Grafting of Oligosaccharides onto Synthetic Polymer Colloids

Abstract

A new method to form colloidally stable oligosaccharide-grafted synthetic polymer particles has been developed. The oligosaccharides, of weight-average degree of polymerization approximately 38, were obtained by enzymatic debranching of amylopectin. Through the use of a cerium(IV)-based redox initiation process, oligosaccharide chains are grafted onto a synthetic polymer colloid comprising electrostatically stabilized poly(methyl methacrylate) or polystyrene latex particles swollen with methyl methacrylate monomer. Ce(IV) creates a radical species on these oligosaccharides, which then propagates, initially with aqueous-phase monomer, then with the methyl methacrylate monomer inside the particles. Ultracentrifugation, NMR, and total starch analyses together prove that the grafting process has occurred, with at least 7.7 wt % starch grafted and a grafting efficiency of 33%. The surfactant used in latex preparation was removed by dialysis, resulting in particles colloidally stabilized with only linear starch as a steric stabilizer. The debranched starch that comprises these oligosaccharides is found to be a remarkably effective colloidal stabilizer, albeit at low electrolyte concentration, stabilizing particles with very sparse surface coverage.

Polysaccharide‐Containing Block Copolymers: Synthesis, Properties and Applications of an Emerging Family of Glycoconjugates

“…In these conditions, the spontaneous anionic polymerization of ACA is sufficiently delayed to allow the occurrence of a redox radical polymerization initiated by dextran in presence of cerium (IV) ions affording latex particles mainly composed of dextran-b-PACA copolymer with surface active-properties. [62] Mange et al [60] reported a new method of latex stabilization where linear oligosaccharides (DP % 38), obtained by enzymatic debranching of starch, are grafted onto poly(methyl methacrylate) latex particles swollen with methyl methacrylate monomer. Ce(IV) was used to create initiating radicals on these oligosaccharide chains, which then propagate, initially with aqueous-phase monomer, then with the methyl methacrylate monomer inside the particles.…”

“…[59] The mechanism involves the formation of a complex between ceric ions and hydroxyl groups followed by its disproportionation which generates an aldehyde or ketone and a free radical through the CÀC bond cleavage of 1,2-diol. [58,60] It has been shown that grafting on polysaccharide chains occurs predominantly at the reducingend hemiacetal group and at the C2ÀC3 glycol groups in anhydroglucose units. [61] Few studies reported on the use of cerium oxidation for synthesizing block copolymers from polysaccharides.…”

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

“…Another interesting reaction of Ce 4+ with starch takes place at the hemiacetal reducing end of the starch molecule, where the reaction with Ce 4+ is much faster than at the 1,2‐diols in the body of the starch chains 8, 10. Contrary to our previous work using oligosaccharides,11 the starches used in this work are amylopectins with molecular weights of the order of 10 7 to 10 8 . As there is only one reducing end per starch molecule and 10 5 to 10 6 anhydroglucose units in amylopectin, it follows that most radical sites formed by direct Ce 4+ oxidation of amylopectin will be in the body of the starch chains.…”

The use of amylose‐rich starch nanoparticles in emulsion polymerization

“…There exists an additional possibility that the water phase starches are grafted to the synthetic monomer during the nucleation phase to the point where they would reach their critical chain length and be hydrophobic enough to form a particle, but this is evidently not the dominant mechanism (i.e., the viscosity of the latex would not increase drastically by the end of the polymerization). A common strategy for including polysaccharides in emulsion polymerizations while maintaining stability (i.e., in regards to viscosity) is to severely reduce their molecular weight, often in situ …”