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ABSTRACT Rotational and oscillatory shear rheometry were used to quantify the flow behavior under minimal and significant solvent evaporation conditions for polymer solutions used to fabricate isoporous asymmetric membranes by the self‐assembly and non‐solvent induced phase separation (SNIPS) method. Three different A‐B‐C triblock terpolymer chemistries of similar molar mass were evaluated: polyisoprene‐b‐polystyrene‐b‐poly(4‐vinylpyridine) (ISV); polyisoprene‐b‐polystyrene‐b‐poly(N,N‐dimethylacrylamide) (ISD); and polyisoprene‐b‐polystyrene‐b‐poly(tert‐butyl methacrylate) (ISB). Solvent evaporation resulted in the formation of a viscoelastic film typical of asymmetric membranes. Solution viscosity and film viscoelasticity were strongly dependent on the chemical structure of the triblock terpolymer molecules. A hierarchical magnitude (ISV > ISB > ISD) was observed for both properties, with ISV solutions displaying the greatest solution viscosity, fastest film strength development, and greatest strength magnitude. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2019,136, 47038.
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A Unified Picture of Aggregate Formation in a Model Polymer Semiconductor during Solution Processing
Abstract One grand challenge for printed organic electronics is the development of a knowledge platform that describes how polymer semiconductors assemble from solution, which requires a unified picture of the complex interplay of polymer solubility, mass transport, nucleation and, e.g., vitrification. One crucial aspect, thereby, is aggregate formation, i.e., the development of electronic coupling between adjacent chain segments. Here, it is shown that the critical aggregation temperatures in solution (no solvent evaporation allowed) and during film formation (solvent evaporation occurring) are excellent pointers to i) establish reliable criteria for polymer assembly into desired aggregates, and ii) advance mechanistic understanding of the overall polymer assembly. Indeed, important insights are provided on why aggregation occurs via a 1‐ or 2‐step process depending on polymer solubility, deposition temperature and solvent evaporation rate; and the selection of deposition temperatures for specific scenarios (e.g., good vs bad solvent) is demystified. Collectively, it is demonstrated that relatively straightforward, concurrent in situ time‐resolved absorbance and photoluminescence spectroscopies to monitor aggregate formation lead to highly useful and broadly applicable criteria for processing functional plastics. In turn, improved control over their properties and device performance can be obtained toward manufacturing sensors, energy‐harvesting devices and, e.g., bioelectronics systems at high yield.
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- Award ID(s):
- 2108123
- PAR ID:
- 10558802
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Functional Materials
- Volume:
- 34
- Issue:
- 50
- ISSN:
- 1616-301X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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