Cellulose Diacetate-g-poly(p-dioxanone) Co-polymer: Synthesis, Properties and Microsphere Preparation
A novel biodegradable graft co-polymer based on cellulose diacetate (CDA) and poly(p-dioxanone) was synthesized by ring-opening polymerization of p-dioxanone (PDO). The molecular structure of co-polymers was characterized by one- and two-dimensional NMR. The graft co-polymers with different lengths of PPDO side-chains could be controllably synthesized by changing the in-feed ratio of CDA/PDO. It was found that the PPDO content had great effect on the thermal transition behavior, crystallization ability and thermal stability of the graft co-polymer. The in vitro degradation rates of CDA-g-PPDO were higher than that of linear PPDO due to their lower crystallinity. Moreover, porous microspheres of graft co-polymers with a diameter of about 5 μm, prepared through the solvent evaporation of water-in-oil emulsion (W/O), indicated it may have potential applications in drug-delivery systems.
Self-assembly of cationic amphiphilic cellulose-g-poly (p-dioxanone) copolymers.
Cationic amphiphilic cellulose copolymers were prepared through grafting hydrophobic poly (p-dioxanone) (PPDO) chains onto hydrophilic quaternized cellulose derivatives (QC) via ring-opening polymerization (ROP) reaction, which was performed in 1-butyl-3-methylimidazolium chloride (BmimCl) and using 4-dimethylaminopyridine (DMAP) or 1,8-diazabicyclo (5.4.0) undec-7-ene (DBU) as catalyst. Their chemical structures and physical properties were confirmed by FT-IR, 1H-, 13C-, 2D HSQC-NMR, X-ray diffraction (XRD), and thermal stability (TGA) techniques, while self-assembly behavior was characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and fluorescence techniques. Both of the sizes and critical micelle concentration (CMC) values of micelles were decreased with increasing grafting contents of PPDO in the copolymers, which were in the ranges of 110-246 nm and 64-253 μg/mL, respectively. The ζ-potentials of micelles were cationic andranged from 39.1 mV to 45.4 mV. The highest encapsulation efficiencyof paclitaxel (PTX) into the micelles was 61.8% and 92.0% of loaded PTX was continuously released from micelles in phosphate buffered saline medium for 36 h.
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.