Graft polymerization of vinyl acetate onto granular starch: Comparison on the potassium persulfate and ceric ammonium nitrate initiated system

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Abstract

This work was undertaken to discuss in depth the vital differences in the morphological development during synthesis, and properties of starch-g-poly-(vinyl acetate) copolymers using two different initiators, potassium persulfate (KPS) and ceric ammonium nitrate (CAN). KPS-initiated system gave relatively low values of grafting ratio and grafting efficiency, indicating a great tendency for the formation of poly(vinyl acetate) homopolymer (PVAc). Yet, higher values were seen for the CAN-initiated system. Transmission electron microscope observations indicated a relatively broad distribution of latex particles for the KPS-initiated system. The surface potential of latex particles was about −3.5 mV, which turned out to be insufficient to maintain stability of latex particles. On the other hand, a uniform particle size distribution was found for the CAN-initiated system, as the surface potential of latex particles was 21.5 mV. Moreover, radicals on starch molecules were generated directly through a redox reaction with positively charged ceric ion. The hydrophobic PVAc chains were thus grafted on starch, resulting in an amphiphilic graft copolymer, which provides a sufficient stabilization degree as a role of surfactant to render a relatively uniform distribution of latex particles. The synthesized starch-g-poly(vinyl acetate) copolymers were further converted to starch-g-poly(vinyl alcohol) through saponification, which were subjected to evaluations regarding the biodegradation and cell culture capability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3017–3027, 2006

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