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  • 1
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 10 (1985), S. 391-402 
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The azeotropic 80:20 styrene-acrylonitrile mixture was polymerized in 190nm- and 300nm-diameter monodisperse polystyrene seed latexes by batch, batch-with-equilibrium-swelling, and semi-continuous polymerization. Polystyrene seed latexes were used to determine the degree of grafting of the substrate as well as the styrene-acrylonitrile copolymer. The Arrhenius plot of log (polymerization rate) of the seeded batch copolymerizations with reciprocal temperature comprised two linear regions with a sharp inflection point at 65°C. Specific volume measurements showed that the Tg of the monomer-swollen styrene-acrylonitrile copolymer was also 65°C. The final latex comprised the original seed particles grown to a larger size and, in some cases, a new crop of particles formed during the polymerization. The critical factor determining the formation of new particles was the surface area of the seed latex: at or above 226 m2/dl, new particles were not formed; at or below 179 m2/dl, a new crop of particles was nucleated, the number increasing with decreasing surface area. The degree of grafting of the polystyrene seed substrate was greater for the smaller particle size seed latex, and increased exponentially with increasing seed surface area. The amount of grafted styrene-acrylonitrile copolymer determined the stability of the grafted particles in acetone, a good solvent for the copolymer. Dynamic mechanical spectroscopy showed that the continuous phase was either the polystyrene substrate (Tg 104°C) or the styrene-acrylonitrile copolymer phase (Tg 120°C) except where the degree of grafting was high, in which case, the Tg was intermediate between the two values. Electron microscopy of thin film sections stained with ruthenium tetroxide confirmed which phase was continuous and showed interpenetrating networks for those systems of intermediate Tg.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 1403-1415 
    ISSN: 0887-624X
    Schlagwort(e): emulsion polymerization, role of particle/water interface ; vinyl acetate, emulsion copolymerization ; copolymerization in emulsion, mathematical model ; mathematical model, vinyl acetate/reactive surfactant emulsion copolymerization ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A mathematical model was developed to aid in the further understanding of the growth of latex particles in the emulsion polymerization of vinyl acctate using a polymerizable surfactant, sodium dodecyl allyl sulfosuccinate (TREM LF-40). The model incorporates the main features of the system observed experimentally: copolymerization in the aqueous phase, at the particle surface, and chain transfer to TREM LF-40. The reactions at the particle/water interface and, more specifically, the chain transfer to TREM LF-40 leading to a decrease in the average number of radicals per particle, was found to be the most significant mechanism for explaining the difference in kinetic results found for TREM LF-40 and its nonpolymerizable counterpart. The copolymerization of vinyl acetate with TREM LF-40 was also shown to slow the overall polymerization rate. However, the copolymerization alone was not sufficient to account for the decreased polymerization rates observed experimentally. A combination of copolymerization and chain transfer to TREM LF-40 was found to provide a good fit of the experimental results. © 1993 John Wiley & Sons, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2633-2649 
    ISSN: 0887-624X
    Schlagwort(e): dispersion polymerization ; polystyrene ; steric stabilizer ; poly(styrene-block-polybutadiene) ; tetrahydrofuran ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Anionic dispersion polymerization in a hexane medium has been applied to the synthesis of monodisperse polystyrene particles in the size range of 1.41-6.16 μm, and having narrow molecular weight distributions Mw/Mn of 1.02-1.28. sec-Butyllithium was used as the initiator. Polystyrene-block-polybutadiene diblock copolymer containing 23% polystyrene block, (i.e., Stereon 730A) with a molecular weight of 147,000 g/mol and a polydispersity of 1.05, was found to be a suitable steric stabilizer for the preparation of micron-size polystyrene particles with narrow size distribution. Tetrahydrofuran (THF) was used as a promoter for obtaining narrow molecular weight distributions. However, this study revealed that the addition of small amounts of THF as promoter broadened the particle size distribution. High solids content polystyrene dispersions were also prepared without using any promoter by both batch and/or multi-addition monomer processes. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2651-2664 
