Correlation Between Molecular Structure, Microscopic Morphology, and Optical Propertiesof Poly(tetraalkylindenofluorene)s

Abstract

The emission properties of polyindenofluorenes with various proportions of straight‐ and branched‐chain alkyl substituents have been compared. The polymer with straight octyl substituents shows green emission due to formation of aggregates, while the polymer with branched 2‐ethylhexyl substituents shows blue emission. Studies of the film morphology show the presence of ordered structures due to π‐stacking of the polymer chains for the octyl‐substituted polymer, whereas the polymer with branched side‐chains shows no such order. Copolymers show intermediate behavior. A clear correlation is established between the degree of straight‐chain alkyl substitution, the formation of ordered structures in the films, and the amount of long wavelength emission in the solid‐state spectra.

Microscopic Morphology of Polyfluorene–Poly(ethylene oxide) Block Copolymers: Influence of the Block Ratio

“…The hypothesis that the fibrillar morphology observed in this block copolymer originates from the p±p interactions between the polyfluorene segments is supported by the fact that the same morphology is found for the corresponding homopolyfluorene (with the same average chain length). [30,32] Moreover, other conjugated polymers (including poly(para-phenylene ethynylene) [29,33,34] and poly(2,8-indenofluorene) [35] ) and ªrod±coilº copolymers (including poly(para-phenylene)±polystyrene, [36] poly(paraphenylene vinylene)±poly(ethylene oxide) [37] ) also form this type of structure. Due to the small average volume ratio of PEO (f PEO = 0.09), the short PEO blocks are not expected to interfere strongly with the p-stacking of the PF segments.…”

Phenylene‐Based Ladder Polymers

“…As the proportion of double-stranded linkages decreases the emission redshifts so that polymers based on ladder-type pentaphenylenes 5 exhibit pure blue emission with spectra very similar to those of LPPPs [9]. As with LPPPs, instability in the emission color due to formation of emissive defects has been a problem for regular stepladder polyphenylenes [42,61]. This can be suppressed by using aryl substituents at the bridgeheads [62][63][64][65] or by ensuring their complete alkylation [66].…”

Supramolecular Organization in Fluorene/Indenofluorene- Oligothiophene Alternating Conjugated Copolymers

“…Therefore, fibrillar structures are not expected to be formed in this case, highlighting the fact that the substitution patterns can have a huge influence on the chain packing of such copolymers, as already observed in indenofluorene homopolymers. [14] For P(IF-alt-T4R4), no fibrillar texture was observed, but rather untextured deposits as in P(IF-alt-T2) and P(IF-alt-T3R2). In P(IF-alt-T4R4), both the lack of ªcommensurabilityº between the comonomers (IF vs. T4) and the presence of substituents on thiophene rings prevent the assembly into regular p-stacked structures.…”