Starch‐graft‐copolymer latexes initiated and stabilized by ozonolyzed amylopectin

Abstract

A method is presented for synthesizing surfactant-free latexes comprising a starch-graft-vinyl polymer, (1) starting with a suspension of the highly branched starch amylopectin, either native or degraded, (2) then using ozonolysis to create free-radical initiation sites on this amylopectin scaffold, and (3) finally adding the monomer and inducing polymerization. The ozone simultaneously thins the starch and creates initiating/grafting sites on the starch, from which starch-graft-copolymer latexes can be grown. The encapsulation of starch inside the hydrophobic polymer particles created by a heterogeneous free-radical polymerization process is demonstrated with energy-dispersive spectroscopy; this is the first time that the particle morphology of such a latex has been so characterized. The data unambiguously prove that low-molar-mass degraded starch can be encapsulated within a latex particle. The underlying mechanisms have been explored, and data quantifying the rates of production of hydroperoxides by ozone, the thermal decomposition of the starch hydroperoxides so formed, and the degradation of amylopectin by ozone are reported. The activation energy for the thermal decomposition of the starch macroinitiator, determined in this work to be 125 6 8 kJ mol À1 , is consistent with the proposition that the initiating species are mainly hydroperoxides. Colloidally stable poly(styrene-co-n-butyl acrylate) latexes based on high-molar-mass amylopectin have been developed. These are stable against electrolytes (several months in 4 mol L À1 NaCl), with 20% of the starch effectively grafted to the particles. Films cast from such latexes are more pliable than starch films and are readily redispersed in water. V V C 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: [5832][5833][5834][5835][5836][5837][5838][5839][5840][5841][5842][5843][5844][5845] 2006

Starch‐graft‐(synthetic copolymer) latexes initiated with Ce4+ and stabilized by amylopectin

“…Latexes 1 to 5 were ultrasonicated (Sonics Vibracell, 30%, 5 min), after which their viscosities reduced to approximately that of the equivalent raw starch suspensions (5–30 cP for 1–5 wt % starch suspensions respectively). This is strong evidence of the “scaffold” structure of the latex and the associated gelation mechanism described in detail in our previous paper 3. Native amylopectin can degrade under shear 28.…”

“…This thinning appears to be necessary to avoid gelation of the latex under the experimental conditions used in the past. This article extends previous work, based on ozone grafting/initiation,3 to a Ce 4+ ‐based method for producing stable synthetic polymer latexes with a high proportion of high molecular weight starch grafted to the latex particles.…”

Preparation, characterization, and water resistance of cationic acetylated starch‐g‐poly(styrene‐butyl acrylate) surfactant‐free emulsion

“…Yeng et al 11 reported acrylamide modified sago starch which was utilized as paper coatings to improve paper surface physical and mechanical properties. De Bruyn et al 12 adopted ozonolyzed AP as initiator and stabilizer to initiate the graft copolymerization of St, BA, and vinyl acetate onto starch to obtain starch‐ graft ‐copolymer surfactant‐free latexes. De Bruyn et al 13 used Ce 4+ initiator and AP stabilizer to successfully produce native wx starch grafted poly(styrene‐butyl acrylate‐vinyl acetate) surfactant‐free latexes.…”

Preparation and characterization of oxidized starch-graft-poly(styrene-butyl acrylate) latex via emulsion polymerization

“…Starch can be grafted to produce new materials with properties that combine the advantages of natural and synthetic polymers. Published studies have proven that the application properties of the starch graft copolymer are better than the commonly used mixtures of synthetic polymer latex and starch [10,11]. Furthermore, replacing part of the synthetic monomer with OS can reduce the cost of latex and benefit the environment because of the low cost and biodegradability of starch.…”