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  • 1
    Electronic Resource
    Electronic Resource
    Use of lectins for a comparative study of cell wall composition of different anaerobic rumen fungal strains (1990)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 67 (1990), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The technique based on fluorescein-linked lectins used to determined the cell wall structure of anaerobic rumen fungi belonging to genera: Neocallimastix, Piromonas and Sphaeromonas, appears to be an interesting tool for distinguishing between stains. Futhermore this technique shows differences of cell wall composition between different parts of the thallus (spores, sporangia, rhizoïds).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1990.tb13853.x
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  • 2
    Electronic Resource
    Electronic Resource
    Polystyrene(1)/poly(butyl acrylate-methacrylic acid)(2) core-shell emulsion polymers. Part II: Thermomechanical properties of latex films (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 1208-1221 
    Details
    ISSN: 1435-1536
    Keywords: Polystyrene(1)/poly(butyl acrylate-methacrylic acid)(2) ; core-shell ; morphology ; latex films ; phase arrangement ; mechanical properties ; differential thermal analysis ; scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Polystyrene(1)/poly(n-butyl acrylate-methacrylic acid)(2) structured latex particles were prepared through a two-stage emulsion polymerization procedure, using a polystyrene (PS) latex seed (118 nm), and differentn-butyl acrylate (BA)/methacrylic acid (MAA) ratios. Polymerization kinetics, particle morphology, and MAA location have already been discussed in the first part of this series. In this second part the thermomechanical behavior of films cast from these latexes was studied. Differential Thermal Analysis and Dynamic Mechanical Analysis (DMA) were employed as characterization techniques for the films. Two polymer phases corresponding to polystyrene and a poly(BA-MAA) copolymer were distinguished. Comparison was made to analogous unfunctionalized PS/PBA systems, as a result of which an effect of MAA upon the phase arrangement in the film was found. Scanning Electron Microscopy of film samples and DMA showed that the evolution of the phase arrangement as a result of annealing was strongly dependent on the type of mechanical and heat treatments being applied to functionalized systems. Finally, the thermomechanical behavior of films was related to the structural features of the corresponding latexes, and computer simulation techniques wer eemployed to establish a mechanistic support for these relationships.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01095062
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  • 3
    Electronic Resource
    Electronic Resource
    Polystyrene(1)/poly(butyl acrylate-methacrylic acid)(2) core-shell emulsion polymers. Part I. Synthesis and colloidal characterization (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 812-824 
    Details
    ISSN: 1435-1536
    Keywords: Polystyrene seed ; poly(butyl acrylate-methacrylic acid) shell ; particle mophology ; location of carboxylic groups ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Polystyrene (PS) (1)/Poly(n-butyl acrylate (BA)-methacrylic acid (MAA)) (2) structured particle latexes were prepared by emulsion polymerization using monodisperse polystyrene latex seed (118 nm) and different BA/MAA ratios. Three main aspects have been investigated: i) the polymerization kinetics; ii) the particle morphology as a function of reaction time; iii) the distribution of MAA units between the water phase and the polymer particles. The amount of MAA in the shell copolymer was found to be the main factor controlling the particle shape and morphology. The shape of the structured particles was, generally, non-spherical, and the shape irregularities increased as a particles was, generally, non-spherical, and the shape irregularities increased as a function of reaction time. At the beginning of the second stage reaction, new small particles were observed, which coalesced onto the PS seed as the polymerization proceeded. The distribution of the MAA groups in the latex particles and the serum was analyzed by alkali/back-acid titration, using ionic exchanged latexes. No MAA groups were detected in the latex serum. Due to the lowTg of the BA-MAA copolymers, alkali conductimetric titrations accounted for all the MAA groups on and within the polymer particles. Therefore, for these systems, this method is not only limited to a thin surface layer, as it is often assumed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657448
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  • 4
    Electronic Resource
    Electronic Resource
