摘要:

Many types of polymers have been used for medical devices for blood contacting application. Polyurethanes have been determined to be one of the more blood‐compatible. However, there is variability within types of polyurethanes and even within the same type of polyurethane as far as hemocompatibility. This variability stems in part from differences in processing aids, including waxes, which manufacturers add. An understanding of the surface chemical properties is essential for the determination of the hemocompatibility of polyurethanes. For this presentation, we describe analysis of the wax component of the surface of a polyurethane commonly used for extruded medical devices, Pellethane 2363 (Dow), by Fourier‐transform infrared‐attenuated total reflection (FTIR‐ATR) and x‐ray photoelectron spectroscopy (XPS), and the effect of its presence on the hemocompatibility of Pellethane. Solvent cleaned samples, demonstrating reduced amide processing wax component by the two techniques, are also evaluated for blood–surface interactions. Tubing samples are evaluated for hemocompatibility by exposure to human platelet/plasma solutions followed by analysis using scanning electron microscopy. There is a direct correlation between the amount of amide processing wax in Pellethane as determined by FTIR‐ATR and XPS and the in‐vitro hemocompatibility.

ISSN:0734-2101    

DOI:10.1116/1.578923

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Molecular arrangements and structural defects in lignoceric and stearic acid monolayers were investigated with transmission electron and atomic force microscopes. Lignoceric acid molecules in the monolayer, prepared by a continuous compression method, were regularly arranged in a hexagonal array with the (10) spacing of 0.43 nm. The hexagonal array with crystallographical distortion of 4.0% was extended over 10 nm (crystallographical continuity), and the locally disordered molecular arrangements in the monolayer were also observed. On the other hand, stearic acid molecules in the monolayer, prepared by a multistep creep method, were regularly arranged in a hexagonal array with the (10) spacing of 0.42 nm. The hexagonal array with the crystallograhical distortion of 2.0% was extended over 20 nm. Distinctly disordered molecular arrangement was not observed in the case of the stearic acid monolayer. The higher crystallographical regularity of the stearic acid monolayer might be attributed to effective sintering at interfaces among crystalline domains during the multistep creep procedure.

ISSN:0734-2101    

DOI:10.1116/1.578924

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A new polymerizable lipid, ethyl morpholine pentacosadiynoic amide (EMPDA), was synthesized. Monomeric and polymeric films formed from this lipid at the air–water interface were investigated by microfluorescence filmbalance techniques. Below 25 °C, monomeric EMPDA exhibited a pronounced fluid–solid coexistence with a transition enthalpy of ∼100 kJ/mol at room temperature. The coexistence pressure was found to increase with decreasingpH; belowpH 4.5 no fluid–solid coexistence was measurable. Microfluorescence revealed that large achiral single‐crystalline domains grow in the coexistence regime. Upon ultraviolet exposure only the lipids in the crystalline domains were found to polymerize, indicating that the polymerization is a topochemical reaction. The polymerized domains exhibited a pronounced intrinsic fluorescence with a strong excitation anisotropy which is correlated with the macroscopic crystal axises. Polymerized films transferred onto wafers with thermally grown silicon oxide were investigated by atomic force microscopy. In the polymeric domains, stripelike corrugations were found with an orientation parallel to the fluorescence polarization. At high magnifications molecular resolution images were obtained. The lattice constants of the crystalline arrangement of the lipids area=0.51±0.03 nm,b=0.48±0.06 nm, α=74±7°. Lateral force images revealed that the friction between tip and sample is dependent on the orientation of the polymer backbone with respect to the fast scan direction.

ISSN:0734-2101    

DOI:10.1116/1.578925

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

There is a considerable interest in the use of biological materials in electronic device applications. For example the purple membrane, a photoactive biological material, may have an application in artificial retinas. To fabricate devices such as artificial retinas from the purple membrane, a means of patterning the biological material on the substrate surface is needed. We have explored the use of self‐assembled monolayers to achieve the control of the adsorption of the purple membrane to a glass surface. By changing the terminal group of the self‐assembled monolayer, the affinity of the surface for the purple membrane is controlled. The adsorbed purple membrane films have been examined with x‐ray photoelectron spectroscopy and fluorescence microscopy. The x‐ray photoelectron spectroscopy data reveal that the purple membrane adsorbs to a clean glass surface in the amount 0.84 μg/cm2. Modifying the glass surface with a fluorocarbon‐based self‐assembled monolayer reduces the amount of purple membrane adsorbed by a factor of 9.3, to 0.09 μg/cm2. In the future, these results combined with one of the existing methods for patterning self‐assembled monolayers, will provide a means of spatially controlling the adsorption of the purple membrane on a substrate. Thus, this work represents an important first step in the patterning of purple membrane structures and devices on a surface.

ISSN:0734-2101    

DOI:10.1116/1.578926

出版商:American Vacuum Society    

年代:1994

数据来源: AIP