Preparation and characterization of polypropylene/mesoporous silica nanocomposites with confined polypropylene

Abstract

Polypropylene (PP)/Ti‐MCM‐41 nanocomposites were prepared by isospecific propylene polymerization with Ti‐MCM‐41/Al(i‐C4H9)3 catalyst. The cross polarization/magic angle spinning (CP/MAS) 13C NMR spectrum of the composite was similar to that of the conventional isotactic PP, and the decrease in the pore volume of Ti‐MCM‐41 in the nanocomposites, as measured by N2 adsorption, was consistent with the value calculated from the weight loss in the thermogravimetric analysis (TGA) curve; both these facts attest to propylene polymerization within the mesopores of Ti‐MCM‐41. Alkali treatment followed by extraction with o‐dichlorobenzene allows us to extract the confined PP out of the Ti‐MCM‐41 mesopores. Although the PP/Ti‐MCM‐41 nanocomposites do not exhibit a crystalline melting point, the same PP when extracted from the mesopores showed a clear melting point at 154.7 °C; this indicates that the crystallization of PP confined in mesopores is strongly hindered. For the PP polymerized within the confinement, the molecular weight (Mw) and molecular weight distribution (Mw/Mn) were 84,000 and 4.3, respectively; these values were considerably smaller than those of the PP polymerized concurrently outside the Ti‐MCM‐41 mesopores (Mw = 200,000–450,000, Mw/Mn = 40–75). Therefore, the confinement also has a marked effect on the molecular weight of the PP. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3324–3332, 2003

Hybrid HDPE/MCM-41 nanocomposites: Crystalline structure and viscoelastic behaviour

“…But after the alkaline dissolution of the mesoporous material, the melting of PP was visible in the DSC thermogram. This experiment demonstrates that the crystallisation of nascent PP formed inside the pores of Ti-MCM-41 was prevented, due to the restrictions imposed to polymer chain mobility by confinement within MCM-41 [27].…”

“…Moreover, the half-time of crystallisation was shortened in presence of the CNT, thus pointing out its effect as nucleating agent, causing the fast crystallisation of the surrounding polymer [24][25][26]. Nakajima et al investigated PP/Ti-MCM-41 nanocomposites prepared by in situ polymerisation [27]. After removal of polypropylene formed in the outside of Ti-MCM-41 particles (by extraction with boiling xylene), the DSC analysis of the polymer remaining inside the mesoporous material did not show a melting point.…”

Self-Reinforced Hybrid Polyethylene/MCM-41 Nanocomposites: <I>In-Situ</I> Polymerisation and Effect of MCM-41 Content on Rigidity

“…14 The research papers published recently reported various methods for the synthesis of nanocomposites combining natural and synthetic zeolites, or other layered materials, with in-situ polymerisation of olefins. [14][15][16][17][18][19] The M41S materials and, in particular, the MCM-41 one with a hexagonal array of unidirectional pores show promising results when used as carriers for single-site olefin polymerisation catalysts. Moreover, they can keep steadily their 3D frameworks and the polymers formed under the extreme confinement imposed by these carriers might show unusual morphologies and mechanical properties.…”

Mesoporous silica as nanoreactor for olefin polymerization

“…Figure 7 shows the X-ray diffraction patterns of Ti-MCM-41 after propylene polymerization and the PP/Ti-MCM-41 nanocomposite [20]. The reduction in the diffraction peak intensities in the XRD pattern of Ti-MCM-41 after polymerization ( figure 7 (a)) is attributable to the formation of polypropylene.…”

“…The retention of the Ti-MCM-41characteristic diffraction peaks in the X-ray diffraction pattern of the PP/T-MCM-41 nanocomposite indicates that the hexagonal framework structure of MCM-41 -0 ----2 Al-MCM-41 13.4 Trace ----3 Ti-MCM-41 30.9 1296 153.7 42 44 38 4 Mn Ti-MCM-41 is retained during and after the propylene polymerization. Figure 8(a) shows the 13 C CP/MAS NMR spectrum of the PP/Ti-MCM-41 nanocomposite [20]. For a reference, the spectra of isotactic polypropylene (a-form, M w ¼ 190; 000, M w and M w /M n ¼ 5:2, [mmmm] = 99%) and atactic polypropylene (M w ¼ 350; 000, M w and M w /M n ¼ 4:2) are also shown.…”