Phase-Separation-Induced Gelation of Poly(9,9-dioctylfluorene)/Methylcyclohexane Solution

Chen, Chun-Yu; Chang, Cheng-Shang; Huang, Siao-Wun; Chen, Jean-Hong; Chen, Hsin‐Lung; Su, Ching‐Iuan; Chen, Show‐An

doi:10.1021/ma100335c

Cited by 39 publications

(66 citation statements)

References 37 publications

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“…At room temperature, the optical characteristics matching those of the PF8 β phase are found for PF7 and PF9 in MCH both at high (∼1 vol %) [32] and low (∼0.002 vol %) [34] concentrations, while the same is seen for PF10 in thin films [35], with its thermal dependency following the lower T * mem [33]. The presence of sheetlike assemblies [26] or membranes [33] in PFs mixed with MCH (or PF N -MCH) is well established and discussed in terms of their internal structure [32] and macrophase separation [30], thermal behavior [30,32], and the existence of β phase [25,34,35]. Attention should also be placed on the density fluctuations or aggregation of the sheetlike assemblies.…”

Section: Kitts and Vanden Boutmentioning

confidence: 64%

“…Chen et al [30] studied initially isotropic PF8-MCH over a broad concentration range (0.001-3 wt % or ∼0.0008-2.3 vol %) at room temperature by aging it over several TABLE II. Parameters estimated from the fits to the SANS data of 10 mg/mL PF N -MCH-d 14 .…”

Section: Resultsmentioning

confidence: 99%

“…They put forward an idea of interconnected PF8 morphology and the idea of concentration fluctuations amongst the sheets. Chen et al found, in particular, that the gelation is driven by a macrophase separation that leads to the coexistence of sheets (what they called the liquid crystalline phase) and isotropic liquid [30]. True macrophase separation eventually takes place.…”

Section: Resultsmentioning

confidence: 99%

“…Attention should also be placed on the density fluctuations or aggregation of the sheetlike assemblies. This system may be called a lyotropic phase with solvent coexistence [33] and the fluctuations called "heterogeneities in the liquid crystalline domains" as suggested by Chen et al [30]. We should also be aware of the coexistence of these density fluctuations and assemblies themselves and the coexisting assembly types, i.e., membranes, β sheets, and free chains [33].…”

Section: Kitts and Vanden Boutmentioning

confidence: 97%

“…Stiff chains tend to pack in a unidirectional fashion within the polymer assemblies justifying the term segmental alignment [27]. In MCH, the sheetlike assemblies appear with decreasing temperature [26] or by room temperature aging driven by macrophase separation, which leads to coexistence of an isotropic phase and an assembly-rich phase with local heterogeneities [30]. The gel-like appearance and optical characteristics of the β phase follow from the polymer assemblies and a sharp transition back to the isotropic phase is observed upon heating.…”

Section: Introductionmentioning

confidence: 99%

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Network structure of polyfluorene sheets as a function of alkyl side chain length

et al. 2011

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The formation of self-organized structures in poly(9,9-di-n-alkylfluorene)s ∼1 vol % methylcyclohexane (MCH) and deuterated MCH solutions was studied at room temperature using neutron and x-ray scattering (with the overall q range of 0.000 58-4.29Å−1 ) and optical spectroscopy. The number of side chain carbons (N ) ranged from 6 to 10. The phase behavior was rationalized in terms of polymer overlap, cross-link density, and blending rules. For N = 6−9, the system contains isotropic areas and lyotropic areas where sheetlike assemblies (lateral size of >400Å) and free polymer chains form ribbonlike agglomerates (characteristic dimension of >1500Å) leading to a gel-like appearance of the solutions. The ribbons are largely packed together with surface fractal characteristics for N = 6−7 but become open networklike structures with mass fractal characteristics for N = 8−9, until the system goes through a transition to an isotropic phase of overlapping rodlike polymers for N = 10. The polymer order within sheets varies allowing classification for loose membranes and ordered sheets, including the so-called β phase. The polymers within the ordered sheets have restricted motion for N = 6−7 but more freedom to vibrate for N = 8−9. The nodes in the ribbon network are suggested to contain ordered sheets cross-linking the ribbons together, while the nodes in the isotropic phase appear as weak density fluctuations cross-linking individual chains together. The tendencies for macrophase separation and the formation of non beta sheets decrease while the proportion of free chains increases with increasing N. The fraction of β phase varies nonlinearly, reaching its maximum at N = 8.

