Materials Engineering Department
BS in Materials Engineering
Polymers of Intrinsic Microporosity (PIMs) are an emerging polymeric material class for molecular sieving applications. This study focuses on PIM-1, an alternating copolymer of 5,5’,6,6’-tetrahydroxy-3,3’,3,3’-tetramethyl-1,1’-spirobisindane and tetrafluoroterephthalonitrile synthesized via nucleophilic aromatic substitution. PIM-1 been widely studied as a gas separating material and filtering membrane, but in this case, it is studied as a battery separator material. PIM-1’s microporous (pore diameters less than 2 nm) structure allows smaller favorable ions to transport while preventing larger ions and compounds from transporting. Two synthesis methods, round bottom flask synthesis and ball mill synthesis, of PIM-1 are compared to see any improved characteristics. The primary goal of this study is to observe an increase in molecular weight, but other properties are evaluated as well. The calculated yield was higher for ball milled PIM-1 (51.5% round bottom flask vs. 62.8% ball mill). Size-exclusion chromatography (SEC), nuclear magnetic resonance (NMR) spectroscopy, and Brunauer- Emmett-Teller (BET) analysis were used to characterize each synthesized batch. Both PIM-1s had the same overall molecular weight (98,468 round bottom flask vs. 97,331 ball mill), but the ball milled PIM-1 had a lower polydispersity (2.372 round bottom flask vs. 1.728 ball mill). The ball-milled PIM-1 also revealed broader peaks and fewer impurities than RBF PIM-1 with NMR analysis. BET analysis revealed that both PIM-1s had similar expected porosities (658 m2/g vs. 642 m2/g). More research is needed to affirm that ball milling is a superior method.