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Chorng-shyan Chern - One of the best experts on this subject based on the ideXlab platform.
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Nonconventional Emulsion Polymerization of Styrene with Mixed Anionic and Nonionic Emulsifiers.
Polymer Journal, 2000Co-Authors: Shi-yow Lin, Ignác Capek, Tien-jung Hsu, Chorng-shyan ChernAbstract:Emulsion polymerization of styrene (St) in the presence of mixed anionic/nonionic emulsifiers (SDS/NP 40) has been investigated. The polymerization rate (R p ) vs. conversion (X) curves show a relatively constant R p region (Smith-Ewart Interval 2) in the range ofX=20-40% and a shoulder at X=ca. 75%. R p is independent of the emulsifier charge composition except the run with SDS or NP 40 as the sole emulsifier. The latex particle size (d w ) increases with increasing X and the degree of the increased d w is more pronounced at low X. The number of latex particles strongly increases up to ca. 20% conversion and then remains relatively constant toward the end of polymerization. The particle size distribution of latex particles is quite narrow. The average number of free radicals per particle (n) is below or close to 0.5 for the polymerization system with SDS alone and mixed SDS/NP 40 emulsifiers before the system experiences the gel effect at high X. On the contrary, for the system with NP 40 alone, n increases significantly with increasing X and it is well above 0.5 throughout the reaction. The colloidal and kinetic data obtained from this work are discussed in terms of the hairy or close-packed particle (droplet) surface layer, the decreased entry and exit rates of radicals, the relatively high oil-solubility of NP 40, accumulation of polystyrene and NP 40 within the monomer droplets, preservation of monomer droplets during polymerization and formation of double emulsion droplets. The increased uniformity and stability of the initial emulsion may promote the monomer-starved condition even at a relatively low level ofX.
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Kinetics of styrene miniemulsion polymerization stabilized by nonionic surfactant/alkyl methacrylate
Polymer, 1999Co-Authors: Chorng-shyan Chern, Yuh-cherng LiouAbstract:Abstract The effects of various reaction parameters on the styrene miniemulsion polymerizations stabilized by nonylphenol polyethoxylate with an average of 40 ethylene oxide units per molecule (NP-40) and dodecyl methacrylate (DMA) at 80°C were investigated. These parameters include the concentrations of DMA ([DMA]), NP-40 ([NP-40]), sodium persulfate ([SPS]), and 2,2′-azobisisobutyronitrile ([AIBN]). A water-insoluble dye was also incorporated into the reaction system to gain a better understanding of the related particle nucleation mechanisms. The polymerization rate decreases with increasing [DMA], whereas it increases with increasing [NP-40], [SPS] and [AIBN]. Several competitive events (e.g. coalescence among the monomer droplets, nucleation in the monomer droplets and micelles, formation of particle nuclei in water, and particle growth) occur simultaneously in the course of polymerization. This is due to the fact that the steric stabilization effect provided by NP-40 is greatly reduced at 80°C and the CMC of the miniemulsion is far below the NP-40 concentrations used in this work. Mixed modes of particle nucleation are operative in this reaction system, but monomer droplet nucleation becomes more important by increasing [DMA] or decreasing [NP-40], [SPS] and [AIBN].
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Effects of mixed surfactants on the styrene miniemulsion polymerization in the presence of an alkyl methacrylate
Macromolecular Chemistry and Physics, 1998Co-Authors: Chorng-shyan Chern, Yuh-cherng LiouAbstract:The influence of the mixed surfactants sodium dodecyl sulfate (SDS) and nonylphenol poly-ethoxylate with an average of 40 ethylene oxide units per molecule (NP-40) on the styrene (ST) miniemulsion polymerization in the presence of dodecyl methacrylate (DMA) and stearyl methacrylate (SMA) was investigated. Both Ostwald ripening and creaming could not be neglected for the miniemulsions stabilized by SDS/NP-40 in combination with DMA upon aging at 35°C, whereas no appreciable Ostwald ripening and creaming were detected for the SMA containing miniemulsions. For both the DMA and SMA containing polymerizations at 80°C, the rate of polymerization (R p ) decreases with increasing NP-40 concentration ([NP-40]). Incorporation of a small quantity of the extremely water-insoluble blue dye into the reaction system was applied to probe the particle nucleation loci. For the DMA containing polymerizations with [NP-40] = 0, 1.25, and 2.50 mM and the SMA polymerization with [NP-40] = 0 mM, homogeneous or micellar nucleation can not be ignored. On the other hand, the more hydrophobic SMA in combination with SDS/ NP-40 effectively retards the particle nucleation occurring in the aqueous or micellar phase.
