Abstract We report a new nanoconfinement phenomenon whereby surface confinement leads to the amorphization of polyethylene oxide (PEO) in porous ultrahigh molecular weight polyethylene membrane (UHMWPE). The surface confinement was… Click to show full abstract
Abstract We report a new nanoconfinement phenomenon whereby surface confinement leads to the amorphization of polyethylene oxide (PEO) in porous ultrahigh molecular weight polyethylene membrane (UHMWPE). The surface confinement was achieved through a monolayer attachment of PEO onto the UHMWPE nanofibril surfaces‒pore bounding edges‒in the membrane via amphiphilic interactions of polypropylene oxide (PPO) blocks in the triblock copolymer of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO). Full amorphization of PEO is corroborated through the lack of phase transitions under differential scanning calorimetry (DSC), and liquid-like vibrational absorption responses under Fourier transform infrared spectroscopy (FTIR). Monolayer confinement of PEO in the membrane is quantified using a combination of Brunauer-Emmett-Teller (BET), time-of-flight secondary ion mass spectrometry (ToF-SIMS) molecular depth profiling and scanning electron microscopy (SEM). The total amount of PEO confined in the porous membrane is 7.7 wt% agreeing with that expected from the total BET surface area of the UHMWPE membrane; ToF-SIMS depth profiling using argon cluster ion reveals the homogeneous PEO distribution along the membrane depth; and surface topology analysis by SEM shows no obvious topological changes after PEO confinement.
               
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