    Emulsifier-free emulsion copolymerization of styrene and butyl acrylate. I.Part II of this series has been published in the Journal of Polymer Science Part A: Polymer Chemistry, Volume 26, Number 7, 1988 on page 1937. Kinetic studies in the absence of surfactant (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 119-136 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Soapless emulsion copolymerization of styrene (S) and n-butyl acrylate (BuA) has been investigated using two types of initiator and different comonomer feed mixtures. When using K2S2O8 as initiator, the particle size and size distribution of the final latexes (500 nm and 1.003, respectively) is not significantly affected by the comonomer feed composition, whereas the molecular weight and surface characteristics were found to sharply change at high butyl acrylate content. Based on the most probable particle nucleation mechanism and type of chain termination in the monomer swollen particles, a tentative explanation of these results has been proposed. Replacing persulfate by a carboxylic initiator (4-4′-azobiscyanopentanoic acid) results in the formation of stable particles as α observed with the persulfate, provided the aqueous phase pH is fixed in between 6 and 7. Results on the initiator residue location as a function of the conversion point out that the particle flocculation mechanism is strongly significant in the preparation of such latexes.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280109
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  • 5
    Electronic Resource
    Electronic Resource
    Emulsifier-free emulsion copolymerization of styrene and butyl acrylate. III. Kinetic studies in the presence of a surface active comonomer, the sodium acrylamido undecanoate (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 137-152 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Emulsion terpolymerization of styrene (S), butylacrylate (BuA) and sodium acrylamido undecanoate (AUNa), a surface active functional monomer have been carried out using a batch process in the presence of sodium 4-4′-azobiscyanopentanoate as initiator. Varying the AUNa concentration, stable particles bearing only carboxylic charges have been produced with diameters ranging from 200 to 500 nm at solids content as high as 40%. However a low AUNa yield at the particle surface has been found (30-35%), which could be explained by very unfavorable reactivity ratios of AUNa with S and BuA. Most of the AUNa seems to be wasted in the water phase (unpolymerized and forming hydrosoluble chains). Furthermore, a concentration of AUNa higher than 10-2 mol L-1 results in the latex destabilization, presumably caused by the formation of a large amount of polyelectrolytes. Kinetic studies of the AUNa consumption show that the AUNa is mainly fixed at the particle surface between 90 and 100% conversion, which indicates that the AUNa is mainly polymerized in the water phase and not at the particle surface. An attempt has been made to increase the surface charge density by polymerizing a shell of AUNa/S/BuA on a seed latex. It turned out to be unsuccessful (low surface yield, formation of new particles).
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280110
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  • 6
    Electronic Resource
    Electronic Resource
    A comparison of methods for the estimation of polymer/monomer interaction parameters: The polystyrene/n-butyl methacrylate system methacrylate system (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 1823-1832 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: To measure the polymer/monomer interaction parameter as a function of composition, a set of partially cross-linked synthetic latices has been produced by batch and semicontinuous emulsion polymerization. The degrees of cross-linking have been measured by DMA and also predicted by computer simulation based on kinetic data. With equilibrium monomer swelling experiments achieved on films made from these polymers, two curves of the interaction parameter vs. the polymer fraction have been computed. These curves compare favorably with a theoretical model based on a Unifac procedure for the estimation of monomer activity. Two different data bases, liquid-liquid and liquid-vapor equilibria, have been used in the Unifac model. For the polystyrene/n-butyl methacrylate system, a linear relationship found between the interaction parameter and composition is both predicted and measured experimentally. In all cases, this interaction parameter is found to increase with polymer concentration. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070521217
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  • 7
    Electronic Resource
    Electronic Resource
    Determination of interfacial tensions for latex particles (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 1469-1476 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The possibility of measuring in situ the interfacial tension at the monomer-swollen polymer-water interface of synthetic latices is considered in detail. Experimental measurements of certain liquid or vapor phase properties of the latex can, in principle, yield values of the desired interfacial tension. This technique requires the evaluation and comparison of the Flory-Huggins term and the Morton term of the thermodynamic expression for the chemical potential of the monomer in the latex particle. While each term can be evaluated, it turns out that the relative magnitudes of the two terms are such that unrealistically high precision is required in the experimental measurements for this technique to be useful for obtaining reasonably accurate interfacial tensions. At saturated swelling conditions with highly surface-active emulsifiers (e.g., sodium dodecyl sulfate), the interfacial tension values obtained have a precision of only about ±50%. The reliability of these approximate values degrades rapidly as one moves away from saturation conditions, so as to render in situ experimental techniques inappropriate for gaining accurate knowledge about the surface energy at the latex particle-water interface at any monomer-polymer ratio. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070531109
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