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Effect of initiator on styrene emulsion polymerisation stabilised by mixed SDS/NP-40 surfactants
Polymer, 1998Co-Authors: Chorng-shyan Chern, S.y. Lin, S.c. Chang, J.y. Lin, Y.f. LinAbstract:This paper deals with the effects of initiator concentration ([I]) on the styrene (STY) emulsion polymerisation stabilised by the mixed anionic/nonionic surfactants, sodium dodecyl sulfate (SDS)/nonylphenol polyethoxylate with an average of 40 ethylene oxides per molecule (NP-40). The reaction system stabilised only by SDS ([NP-40] = 0 wt%) results in an increase in the rate of polymerisation (Rp) with [I]. For the system stabilised only by NP-40 ([NP-40] = 100 wt%). Rp remains relatively constant when [I] increases. For the system with [NP-40] = 50 or 80 wt%, Rp first increases to a maximum and then decreases with increasing [I]. Furthermore, the total scrap, presumably caused by bridging flocculation and/or formation of complex between the ethylene oxide units of NP-40 and the particle surface SO4− end-groups derived from the persulfate initiator, first remains relatively constant and then increases rapidly to a maximum with increasing [I]. Beyond the maximum, the total scrap starts to decrease with increasing [I]. Smith—Ewart case II theory (i.e., ns = 0.6 and ni = 0.4 in the relationship Np~[S]n[I]n) is only applicable to the system with [NP-40] = 0 wt%. At [I] = 1.38 × 10−3 M, systems with [NP-40] = 0, 50 and 80 wt% result in comparable latex particle sizes (dp) and relatively monodisperse size distributions throughout the reaction. On the other hand, the system with [NP-40] = 100 wt% shows the largest dp and the broadest size distribution, which is attributed to the long particle nucleation period and/or limited flocculation.
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Emulsion polymerization of styrene stabilized by mixed anionic and nonionic surfactants
Polymer, 1997Co-Authors: Chorng-shyan Chern, Shi-yow Lin, Li-jen ChenAbstract:Abstract The mixed SDS/NP-40 (anionic/nonionic) surfactants were used to examine the generality of Smith-Ewart theory which was originally proposed for emulsion polymerization systems containing anionic surfactants. Our results are consistent with Smith-Ewart theory only when the wt% of NP-40 in the surfactant mixture ([NP-40]) is less than 30%. However, the reaction system deviates from Smith-Ewart theory dramatically when [NP-40] is greater than 50%. The steric stabilization effect provided by pure NP-40 is not strong enough to prohibit the interactive particles from flocculating with one another. On the other hand, the mixed surfactant system can greatly improve the latex stability via the synergetic effects provided by both the electrostatic and steric stabilization mechanisms and, thereby, retard the limited flocculation process. The mixed surfactant system SDS/NP-40 ( 20 80 ) is the best, because it results in the best reproducibility of the experiment and the greatest polymerization rate.
Osamu Matsubara - One of the best experts on this subject based on the ideXlab platform.
