higher in the absence of an aqueous-phase radical scavenger than in its presence. Furthermore, in the absence of an aqueous-phase radical scavenger, the miniemulsion polymerization rate increased with reduced droplet size, whereas in the presence of an aqueous-phase radical scavenger, the trend was reversed. It is concluded that (1) for macroemulsion polymerization, the contribution from free radicals originating in the aqueous-phase is predominant in the micellar nucleation of particles; (2) free radicals originating in the particle phase contribute to the rate of polymerization and the contribution increases with an increase in the particle size; and (3) for polymer particles with diameters of up to approximately 100 nm, polymerization is initiated fromfree radicals originating in the aqueous phase.
emulsion, macroemulsion, miniemulsion, initiation, nucleation, free radical, colloids, polymerization
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罗英武, YINGWU LUO, ZHIXUE WENG, ZHIMING HUANG, ZUREN PAN
,-0001,():
-1年11月30日
The concept of effective crosslinking density proposed by Scanlan is extended to heterogeneously crosslinking polymer. A kinetic-statistical model of effective crosslinking density of the gel is developed in free-radical heterogeneously crosslinking polymerization. The model is applied to the vinyl chloride (VC)/dially phthalate (DAP) suspension process. It is concluded that the model successfully predicts the development of effective crosslinking density of the gel. It is suggested that the degree of swelling of the gel is determined by its effective crosslinking density. However, when the crosslinking density is high, the physical entanglements would greatly influence the degree of swelling.
crosslinking copolymerization, free radical, effective crosslinking density, degree of swelling
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【期刊论文】Nanoencapsulation of a Hydrophobic Compound by a Miniemulsion Polymerization Process
罗英武, YINGWU LUO, XIANGDONG ZHOU
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 42, 2145-2154(2004),-0001,():
-1年11月30日
The nanoencapsulation of hydrophobic compounds by miniemulsion polymerization, a convenient one-step encapsulation technique for nanocapsules, was investigated in terms of the thermodynamics and kinetics. The encapsulation was achieved by polymerization inducing phase separation within minidroplets dispersed in an aqueous phase. Thermodynamic factors (the level and type of surfactant, the level of the hydrophilic comonomer, and the monomer/paraffin ratio), kinetic factors (the level of the crosslinking agent or chain-transfer agent), and nucleation modes were all found to have a great influence on the latex morphology. Specifically, for a styrene/paraffin system, there were optimum levels of sodium dodecyl sulfate (1.0 wt%), the hydrophilic comonomer (1.0 wt% methyl acrylate acid), and the chain-transfer agent (0.2 wt% n-dodecanethiol) for obtaining well-defined nanocapsules of paraffin with a styrene/paraffin ratio of 1:1. When the styrene/paraffin ratio was reduced, however, it was more difficult to achieve a fully encapsulated particle morphology. Homogeneous nucleation could compete with encapsulation, and this resulted in a pure polymer particle and a half-moon morphology. Conditions were also found under which complete encapsulation could be observed with a water-soluble initiator (potassium persulfate), contrary to certain reports. Replacing potassium persulfate with an oil-soluble initiator (2,2-azobisisobutyronitrile) had little influence on the morphology under those conditions.
encapsulation, miniemulsion polymerization, nanocapsules, emulsion polymerization, morphology, nanocomposites
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罗英武, YINGWU LUO, XINZHI LIU
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 42, 6248-6258(2004),-0001,():
-1年11月30日
In the reversible addition-fragmentation transfer (RAFT) copolymerization of two monomers, even with the simple terminal model, there are two kinds of macroradical and two kinds of polymeric RAFT agent with different R groups. Because the structure of the R group could exert a significant influence on the RAFT process, RAFT copolymerization may behave differently from RAFT homopolymerization. The RAFT copolymerization of methyl methacrylate (MMA) and styrene (St) in miniemulsion was investigated. The performance of the RAFT copolymerization of MMA/St in miniemulsion was found to be dependent on the feed monomer compositions. When St is dominant in the feed monomer composition, RAFT copolymerization is well controlled in the whole range of monomer conversion. However, when MMA is dominant, RAFT copolymerization may be, in some cases, out of control in the late stage of copolymerization, and characterized by a fast increase in the polydispersity index (PDI). The RAFT process was found to have little influence on composition evolution during copolymerization. The synthesis of the well-defined gradient copolymers and poly [Stb-(St-co-MMA)] block copolymer by RAFT miniemulsion copolymerization was also demonstrated.
reversible addition fragmentation chain transfer (, RAFT), , copolymerization, miniemulsion polymerization, block copolymers
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【期刊论文】Theoretical Aspects of Particle Swelling in Living Free Radical Miniemulsion Polymerization
罗英武, Yingwu Luo, John Tsavalas, and F. Joseph Schork*
Macromolecules, Vol. 34, No.16, 2001,-0001,():
-1年11月30日
Living free radical reactions originally were carried out in bulk or solution. Recently, this chemistry has been carried out in water-based systems (emulsion and miniemulsion living free radical polymerization). Significant colloidal instability early in the polymerization has been found in several of these systems. With the hypothesis that something unique to living free radical polymerization was causing colloidal instability beyond that found in conventional free radical emulsion polymerization, the swelling of polymer particles during the early stages of living free radical miniemulsion polymerization was investigated. A new superswelling state caused by the presence of a large number of oligomers was found. This superswelling could be used to explain the instability issues reported. The effect of various factors on the superswelling state was studied. It was found that superswelling state is rather sensitive to recipe variations. Simply increasing the costabilizer level and/or using a nonionic polymeric surfactant would probably eliminate superswelling and hence the instability.
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【期刊论文】Synthesis and Properties of Magnets/Polyethylene Composites
罗英武, XINPEI CAO, YINGWU LUO, LINXIAN FENG
Journal of Applied Polymer Science, Vol. 74, 3412-3416(1999),-0001,():
-1年11月30日
Polyethylene-based magnetic composites have been prepared by ethylene polymerization on the surface of NdFeB magnets, which is previously activated by ball milling with catalyst components. The level of magnets has been controlled by catalyst preparation and polymerization parameters such as Al/Ti ratio and polymerization temperature. The coertivity and the residual magnetizability were investigated. It was found that the magnetic properties of magnet powders are largely retained. In addition, in contrast to composites prepared by melt mixing, the adhesion force between magnets and polymer matrix is improved significantly and better mechanical properties are expected.
magnetic composites, ethylene polymerization, ball-milling procedure, Al/, Ti ratio
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