Study of the Two-Component Segmental Dynamics of Poly(vinylethylene)/Polyisoprene Miscible Blends

Álvarez, F.; Alegría, A.; Colmenero, Juan

doi:10.1021/ma960975x

Cited by 67 publications

(77 citation statements)

References 16 publications

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“…However, Alegria et al [2] found that miscible blends of cis-polyisoprene (PI) and poly(vinyl ethylene) (PVE) exhibit bimodal dielectric loss curves for the local segmental relaxation (a relaxation). Similar dielectric behavior was observed for polymer blends in which the difference of glass transition temperatures T g of the components is larger than 70 K [3][4][5][6][7][8][9][10]. Hereafter the term 'bimodal' means that a loss curve clearly exhibits two peaks or a main peak and a shoulder.…”

Section: Introductionsupporting

confidence: 68%

Dielectric study of dynamical heterogeneity in blends of polyethers

Hirose¹,

Adachi²

2006

Journal of Non-Crystalline Solids

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Section: Introductionsupporting

confidence: 68%

Dielectric study of dynamical heterogeneity in blends of polyethers

Hirose¹,

Adachi²

2006

Journal of Non-Crystalline Solids

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“…The design, selection, and performance of polymer blends crucially depend on the ability to predict and control their phase behavior and morphology. Many techniques have been extensively used to investigate the miscibility, molecular dynamics and phase separation kinetics of polymer blends, such as, differential scanning calorimetry (DSC), [1,2] NMR, [3][4][5][6] dielectric spectroscopy, [7][8][9][10][11][12] dynamic mechanical measurements, [13][14][15][16][17] and time-resolved light scattering. [18][19][20][21][22][23] We have recently investigated the miscibility, dielectric spectroscopy, viscoelastic properties and morphology under Summary: The phase separation kinetics of a poly(methyl methacrylate), PMMA, and poly(a-methylstyrene-co-acrylonitrile), PaMSAN, blend exhibiting a LCST-type phase diagram have been investigated as functions of temperature and demixing time for the near critical composition (PaMSAN/PMMA ¼ 25:75) using a time-resolved light scattering technique.…”

Section: Introductionmentioning

confidence: 99%

Spinodal Decomposition in Binary Blend of Poly(methyl methacrylate)/Poly(α‐methyl styrene‐co‐acrylonitrile): Analysis of Early and Late Stage Demixing

Madbouly

Ougizawa

2004

Macro Chemistry & Physics

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Summary: The phase separation kinetics of a poly(methyl methacrylate), PMMA, and poly(α‐methylstyrene‐co‐acrylonitrile), PαMSAN, blend exhibiting a LCST‐type phase diagram have been investigated as functions of temperature and demixing time for the near critical composition (PαMSAN/PMMA = 25:75) using a time‐resolved light scattering technique. We found that the scattering data in the early stage spinodal decomposition (SD) can be well described by the linearized Cahn–Hilliard theory. Spinodal temperature Ts ∼ 171 °C was determined from Dapp versus T and q versus T based on the analysis of Cahn theory in the early stage SD, where Dapp is the apparent diffusion coefficient and qm is the scattering vector at the maximum scattering intensity. The value of Ts obtained from the analysis of light scattering data was in good agreement with the phase diagram obtained visually at the equilibrium condition. The LCST‐type phase diagram of this blend was also calculated using the Flory–Huggen theory. The estimated interaction parameter used for the calculation of the phase diagram was found to be composition and temperature dependent. The coarsening behavior of the blend at the late stage SD was also studied by analyzing the magnitudes of qm and Im at various demixing times and temperatures based on the nonlinear statistical theories. Both of qm and Im obtained at different times and temperatures can be superposed and reduced to the respective master curves by horizontal shifting when they are plotted against log (t/aT) at a given reference temperature, where aT is the temperature‐dependent shift factor. The shape of the phase separation domain structures as a function of time during the SD was also considered. The scaling structure function F(x,t;T) = qm(t;T)3I(q,t;T) versus q/qm was found to be time independent and falls onto a universal curve in the late stage SD as a result of the dynamical self‐similarity accompanying with the phase separation process.Optical microscopy pictures for the structure development of spinodal decomposition for PαMSAN/PMMA = 25:75 blend at 180 °C for different demixing times.imageOptical microscopy pictures for the structure development of spinodal decomposition for PαMSAN/PMMA = 25:75 blend at 180 °C for different demixing times.

