Molecular design principles for achieving strong chiroptical properties of fluorene copolymers in thin films

\u3cp\u3eUnderstanding the molecular level origin of chiroptical properties in enantiopure π-conjugated polymers is essential for tailoring these materials for application in organic light-emitting diodes and photonic devices. Here we have studied poly(9,9′-dialkylfluorene-alt-2,5-dialkoxyphenyl)s as prototypical copolymers to investigate their structure-chiroptical property relationship. The effect of a systematic variation of the location and configuration (S or R) of chiral and achiral side chains in the repeating units on the liquid crystalline ordering and its relationship to chiroptical properties were investigated. The results clearly indicate that enantiopure side chains on the fluorene units are critical for obtaining the cholesteric liquid crystalline ordering and thereby strong chiroptical properties in both absorption and photoluminescence in annealed thin films. Finally, solution-processed organic light-emitting diodes constructed from a liquid crystalline polymer show strong emission of circularly polarized light, demonstrating the potential application of these systems.\u3c/p\u3

Amplifying (im)perfection:the impact of crystallinity in discrete and disperse block co-oligomers

\u3cp\u3eCrystallinity is seldomly utilized as part of the microphase segregation process in ultralow-molecular-weight block copolymers. Here, we show the preparation of two types of discrete, semicrystalline block co-oligomers, comprising an amorphous oligodimethylsiloxane block and a crystalline oligo-l-lactic acid or oligomethylene block. The self-assembly of these discrete materials results in lamellar structures with unforeseen uniformity in the domain spacing. A systematic introduction of dispersity reveals the extreme sensitivity of the microphase segregation process toward chain length dispersity in the crystalline block.\u3c/p\u3

One-pot synthesis of ABCDE multiblock copolymers with hydrophobic, hydrophilic, and semi-fluorinated segments

The scope and accessibility of sequence-controlled multiblock copolymers is demonstrated by direct in situ polymerization of hydrophobic, hydrophilic and fluorinated monomers. Key to the success of this strategy is the ability to synthesize ABCDE, EDCBA and EDCBABCDE sequences with high monomer conversions (>98 %) through iterative monomer additions, yielding excellent block purity and low overall molar mass dispersities (Ð<1.16). Small-angle X-ray scattering showed that certain sequences can form well-ordered mesostructures. This synthetic approach constitutes a simple and versatile platform for expanding the availability of tailored polymeric materials from readily available monomers