Anomalous phase separation behavior in dynamically asymmetric LCST polymer blends

Yeganeh, Jafar Khademzadeh; Goharpey, Fatemeh; Foudazi, Reza

doi:10.1039/c3ra47299j

Cited by 24 publications

(24 citation statements)

References 64 publications

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“…spinodal decomposition (SD) and nucleation and growth (NG). Various phase separation mechanisms apart from NG and SD mechanisms like transient gel induced viscoelastic phase separation (T-VPS), nucleation of aggregate-like PS-rich in the stable disperse-matrix morphology (ANG) and also aggregate-like PS-rich phase nucleates in the early stages of phase separation, and forms a percolating network of the minor PS-rich phase through coalescence at later stages (C-VPS) observed by Yeganeh et al 57 Various phase separation mechanisms like fracture phase separation (FPS) 54 and viscoelastic phase separation (VPS) at various quench depths, showing transitions like brittle to ductile fracture in PS/PVME. 58…”

Section: Rod Shaped Particlesmentioning

confidence: 99%

Nanoparticle induced miscibility in LCST polymer blends: critically assessing the enthalpic and entropic effects

Xavier

Rao

Bose

2016

Phys. Chem. Chem. Phys.

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The use of copolymer and polymer blends widened the possibility of creating materials with multilayered architectures. Hierarchical polymer systems with a wide array of micro and nanostructures are generated by thermally induced phase separation (TIPS) in partially miscible polymer blends. Various parameters like the interaction between the polymers, concentration, solvent/non-solvent ratio, and quenching temperature have to be optimized to obtain these micro/nanophase structures. Alternatively, the addition of nanoparticles is another strategy to design materials with desired hetero-phase structures. The dynamics of the polymer nanocomposite depends on the statistical ordering of polymers around the nanoparticle, which is dependent on the shape of the nanoparticle. The entropic loss due to deformation of polymer chains, like the repulsive interactions due to coiling and the attractive interactions in the case of swelling has been highlighted in this perspective article. The dissipative particle dynamics has been discussed and is correlated with the molecular dynamics simulation in the case of polymer blends. The Cahn-Hillard-Cook model on variedly shaped immobile fillers has shown difference in the propagation of the composition wave. The nanoparticle shape has a contributing effect on the polymer particle interaction, which can change the miscibility window in the case of these phase separating polymer blends. Quantitative information on the effect of spherical particles on the demixing temperature is well established and further modified to explain the percolation of rod shaped particles in the polymer blends. These models correlate well with the experimental observations in context to the dynamics induced by the nanoparticle in the demixing behavior of the polymer blend. The miscibility of the LCST polymer blend depends on the enthalpic factors like the specific interaction between the components, and the solubility product and the entropic losses occurring due to the formation of any favorable interactions. Hence, it is essential to assess the entropic and enthalpic interactions induced by the nanoparticles independently. The addition of nanoparticles creates heterogeneity in the polymer phase it is localized. This can be observed as an alteration in the relaxation behavior of the polymer. This changes the demixing behavior and the interaction parameter between the polymers. The compositional changes induced due to the incorporation of nanoparticles are also attributed as a reason for the altered demixing temperature. The particle shape anisotropy causes a direction dependent depletion, which changes the phase behavior of the blend. The polymer-grafted nanoparticles with varying grafting density show tremendous variation in the miscibility of the blend. The stretching of the polymer chains grafted on the nanoparticles causes an entropy penalty in the polymer blend. A comparative study on the different shaped particles is not available up to date for understanding these aspects. Hence, we have juxtaposed the ...

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Section: Rod Shaped Particlesmentioning

confidence: 99%

Nanoparticle induced miscibility in LCST polymer blends: critically assessing the enthalpic and entropic effects

Xavier

Rao

Bose

2016

Phys. Chem. Chem. Phys.

