Polymer physics: Heterogeneties and surface dependence molecular organization

In this talk, we will present some studies regarding interphases and dependences of the polymer matrix/substrate. Surfaces structuring and modification of substrates plays an important role in the studies of these dependences. For these goals, different modified surfaces can be used, chemically or physically. One type of surfaces used for these structures as PTFE (poly(tetrafluoroethylene)) nanoribbons on glass/Si substrate – a polymer induced alignment. It was observed that this anti-adhesive substrate can induce a oriented structure in polymer crystal structures like ε- PLC (poly(caprolactone)). Another type of modified surface structure used in our projects is chemically modified microstructures using micro-contact printing technique. Variation of the character of the surface, hydrophilic or hydrophobic, by chemical treatment leads to different molecular interactions and thus different interphases properties. The third polymer/substrate concept for interphases studies is a 3D network confinement: well-defined network as Al templates and inhomogeneous network as porous glasses. A selective penetration of the polymer system into pores or preferential adsorption effect will be discussed. Nanocomposites made of silica nanoparticles- reactive polymers and alumina nanoparticles-SBR (styrene-butadiene rubber) give unique mechanical properties due to the combination of high elasticity with high strength.
Investigation of interphases using different types of modified substrate will be point out from two ways: structure resolving, mechanical, dielectrical and calorimetrical properties. Conventional microscopic techniques, such as AFM and SEM, are specific for locally investigated structures on a nanometer scale. Using these complementary microscopic techniques, we are able to distinguish different topographic information of designed substrate. Moreover, in the view of the interphases investigation, HarmoniXTM AFM is used as a mechanical property mapping technique which is able to provide quantitative mechanical characterization of stiffness, elastic modulus, adhesion and energy dissipation of a polymer surface with high lateral resolution (> 20 nm). Mechanical properties are investigated using DMTA ( dynamic mechanical thermal analyzer) and TMA (thermo-mechanical analysis) - for determining the static elastic modules of solid or solid-like sample (polymer matrix), being able to analyze and characterize bulk-like sample at lower or higher frequencies than the dispersion o polymer regime. The temperature range is 80K-500K. Modulated differentia scanning calorimetry (MDSC) is used to examine chemical and physical aspect of the studied system. The simultaneous determination of chemical reaction heat and the specific heat capacity is used to study the curing behavior of nanocomposite network. Dielectric spectroscopy (DS) is a versatile tool to investigate local molecular dynamic for a polymeric/3D confinement network or nanocomposite network.