Orthopedic procedures often require repair materials that can carry large loads without excessive deformation or failure. To this end, we designed composites using two biocompatible/bioabsorbable polymers, poly(L-lact...
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Orthopedic procedures often require repair materials that can carry large loads without excessive deformation or failure. To this end, we designed composites using two biocompatible/bioabsorbable polymers, poly(L-lactic acid) (PLLA) and polycaprolactone (PCL). The latter was filled with nano-needles of hydroxyapatite (HA), while the PLLA was used in long-fiber form. Theory advises that the HA nano-needles must be of high aspect ratio and be aligned in the matrix to gain sufficient stiffness. We have explored several processing techniques for accomplishing this task, and have successfully made composites in the 8-to 10-GPa range. Variations of this structure will also be described.
作者:
Jian WuQing GePatrick T Matherwujian@mail.pse.umass.edu
University of Connecticut Chemical Engineering DepartmentPolymer Program Institute of Materials Science 97 North Eagleville Road Storrs CT 06269 United States Qing@***
University of Connecticut Chemical Engineering Departmentand Polymer ProgramInstitute of Materials Sciece Storrs CT 06269 United States ptmather@syr.edu
University of Connecticut Chemical Engineering Departmentand Polymer ProgramInstitute of Materials Sciece Storrs CT 06269 United States
A series of unique hybrid thermoplastic polyurethanes (TPUs) was synthesized using PEG as soft segment and incorporating an isobutyl-functionalized POSS diol (TMP POSS diol) in the hard segment. The molecular weight o...
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A series of unique hybrid thermoplastic polyurethanes (TPUs) was synthesized using PEG as soft segment and incorporating an isobutyl-functionalized POSS diol (TMP POSS diol) in the hard segment. The molecular weight of PEG was systematically varied to include 10, 20, and 35 kDa, while the mole ratio of POSS diol (as chain extender) to PEG was in range from 3:1 to 8:1 with samples featuring a PEG molecular weight of 10 kDa. The diisocyanate employed for TPU polymerization was 4,4'-methylenebis(phenyl-isocyanate) (MDI). We found that the hydrophobic hard segments (POSS) can form crystalline structures driven by micro-phase separation, this being due to significant thermodynamic incompatibility between POSS and ethylene oxide units. The POSS nano-crystals thus formed serve as physical crosslinking sites within an inorganic-organic hybrid network. This affords a new hybrid organic-inorganic hydrogel in the water-swollen state. The equilibrium swelling ratio increased monotonically with PEG loading and ranged from ∼70% to ∼600%. The shear modulus, G, of the hybrid hydrogels was observed to span 0.3 < G < 4.0 MPa – C values commonly found for elastomers, not hydrogels. Indeed, the hydrogel stiffness can be finely tuned through the POSS:PEG molar ratio, as this predictably controls swelling in water.
Manufacturing of drug delivery systems through the extrusion process is of great interest in academia and pharmaceutical industry alike. Even though significant amount of research has been conducted in this field, the...
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Manufacturing of drug delivery systems through the extrusion process is of great interest in academia and pharmaceutical industry alike. Even though significant amount of research has been conducted in this field, there are still many challenges to be addressed such as: thermal stability of drugs, difficult downstream handling of extrudates and high density of the extrudates. Recently, the foaming process is being seen as an answer for some of these problems. This paper reviews the role of polymeric foams in the manufacture of oral drug delivery systems. A case study analyzing the influence of foaming on the dissolution profile of a polymeric excipient in water is discussed in more detail.
Biodegradable polymers with high mechanical strength, flexibility and optical transparency, optimal degradation properties and biocompatibility are critical to the success of tissue engineered devices and drug deliver...
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Biodegradable polymers with high mechanical strength, flexibility and optical transparency, optimal degradation properties and biocompatibility are critical to the success of tissue engineered devices and drug deliver...
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Biodegradable polymers with high mechanical strength, flexibility and optical transparency, optimal degradation properties and biocompatibility are critical to the success of tissue engineered devices and drug delivery systems. In this work, microfluidic devices have been fabricated from elastomeric scaffolds with tunable degradation properties for applications in tissue engineering and regenerative medicine. Most biodegradable polymers suffer from short half life resulting from rapid and poorly controlled degradation upon implantation, exceedingly high stiffness, and limited compatibility with chemical functionalization. Here we report the first microfluidic devices constructed from a recently developed class of biodegradable elastomeric poly(ester amide)s, poly(1,3-diamino-2-hydroxypropane-co-polyol sebacate)s (APS), showing a much longer and highly tunable in vivo degradation half-life comparing to many other commonly used biodegradable polymers. The device is molded in a similar approach to that reported previously for conventional biodegradable polymers, and the bonded microfluidic channels are shown to be capable of supporting physiologic levels of flow and pressure. The device has been tested for degradation rate and gas permeation properties in order to predict performance in the implantation environment. This device is high resolution and fully biodegradable; the fabrication process is fast, inexpensive, reproducible, and scalable, making it the approach ideal for both rapid prototyping and manufacturing of tissue engineering scaffolds and vasculature and tissue and organ replacements.
There have been reports of improvements in the thermoelectric figure of merit through the use of nanostructured materials to suppress the lattice thermal conductivity. Here, we report on a fundamental study of the com...
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作者:
Jae Ok KimHyeon Ju RyuWoo SeokNohJae Cheol ParkDepartment of Applied Chemistry
Kumoh National Institute of Technology1 Yangho-dongGumiGyeongbuk730-701Korea Department of Polymer Science and EngineeringKumoh National Institute of Technology1 Yangho-dongGumiGyeongbuk730-701Korea Department of Environmental EngineeringKumoh National Institute of Technology1 Yangho-dongGumiGyeongbuk730-701Korea
There have been reports of improvements in the thermoelectric figure of merit through the use of nanostructured materials to suppress the lattice thermal conductivity. Here, we report on a fundamental study of the com...
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There have been reports of improvements in the thermoelectric figure of merit through the use of nanostructured materials to suppress the lattice thermal conductivity. Here, we report on a fundamental study of the combined effects of defect planes and surface scattering on phonon transport and thermoelectric properties of defect-engineered InAs nanowires. A microfabricated device is employed to measure the thermal conductivity and thermopower of individual suspended indium arsenide nanowires grown by metal organic vapor phase epitaxy. The four-probe measurement device consists of platinum resistance thermometers and electrodes patterned on two adjacent SiNx membranes. A nanowire was suspended between the two membranes, and electrical contact between the nanowire and the platinum electrodes was made with the evaporation of a Ni/Pd film through a shadow mask. The exposed back side of the device substrate allows for characterization of the crystal structure of the suspended nanowire with transmission electron microscopy (TEM) following measurement. The 100-200 nm diameter zincblende (ZB) InAs nanowire samples were grown with randomly spaced twin defects, stacking faults, or phases boundaries perpendicular to the nanowire growth direction, as revealed by transmission electron microscopy (TEM) analysis. Compared to single-crystal ZB InAs nanowires with a similar lateral dimension, the thermal conductivity of the defect-engineered nanowires is reduced by fifty percent at room temperature.
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