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Schematic Illustration (schematic + illustration)
Selected AbstractsTemperature-Triggered Nanosphere Formation Through Self-Assembly of Amphiphilic PolyphosphazeneMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2006Jian Xiang Zhang Abstract Summary: An amphiphilic graft polyphosphazene with a molar ratio of poly(N -isopropylacrylamide) (PNIPAm) to ethyl glycinate (GlyEt) of 0.54:1 was synthesized. This copolymer in aqueous solution exhibited two temperature induced phase transitions at 17.2 and 33.7,°C, which correspond to the transformation of primary aggregate morphology (at Tph1) and the collapse of PNIPAm chains (at Tph2) respectively. Network micelles were assembled in water at lower temperature (far below Tph1), and then narrowly dispersed nanoparticles were formed above Tph1, while inter-nanoparticle aggregation occurred due to the collapse of PNIPAm chains surrounding the GlyEt core when the temperature was above Tph2. Through solubilization of the hydrophobic drug ibuprofen into polymeric aggregates at lower temperature, drug loaded nanospheres were prepared successfully. In vitro release revealed that sustained drug release was achieved with this novel delivery system. These results suggest that this novel copolymer could be used as a potential drug carrier, especially for the delivery of hydrophobic biocompounds through parenteral administration. Schematic illustration of the temperature-triggered self-assembly process of PNIPAm/GlyEt-PPP in aqueous solution. [source] Role of Star-Like Hydroxylpropyl Lignin in Soy-Protein PlasticsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 5 2006Ming Wei Abstract Summary: Star-like hydroxypropyl lignin (HL) was compounded into soy protein isolated (SPI) to develop a potential biodegradable plastic with better mechanical performance than pure sheet-SPI. The structure and properties of the composite materials were characterized by WAXD, DSC, SEM, TEM and tensile tests. The addition of just 2 wt.-% HL resulted in tensile strength (,b) of 16.8 MPa, 2.3 times that of pure sheet-SPI, with no accompanying decrease in elongation at break as a result of strong interaction and with good miscibility among components. As the HL content increased, the HL molecules could self-aggregate as oblate supramolecular domains, while the stronger interactions between HL and glycerol resulted in the detaching of glycerol from the SPI matrix. It can be concluded that the insertion of HL as single molecules into the SPI matrix would provide materials with optimum mechanical properties. Compared with other lignin/SPI composites, the stretching chains on HL play a key role in the improvement of mechanical properties because of a stronger adhesion of HL onto the SPI matrix as well as the interpenetration of SPI into supramolecular HL domains. Schematic illustration of the supramolecular domain created by the aggregation of hydroxypropyl lignin, which can interpenetrate with soy protein isolate. [source] Surface Functionalization of Fe3O4 Magnetic Nanoparticles via RAFT-Mediated Graft PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 19 2006Wen-Cai Wang Abstract Summary: Surface functionalization of Fe3O4 magnetic nanoparticles (MNP) via living radical graft polymerization with styrene and acrylic acid (AAc) in the reversible addition-fragmentation chain transfer (RAFT)-mediated process was reported. Peroxides and hydroperoxides generated on the surface of Fe3O4 nanoparticles via ozone pretreatment facilitated the thermally initiated graft polymerization in the RAFT-mediated process. A comparison of the MNP before and after the RAFT-mediated process was carried out using transmission electron microscopy (TEM) analysis, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). Gel permeation chromatography (GPC) was used to determine the molecular weight of the free homopolymer in the reaction mixture. Well-defined polymer chains were grown from the MNP surfaces to yield particles with a Fe3O4 core and a polymer outer layer. The resulting core,shell Fe3O4 - g -polystyrene and Fe3O4 - g -poly(acrylic acid) (PAAc) nanoparticles formed stable dispersions in the organic solvents for polystyrene (PS) and PAAc, respectively. Schematic illustration of thermally induced graft polymerization of styrene and AAc with the ozone-treated Fe3O4 MNP. [source] A Cyclodextrin Microgel for Controlled Release Driven by Inclusion EffectsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004Yu-Yang Liu Abstract Summary: A novel intelligent delivery system based on the environmental dependence of the inclusion effect of , -cyclodextrin (, -CD) with guest molecules, using a , -CD polymer (CDP) microgel as carrier, is proposed. Compared with smart hydrogels, which are driven by the phase-volume transition, controlled release from the CDP microgel is driven by "host-guest" inclusion effects. With the pH-dependent inclusion complexation of methyl orange (MO) with , -CD as a model system, the behavior of the controlled release of a CDP microgel was tested by changing the pH, showing that the mechanism is reasonable. Schematic illustration of the pH-dependent inclusion complexation of MO with , -CD in the CDP microgel. [source] A Self-Assembly Approach to Temperature-Responsive Polymer NanocontainersMACROMOLECULAR RAPID COMMUNICATIONS, Issue 17 2004Xiangrong Chen Abstract Summary: Thermosensitive polymer nanocontainers were formed by self-assembly of diblock copolymers poly(2-cinnamoylethyl methacrylate)- block -poly(N -isopropylacrylamide) (PCEMA- block -PNIPAM) and subsequent photo-crosslinking of the PCEMA shells. It was found that the diameter of the nanocontainers ranges from tens of nanometers to thousands of nanometers, depending on the self-assembly conditions. The phase transition of the nanocontainers takes place at 32,°C; the structural changes are reversible in a heating and cooling cycle. Schematic illustration of the structural transition behavior of the thermosensitive polymer nanocontainers. [source] | ||||||||||