Adding fillers to polymer, thereby creating polymer composites, leads to significantly improved properties relative to native polymers. This presentation focuses on a molecular understanding of basic mechanisms that are important for the reinforcement in polyolefins. The key role in this process is ascribed to a bound polymer that physically adsorb on the filler surface and engages with the matrix as well as with adjacent fillers. So far, this understanding on a molecular scale was impeded by the lack of experimental tools to directly probe the bound chains buried in a polymer matrix composed of the same polymer. In order to provide insight into the structure and dynamics of the bound polymer, we used a carbon fiber (CF) filled isotactic polypropylene (iPP) system as a rational system. Based on previous experience, we prepared bound chains composed of hydrogenated iPP on CF surfaces. Utilizing neutron small angle scattering and neutron backscattering scattering techniques, both the structure of the bound chains (in a deuterated solvent) on the nm scale as well as the segmental dynamics on scales up to nearly 2 ns were probed. In addition, we mimicked the interface using iPP thin films deposited on carbon layer coated planar silicon substrates. The crystalline structures and the melting behavior of the bound polymer layer (extracted after a solvent rinsing process) were investigated by using atomic force microscopy and grazing-incidence X-ray diffraction and small-angle x-ray scattering. We will also discuss the effect of maleic acid groups, which were introduced to improve the compatibility with CF, on the structures and dynamics of the bound polymer.

Unraveling the interfacial structures and dynamics of polypropylene/carbon fiber composites

ACS Spring 2022

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