Characterization of surface NH3+Cl- groups on poly(styrene-co-Boc-aminostyrene) microspheres obtained by controlled acidic treatment.
Different samples of aminated latex of poly(styrene-co-Boc-aminostyrene) microspheres with mean diameters varying from 0.7 to 1.0 microm were prepared by dispersion copolymerization of styrene (ST) and Boc-aminostyrene (Boc-AMST). The copolymer compositions determined by nuclear magnetic resonance (1H NMR) were Boc-AMST/ST 6.9/93.1 mol/mol % (BOC7 sample) and Boc-AMST/ST 31.3/68.7 mol/mol % (BOC30 sample). The average molecular weights determined by gel permeation chromatography were 126 kDa (BOC7 sample) and 51 kDa (BOC30 sample). The latex containing NH-carbo-tert-butoxy groups (NH-Boc) were treated with 2 M HCl in isopropyl alcohol/water (1:1 vol/vol), at 50 degrees C for 3, 6, 9, 24, and 30 h, in order to control the extent of deprotection reaction of the NH-Boc. The deprotection reaction resulted in the formation of NH3+Cl- groups on the particle surfaces. The kinetic of the deprotection reaction was investigated by 1H NMR analyses and the yield varied from 20 to 40%. The resulting -NH3+Cl- groups on the microsphere surfaces were examined, in particular, by electron spectroscopy imaging (ESI) using an energy-filtered transmission electron microscope (EFTEM) that clearly demonstrated the presence of Cl on the particle surfaces. Scanning electron photomicrographs recorded for the above samples showed that the particle morphology was maintained after the acidic treatment.
Preparation of Aminated Polystyrene Latexes by Dispersion Polymerization
The preparation and characterization of aminated polystyrene-based latexes as attainable by dispersion polymerization technique are reported. Mixtures of Boc-p-aminostyrene and styrene monomers at various compositions were copolymerized under dispersion conditions in 2-propanol/water 3:1 by volume in the presence of α,α‘-azobis(isobutyronitrile) as free radical initiator at 75 °C. Copolymer microspheres with uniform size distributions and average diameters comprised between 0.9 and 1.8 μm were obtained. Aminated microspheres were obtained by the simple removal of the Boc protective group under acidic conditions followed by neutralization, thus leading to p-aminostyrene/styrene copolymers. These chemical treatments when carried out under mild conditions (room temperature and dilute acid and basic solutions), demonstrated to be efficient without causing any major alteration of the microspheres morphology. XPS analysis of the prepared microspheres showed an increase of NH2 groups with the increasing of the B...
Thermodynamics on the Carbochlorination of Titanium-bearing Ores
The equilibrium compositions of the multi-component, multi-phase and multi-reaction system of carbochlorination of titanium-bearing ores are calculated with HSC, a computational chemistry software. The thermodynamic equilibrium calculation of the reaction system shows that a complete conversion of titanium-bearing ores is feasible at a temperature near 200oC. At temperatures ranging from 800 to 1600oC, the products of the reaction system are all in gaseous phase. Thermodynamic analysis accords with the industrial practice. The simulated results provide reasonable scientific basis for improving suitable technological conditions of the carbochlorination reduction.