Nanoextrusion or synthesis in confinement is one of the most promising methods for production of polymeric nanofibers. While many arguments exist for pressure-driven extrusion of nanofibers with chain-extended crystals out of confinement, and, thus, need to use of stable and mechanically strong nano-templates, some evidence puts this process in doubt. Unlike previous reports, here we reported rather mechanically weak clay layered structure can be used as confined polymerization nano-template. Ziegler-Natta catalyst supported between clay galleries with and without MgCl<sub>2</sub>, in order to provide polymerization media without and with nanoconfinement, respectively. Microscopic images showed a considerable amount of nanofibers with various lengths and diameters only in the sample that produced under confinement. The diameters of detectable single nanofibers are typically in the range around 30 to 50 nm, rarely exceeding 50 nm. The nanofibrous sample showed significant differences between melting peaks temperature and heat of fusion in the first and second heating scans of DCS tests. Structural and morphological analysis along with considering weak interlayer interactions of clay layers support showed that pressure driven extrusion is not the only reason for nanofiber formation. While our data shows that reduction in entanglement density for synthesized polymers in confinement, their phase separation and assembly is responsible here for fibrous morphology, relating high melting point of the first DSC scan to presence of chain-extended crystals or just weakly entangled polymer network is not conclusive.

Formation mechanism of polyethylene nanofibers produced via polymerization in confinement

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.