			Home About us Contact

Porous Poly (porous + poly)

Distribution by Scientific Domains

Polymers and Materials Science	54%
Life Sciences	36%

Selected Abstracts

Estimation of Morphology Characteristics of Porous Poly(propylene) Particles from Degassing Measurements

MACROMOLECULAR REACTION ENGINEERING, Issue 2 2008
Marek Bobak
Abstract The transport of reaction species in polyolefin particles affects both the polymerization and the degassing of the powder in the down-stream processing. The morphology of particles , that is, the distribution of polymer and pore phases , predetermines their degassing behavior. We utilize gravimetric measurements to obtain the dynamics of degassing and to determine morphology characteristics of porous poly(propylene) particles. We found that Fick's diffusion model is not generally capable of fitting the shape of degassing curves of porous particles. Therefore we propose a particle model including two sizes of compact polymer granules and demonstrate that the degassing can be described by this model and that the model is capable of estimating fractions of large and small compact zones and the size of large compact zones. [source]

Monte Carlo Simulation of Degradation of Porous Poly(lactide) Scaffolds, 1

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 9 2006
Effect of Porosity on pH
Abstract Summary: Monte Carlo method was used to simulate the degradation of porous PLA scaffolds. The simulated volume was assumed to be divided homogeneously between the pore and solid PLA with the ratio equal to the bulk porosity of the scaffold. The volume was divided into surface and bulk elements where the surface elements were in direct contact with the aqueous degradation medium, while the bulk elements were surrounded by the pore and solid PLA. The effect of degradation time on PLA ester groups and carboxylic acid end-groups for surface and bulk elements, pH, PLA degradation rate and mass loss, and PLA molecular weight distribution was simulated. For surface elements, pH remained constant at 7.4 over the entire time of degradation, while for bulk elements its value decreased significantly to as low as 5.8. The highest drop in pH within the scaffold was observed for the highest porosity of 90%. There was a lag time of at least 7 weeks in the mass loss for surface as well as bulk elements for porosities ranging from 70 to 90%. The mass loss for bulk elements was considerably faster than the surface elements. This difference in the rate of mass loss between the surface and bulk elements could affect the 3D morphology and dimensional stability of the scaffold in vivo as degradation proceeds. The simulation predicts that, due to differences in the rate of bulk and surface degradation, hollow structures could form inside the scaffold after 19, 17, and 15 weeks for initial porosities of 70, 80, and 90%, respectively. A schematic diagram illustrating the degradation of an element on the outer surface of the scaffold (surface element) versus an element within the volume of the scaffold (bulk element). [source]

Porous polymer monolith for surface-enhanced laser desorption/ionization time-of-flight mass spectrometry of small molecules

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2004
Dominic S. Peterson
Porous poly(butyl methacrylate- co -ethylene dimethacrylate), poly(benzyl methacrylate- co -ethylene dimethacrylate), and poly(styrene- co -divinylbenzene) monoliths have been prepared on the top of standard sample plates used for matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and the modified plates were used for laser desorption/ionization mass spectrometry (LDI-MS). The hydrophobic porous surface of these monoliths enables the transfer of sufficient energy to the analyte to induce desorption and ionization prior to TOFMS analysis. Both UV and thermally initiated polymerization using a mask or circular openings in a thin gasket have been used to define spot locations matching those of the MALDI plates. The desorption/ionization ability of the monolithic materials depends on the applied laser power, the solvent used for sample preparation, and the pore size of the monoliths. The monolithic matrices are very stable and can be used even after long storage times in a typical laboratory environment without observing any deterioration of their properties. The performance of the monolithic material is demonstrated with the mass analysis of several small molecules including drugs, explosives, and acid labile compounds. The macroporous spots also enable the archiving of samples. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Open-tubular capillary columns with a porous layer of monolithic polymer for highly efficient and fast separations in electrochromatography

