Roberta Saini

Influence of regioirregular structural units on the crystallization of isotactic polypropylene

Seven samples of isotactic polypropylene were examined to study the influence on the formation of the y crystalline phase of possible regiodefects along the chain. Wide-angle X-ray diffraction allowed the determination of the percentage of the γ phase in the samples and 13 C-NMR spectroscopy was used to correlate the development of the y phase with the existence of regioirregular structural units along the chain. Furthermore, it was possible to appraise the contributions given by the different families of lamellae to the small-angle X-ray diffraction patterns.

A direct SAXS approach for the determination of specific surface area of clay in polymer-layered silicate nanocomposites.

The interfacial area between the matrix and the filler is a key parameter which shapes the performance of polymer-based composites and nanocomposites, even though it is difficult to quantify. A very easy SAXS method, based on the Porod equation, is proposed for measuring the specific surface area of nanofillers embedded in a polymer matrix. In order to assess its reliability, this approach was applied to natural rubber- or styrene butadiene-based samples containing different types of montmorillonite clay. A wide range of specific surfaces was detected. SAXS data were compared to complementary X-ray diffraction and TEM information, obtaining a good agreement. Interpretation of the tensile properties by theoretical models and comparison with the literature corroborated the validity of the specific surface area measurement. The possibility to quantify this feature of composites allows the rational design of such materials to be improved.

Preparation and Characterization of Conductive Polymer Blends of Polypyrrole and Poly(ethylene oxide)

Conductive polymer blends of polypyrrole (PPy) and poly(ethylene oxide) (PEO) were obtained in the form of films and fibers, respectively by solvent casting and electrospinning. Different amounts of PPy were introduced in the blends in order to study the effect of the conductive polymer on the properties of the final material and in particular to elucidate the influence of the different morphology on conductivity. The structure and morphology of PPy/PEO blends were characterized by wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to understand the influence of different PPy content on thermal behavior and stability, electrospun fibrous mats were examined by scanning electron microscopy (SEM). The conductivity of the films and fibrous mats was measured and correlation with morphology was highlighted.