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Abstract Tailor‐made auxiliaries are generally less stereochemically discriminating of crystals grown from the melt than crystals grown from solution. However, it is possible to make supramolecular inferences using well‐chosen additives in the manner taught to us by Lahav and Leiserowitz. Spherulites manifesting needle‐like growth and small angle branching grow frequently from supercooled melts under high crystallization driving forces, along one principal crystallographic direction. If this direction is polar, it is important to establish its absolute sense as a basis for understanding growth at the interface between crystals and melt. This assignment, for polycrystalline ensembles, is beyond the capabilities of X‐ray crystallography. Two examples of this discrimination are described with tailor‐made additives, one for theβform of resorcinol and another for form I ofL‐malic acid. Assigning the absolute sense of a polar axis with molecular additives is a problem that resembles both the science and style of previous experiments from the Weizmann Institute.
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Orienting and shaping organic semiconductor single crystals through selective nanoconfinement
For organic semiconductor crystals exhibiting anisotropic charge transport along different crystallographic directions, nanoconfinement is a powerful strategy to control crystal orientation by aligning the fast crystallographic growth direction(s) with the unconfined axis(es) of nanoconfining scaffolds. Here, design rules are presented to relate crystal morphology, scaffold geometry, and orientation control in solution-processed small-molecule crystals. Specifically, organic semiconductor triisopropylsilylethynyl pyranthrene needle-like crystals with a dimensionality of n = 1 and perylene platelike crystals with n = 2 were grown from solution within nanoconfining scaffolds comprising cylindrical nanopores with a dimensionality of m = 1, representing one unconfined dimension along the cylinder axis, and those comprising nanopillar arrays with a dimensionality of m = 2. For m = n systems, native crystal growth habits were preserved while the crystal orientation in n = m direction(s) was dictated by the geometry of the scaffold. For n ≠ m systems, on the other hand, orientation control was restricted within a single plane, either parallel or perpendicular to the substrate surface. Intriguingly, control over crystal shape was also observed for perylene crystals grown in cylindrical nanopores ( n > m ). Within the nanopores, crystal growth was restricted along a single direction to form a needle-like morphology. Once growth proceeded above the scaffold surface, the crystals adopted their native growth habit to form asymmetric T-shaped single crystals with concave corners. These findings suggest that nanoporous scaffolds with spatially-varying dimensionalities can be used to grow single crystals of complex shapes.
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- Award ID(s):
- 1846178
- PAR ID:
- 10212225
- Date Published:
- Journal Name:
- Soft Matter
- ISSN:
- 1744-683X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D0SM01928C