ELECTROPHORESIS, Issue 21 2006
Sebastiaan Eeltink
Abstract Open-tubular columns for CEC separations having inner-wall coated with a thin layer of porous monolithic polymer have been studied. A two-step process including (i),UV-initiated polymerization leading to a layer of porous poly(butyl methacrylate- co -ethylene dimethacrylate), and (ii),UV-initiated grafting of ionizable monomers appear to be well suited for the preparation of these columns. The thickness of the porous polymer layer is controlled by the percentage of monomers in the polymerization mixture and/or length of the irradiation time. The layer thickness significantly affects retention, efficiency, and resolution in open-tubular CEC. Under optimized conditions, column efficiencies up to 400,000 plates/m can be achieved. Use of higher temperature and application of pressure enables a significant acceleration of the open-tubular CEC separations. [source]

In vitro evaluation of porous poly(L -lactic acid) scaffold reinforced by chitin fibers

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009
Xiaoming Li
Abstract In this study, the previously reported porous three-dimensional poly(L -lactic acid) (PLLA) scaffolds reinforced by the chitin fibers (PLLA/CF) with and without the link were evaluated in vitro. Firstly, pH value of the phosphate buffered saline lixiviums of the PLLA/CF with different content of the chitin fibers was measured to get an appropriate content of the chitin fibers in the PLLA/CF. Then, the cell functions (attachment, proliferation, alkaline phosphatase per unit cell, total protein per unit cell, and osteonectin, osteopontin, and osteocalcin gene expression) of human osteoblast-like cells (SaOS2) cultured on the PLLA/CF with the link, PLLA/CF without the link and PLLA scaffold were compared. The results showed that the link treatment did not significantly influence the pH value of the lixiviums of the scaffolds, 30% volume content might be an appropriate content of the chitin fibers in PLLA/CF scaffold to keep the pH value of the lixiviums of the scaffolds between 7.0 and 7.2 during the lixiviation time of 16 weeks, the PLLA/CF scaffold was significantly better for the attachment, proliferation, differentiation, and mineralization of the osteoblast than PLLA, the link treatment did not significantly influence these cells activities, which further suggested that PLLA/CF with the link treatment might be an appropriate scaffold for tissue engineering. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source]

Synthesis of metal/polymer colloidal composites by the tailored deposition of silver onto porous polymer microspheres

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2004
Jin-Woong Kim
Abstract A new colloidal silver system is presented in which a fine colloidal silver is in situ deposited onto functionalized porous poly(ethylene glycol dimethacrylate) [poly(EGDMA)] microspheres. The effectiveness of the silver deposition has been investigated through an examination of the surface characteristics of poly(EGDMA) microspheres. The result reported in this study demonstrate that the control of the surface area and surface functionality (in this study, a hydroxyl group) of poly(EGDMA) microspheres is an important factor that practically determines the degree of deposition of colloidal silver. X-ray analysis has shown that silver nanoparticles are dispersed evenly on inner and outer surfaces and have a face center cubic phase. Preservation testing has shown that silver-containing poly(EGDMA) microspheres have powerful antibacterial properties and, therefore, have significant potential as new preservatives. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2551,2557, 2004 [source]

Estimation of Morphology Characteristics of Porous Poly(propylene) Particles from Degassing Measurements

Electroactive composite systems containing high conductive polymer layers on poly(ethylene) porous films,

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9-10 2006
G. K. Elyashevich
Abstract New composite electroactive materials containing conducting polymers were elaborated by oxidative polymerization of aniline and pyrrole onto porous poly(ethylene) films. The morphology of the conducting phase on the surface of the composites was investigated by scanning electron microscopy. The influence of preparation method and porous support structure on electric and mechanical properties of the composite materials was studied. The correlation between the composites electroconductivity and the absorbance of electromagnetic radiation in the IR region was observed. It was found that gas separation and ion-exchange membrane properties of the composites strongly depend on their conductivity and content of conducting component. Copyright © 2006 John Wiley & Sons, Ltd. [source]

