Temperature-Dependent Reversibility of Epitaxy between Isotactic Polystyrene and Polypropylene

Abstract

Epitaxial crystallization of isotactic polystyrene (iPS) on the oriented isotactic polypropylene (iPP) substrate and the reverse process, that is, epitaxial growth of iPP crystals on the oriented iPS film initially generated by epitaxy of it on iPP, have been investigated through transmission electron and atomic force microscopies. Epitaxy of iPS on the ordered iPP substrate was achieved by cold crystallization of an amorphous thin film at 130 °C for 2 h. The results indicate that epitaxy of iPS on the iPP substrate has parallel chain relationship. Epitaxial growth of iPP on the oriented iPS film was realized by selective melting of the iPP in the epitaxial iPP/iPS system at 190 °C for 5 min and then crystallizing at varied temperatures. It was found that oriented recrystallization of iPP on the itself-induced iPS epitaxially oriented substrate occurs at temperatures below 30 °C and produces exactly the same parallel mutual chain alignment, indicating the reversibility of epitaxy between iPP and iPS. It does, however, not happen at temperatures over 60 °C, reflecting a temperature-dependent epitaxial growth of iPP on iPS oriented films. This was explained by secondary nucleation and indicates that a larger dimension of substrate crystals than the depositing epitaxial ones is necessary for the occurrence of polymer epitaxy. This provides a theoretical basis for the substrate selection of polymer epitaxies.

Seeded Epitaxial Growth of Crystallizable Polymers Governed by Crystallization Temperatures

“…For example, using a 2D PCL platelet micelle formed at 4 °C as a crystalline substrate, the attempt to grow a second layer of PCL crystal at 25 °C results in a defective platelet micelle, which is another evidence in terms of core matching requirement in their lamellar thicknesses. Our finding is well consistent with the temperature-dependent surface-induced crystallization of isotactic polypropylene ( i PP) on highly oriented isotactic polystyrene ( i PS) films reported by Yan’s group …”

“…Our finding is well consistent with the temperature-dependent surface-induced crystallization of isotactic polypropylene (iPP) on highly oriented isotactic polystyrene (iPS) films reported by Yan's group. 64…”

A β-Form Crystal Modification of Poly(glycolic acid): Formation, Stabilization, and β–α Transition

“…Polymer crystallization is a typical nonequilibrium physical concept, which regards a multiscale process from random coil state to ordered crystalline state. − According to the conformation and stacking of the molecular chains in the crystalline state, many semicrystalline polymers exhibit a variety of crystal modifications, namely, polymorphic polymers. − The formation of specific crystal modification depends on a combination of factors such as crystallization kinetics, thermodynamic stability of crystals, external force, and selective nucleation agent. − Polymorphic polymers with different crystal modifications often exhibit varying physical properties, − as evidenced by notable examples like polypropylene and polybutene-1 . The studies on the crystalline phase transition of polymers have attracted much attention over the years.…”

Directional Epitaxy Intensifying Intermolecular =C–H···O=C Hydrogen Bonding to Expedite Bulk Crystallization of Biobased Poly(butylene 2,5-furandicarboxylate)

“…33 Meanwhile, a molecular-level comprehension of the epitaxial mechanism remains controversial and is still far from conclusive. 15,[21][22][23][24][25][26][27][28][29]32,33 Therefore, understanding and controlling polymer crystallization via epitaxy especially in bulk materials on foreign surfaces have been and remain to be a serious challenge in polymer physics. [13][14][15][16][17]33 Furan-aromatic polyesters produced from biomass-derived furandicarboxylic acid (FDCA) are considered the renewable alternatives of petrol-based benzene-aromatic polyesters.…”