    ISSN: 0887-624X
    Schlagwort(e): anionic dispersion polymerization ; particle formation ; polystyrene-block-polybutadiene stabilizer ; monomer multi-addition ; micron-size particles ; adsorption kinetics ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The mechanism for the formation of uniform micron-size polystyrene particles by anionic dispersion polymerization of styrene in hexane medium was investigated. Uniform particles in the range of 2.28-7.14 μm were obtained by varying the polymerization parameters such as the stabilizer, initiator, monomer multi-addition, and temperature. Particles of larger size and narrow molecular weight distribution were formed by increasing the initiator concentration. The particle size also increased with decreasing stabilizer concentration and polymerization temperature. The formation of larger size particles at lower temperature, lower stabilizer, and higher initiator concentrations provides supporting evidence that particle nucleation in anionic dispersion polymerization is due to a polymer chain aggregation mechanism. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2193-2206 
    ISSN: 0887-624X
    Schlagwort(e): multicomponent ; latex ; interpenetrating polymer networks ; IPN ; core/shell ; morphology ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A series of novel structured latex particles with interpenetrating polymer network (IPN) cores and glassy SAN shells were developed in an attempt to investigate the feasibility of these polymers as both toughening and damping agents in thermoplastics. The IPN cores were composed of one impact part (polybutadiene based) and one damping part (acrylic based, with Tg around +10°C). The particle morphologies of these polymers were determined by TEM. The glass transitions and mechanical behavior of the polymers were characterized from DMS. The effect of different components on the final core/shell particle morphologies and mechanical properties was studied. The mechanical behavior of core/shell particles with IPN cores was also compared with that of separate core/shell and multilayered core/shell particles. In addition, normal core/shell synthesis (rubbery part first then the glassy part) and inverted core/shell synthesis (glassy part first then the rubbery part) were performed to provide another access for morphology control. It was found that the core/shell latex particles with poly(butyl acrylate) based copolymers are more miscible than poly(ethylhexyl methacrylate)-based copolymers. The high grafting efficiency of poly(butyl acrylate) plays an important role in governing phase miscibility. The latex particles synthesized by the inverted core/shell mode showed higher miscibility than the normal synthesized ones. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2193-2206, 1997
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 1219-1233 
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The particle morphology and percent grafting were investigated as a function of the crosslink density of the seed latex in two systems of core/shell latexes of polybutadiene/polymethyl methacrylate (PB/PMMA) and styrene-butadiene rubber/polymethyl methacrylate (SBR/PMMA) prepared by seeded emulsion polymerization at 50°C. The thin layer chromatography/flame ionization detection (TLC/FID) technique was used to characterize the grafting efficiency of the core/shell latexes. The percent grafting of the shell polymer was found to decrease with increasing the crosslink density of the core material. The particle morphology and precent grafting were also investigated as a function of composition and structure of the core material in four core/shell latex systems: polybutadiene/styrene-acrylonitrile copolymer (PB/SAN), (styrene-butadiene) random copolymer/styrene acrylonitrile copolymer (S:B/SAN), polystyrene : polybutadiene/styrene-acrylonitrile copolymer (PS:PB/SAN) and Kraton/styrene-acrylonitrile copolymer (Kraton/SAN), which were prepared by direct emulsification for the seed followed by emulsion polymerization at 70°C for the shell polymer. Grafting and crosslinking of the core material were found to be competitive reactions depending on the microstructure of the seed latex.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 1755-1767 
