Mechanically Tough Syndiotactic Polypropylene (sPP) Gels Realized by Fast Quenching Using Liquid Nitrogen

Physical gels have attracted considerable attention due to the remoldability deriving from the reversible cross-linking points made of noncovalent bonds. In this study, we report a facile method to realize a mechanically tough syndiotactic polypropylene (sPP) gel, one of the physical gels made of semicrystalline polymers. The sPP/decahydronaphthalene gel quenched using liquid nitrogen (GEL LN) presented the fracture stress of over 2 MPa with the fracture strain as high as ∼0.7, while the sPP gel prepared at room temperature (GEL 25) presented the fracture stress of only 315 kPa and the fracture strain of ∼0.3. The fracture stress was found to increase with the increase in the sPP concentration. Furthermore, the structural analyses of the sPP gels revealed that the quenching of the sPP gel suppressed the phase separation, eventually forming homogeneous nanocrystalline cross-linking network structures to produce a mechanically tough sPP gel.