A Mechanistic Investigation of the Directional Entrapping Modification on the Semicrystalline Polypropylene Surface

This article concerns a detailed mechanistic investigation of the directional entrapping modification on the polypropylene (PP) surface, when stearyl-alcohol poly(ethylene oxide) ether (AEO) was applied as the modifier. The results of swelling degree and contact angle are found to exhibit similar evolutions as functions of swelling temperatures and swelling time, revealing that the modifier implantation is closely related to the swelling level of swollen PP. A solvent-induced crystallization (SINC) and a subsequent crystalline collapse are indicated to occur during surface swelling. Both the amorphous regions on PP surfaces and the microvoids induced by SINC are suggested to contribute to surface swelling and to provide embedding sites for modifier implantation. XRD and DSC analyses reveal a considerably homogeneous distribution of the stearyl segments of AEO in modified surfaces and confirm that the stearyl chain is partially compatible with PP. A thermodynamically stable phase-mixed structure of modified PP is proposed. The mechanistic investigation gives comprehensive insights into the directional entrapping modification and is significant for the extensive applications of the entrapping method for semicrystalline polymers.