A cell leakproof PLGA-collagen hybrid scaffold for cartilage tissue engineering

BIOTECHNOLOGY PROGRESS, Issue 3 2010
Naoki Kawazoe
Abstract A cell leakproof porous poly(DL -lactic-co-glycolic acid) (PLGA)-collagen hybrid scaffold was prepared by wrapping the surfaces of a collagen sponge except the top surface for cell seeding with a bi-layered PLGA mesh. The PLGA-collagen hybrid scaffold had a structure consisting of a central collagen sponge formed inside a bi-layered PLGA mesh cup. The hybrid scaffold showed high mechanical strength. The cell seeding efficiency was 90.0% when human mesenchymal stem cells (MSCs) were seeded in the hybrid scaffold. The central collagen sponge provided enough space for cell loading and supported cell adhesion, while the bi-layered PLGA mesh cup protected against cell leakage and provided high mechanical strength for the collagen sponge to maintain its shape during cell culture. The MSCs in the hybrid scaffolds showed round cell morphology after 4 weeks culture in chondrogenic induction medium. Immunostaining demonstrated that type II collagen and cartilaginous proteoglycan were detected in the extracellular matrices. Gene expression analyses by real-time PCR showed that the genes encoding type II collagen, aggrecan, and SOX9 were upregulated. These results indicated that the MSCs differentiated and formed cartilage-like tissue when being cultured in the cell leakproof PLGA-collagen hybrid scaffold. The cell leakproof PLGA-collagen hybrid scaffolds should be useful for applications in cartilage tissue engineering. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source]

Insulin transport across porous charged membranes: Effect of the electrostatic interaction

BIOTECHNOLOGY PROGRESS, Issue 5 2009
Shaoling Zhang
Abstract Insulin transport phenomena across a series of porous charged membranes were studied at two pH conditions (pH 3.3 and pH 7.4) in this article. The membranes were prepared by pore-surface modification of porous poly(acrylonitrile) (PAN) membranes by grafting with weak acidic and basic functional groups. The insulin partition coefficient K between the membrane and solution was estimated from the equilibrium adsorption amount in the batch adsorption experiment. The insulin effective diffusion coefficient D inside the membrane was determined as a fitting parameter by matching the diffusion model with the experimental data of the diffusion measurement. Both K and D correlated well with the charge properties of the insulin and membrane: when the insulin and membrane carried opposite net charge, the partition coefficient showed relatively larger values, while the effective diffusion coefficient was reduced. The insulin permeability coefficient P obtained from the experimental results agreed with that estimated from the partition coefficient and effective diffusion coefficient. These results suggested that the combined effects of the solubility and diffusivity on the permeability coefficient complicated the relationship between the permeability and the charge properties of the insulin and membrane. Additionally, our calculation supported that insulin permeability was reduced by the boundary layer between the membrane and solution. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]

Insulin adsorption into porous charged membranes: Effect of the electrostatic interaction

BIOTECHNOLOGY PROGRESS, Issue 4 2009
Shaoling Zhang
Abstract Insulin adsorption into a series of porous charged membranes was investigated by batch adsorption experiments, and the experimental results were analyzed by the homogeneous diffusion model. The membranes used in this study were prepared by pore-surface modification of porous poly(acrylonitrile) (PAN) membranes by grafting with weak acidic and basic functional groups. The amount of insulin adsorbed into the membrane was determined from the material balance of insulin. The insulin partition coefficient K between the membrane and solution was estimated from the equilibrium adsorption amount, and the effective diffusion coefficient D was estimated by matching the model with the experimental data as a fitting parameter. The dependence of K and D on the charge properties of the insulin and membrane is observed and discussed. The partition coefficient K increased when the insulin and the membrane carried opposite charges, on the other hand, the effective diffusion coefficient D was reduced. These results indicate that the electrostatic interaction between the insulin and the membranes played an important role in the insulin adsorption. © 2009 American Institute of Chemical Engineers Biotechnol. Prog. 2009 [source]