Mechanical spectroscopy of laser deposited polymers

Abstract

Pulsed laser deposition (PLD) at 248 nm in ultra high vacuum was used to produce thin poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) films. The ablation and deposition mechanisms were found to be similar in both systems. Having the same backbone, these polymers differ in the size of their polar side groups leading to changes in their dynamics. Studies of the relaxation processes were performed using mechanical torsion and bending spectroscopy by means of a doublepaddle oscillator (DPO) and an in-situ plasma plume excited reed (PPXR), respectively. A strong increase of the mechanical damping was observed during annealing of the polymer films well above the glass transition temperature T g , while in-situ X-ray measurements did not reveal any structural changes. For PEMA, the glass transition temperature T g = 335 K and the main absorption maximum appear at lower temperatures compared to PMMA (T g = 380 K), allowing one to measure the mechanical properties in a much wider range above T g .

Relaxation Processes of Poly(tert‐butyl acrylate) Chemically Confined via Hydrogen Bonds

“…This field is well‐accessible via mechanical spectroscopy, which represents a powerful technique for the determination of relaxation modes 4–8. This spectroscopy is qualified for measuring and following changes in the modulus below and above the glass transition temperature, as, for example, the change from γ‐ over β‐ to α‐processes in polymers and in metallic glasses 4, 6, 9. This method is also capable of determining systematic changes in the relaxation spectra, which are produced, for example, by sterically demanding side groups or a chemical confinement (cc) 4, 7, 10…”