Probing the tightly bound layer in poly(vinyl alcohol) thin films using swelling measurements

Abstract

A strongly adsorbed, tightly bound polymer layer can exist at the polymer/substrate interface in polymer thin films and polymer nanocomposites. The characteristics of the tightly bound layer have long been...

Determining the Characteristics of Ultrathin Polymer Films: A Spectroscopic Ellipsometry Approach

“…As the thin film samples were verified to be optically transparent (extinction coefficient, k ≈ 0), the λ dependence of the refractive index can be modeled using the Cauchy dispersion equation given by, n false( λ false) = A + B λ 2 + C λ 4 where the A , B , and C are fit parameters. The C in eq has often been set to 0 without significantly affecting the quality of the fits. − ,,, In the current work, we have verified that the inclusion of the term corresponding to C reduced the RMSE by less than 0.5%. In addition, the values of B and C were highly correlated which suggested that one of the two might be redundant.…”

“…After thoroughly rinsing with DI water and flushing with dry nitrogen gas, the substrates retained a SiO 2 layer of thickness of approximately 2 nm. Past literature has reported the presence of an oxide layer of similar thickness after such a treatment. ,,, Thin films of chitosan of varying thicknesses were produced by spin coating for 60 s at maximum speeds ranging from 3000 to 9000 rpm achieved using rotational accelerations of either 60 or 100 rpm/s.…”

“…Recent developments in hardware and software have rendered the technique particularly easy to use − not only on single-layer but also on multilayer thin films. , The aforementioned features, when combined, have enabled the widespread use of the technique in a range of industries from semiconductors to medicine . For instance, ellipsometry has been extensively used to investigate thermal transitions, , especially the glass transition, − swelling kinetics in the presence of various solvents and their vapors, − and optical anisotropy ,,− in a wide range of polymeric systems, including homopolymers, copolymers, and composites.…”

“…For instance, AOI close to the Brewster’s angle, θ B , are considered near optimal where the ellipsometry measurement is expected to exhibit high sensitivity − to the values of the fit parameters. Given that for silicon (Si), θ B ≈ 74° at λ ≈ 633 nm, − and partly for historical reasons, ellipsometric measurements of polymer thin films on Si substrates are commonly performed at an AOI ≈ 70°. ,,,,,, Similarly, for glass substrates, as the θ B ≈ 55° at λ ≈ 633 nm, , measurements are performed at an AOI ≈ 60°. , In summary, most measurements on thin films are performed at an AOI between 45° and 80°. ,,,− ,,− ,, Therefore, depending on the range of variation of the physical quantities under investigation, this necessitated preparatory experiments to identify the optimal AOI and λ at which the data were most sensitively dependent on the values of the parameters to be determined from the fits. ,,− , However, such preparatory experiments become unnecessary when using Variable Angle Spectroscopic Ellipsometry (VASE) capable of measuring at multiple AOI and λ.…”

Roles of aqueous nonsolvents influencing the dynamic stability of poly-(n-butyl methacrylate) thin films at biologically relevant temperatures

“…1,13,15 Preparation and processing conditions can be manipulated in bringing about thermomechanical changes in confined thin polymer films. 16–21 The practical difficulty in probing the properties of such thin films using traditional conventional mechanical testing techniques resulted in the development of nonconventional complementary techniques like dewetting, 22,23 wrinkling, 24,25 TUTTUT, 26 capillary leveling, 27 etc. The simplicity of the dewetting process and the ability to understand the polymer chain segment level properties make it a very useful technique.…”