Polyfluorene copolymer with a multiply blocked rotaxane architecture in the main chain: Synthesis and characterization

Abstract

To improve the physical properties of polymer materials, a novel copolymer with a multiply blocked rotaxane architecture in the main chain was synthesized through Suzuki dehalogenative polycondensation from a 2,7-dibromofluorene/c-cyclodextrin (c-CD) inclusion complex and 9,9-dioctylfluorene-2,7-trimethylene diborate in the presence of a tetrakis(triphenylphosphine)palladium (0) catalyst. As demonstrated by computational calculations, the dioctyl groups were large enough to prevent the dethreading of c-CD molecules. A copolymer polyrotaxane with a c-CD/structural unit ratio as high as 1/1.4 and a bimodal molecular weight distribution was obtained, as proved by its 1 H-NMR spectrum and size exclusion chromatography curve, respectively. The polyrotaxane showed lower thermal stability and higher solubility in polar solvents in comparison with the noncomplexed homologue.The fluorescence spectra of both the complexed and noncomplexed copolymers exhibited typical well-resolved blue emission bands that arose from the fluorene chromophore units. In dimethylformamide solutions, the ratio of the intensities of the peaks of the emission spectra (emission spectra intensities 413 for the 0-0 band and emission spectra intensities 437 for the 0-1 band) was higher for the polyrotaxane than the noncomplexed copolymer, and this demonstrated a reduced quenching effect of the environment induced by the protection of the polymer chain by the macrocycle.

Effect of Rotaxane Formation on the Photophysical, Morphological, and Adhesion Properties of Poly[2,7‐(9,9‐dioctylfluorene)‐alt‐(5,5'‐bithiophene)] Main‐Chain Polyrotaxanes

“…The size of the granules depends strongly on the chemical nature of the polymer, temperature, the concentration of the polymer solution and the rotaxane architecture. [38] Although we have shown previously for other copolymers [18] that the formation of rotaxane architecture generally improves the morphological properties, this was not found to be the case for PF-PTÁCD, providing an interesting exception to the rule.…”

“…In addition, the macrocycles can improve the solubility via host-induced guest solubilization and modify the photophysical properties due to its confinement effects. Not surprisingly, numerous studies have been done to understand the influence of rotaxane and pseudorotaxane formation on the electro-optical properties of different threaded conjugated polymers, [17][18][19][20][21][22][23][24][25] but the design and synthesis of such rotaxane or pseudorotaxane architectures has remained a challenge.…”

Synthesis and electro‐optical properties of polyfluorene modified with randomly distributed electron‐donor and rotaxane electron‐acceptor structural units in the main chain

“…The construction of mechanically interlocked molecules, such as rotaxanes and polyrotaxanes, was also investigated as a method of further improvement of electronic properties through insulating the backbones of conjugated polymers for controlling intermolecular interactions 22–31. These studies revealed an attractive approach to achieve higher degree of control over molecular rigidity, prevention of aggregation, fluorescence efficiency, improved solubility, and surface‐morphological properties of the resulting conjugated polyrotaxanes 24–31…”

Synthesis and characterization of novel polyimides containing triazoles units in the main chain by click chemistry

“…The reaction can be performed under mild experimental conditions using a copper (I) catalyst 8–12. This reaction has found a vast number of applications in different research fields, such as material sciences,11, 12 polymer chemistry,13–21 and pharmaceutical sciences 5, 6, 13–16…”

“…[8][9][10][11][12] This reaction has found a vast number of applications in different research fields, such as material sciences, 11,12 polymer chemistry, [13][14][15][16][17][18][19][20][21] and pharmaceutical sciences. 5,6,[13][14][15][16] It has been extensively used in the synthesis of polymers with different composition and topology. 8 In spite of the importance of polyimides (PI), click chemistry has not been widely employed for the preparation of these compounds.…”