Liquid-crystalline behavior of rod-coil diblock copolymers

Matsen, Mark W.; Barrett, C. S.

doi:10.1063/1.477011

Cited by 188 publications

(241 citation statements)

References 26 publications

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“…More recently, new block copolymers have surfaced bearing mesogenic units or rigid blocks, which confer to these systems a liquid crystalline behaviour [1][2][3][4]. Not only these systems are interesting from a fundamental and theoretical point of view, but they have also a high value and potential in applications such as optoelectronics, photovoltaics [5][6][7][8][9][10][11], bioapplications [12], sensoring, etc.…”

Section: Introductionmentioning

confidence: 99%

Self-assembly of rod-coil block copolymers from weakly to moderately segregated regimes

Sary

Brochon²,

Hadziioannou³

et al. 2007

Eur. Phys. J. E

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Abstract. We report on the self-assembly behaviour of two homologue series of rod-coil block copolymers in which, the rod, a π-conjugated polymer, is maintained fixed in size and chemical structure, while the coil is allowed to vary both in molecular weight and chemical nature. This allows maintaining constant the liquid crystalline interactions, expressed by Maier-Saupe interactions, ω, while varying the tendency towards microphase separation, expressed by the product between the Flory-Huggins parameter and the total polymerization degree, χN . Therefore, the systems presented here allow testing directly some of the theoretical predictions for the self-assembly of rod-coil block copolymers in a weakly segregated regime. The two rod-coil block copolymer systems investigated were poly(DEH-p-phenylenevinylene-b-styrene), whose self-assembly takes place in the very weakly segregated regime, and poly(DEH-p-phenylenevinylene-b4vinylpyridine), for which the self-assembly behaviour occurs under increased tendency towards microphase separation, hereby referred to as moderately segregated regime. Experimental results for both systems are compared with predictions based on Landau expansion theories.PACS. 61.46.-w Nanoscale materials -61.30.Vx Polymer liquid crystals -64.60.Cn Order-disorder transformations; statistical mechanics of model systems

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Section: Introductionmentioning

confidence: 99%

Self-assembly of rod-coil block copolymers from weakly to moderately segregated regimes

Sary

Brochon²,

Hadziioannou³

et al. 2007

Eur. Phys. J. E

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“…[29][30][31] At large rod weight fraction, when liquid crystallinity dominates, nematic and smectic phases are the most frequently encountered phases. 27,32,33 However other phases, which strongly differ from coil-coil block copolymer systems, have been theoretically postulated 34 or observed experimentally. 35,36 In general, the rigidity of the rod block and rod-rod interactions, both being intimately related to the nature of the rod considered, are expected to have great influence on the molecular packing and thus on the structure of the thermodynamically stable phases.…”

Section: Introductionmentioning

confidence: 99%

Weakly Segregated Smectic C Lamellar Clusters in Blends of Rods and Rod−Coil Block Copolymers

et al. 2007

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The morphology arising from the self-assembly of π-conjugated poly(diethylhexyloxy-pphenylenevinylene) rod homopolymers (PPV) and poly(diethylhexyloxy-p-phenylenevinylene)-polystyrene (PPV-PS) rod-coil block copolymers is described. Two PPV-PS block copolymers, one with low rod volume fraction (∼17%) and the other with high volume fraction (∼50%), were synthesized by convergent anionic polymerization and atom transfer radical polymerization, respectively. In the first case, given the low volume fraction of the rod block, the pure asymmetrical rod-coil block copolymer formed an isotropic homogeneous phase. However, ordered clusters of alternating PS and PPV domains with characteristic length of the order of several micrometers appeared when PPV rod homopolymers were blended to the PS-PPV diblock. Furthermore, the long-range order of the clusters as well as their volume fraction could be greatly increased when the symmetric rod-coil PPV-PS was blended to PPV homopolymer. Tomographic reconstruction from transmission electron micrographs allowed demonstrating that the clusters were organized in lamellar phase with well-defined width for both the intercalated PS and PPV domains, while wide-angle X-ray scattering showed that within the PPV domains the PPV blocks and PPV homopolymer rods were closely packed. The study of the spacing widths of the PPV and PS domains showed that clusters are organized in a smectic C configuration with large tilt angles of the rods (54°) and stretching of the coil blocks which is typical of weakly segregated block copolymers organized in a lamellar phase. The stability of the rod-to-rod interaction peak at high temperatures (190°C), well beyond the order-disorder transition temperature of the clusters (130°C), suggests that the (i) aggregation of the rods is mediated by π-π interactions and (ii) the clusters are thermodynamically stable structures. The energetic driving force toward the formation of these clusters is discussed in the last part of this work.

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“…[1][2][3] Although the phase diagram of the coil-coil copolymers is now well understood both experimentally and theoretically, 4-6 the rod-coil self-assembly is still under intensive theoretical and experimental investigation. 2,[7][8][9] Recently, in view of more controlled morphologies and enhanced properties, more complicated molecular architectures such as rod-rod diblock copolymer 10,11 or rod-coil-rod 12 and coil-rod-coil 13,14 triblock copolymers have also become the object of several studies.…”

Section: Introductionmentioning

confidence: 99%

Self-Assembly of Polypeptide/π-Conjugated Polymer/Polypeptide Triblock Copolymers in Rod−Rod−Rod and Coil−Rod−Coil Conformations

et al. 2008

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Self-assembly in the bulk of a series of hybrid triblock copolymers formed by a poly(9,9-dihexylfluorene-2,7-diyl) (PHF) middle block and two poly(γ-benzyl-L-glutamate) (PBLG) end blocks has been studied. Since the R-helical secondary structure of the PBLG block may be either maintained or suppressed depending on the solvent casting history, the PBLG-PHF-PBLG copolymers exhibit two different conformations: a rod-rod-rod or coil-rod-coil configuration, respectively. In order to provide insight into the influence of conformation on self-aggregation of these systems, three copolymers with different block ratio were investigated in both conformations using small-and wide-angle scattering techniques and transmission electron microscopy. Time-resolved photoluminescence measurements were performed on the same samples to explore the effect of morphology on photophysical properties. The observed photoluminescence spectra and dominant excited lifetimes of the poly(9,9-dihexylfluorene-2,7-diyl) block were found to differ markedly in rod-rod-rod and coil-rodcoil configurations and were correlated to the morphology of the self-assembled triblock copolymers.

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Liquid-crystalline behavior of rod-coil diblock copolymers

Cited by 188 publications

References 26 publications

Self-assembly of rod-coil block copolymers from weakly to moderately segregated regimes

Self-assembly of rod-coil block copolymers from weakly to moderately segregated regimes

Weakly Segregated Smectic C Lamellar Clusters in Blends of Rods and Rod−Coil Block Copolymers

Self-Assembly of Polypeptide/π-Conjugated Polymer/Polypeptide Triblock Copolymers in Rod−Rod−Rod and Coil−Rod−Coil Conformations

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