2 research outputs found

    Synthesis and Self-Assembly of Perylenetetracarboxylic Diimide Derivatives with Helical Oligo(l‑lactic acid)<sub><i>n</i></sub> Segments

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    Three perylenetetracarboxylic diimide (PDI) derivatives consisting of a short oligo­(l-lactic acid)<sub><i>n</i></sub> (O-LLA) segment at one imide nitrogen were synthesized. The polymers were characterized by <sup>1</sup>H NMR and gel permeation chromatography (GPC). Their properties were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) experiments, scanning electron microscopy (SEM), electronic absorption, and circular dichroism (CD) spectroscopy. The self-assembly behavior of these PDIs in molten state as well as in solvent was examined. It was found that the structure and the morphology of the self-assembly of these polymers depend on the relative length of the O-LLA segment. The PDIs with longer O-LLA chains present liquid crystal properties with an obvious phase transition from disordered phase to an ordered (α) phase, which cannot be found for the PDIs with short O-LLA segments. The long O-LLA segments also caused a left-handed helicity for the aggregates of the PDIs from solution. This research demonstrated that one can control the order, aggregation mode, and morphology of the molecular aggregates by changing the length of the O-LLA chains. This information can be useful in the design of new organic materials that exhibit molecular aggregation

    Oil-in-Water Emulsion Templated and Crystallization-Driven Self-Assembly Formation of Poly(l‑lactide)–Polyoxyethylene–Poly(l‑lactide) Fibers

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    A molecular solution of an amphiphilic block copolymer may act as an oil phase by dispersing into an aqueous micellar system of small-molecular surfactant, forming oil-in-water (O/W) emulsion droplets. In this paper, an as-synthesized triblock copolymer poly­(l-lactide)–polyoxyethylene–poly­(l-lactide) (PLLA–PEO–PLLA) was dissolved in tetrahydrofuran (THF) and then added to an aqueous micellar solution of nonaethylene glycol monododecyl ether (AEO-9), forming initially coalescent O/W emulsion droplets in the size range of 35 nm–1.3 μm. Along with gradual volatilization of THF and simultaneous concentration of PLLA–PEO–PLLA molecules, the amphiphilic copolymer backbones themselves experience solution-based self-assembly, forming inverted core–corona aggregates within an oil-phase domain. Anisotropic coalescence of adjacent O/W emulsion droplets occurs, accompanied by further volatilization of THF. The hydrophilic block crystallization of core-forming PEOs and the hydrophobic chain stretch of corona-forming PLLAs together induce the intermediate formation of rod-like architectures with an average diameter of 300–800 nm, and this leads to a large-scale deposition of the triblock copolymer fibers with an average diameter of ∼2.0 μm. Consequently, this strategy could be of general interest in the self-assembly formation of amphiphilic block copolymer fibers and could also provide access to aqueous solution crystallization of hydrophilic segments of these copolymers
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