Surface chemical analysis of avcothane and biomer by Fourier transform IR internal reflection spectroscopy

Abstract

During the solvent casting process, one side of the polymer film is exposed to air while the other side is in contact with a substrate, used as a mold. We have studied the effect of this difference in exposure during casting on the chemical composition of two types of segmented polyurethane, Biomer and Avcothane, by using Fourier transform IR internal reflection spectroscopy. Also, a depth-composition profile was obtained by placing a thin barrier film between the reflection plate and the polymer film. In Avcothane, the air side, which is the blood-contact side, contains a greater amount of the soft segment than the substrate side, and this is more pronounced in the layer closer to the surface. The anisotropy in composition is more drastic when the silicone content is compared. In a layer about 1.5 mu thick, one can detect a greater amount of silicone in the substrate side than in the air side. However, when one averages the concentration in a layer of about 0.8 microns the trend in reversed; i.e., the greater amount of silicone is now present in the air side than in the substrate side. In Biomer films, the anisotropy in chemical composition is less pronounced. Only a modest increase in the relative content of the soft segment/hard segment is observed in the air side when a depth-composition profile is obtained.

Structure and Properties of Membrane Surfaces of A-B-A Tri-Block Copolymers Consisting of Poly(γ-methyl D,L-glutamate) as the A Component and Polybutadiene as the B Component

“…Merrill et a/. 10 investigated semiquantitatively the relation between the surface composition and thrombogenic potential of segmented polyurethanes by Fourier transform IR internal reflection spectroscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. They found that the composition of these block copolymer membranes at the surface is not necessarily identical to that in the interior if the surface free energy is allowed to act.…”

Structure and composition of the surface of urethane/acrylic composite latex films

“…Thus, the peak at 1550 cm −1 for the stretching vibration of –CONH– group is used as an index for the concentration of polyurethane component, the peaks at 761 cm −1 and 841 cm −1 for the aromatic ring, and–OC 4 H 9 absorbing indicates the concentration of butyl acrylate–styrene copolymer, and therefore the relative concentration of the polyurethane component to the butyl acrylate–styrene copolymer for air‐facing surfaces and substrate‐facing surfaces can be derived from the absorbing intensities of these characteristic peaks, as summarized in Table 3. Table 3 also lists the depth of penetration at some characteristic peaks based on the Harrick equation 6. The relative absorbing intensities of these peaks in the transmission FTIR spectra for the corresponding composite latex bulks, in terms of average composition, are also calculated and shown in Table 3.…”

“…Figure 5 displays a representative XPS survey for air‐facing surfaces of the films obtained from composite latex and blend latex. The binding energies of O 1s and N 1s are about 534–540.0 eV and 402.0 eV, respectively, corresponding to π‐bonded oxygen (O = C), σ‐bonded oxygen (O–C) and σ‐bonded nitrogen (N–C), respectively 6. The binding energies of C 1s are about 283–292 eV.…”

“…Scanning was repeated at least 200 times before the spectra were recorded at a resolution of 2 cm −1 . The penetration depth ( d p ) of sampling is described by the Harrick equation6 where θ is the angle of incidence with respect to the surface normal, n 21 is the ratio of the refractive indexes of the sample ( n 2 ) and the internal reflection element ( n 1 ). The refractive index of ZnSe ( n 1 ) is 2.4, and most organic materials have a refractive index about 1.5, so that the depths of penetration at some characteristic absorbing peaks can be calculated 7…”

Gas Permeation through Polymer/Liquid Crystal Composite Membrane

“…Infrared spectra were obtained by the transmission and attenuated total reflection (A TR) methods, using a Perkin-Elmer 567 Grating Infrared Spectrometer. For the A TR method, the depth of IR beam penetration, dP, was calculated by 15 (1) (2) where n 1 , n 2 , 8, and A. are the refractive indices of the reflection plate (2.37 for KRS-5 16 ) and the sample (1.45 for the PCjEBBA composite membrane), the effective incident angle (45°) and the wavelength of a characteristic absorption band, respectively. n 2 was evaluated, assuming the additivity of the refractive indices of PC 17 and EBBA.…”