Adsorption of PolyCarboxylate Poly(ethylene glycol) (PCP) esters on Montmorillonite (Mmt): Effect of exchangeable cations (Na+, Mg2+ and Ca2+) and PCP molecular structure.

International audienceThis study deals with the adsorption of PolyCarboxylate Poly(ethylene glycol) esters (PCP) superplasticizers on Na-, Mg- and Ca-saturated Montmorillonite (Mmt) clays. The interactions have been examined through different experimental methods: adsorption isotherms, zeta potential measurements and sedimentation experiments. It was found that PCP adsorption depends both on the architecture of PCP molecules and the nature of cation located on the interlayer exchange sites of the Montmorillonite. Whatever the PCP, a larger amount was adsorbed on Na-Mont than on Mg-Mont or Ca-Mont. This indicates the occurrence of two adsorption mechanisms: (i) a superficial adsorption via electrostatic interactions between the carboxylate groups of PCP and positively charged sites on clay surfaces, (ii) intercalation of ether units of the PCP grafts in the interlayer space by displacement of water molecules coordinated to the exchangeable cations.Furthermore, despite the weak negative values of the zeta potential, the addition of PCP promotes the stability of the suspensions which is attributed to steric repulsion acting between particles

Acceleration and improved control of aqueous RAFT/MADIX polymerization of vinylphosphonic acid in the presence of alkali hydroxides

International audienc

Synthesis and characterization of diaminodithio- and aminotrithiophosphoric acid esters

The synthesis and characterization of a series of five new diaminodithiophosphoric acid esters ((RRN)-R-1-N-2)(2)P(S) SR and five new aminotrithiophosphoric acid esters ((RRN)-R-1-N-2)P(S)(SR)(2) are described. The structure of two of these compounds, the diaminodithio derivative (iPr(2)N)(2)P(S)SCH2Ph and the aminotrithio derivative (iPr(2)N)P(S)(SCH2Ph)(2) , has been determined by single crystal X-ray diffraction. These series of compounds are potentially usable as agents for reversible addition-fragmentation chain transfer polymerization