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Efficient Creation and Morphological Analysis of ABC Triblock Terpolymer Libraries

Citation

Murphy, Elizabeth et al. (2022), Efficient Creation and Morphological Analysis of ABC Triblock Terpolymer Libraries, Dryad, Dataset, https://doi.org/10.25349/D9NG89

Abstract

Multiblock copolymers with increasingly complex block sequences—for example, triblock terpolymers—offer unique opportunities to create nanostructured materials, but this potential has been hindered by a vast design space that complicates the exploration of structure–property relationships. Here, we report a versatile and scalable strategy to separate parent ABC and isomeric ACB triblock terpolymers into libraries of fractionated samples spanning a wide range of compositions. Using a combination of controlled polymerization and automated chromatography, the synthesis and separation of less than 10 ABC and ACB parent materials gave rise to over 100 purified triblock terpolymers. Separations follow systematic and predictable trends in volume fraction resulting from an adsorption-based mechanism where chains rich in non-polar blocks elute first followed by more polar derivatives, yielding fractions with improved purity in composition and molar-mass dispersity. As evidenced by small angle X-ray scattering (SAXS), fractionation significantly enhances long-range order compared to as-synthesized parent materials and allows for the definitive identification of various nanoscale morphologies. This user-friendly separation strategy significantly increases the availability of well-defined ABC triblock terpolymer libraries to the polymer community while also improving sample quality and accelerating discovery.

Methods

Nuclear Magnetic Resonance Spectroscopy: Solution state 1H nuclear magnetic resonance (NMR) spectra were recorded on a Varian 600 MHz spectrometer. Chemical shifts (δ) are reported in ppm relative to residual protio-solvent in CDCl3 (7.26 ppm).

Size Exclusion Chromatography: Size-exclusion chromatography (SEC) was conducted on a Waters Alliance HPLC System, 2690 Separation Module using chloroform with 0.25% triethylamine as the eluent with a flow rate of 0.35 mL/min. Refractive index traces from a Waters 2410 Differential Refractometer detector were used for estimates of the molar mass and dispersity relative to linear polystyrene standards with a chloroform mobile phase.

Small Angle X-Ray Scattering: SAXS measurements of bulk samples were conducted using a custom-built SAXS diffractometer at the Materials Research Laboratory (MRL) X-ray facility (University of California, Santa Barbara). For these experiments, 1.54 Å Cu Kα X-rays were generated using a Genix 50 W X-ray microsource (50 μm micro-focus) equipped with FOX2D collimating multilayer optics (Xenocs, France) and high efficiency scatterless single crystal/metal hybrid slits.

Differential Scanning Calorimetry: Differential scanning calorimetry (DSC) was performed using a TA Instruments DSC Q2000 from –90 to 55 °C at a heating/cooling rate of 10 °C/min using 3–5 mg of sample in a sealed Tzero aluminum pan.

Funding

Division of Materials Research, Award: DMR 1720256