DOI: 10.13020/yqn3-ft61
title: Supporting Data for Permeability–Strength Tradeoff in Nanoporous Polyethylene Membranes Derived from Etchable Triblock Polymer Precursors

description: These files contain primary data along with associated output from instrumentation supporting all results reported in Hoehn and Hillmyer, "Permeability–Strength Tradeoff in Nanoporous Polyethylene Membranes Derived from Etchable Triblock Polymer Precursors". In this work we show the strength and toughness of nanoporous polymeric materials can limit their implementation in high performance applications. One way to increase membrane strength without using supports is to reduce membrane void fraction (f_void); however, this can negatively impact permeability. We explored this permeability–strength tradeoff using a library of polylactide-block-polyethylene-block-polylactide triblock polymers which served as precursors to nanoporous membrane materials. The triblock polymers were processed using a solvent casting technique followed by selective polylactide (PLA) removal and oxygen plasma etching to yield nanoporous polyethylene (PE) membranes. The volume fraction of the etchable block (f_PLA) allowed precise control of f_void by modifying the PLA content, determination of the compositional window for network connectivity, and elucidation of relationships between membrane porosity, permeability, and membrane strength. At f_PLA 0.27, isolated PLA domains were unable to be completely hydrolyzed, making these compositions unsuitable for nanoporous membrane generation, and at f_PLA&gt;0.74 we observed a transition from percolating network into isolated PE domains that were also not useful for membrane applications. Between f_void = 0.27 to 0.74, we observed a clear permeability–strength tradeoff, where lower void fraction membranes had high yield stresses (σy = 11–14 MPa) and elastic moduli (E = 400–700 MPa), but low air permeability (6,000 L m2 hr–1 bar–1 at 0.28 bar). In contrast, high porosity membranes exhibited lower yield stresses (σy = 2–8 MPa) but higher air permeabilities (up to 8,000 L m2 hr–1 bar–1 at 0.28 bar). These findings enable future research to strategically tailor block polymer compositions to achieve desired mechanical properties and permeability in nanoporous membranes derived from block polymers.
description: The accompanying files are organized by characterization technique within individual folders (i.e., NMR, DSC, etc.). Within each folder raw data is named based on the sample ID and test type.cheme and structure files are present as Chemdraw files (.cdxml) and images (.png). Nuclear Magnetic Resonance (NMR) files (folders for individual samples and .mnova) can be opened with MNOVA. Size exclusion chromatography (SEC) files (.csv) can be opened with Excel and are present with column 1 representing the elution time in minutes, column 2 representing the light scattering intensity, and column 3 representing the differential refractive index. Thermogravimetric analysis (TGA) files (.csv) can be opened with Excel and are present with time (minutes, column 1), temperature (degree C, column 2), and mass loss percentage (column 3). PLA etching mass analysis files (.csv) can be opened with Excel. Data compares mass before and after etching to determine mass fraction lost and final void fraction of membrane. Small angle X-ray scattering (SAXS) files (.csv) can be opened with Excel and are shown with q-vectors (column 1), scattering intensity (column 2), and error (column 3). Fourier-Transform Infrared (FTIR) spectroscopy files (.CSV) can be opened with Excel and with wavenumber (1st column, cm^-1) and transmission intensity (2nd column). Nitrogen sorption analysis files (.csv) can be opened with Excel and include isotherms and pore size distributions from density functional theory (DFT) analysis. Raw data is also provided in .qps format which can be opened with ASiQwin software. Differential Scanning Calorimetry (DSC) files (.csv) can be opened with Excel and are exported with columns 1-2 representing the temperature and heat flow during the first heating cycle, columns 4-5 representing the temperature and heat flow during the first cooling cycle, and columns 7-8 representing the temperature and heat flow during the second heating cycle. Tensile testing files (.csv) can be opened with Excel; columns are labeled with respective data. Samples are identified in the first row. Air permeability data files (.csv) can be opened with Excel. Data for each membrane type is reported in separate .csv files. Replicates for each membrane type are grouped, where each test is denotated by in the first row. Within each grouping, volumes of permeated gas are reported at their corresponding timepoints at for various pressures. Flux and permeability for each membrane type are also calculated at each pressure. Water contact angle image files are in .bmp format, and contact angle measurements are in .csv files. Scanning electron microscopy (SEM) images files are in .tiff format. Images shown of membranes (after PLA etching) with 2 nm platinum deposited. Images first organized by Figure (i.e., Figure 2A) followed by description of sample. Chemdraw files are saved in both .cdxml (Chemdraw) and .tiff format.