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An allelotype analysis indicating the presence of two distinct ovarian clear-cell carcinogenic pathways: endometriosis-associated pathway vs. clear-cell adenofibroma-associated pathway
Virchows Archiv, 2009Co-Authors: Sohei Yamamoto, Kozue Suzuki, Masashi Takano, Hitoshi Tsuda, Seiichi Tamai, Osamu MatsubaraAbstract:Patterns of allele loss (loss of heterozygosity (LOH)) were studied to identify the genetic backgrounds underlying the two putative carcinogenic pathways of ovarian clear-cell adenocarcinoma: carcinomas thought to arise in endometriosis (endometriosis-associated carcinomas, 20 cases) and carcinomas thought to be derived from clear-cell adenofibroma ((CCAF)-associated carcinomas, 14 cases). Each tumor was assessed for LOH at 24 polymorphic loci located on 12 chromosomal arms: 1p, 3p, 5q, 8p, 9p, 10q, 11q, 13q, 17p, 17q, 19p, and 22q. For all informative loci, the frequency of LOH was not statistically different between the two carcinoma groups: 38% (66/172 loci) in the endometriosis-associated carcinomas and 35% (40/113 loci) in the CCAF-associated carcinomas. In the endometriosis-associated carcinomas, LOH was detected at high frequencies (>50%) at 3p, 5q, and 11q and at low frequencies (
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an allelotype analysis indicating the presence of two distinct ovarian clear cell carcinogenic pathways endometriosis associated pathway vs clear cell adenofibroma associated pathway
Virchows Archiv, 2009Co-Authors: Sohei Yamamoto, Kozue Suzuki, Masashi Takano, Hitoshi Tsuda, Seiichi Tamai, Osamu MatsubaraAbstract:Patterns of allele loss (loss of heterozygosity (LOH)) were studied to identify the genetic backgrounds underlying the two putative carcinogenic pathways of ovarian clear-cell adenocarcinoma: carcinomas thought to arise in endometriosis (endometriosis-associated carcinomas, 20 cases) and carcinomas thought to be derived from clear-cell adenofibroma ((CCAF)-associated carcinomas, 14 cases). Each tumor was assessed for LOH at 24 polymorphic loci located on 12 chromosomal arms: 1p, 3p, 5q, 8p, 9p, 10q, 11q, 13q, 17p, 17q, 19p, and 22q. For all informative loci, the frequency of LOH was not statistically different between the two carcinoma groups: 38% (66/172 loci) in the endometriosis-associated carcinomas and 35% (40/113 loci) in the CCAF-associated carcinomas. In the endometriosis-associated carcinomas, LOH was detected at high frequencies (>50%) at 3p, 5q, and 11q and at low frequencies (<20%) at 8p, 13q, and 17p. In the CCAF-associated carcinomas, LOH was detected at high frequencies at 1p, 10q, and 13q and at low frequencies at 3p, 9p, 11q, and 17q. The frequencies of LOH at chromosomes 3p, 5q, and 11q were significantly higher in the endometriosis-associated carcinomas than in the CCAF-associated carcinomas (P = 0.026, 0.007, and 0.011, respectively). Immunohistochemical analysis demonstrated a close association between the allelic status of the 3p25–26 locus and levels of von Hippel–Lindau (VHL) protein expression (P = 0.0026). These data further support the presence of two distinct carcinogenic pathways to ovarian clear-cell adenocarcinoma; the allelic status of the 3p, 5q, and 11q loci may provide a means to identify the precursor lesions of these carcinomas.
Yuh-cherng Liou - One of the best experts on this subject based on the ideXlab platform.
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Kinetics of styrene miniemulsion polymerization stabilized by nonionic surfactant/alkyl methacrylate
Polymer, 1999Co-Authors: Chorng-shyan Chern, Yuh-cherng LiouAbstract:Abstract The effects of various reaction parameters on the styrene miniemulsion polymerizations stabilized by nonylphenol polyethoxylate with an average of 40 ethylene oxide units per molecule (NP-40) and dodecyl methacrylate (DMA) at 80°C were investigated. These parameters include the concentrations of DMA ([DMA]), NP-40 ([NP-40]), sodium persulfate ([SPS]), and 2,2′-azobisisobutyronitrile ([AIBN]). A water-insoluble dye was also incorporated into the reaction system to gain a better understanding of the related particle nucleation mechanisms. The polymerization rate decreases with increasing [DMA], whereas it increases with increasing [NP-40], [SPS] and [AIBN]. Several competitive events (e.g. coalescence among the monomer droplets, nucleation in the monomer droplets and micelles, formation of particle nuclei in water, and particle growth) occur simultaneously in the course of polymerization. This is due to the fact that the steric stabilization effect provided by NP-40 is greatly reduced at 80°C and the CMC of the miniemulsion is far below the NP-40 concentrations used in this work. Mixed modes of particle nucleation are operative in this reaction system, but monomer droplet nucleation becomes more important by increasing [DMA] or decreasing [NP-40], [SPS] and [AIBN].
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Effects of mixed surfactants on the styrene miniemulsion polymerization in the presence of an alkyl methacrylate
Macromolecular Chemistry and Physics, 1998Co-Authors: Chorng-shyan Chern, Yuh-cherng LiouAbstract:The influence of the mixed surfactants sodium dodecyl sulfate (SDS) and nonylphenol poly-ethoxylate with an average of 40 ethylene oxide units per molecule (NP-40) on the styrene (ST) miniemulsion polymerization in the presence of dodecyl methacrylate (DMA) and stearyl methacrylate (SMA) was investigated. Both Ostwald ripening and creaming could not be neglected for the miniemulsions stabilized by SDS/NP-40 in combination with DMA upon aging at 35°C, whereas no appreciable Ostwald ripening and creaming were detected for the SMA containing miniemulsions. For both the DMA and SMA containing polymerizations at 80°C, the rate of polymerization (R p ) decreases with increasing NP-40 concentration ([NP-40]). Incorporation of a small quantity of the extremely water-insoluble blue dye into the reaction system was applied to probe the particle nucleation loci. For the DMA containing polymerizations with [NP-40] = 0, 1.25, and 2.50 mM and the SMA polymerization with [NP-40] = 0 mM, homogeneous or micellar nucleation can not be ignored. On the other hand, the more hydrophobic SMA in combination with SDS/ NP-40 effectively retards the particle nucleation occurring in the aqueous or micellar phase.
