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
URL:
http://dx.doi.org/10.1002/macp.1985.020101985127
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