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“…This state in which the system behaves as an elastic body is called the frozen state. Then the less viscoelastic phase (the water‐rich phase) nucleates and grows into the more viscoelastic phase . Domain growth induces self‐generated stresses in the more viscoelastic component and preserves the continuity of the elastic phase even when it is the minor phase.…”

Section: Resultsmentioning

confidence: 99%

“…According to optical micrographs, VPS controlled the morphology at 60°C. The percolating PVME‐rich network induced by VPS hinders the flow and thereby results in the significant enhancement of storage modulus at low frequencies .…”

Section: Resultsmentioning

confidence: 99%

Characterization and phase‐transition behavior of thermoresponsive PVME nanogels in the presence of cellulose nanowhiskers: Rheology, morphology, and FTIR studies

Hadaeghnia

Goharpey

Yeganeh

2018

Polymer Engineering & Sci

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The effects of cellulose nanowhiskers (CNWs) and irradiation dose on phase separation behavior as well as rheological and physical properties of Poly vinyl methyl ether (PVME) nanogels are investigated. Interactions between CNWs and polymer chains lead to the dehydration of PVME chains. Increasing the irradiation dose or CNW weight fraction enhances the VPTT, due to the decreased chain mobility. The phase separation behaviors of hybrid and nonhybrid nanogels are investigated at two different quench depths. At the shallow quench depth, the samples phase separate through nucleation and growth (NG) mechanism. However in the case of hybrid nanogels with a higher temperature, as a result of the enhanced dynamic asymmetry induced by the increased quench depth and the interaction of PVME chains with CNWs, the phase separation mechanism changes from NG to viscoelastic phase separation (VPS). The linear rheological behavior of nanogels was well correlated with the evolution of corresponding phase‐separating morphologies. At 40°C, a shoulder appeared in the storage modulus curve in the intermediate frequency range, due to shape relaxation of the droplets formed by NG mechanism. However, a solid‐like behavior was observed due to the existence of a percolated network structure induced by VPS at 60°C. POLYM. ENG. SCI., 59:899–912, 2019. © 2018 Society of Plastics Engineers

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“…PS/PVME blend exhibits a lower critical solution temperature within the experimental temperature . Due to the large difference in their glass transition temperatures (about 125°C), this blend is dynamically asymmetric.…”

Section: Introductionmentioning

confidence: 81%

“…The main purpose of this study was to investigate the effect of CNWs on VPS. For this purpose, the PS/PVME 15/85 blend was selected, where phase separation occurs through VPS at 110°C . We employed two types of CNWs: hydrophobic ones that preferentially wet the PS‐rich phase during phase separation, and hydrophilic ones with preferential affinity to the PVME‐rich phase.…”

Section: Introductionmentioning

confidence: 99%

Effect of selective localization of cellulose nanowhiskers on viscoelastic phase separation

Shahrezaei

Goharpey

Yeganeh

2017

Polymer Engineering & Sci

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Viscoelastic phase separation (VPS) is a fundamental physical phenomenon that creates percolated network structure in dynamically asymmetric mixtures. The object of this study was to investigate the effect of rod shape nanoparticles with different surface chemistries on VPS in the polystyrene/poly(vinyl methyl ether), PS/PVME, blend. For this purpose, hydrophilic (CNWs) and hydrophobic (M‐CNWs) cellulose nanowhiskers (CNWs) were prepared to be used as nanorods. Rheological measurments were employed to investigate the effect of nanowhiskers on phase separation temperature, kinetics of phase separation, and dynamic asymmetry. The evolution of morphology during the phase separation at a fixed quench depth was assessed using polarized optical microscopy. The nanowhiskers were effective in decreasing the correlation length, which slowed down the phase separation. CNWs self‐assembled into the PVME‐rich phase during the phase separation, which led to a decrease in the dynamic asymmetry and beyond a critical volume fraction of CNWs, the VPS mechanism changed to spinodal decomposition (SD). However, in the presence of M‐CNW, the localization of M‐CNWs into the PS‐rich phase enhanced the dynamic asymmetry and at 2 vol% M‐CNWs, the induced PS‐rich network by VPS was arrested. The linear and non‐linear viscoelastic behavior of the samples were studied as well. POLYM. ENG. SCI., 58:928–942, 2018. © 2017 Society of Plastics Engineers

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Anomalous phase separation behavior in dynamically asymmetric LCST polymer blends

Cited by 24 publications

References 64 publications

Nanoparticle induced miscibility in LCST polymer blends: critically assessing the enthalpic and entropic effects

Nanoparticle induced miscibility in LCST polymer blends: critically assessing the enthalpic and entropic effects

Characterization and phase‐transition behavior of thermoresponsive PVME nanogels in the presence of cellulose nanowhiskers: Rheology, morphology, and FTIR studies

Effect of selective localization of cellulose nanowhiskers on viscoelastic phase separation

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