John Ashby - One of the best experts on this subject based on the ideXlab platform.
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Comparative activities of p-nonylphenol and diethylstilbestrol in noble rat mammary gland and uterotrophic assays.
Regulatory toxicology and pharmacology : RTP, 1999Co-Authors: Jeff Odum, I T G Pyrah, John R Foster, Ronald L Joiner, J. P. Miller, John AshbyAbstract:Colerangle and Roy (1996, Endocrine 4, 115-122) have described the apparent ability of both diethylstilbestrol (DES) and p-nonylphenol (NP) to cause extensive cell proliferation and lobular development in the mammary glands of young adult Noble rats. The chemicals were administered over 11 days via subcutaneously implanted minipumps. The dose level of DES used (0.076 mg/kg/day) was about 70 times higher than its minimum detection level in rodent uterotrophic and reproductive toxicology studies. In contrast, the lowest active dose level of NP (0.073 mg/kg/day) in the Noble rat mammary gland study was about 600 times lower than its minimum detection level in rat uterotrophic and multigeneration studies. The apparent enhanced sensitivity of the Noble rat mammary gland to the estrogenic activity of NP was considered worthy of further study. Ovariectomized Noble rat uterotrophic assays with NP (minimum detection level approximately 40 mg/kg/day, 3 or 11 days, oral gavage) revealed similar assay sensitivity to that observed for earlier immature and ovariectomized Alderley Park (AP) rat uterotrophic assays of this chemical. The response of the ovariectomized Noble rat uterotrophic assay to DES and estradiol was also as expected from earlier immature AP rat assays. It is concluded that the general sensitivity to estrogens of the Noble rat and the AP rat is similar. A repeat of the Noble rat mammary gland study with DES (11 x 0.076 mg/kg/day) and NP (11 x either 0.073 or 53.2 mg/kg/day), as originally reported by Colerangle and Roy (1996), revealed a strong positive response to DES and no response to NP. It is concluded that the minimum detection level of NP as a weakly estrogenic material in the rat should be based on the results of rat uterotrophic and multigeneration studies and therefore be set at approximately 40 mg/kg/day. It is also concluded that induced S-phase in the rodent mammary gland is best monitored using BRDU, as opposed to PCNA staining, and that use of subcutaneously implanted minipumps/pellets is inappropriate for risk/hazard assessment studies of chemicals already established as estrogenic in vitro and in vivo, as are NP and DES.
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comparative activities ofp nonylphenol and diethylstilbestrol in noble rat mammary gland and uterotrophic assays
Regulatory Toxicology and Pharmacology, 1999Co-Authors: Jeff Odum, I T G Pyrah, John R Foster, Ronald L Joiner, J. P. Miller, John AshbyAbstract:Abstract Colerangle and Roy (1996,Endocrine4, 115–122) have described the apparent ability of both diethylstilbestrol (DES) andp-nonylphenol (NP) to cause extensive cell proliferation and lobular development in the mammary glands of young adult Noble rats. The chemicals were administered over 11 days via subcutaneously implanted minipumps. The dose level of DES used (0.076 mg/kg/day) was about 70 times higher than its minimum detection level in rodent uterotrophic and reproductive toxicology studies. In contrast, the lowest active dose level of NP (0.073 mg/kg/day) in the Noble rat mammary gland study was about 600 times lower than its minimum detection level in rat uterotrophic and multigeneration studies. The apparent enhanced sensitivity of the Noble rat mammary gland to the estrogenic activity of NP was considered worthy of further study. Ovariectomized Noble rat uterotrophic assays with NP (minimum detection level ∼40 mg/kg/day, 3 or 11 days, oral gavage) revealed similar assay sensitivity to that observed for earlier immature and ovariectomized Alderley Park (AP) rat uterotrophic assays of this chemical. The response of the ovariectomized Noble rat uterotrophic assay to DES and estradiol was also as expected from earlier immature AP rat assays. It is concluded that the general sensitivity to estrogens of the Noble rat and the AP rat is similar. A repeat of the Noble rat mammary gland study with DES (11 × 0.076 mg/kg/day) and NP (11 × either 0.073 or 53.2 mg/kg/day), as originally reported by Colerangle and Roy (1996), revealed a strong positive response to DES and no response to NP. It is concluded that the minimum detection level of NP as a weakly estrogenic material in the rat should be based on the results of rat uterotrophic and multigeneration studies and therefore be set at ∼40 mg/kg/day. It is also concluded that induced S-phase in the rodent mammary gland is best monitored using BRDU, as opposed to PCNA staining, and that use of subcutaneously implanted minipumps/pellets is inappropriate for risk/hazard assessment studies of chemicals already established as estrogenicin vitroandin vivo,as are NP and DES.
