| Popis: |
Polyolefins—such as polyethylenes (PEs), polypropylenes (PPs), and ethylene-propylene copolymers [P(E-co-P)s]—are among the most commonly utilized synthetic polymers. Despite having simple elemental compositions consisting of only carbon and hydrogen, their physical properties are known to be highly dependent on their microstructural features, such as short- and long-chain branchings, stereoregularities, chemical inversions during monomer enchainment, sequence distributions, etc. High-resolution pyrolysis-gas chromatography (Py-GC), which incorporates the pyrolysis-hydrogenation technique and high-resolution capillary column separation, also provides a simple but powerful technique to study the microstructures of polyolefins. Many physical solid-state and solution properties of PPs are strongly affected not only by the average molecular weight and the molecular weight distribution, but also by configurational characteristics such as the average stereoregularity, stereospecific sequence length, and the degree of chemical inversion of the monomer units along the polymer chains. The decomposition of the polymer sample into monomers and dimers results in the complete loss of information regarding its stereoregularity. |
