Scattering Modeling of Nucleation Gels

Chou, Che-Min; Hong, Po‐Da

doi:10.1021/ma800788j

Cited by 10 publications

(16 citation statements)

References 42 publications

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“…The essential feature of a gel is geometrical connections, and hence theoretical works generally emphasize percolation phenomena in the treatment of gelation. [24][25][26] It is known that conjugated polymer solutions undergo physical gelation upon prolonged isothermal aging due to very slow dynamics associated with the structural reorganization. 8,12 To demonstrate such a slow reorganization, we conduct a time-resolved DLS experiment for 1.0 wt % MCH solution.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2010

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The gelation behavior of the solution of a conjugated polymer, poly(9,9-dioctylfluorene) (PF8), with a poor solvent, methylcyclohexane (MCH), induced by aging at room temperature has been investigated. Light scattering and optical microscopy revealed that the gelation was driven by a macrophase separation occurred through a spinodal decomposition mechanism. Although the spinodal decomposition could proceed to the late stage, the interconnected morphology was arrested to give rise to the gel property of the system. The phase-separated gel was composed of an isotropic phase and a PF8-enriched liquid crystalline phase. The liquid crystalline phase was further found to consist of sheetlike aggregates (as revealed by smallangle X-ray scattering) in which a fraction of the PF8 chains formed the β-phase (as disclosed by the optical spectra) which dominated the photoluminescence spectrum of the gel. The PF8/MCH gel could be disintegrated by moderate heating to ca. 70°C. This gel-to-sol transition was accompanied by the disruptions of the sheetlike aggregates and the β-phase which led to homogenization of the solution.

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Section: Resultsmentioning

confidence: 99%

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

et al. 2010

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“…The absorption bands in this region are related to the CF stretching coupled with skeleton stretching . It has been identified that PVDF chains exist as aggregated particles rather than freely separated chains in PC or γ‐BL . Park et al reported that the radii of gyration is concentration‐ and temperature‐independent .…”

Section: Resultsmentioning

confidence: 99%

“…34 It has been identified that PVDF chains exist as aggregated particles rather than freely separated chains in PC or c-BL. 35,36 Park et al reported that the radii of gyration is…”

Section: Full Papermentioning

confidence: 99%

Thermally induced phase separation of poly(vinylidene fluoride)/diluent systems: Optical microscope and infrared spectroscopy studies

Yang

Liang

et al. 2013

J Polym Sci B Polym Phys

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Thermally induced phase separation (TIPS) has been developed to prepare porous membranes. The porous structures are mainly dependent on diluents adopted in the TIPS process. We obtained two typical morphologies of poly(vinylidene fluoride) (PVDF) membranes using cyclohexanone (CO) and propylene carbonate (PC) as diluents, respectively. SEM observation displays that porous spherulites are formed from PVDF/CO system, whereas smooth particles result from PVDF/PC system. The TIPS processes of these two systems have been investigated in detail by optical microscope observation and temperature‐dependent FTIR combined with two‐dimensional infrared correlation analysis. Rapid crystallization of PVDF can be seen around 110 °C in the PVDF/CO system, which is consistent with the results of temperature‐dependent FTIR spectra. The spectral evolution indicates a transform of PVDF from amorphous to α‐phase after 110 °C. The νs(CO) band at 1712 cm−1 narrows and the νs(CF) band at 1188 cm−1 shifts to 1192 cm−1 before crystallization, which implies the destruction of interaction between PVDF and CO. In contrast, the PVDF/PC system shows slow crystallization with all‐trans conformation assigned to β‐phase and γ‐phase below 60 °C but no obvious change of polymer−diluent interaction. We propose two mechanisms for the different phase behaviors of PVDF/CO and PVDF/PC systems: a solid−liquid phase separation after destruction of polymer−diluent interaction in the former, and a liquid−liquid phase separation process coupled with rich‐phase crystallization in the later. This work may provide new insight into the relationship among morphologies, crystal forms, and phase separation processes, which will be helpful to adjust membrane structure. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1438–1447

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“…Later, we knew that the structural information does exist and can be extracted by our scattering modeling approach. 24,25 For the scattering from an evolving hierarchical structure, giving the explicit analytical form of the scattering pattern is rather difficult or even impossible. Instead, the scattering modeling is a compromising phenomenological approach which can lead to a better understanding of the interrelation/interaction between scatterers at different timing and hierarchy during the process.…”

Section: Experimental Methodsmentioning

confidence: 99%

Spatiotemporal Evolution in Morphogenesis of Thermoreversible Polymer Gels with Fibrillar Network

Chou

Hong

2010

Macromolecules

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A scattering modeling approach is used to clarify the formation of the thermoreversible polymer gel with a fibrillar network. We find that the gelation has to do with the spatiotemporal evolution of the so-called "coherent structure"-the nonlocalized, fibril nucleation via the fluctuation instability and fibril growth coupled with a cooperatively coarsening concentration wave-and is a direct consequence of the spinodal crystallization far from equilibrium in the solution. The present result rejects the common opinion that the gelation is nothing more than the percolation problems and poses an interesting question about the entropy-driven crystallization.

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Scattering Modeling of Nucleation Gels

Cited by 10 publications

References 42 publications

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

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

Thermally induced phase separation of poly(vinylidene fluoride)/diluent systems: Optical microscope and infrared spectroscopy studies

Spatiotemporal Evolution in Morphogenesis of Thermoreversible Polymer Gels with Fibrillar Network

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