Macromolecular Chemistry and Physics, 2018, vol 219, 23, pp. 1800362
In this study, different degrees of ethylene-confined polymerization (non-confined, slightly confined, and highly confined) are presented in porous polymer microspheres (PPMs) with an interconnected tri-modal pore structure. First, three catalysts, Cp2ZrCl2, Cp2TiCl2, and TiCl4, are attached to the interface of PPMs to form a nano-confined space for ethylene polymerization. Then three types of polyethylene with different degrees of ethylene-confined polymerization are obtained through polymerization. Results of SEM, BET, FTIR, XPS confirm the existence of the interconnected tri-modal pore structure in PPMs after catalyst loading, which can provide nanospace for confined polymerization. Typical characteristics of confined polymerization (nanofibers and high molecular weight) are observed through SEM and GPC tests. The results reveal that polyethylene by PPM-supported TiCl4 is performed as a highly confined reaction and generates microspheres with the highest molecular weight and T m2. In addition, the product is line polyethylene (PE) regardless of the degrees of confined polymerization. The data of SAXS reveal that high melting point of confined PE is owed to low surface free energy, rather than lamellar thickness in confined space of PPMs. Furthermore, low surface free energy is ascribed to the entanglement of PE chain, which is caused by the interconnected tri-modal pore structure.