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Hydrophobic Polymers (hydrophobic + polymer)
Selected AbstractsAn Integrated Atmospheric Microwave Plasma SourcePLASMA PROCESSES AND POLYMERS, Issue S1 2009Reinhold Kovacs Abstract Atmospheric plasma processes become more and more popular in recent times. A new integrated atmospheric plasma source is presented which consists of a microwave resonator combined with a solid-state power oscillator. This allows for a very compact and efficient design of a microwave plasma source without external microwave power supply and matching units. Hydrophobic polymers have to be activated to ensure an effective painting or glueing. The performance of this new plasma source has been investigated with respect to surface activation depending on axial and radial distance to the substrate, process time, process gas, and flow velocity. Several polymeric materials have been compared. Polyethylene, polyamide, polystyrene, polypropylene, polycarbonate, and polytetrafluorineethylene show good activation results. This tool can be used especially for bulky goods and/or mass products, when a vacuum process is not possible or too expensive. [source] Controlled radical polymerization of 2-hydroxyethyl methacrylate with a hydrophilic ruthenium complex and the synthesis of amphiphilic random and block copolymers with methyl methacrylate,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2002Yusuke Fuji Abstract A hydrophilic ruthenium complex with ionic phosphine ligands {1: RuCl2[P(3-C6H4SO3Na)(C6H5)2]2} induced controlled radical polymerization of 2-hydroxyethyl methacrylate (HEMA) in methanol under homogeneous conditions; the initiator was a chloride (R-Cl) such as CHCl2COPh. The number-average molecular weights of poly(HEMA) increased in direct proportion to monomer conversion, and the molecular weight distributions were relatively narrow (Mw/Mn = 1.4,1.7). A similar living radical polymerization was possible with (MMA)2 -Cl [(CH3)2C(CO2CH3)CH2C(CH3)(CO2CH3)Cl] as an initiator coupled with amine additives such as n -Bu3N. In a similar homogeneous system in methanol, methyl methacrylate (MMA) could also be polymerized in living fashion with the R-Cl/1 initiating system. Especially for such hydrophobic polymers, the water-soluble ruthenium catalyst was readily removed from the polymers by simple washing with an aqueous dilute acid. This system can be applied to the direct synthesis of amphiphilic random and block copolymers of HEMA and MMA. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2055,2065, 2002 [source] Development of New Microencapsulation Techniques Useful for the Preparation of PLGA MicrospheresMACROMOLECULAR RAPID COMMUNICATIONS, Issue 21 2006Hongkee Sah Abstract Summary: Intensive efforts were made to develop an efficient, novel microencapsulation system useful to encapsulate a model drug, risperidone, to PLGA microspheres. Methyl dichloroacetate was used as a dispersed solvent for the first time, since it possessed excellent solvency power on PLGA and readily underwent ammonolysis. A dispersed phase composed of methyl dichloroacetate, risperidone, and PLGA was emulsified in an aqueous phase to form an O/W emulsion. Adding ammonia solution into the emulsion rapidly converted methyl dichloroacetate into water-soluble dichloroacetamide and methanol. As a result, emulsion droplets were immediately transformed into hardened microspheres. The new microencapsulation system allowed us to make PLGA microspheres with a drug payload of >40 wt.-% and attain almost complete encapsulation efficiencies. In summary, preparing an O/W emulsion and subjecting the emulsion to ammonolysis led to development of an efficient, novel microencapsulation system. It was anticipated that the new system could make it possible to load other bioactive materials into microspheres made of various types of hydrophobic polymers. SEM micrographs of the external and internal morphology of PLGA/risperidone microspheres. [source] The physiological relevance of wet versus dry differential scanning calorimetry for biomaterial evaluation: a technical notePOLYMER INTERNATIONAL, Issue 10 2010Dimitrios I Zeugolis Abstract Collagen and its denatured form, gelatin, have been extensively used as scaffolds for tissue engineering and tissue repair applications. Denaturation temperature, commonly measured using differential scanning calorimetry (DSC), for biomaterial applications is a significant physical property that will determine the stability of a potential implant at body temperature. In order to imitate a clinical setting, DSC should be run under fully hydrated conditions. We show here that for hydrophobic polymers such as poly(,-caprolactone) and chitosan there is no significant difference between dry and wet DSC operation (p > 0.05). In contrast, for hydrophilic polymers such as collagen, gelatin, poly(ethylene glycol) (40 kDa) and poly(ethylene oxide) (900 kDa) significant differences occur between measurements in the dry and the wet state (p < 0.0011). Moreover, we demonstrate that only when wet DSC is carried out are we able to separate the unique crystalline structure of collagen from its randomly coiled heat-denatured by-product gelatin (p < 0.0005). We therefore recommend running DSC under fully hydrated conditions when the function and properties of a biomaterial are under investigation. Copyright © 2010 Society of Chemical Industry [source] | ||||||||||