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Section: Kitts and Vanden Boutmentioning

confidence: 64%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Kitts and Vanden Boutmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Network structure of polyfluorene sheets as a function of alkyl side chain length

et al. 2011

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Methods for Controlling Structure and Photophysical Properties in Polyfluorene Solutions and Gels

2013

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Knowledge of the phase behavior of polyfluorene solutions and gels has expanded tremendously in recent years. The relationship between the structure formation and photophysics is known at the quantitative level. The factors which we understand control these relationships include virtually all important materials parameters such as solvent quality, side chain branching, side chain length, molecular weight, thermal history and myriad functionalizations. This review describes advances in controlling structure and photophysical properties in polyfluorene solutions and gels. It discusses the demarcation lines between solutions, gels, and macrophase separation in conjugated polymers and reviews essential solid state properties needed for understanding of solutions. It gives an insight into polyfluorene and polyfluorene beta phase in solutions and gels and describes all the structural levels in solvent matrices, ranging from intramolecular structures to the diverse aggregate classes and network structures and agglomerates of these units. It goes on to describe the kinetics and thermodynamics of these structures. It details the manifold molecular parameters used in their control and continues with the molecular confinement and touches on permanently cross-linked networks. Particular focus is placed on the experimental results of archetypical polyfluorenes and solvent matrices and connection between structure and photonics. A connection is also made to the mean field type theories of hairy-rod like polymers. This altogether allows generalizations and provides a guideline for materials scientists, synthetic chemists and device engineers as well, for this important class of semiconductor, luminescent polymers.

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Synthesis and optical properties of organic-inorganic hybrid semi-interpenetrating polymer network gels containing polyfluorenes

Naga

Miyanaga

Furukawa

2014

J. Polym. Sci. Part A: Polym. Chem.

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Organic-inorganic hybrid semi-interpenetrating polymer network (semi-IPN) gels containing polyfluorenes (PFs) are synthesized by hydrosilylation reaction of joint and rod molecules in toluene, where PFs are poly(9,9-dihexylfluorene-2,7-diyl) (PF6) or, poly(9,9-dioctylfluorene-2,7-diyl) (PF8), joint molecules are 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS), or 1, 3,5,7,9,11,13,15-octakis(dimethylsilyloxy)pentacyclo-[9,5,1,1,1, 1]octasilsesquioxane (POSS), and rod molecules are 1,5-hexadiene (HD) or 1,9-decadiene (DD). The semi-IPN gels containing low molecular weight PF6 show higher photoluminescence efficiency (/ g ) than the toluene solution of PF6L (/ s ). The semi-IPN gels composed of long rod molecule of DD and cubic joint molecule of POSS show the most effective increase in the emission intensity. The emission intensity of PF6L increases as formation of the network in the POSS-DD semi-IPN gel. The POSS-DD semi-IPN gels containing high molecular weight PF6 and PF8 also show the increase of emission intensity than those of the toluene solutions. The semi-IPN synthesized in cyclohexane show syneresis and phase separation between network structure and PF chains. The semi-IPN gels containing PF8 show emission peaks at 450 and 470 nm derived from b-sheet structure of PF8. A systematic study clears correlation between emission property and network structure and/or composition of semi-IPN gels. The semi-IPN gels provide emissive self-standing soft materials with high efficiency and in a narrow wavelength range emission.

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Phase-Separation-Induced Gelation of Poly(9,9-dioctylfluorene)/Methylcyclohexane Solution

Cited by 39 publications

References 37 publications

Network structure of polyfluorene sheets as a function of alkyl side chain length

Network structure of polyfluorene sheets as a function of alkyl side chain length

Methods for Controlling Structure and Photophysical Properties in Polyfluorene Solutions and Gels

Synthesis and optical properties of organic-inorganic hybrid semi-interpenetrating polymer network gels containing polyfluorenes

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