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“…Such behaviors have been reported even for miscible polymer blends and are called "dynamical heterogeneity". 19,20 However in those literatures referred above, the interest has been centered mostly on the spectral shapes of the relaxation processes and the relationship between the dynamical heterogeneity and the cooperativity has been scarcely investigated.What factors result in the dynamical heterogeneity in polymer/diluent systems? An intuitive conjecture to this question is that if the size of the dynamical units of the polymer segments is much larger than the size of the diluent molecule, their motions are decoupled.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Dielectric Study of Dynamical Heterogeneity in Blends of Polystyrene and Low Mass Compounds

Hori

Urakawa

Adachi

2003

Polym J

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ABSTRACT:We investigated the dielectric relaxation in blends of 4-n-pentyl-4 -cyanobiphenyl (5CB) and polystyrene (PS) in order to examine the size effect of low mass molecules on the cooperativity of local dynamics. To obtain the dielectric data in the isotropic state, the phase diagram was produced. The temperature (T ) dependence of the dielectric loss factor ε of PS/5CB blends containing 20 to 30 wt% of 5CB exhibited a bimodal peak near the calorimetric glass transition temperature T g . The bimodal peak was resolved into two peaks termed α and β. The α process locates above T g and can be assigned to cooperative motions of the PS segments and the 5CB molecules. The β process is responsible to independent reorientation of the 5CB molecules in the glassy PS matrix. The α and β loss peaks tend to merge with increasing T . This behavior contrasts to the dielectric behavior of the PS/toluene system which exhibits loss peaks due to segmental motions of PS and rotation of the toluene molecules in well separated temperature regions. The toluene molecule has a size of ca. 1/3 of the 5CB molecule and does not move cooperatively with PS but the 5CB molecule does. From the intensity of the α and β peaks, the fraction of the 5CB molecules moving cooperatively with PS has been estimated to be 0.25 and 0.63 for the blends containing 30 and 20 wt% of 5CB, respectively.KEY WORDS Polystyrene / 4-n-Pentyl-4 -cyanobiphenyl / Dielectric Relaxation / Dynamical Heterogeneity / Cooperativity / Diluent / Segmental Motion / Dynamics of low molecular weight molecules dissolved in polymer matrices has been studied long by means of dielectric, 1-8 mechanical, 7, 8 NMR,6,7,9,10 light scattering, 7 fluorescence depolarization, 11 ESR,12 and thermal methods. 6, 13 Adachi et al. 4 and Yoshizaki et al. 1 reported the dielectric behaviors of the systems consisting of polystyrene (PS) and alkylbenzene such as toluene, ethylbenzene and butylbenzene. It was reported that the relaxation due to rotation of the solvent molecules (β process) and that due to segmental motions of PS (α process) occur separately in different temperature-frequency regions. 1, 4 Similar bimodal mobilities of components are reported for various systems consisting of large and small molecules. 5,6,9,10 This behavior is not in harmony with a generally believed view of cooperativity 14-18 of local motions in supercooled liquids near the glass transition temperature T g . For instance if the PS chains and the toluene molecules in the PS/toluene system move cooperatively, the splitting into the two different relaxation processes would not occur. Such behaviors have been reported even for miscible polymer blends and are called "dynamical heterogeneity". 19,20 However in those literatures referred above, the interest has been centered mostly on the spectral shapes of the relaxation processes and the relationship between the dynamical heterogeneity and the cooperativity has been scarcely investigated.What factors result in the dynamical heterogeneity in polymer/diluent systems? ...

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Study of the Two-Component Segmental Dynamics of Poly(vinylethylene)/Polyisoprene Miscible Blends

Cited by 67 publications

References 16 publications

Dielectric study of dynamical heterogeneity in blends of polyethers

Dielectric study of dynamical heterogeneity in blends of polyethers

Spinodal Decomposition in Binary Blend of Poly(methyl methacrylate)/Poly(α‐methyl styrene‐co‐acrylonitrile): Analysis of Early and Late Stage Demixing

Dielectric Study of Dynamical Heterogeneity in Blends of Polystyrene and Low Mass Compounds

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