Ring‐Banded Spherulitic Crystals of Poly(3‐butylthiophene) via Controlled Solvent Evaporation

Abstract

The preparation of ring‐banded spherulites in poly(3‐butylthiophene) via controlled solvent evaporation of solution‐cast films is reported. The spherulites display unusual concentric ring‐banded structures under both polarized and unpolarized lights. The size of the ring‐banded spherulites is 300 ± 100 µm in diameter and the periodicity of the bands is 15 ± 2 µm. The periodic bands of the spherulite consist of alternating ridge and valley surface patterns and the crystalline lamellae in the bands are more or less parallel to the radial growth direction of the spherulites. Local lamellar bending and branching are observed analogous to that of classical non‐conjugated polymers. A possible diffusion‐induced rhythmic growth mechanism is proposed to interpret the formation of periodic banding of the spherulite.

Supramolecular Assembly of Oriented Spherulitic Crystals of Conjugated Polymers Surrounding Carbon Nanotube Fibers

“…Figure b shows a typical optical micrograph of poly(3‐butylthiophene) (P3BT) under crossed polarizers in the absence of CNT fibers at room temperature of 20 °C. The P3BT sample demonstrates strong birefringent spherulites with characteristic Maltese cross extinction patterns, similar to the recent reports on P3BT spherulites . The diameter of spherulites is about 55 ± 5 µm.…”

“…As a result, highly anisotropic electronic properties and improved device performance have been achieved . Recently, micrometer scale spherulitic crystals of conjugated polymers have been reported using controlled solvent vapor annealing . Interestingly, the growth of spherulites is highly dependent on the solvent vapor pressure.…”

“…Extra solvent of carbon disulfide (CS 2 ) was added to the sealed container to balance the solvent vapor pressure and to control the slow sample evaporation in order to obtain well‐defined spherulitic crystals . The solvent vapor pressure inside the container allows a nucleation density suitable for spherulitic crystallization . After complete solvent evaporation, the optical textures of the solid film were studied using polarized optical microscope (POM).…”

“…Based on the experimental data and our analysis, a schematic representation of TC microstructures of P3AT‐conjugated polymers surrounding the CNT fiber was proposed (Figure d). During the solution crystallization, local thermal fluctuations cause the P3AT chains to undergo a transition from a coil‐like to rod‐like conformation to minimize the total free energy . Because of strong π–π interactions between the conjugated backbone of P3ATs and the crystalline graphite surface of CNTs, the rod‐like structure of P3ATs will adopt parallel alignment along the long axis of CNTs .…”

Self-organization of nanoparticles and molecules in periodic Liesegang-type structures

“…+ D → E, v 4 = k 4 bd(d − d * ) , k 4 = 10 2 (5) B + D + E → 2E, v 5 = k 5 bde(e − e * ) , k 5 = 10 ─1(6)E + E → 2F, v 6 = k 6 e 2 , k 6 = 1(7) …”