Sohei Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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An allelotype analysis indicating the presence of two distinct ovarian clear-cell carcinogenic pathways: endometriosis-associated pathway vs. clear-cell adenofibroma-associated pathway
Virchows Archiv, 2009Co-Authors: Sohei Yamamoto, Kozue Suzuki, Masashi Takano, Hitoshi Tsuda, Seiichi Tamai, Osamu MatsubaraAbstract:Patterns of allele loss (loss of heterozygosity (LOH)) were studied to identify the genetic backgrounds underlying the two putative carcinogenic pathways of ovarian clear-cell adenocarcinoma: carcinomas thought to arise in endometriosis (endometriosis-associated carcinomas, 20 cases) and carcinomas thought to be derived from clear-cell adenofibroma ((CCAF)-associated carcinomas, 14 cases). Each tumor was assessed for LOH at 24 polymorphic loci located on 12 chromosomal arms: 1p, 3p, 5q, 8p, 9p, 10q, 11q, 13q, 17p, 17q, 19p, and 22q. For all informative loci, the frequency of LOH was not statistically different between the two carcinoma groups: 38% (66/172 loci) in the endometriosis-associated carcinomas and 35% (40/113 loci) in the CCAF-associated carcinomas. In the endometriosis-associated carcinomas, LOH was detected at high frequencies (>50%) at 3p, 5q, and 11q and at low frequencies (
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an allelotype analysis indicating the presence of two distinct ovarian clear cell carcinogenic pathways endometriosis associated pathway vs clear cell adenofibroma associated pathway
Virchows Archiv, 2009Co-Authors: Sohei Yamamoto, Kozue Suzuki, Masashi Takano, Hitoshi Tsuda, Seiichi Tamai, Osamu MatsubaraAbstract:Patterns of allele loss (loss of heterozygosity (LOH)) were studied to identify the genetic backgrounds underlying the two putative carcinogenic pathways of ovarian clear-cell adenocarcinoma: carcinomas thought to arise in endometriosis (endometriosis-associated carcinomas, 20 cases) and carcinomas thought to be derived from clear-cell adenofibroma ((CCAF)-associated carcinomas, 14 cases). Each tumor was assessed for LOH at 24 polymorphic loci located on 12 chromosomal arms: 1p, 3p, 5q, 8p, 9p, 10q, 11q, 13q, 17p, 17q, 19p, and 22q. For all informative loci, the frequency of LOH was not statistically different between the two carcinoma groups: 38% (66/172 loci) in the endometriosis-associated carcinomas and 35% (40/113 loci) in the CCAF-associated carcinomas. In the endometriosis-associated carcinomas, LOH was detected at high frequencies (>50%) at 3p, 5q, and 11q and at low frequencies (<20%) at 8p, 13q, and 17p. In the CCAF-associated carcinomas, LOH was detected at high frequencies at 1p, 10q, and 13q and at low frequencies at 3p, 9p, 11q, and 17q. The frequencies of LOH at chromosomes 3p, 5q, and 11q were significantly higher in the endometriosis-associated carcinomas than in the CCAF-associated carcinomas (P = 0.026, 0.007, and 0.011, respectively). Immunohistochemical analysis demonstrated a close association between the allelic status of the 3p25–26 locus and levels of von Hippel–Lindau (VHL) protein expression (P = 0.0026). These data further support the presence of two distinct carcinogenic pathways to ovarian clear-cell adenocarcinoma; the allelic status of the 3p, 5q, and 11q loci may provide a means to identify the precursor lesions of these carcinomas.
