Poly films measurement methods

X-ray diffraction techniques can be used to establish the structure of crystalline polymers. Measurements are typically made on crystalline lamellar platelets grown from dilute solution, fibres or stretched films. Such methods have been applied to several different inorganic polymers. For example, based on measurements on stretched samples of silicone rubber, poly(dimethylsiloxane) (Me2SiO) has been shown to possess a helical conformation (Figure 8.4). ... 

Etchenique and Calvo [75, 76] developed a fast real time measurement of R and XL element of the electroacoustic impedance applied the LEM model of Martin to measure the rheological properties of poly(allylamine)-GOx hydrogels under fast electrochemical perturbations and derived the viscoelastic properties of the film from the quartz equivalent parameters. For thin viscoelastic films, this method was able to separate the mass due to ions and solvent exchange and the viscosity changes, when the density and the elasticity of the overlayer was known. 

Although the electronic conductivity of an interphase that is present on an electrode can be related to various optoelectronic properties that are also measurable with spectroscopic techniques, the direct measurement of surface conductivities is not a spectroelectrochemical method. It is nevertheless a surface sensitive method that provides results closely related to those of other methods discussed in this book. Data on the electrosorption of alcohols on gold electrodes [45] or the electrode potential dependent conductivity of intrinsically conducting polymers [46] have been obtained with in situ surface conductivity measurements. Figure 4.4 shows the electrical resistance of a poly(2-propylaniline) film measured in situ under experimental conditions suppressing any influence of solution phase conduction. The influence of... 

C. Permeability coefficients of poly(vinyl alcohol) andEVAL-F fix>m different laboratories are very different according to the measuring conditions and film preparation methods because poly(vinyl alcohol) and EVAL-F are very sensitive to humidity. 

Variation in IR spectra of a thin poly(methyl methacrylate) PMMA film measured with different methods are shown in Fig. 3.26 [7]. The vC = O band at 1730 cm is the most distorted due to its relatively high oscillator strength. 

Figure 3.26. Comparison of simulated spectra for poly(methyl methacrylate) (PMM/ film measured with different methods (a) decay constant, a/IOOO, (b) transmission d2=2[im, ip- =0°), (c) ATR (n- =2.4, =45°, s-polarization), (d) IRRAS on Au ( >i =0°), (e) IRRAS...

As will be shown in the theory, the electrostriction effect plays an important role in the piezoelectric effect of polymer films. Moreover, a knowledge of the complex electrostriction constant as a function of frequency reveals a new aspect of the relaxational behavior of polymers. In this review a new method for measuring complex electrostriction constant with varying frequency will be presented with some results for poly(vinylidene fluoride). 

The results illustrated above show that the CFT method is suitable for making chemical-sensor measurements using both bulk polymers and, in particular, thin film materials that are intrinsically weak conductors. Therefore, the CFT looks premising for such materials as poly(phenylacetylene) derivatives 24., for which carefully shielded electrometer measurements have been required in the past because of current levels at the threshold of detectability. Furthermore, the fact that the CFT always makes AC measurements reduces the problem of DC polarization of electrodes. In addition, the CFT approach should be suitable for other "chemiresistor" applications, such as the metal-substituted phthalocyanines proposed by Jarvis et. al. 2 and for Langmuir—Blodgett films 26. which, because they are so thin, may prove impossible to use in parallel-plate form, but which can be routinely used with the high-sensitivity interdigi-tated-electrode approach provided by the CFT. 

Polyimide surface modification by a wet chemical process is described. Poly(pyromellitic dianhydride-oxydianiline) (PMDA-ODA) and poly(bisphenyl dianhydride-para-phenylenediamine) (BPDA-PDA) polyimide film surfaces are initially modified with KOH aqueous solution. These modified surfaces are further treated with aqueous HC1 solution to protonate the ionic molecules. Modified surfaces are identified with X-ray photoelectron spectroscopy (XPS), external reflectance infrared (ER IR) spectroscopy, gravimetric analysis, contact angle and thickness measurement. Initial reaction with KOH transforms the polyimide surface to a potassium polyamate surface. The reaction of the polyamate surface with HC1 yields a polyamic acid surface. Upon curing the modified surface, the starting polyimide surface is produced. The depth of modification, which is measured by a method using an absorbance-thickness relationship established with ellipsometry and ER IR, is controlled by the KOH reaction temperature and the reaction time. Surface topography and film thickness can be maintained while a strong polyimide-polyimide adhesion is achieved. Relationship between surface structure and adhesion is discussed. 

Figure 7 shows CO2 evolution from the PET films with different thermomechanical histories and consequent differences in film thickness, ciystallinity and molecular orientation (9). In all three cases strong CO2 generation was observed and could be measured with good repeatability. Similar measurements have been made on poly(8-caprolactone) (PCL) and on PCL/PVC blends (10). These measurements on different polyesters demonstrate the applicability of the CO2 method to materials for which carbonyl absorption measurement is not very suitable. 

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