Xiaoling Huang

Preparation of organoclay, its copolymerization with MMA, and use to produce PVC nanocomposites:

Two quaternary ammonium compounds with polymerizable vinyl group were designed and synthesized for use as clay modifiers. Copolymerization of quaternary ammonium compounds modified MMT platelets with methyl methacrylate was studied under a range of different reaction conditions and two kinds of polymeric surfactant-modified MMTs were prepared. These polymeric surfactant-modified MMTs were introduced to produce a series of PVC/MMT composites by melt compounding. XRD, TEM, and TGA confirmed that the better organic coverage of the platelets and the bigger interlayer spacing could be obtained for the copolymer of long-chain quaternary ammonium compounds modified MMT and methyl methacrylate (PMMA-H-MMT). The platelet fillers with better organic coverage represented much more useful functional fillers than the conventional ammonium-treated fillers due to their potential to exfoliate to a greater extent when melt-compounded with the PVC matrices. The experiment proved that PMMA-H-MMT shows better performance in increasing thermal stability of PVC/MMT composites.

Gelation Behavior of Thermo-Responsive Poly(ethylene oxide) and Poly(propylene oxide) Multiblock Polycarbonates

Multiblock polycarbonates were facilely synthesized by covalently binding poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) blocks, using triphosgene as coupling agent. The resulting multiblock polycarbonates exhibited thermo-responsive gelation behavior. A pronounced viscosity increase was observed when the temperature increased, which was traced to the formation of a network of micelles. With further heating, the viscosity began to drop, which reflected breaking down of the network. Viscoelastic properties of the multiblock polycarbonates in aqueous solutions were probed by dynamic oscillatory techniques. At low frequencies, the systems showed a typical liquid-like behavior and at high frequencies they behaved as elastic materials. Data also showed that the network formed by polycarbonates with less EO/PO composition ratio evolved and strengthened, thus exhibited more elastic behavior. Temperature sweep results revealed that the aqueous solutions of polycarbonates underwent a sol-gel-sol transition with increasing temperature. By properly regulating the EO/PO composition, gelation occurred upon increasing the temperature to 37°C, which made it a promising candidate for an injectable drug delivery system.

Fabrication of cucurbit[6]uril mediated alginate physical hydrogel beads and their application as a drug carriers

Abstract A novel cucurbit[6]uril (CB[6]) mediated alginate physical hydrogel bead was prepared for the first time, which is based on the electrostatic attraction and ion-dipole interaction between sodium alginate and CB[6]. These alginate/CB[6] gel beads are useful in controlled drug delivery and other biomedical applications. The potential of alginate/CB[6] gel beads as carrier for 5-Fluorouracil (5-Fu) was studied in this paper. The properties of alginate/CB[6] gel beads were studied by FT-IR, XRD and TGA. The process of the formation of alginate/CB[6] gel beads was recorded by Digital cameras. The external morphology of the dried beads were observed using SEM. Alginate/CB[6] gel beads first was formed as a thin film on the surface of the alginate solution droplet, holding its spherical shape. The color of the alginate/CB[6] gel beads changed from almost colorless to white with the increase of gel time, and also the beads became small and compact. The dried alginate/CB[6] gel beads were about 900-1000 μm, irregular spherical and the surface of dried beads showed a corrugated surface having a uniform distribution of regular nodules and cavities.