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The grafting of methyl methacrylate (MMA) onto polybutadiene (PB) latexes prepared by seeded emulsion polymerization at 50°C was investigated as a function of: (a) initiator concentration used in the secondary polymerization, (b) monomer-to-polymer ratio, (c) the specific surface area of the seed latex, and (d) the degree of conversion. The thin layer chromatography/flame ionization detection (TLC/FID) technique was used to determine the proportion of graft copolymer in the core/shell latex, It was found that grafting PMMA onto PB depended upon the concentration of initiator, decreasing as the concentration was increased. The amount of grafting increased with increasing specific surface area of the seed latex, while the molecular weight of the acetone-soluble graft copolymer decreased. The amount of graft copolymer was found to decrease concurrently with increasing monomer-to-polymer ratio and degree of conversion. These results suggest a hydrogen abstraction mechanism in the formation of graft PB-PMMA through a chain transfer process.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 2631-2644 
    ISSN: 0887-624X
    Schlagwort(e): emulsion polymerization, vinyl acetate ; emulsion polymerization, polymerizable surfactant ; emulsion polymerization, latex characterization ; emulsion polymerization, competitive growth seeded polymerization ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The mechanism of growth of latex particles in the emulsion polymerization of vinyl acetate using a polymerizable surfactant, sodium dodecyl allyl sulfosuccinate (TREM LF-40; Henkel) was investigated. Both the aqueous phase and the particle/water interface were found to be loci for the copolymerization of TREM LF-40 with vinyl acetate. Competitive growth experiments using TREM LF-40 and its nonpolymerizable derivative were conducted to separate the effects of aqueous phase and particle surface. Particle size analysis of the seeded and unseeded polymerizations coupled with kinetic results suggested that the reactions at the particle/water interface are more important and that the particle size of the latexes is a key parameter controlling the polymerization rate through copolymerization and chain transfer to the polymerizable surfactant at the particle surface. A decrease in particle size lead to an increase in the amount of TREM LF-40 polymerized at the particle surface and to a decrease in polymerization rate. © 1992 John Wiley & Sons, Inc.
    Zusätzliches Material: 18 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 857-867 
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Monodisperse microscopic poly (methyl methacrylate)/polystyrene composite particles of 1-10 μm diameter were prepared by seeded emulsion polymerization of styrene in poly (methyl methacrylate) seed particles which were initially prepared by dispersion polymerization. The resulting composite particles were characterized by transmission and scanning electron microscopy. The unique morphology of the composite particles comprised three types of polystyrene domains embedded in a continuous poly (methyl methacrylate) matrix: the dispersed “internal” domains in the interior, the interconnected “subsurface” domains that from a crust beneath the surface, and the separated “surface” domains at the surface. In addition to thermodynamics and kinetics, the phase separation in composite particles is affected by polymerization mechanism. The complicated particle morphology found is attributed to the coexistence of bulk polymerization and emulsion polymerization (radical absorption and desorption) mechanisms. An explanation of the formation of the observed morphology is proposed. With varying poly (methyl methacrylate)/styrene ratio, the internal viscosity and the competition between the two polymerization mechanisms resulted in a series of interesting morphologies.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 2619-2629 
    ISSN: 0887-624X
    Schlagwort(e): emulsion polymerization, vinyl acetate ; emulsion polymerization, polymerizable surfactant ; emulsion polymerization, kinetics ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A polymerizable surfactant, sodium dodecyl allyl sulfosuccinate (TREM LF-40; Henkel) and its nonpolymerizable counterpart were used in comparative studies of the emulsion polymerization of vinyl acetate. The conversion-time behavior differed for the two surfactants; the TREM LF-40 showed a decrease in the polymerization rate with increasing concentration while its hydrogenated derivative showed the opposite behavior, the rate increasing with increasing surfactant. Particle size analysis revealed a decreasing particle size with increasing surfactant concentration for both series of reactions. An explanation for the seemingly ambiguous results obtained for the polymerizable surfactant was sought by examining the reactivity of its vinyl group in copolymerization with vinyl acetate and its allylic group in a chain transfer reaction. The results suggest that both the copolymerization and chain transfer reactions can lead to the observed reduction in polymerization rate with increasing TREM LF-40 concentration. © 1992 John Wiley & Sons, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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