Dielectric investigation of the molecular dynamics in blends: polymers with similar molecular architecture (TMPC/PC blend)

Mansour, Ahmed S.; Madbouly, Samy A.

doi:10.1002/pi.1995.210360306

Cited by 24 publications

(29 citation statements)

References 17 publications

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“…The miscibility should take place on a structural level bigger than the segmental level to maintain the local environment unchanged and should be small enough to give only one common T g for the miscible blend. This fact is consistent with the previous measurements for TMPC/PC 31 and TMPC/PS 42 blends.…”

Section: Resultssupporting

confidence: 94%

“…The miscibility should take place on a level somewhat between the segmental and molecular level, this level must be big enough to maintain the local environment unchanged and in the same time small enough to give only one glass relaxation process for the miscible blend. This behavior is in good agreement with the previous data for TMPC/PC 31 and TMPC/PS 42 blends, where the dynamics of the β-relaxation process of TMPC was unchanged by blending.…”

Section: Molecular Dynamics Of β-Relaxation Processsupporting

confidence: 92%

“…31 The similar molecular architecture of TMPC and PC leads to better packing of the polymer chains without creation additional structure defects over those existing in the pure polymers. 31 The total number of quasi-dislocations per segment is given by…”

Section: Pmma/pαmsan Blendsmentioning

confidence: 99%

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Broadband Dielectric Spectroscopy for Poly(methyl methacrylate)/Poly(α-methyl styrene-co-acrylonitrile) Blend

Madbouly

2002

Polym J

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ABSTRACT:Blends of poly(methyl methacrylate), PMMA, and Poly(α-methyl styrene-co-acrylonitrile), PαMSAN, random copolymer have been studied by broadband dielectric relaxation spectroscopy and differential scanning calorimeter (DSC). The dielectric measurements were carried out over a wide range of frequency (10 −1 to 10 6 Hz) and temperature (30-155• C). The molecular dynamics of the glass relaxation process, α-process, was investigated as functions of composition, frequency and temperature. It has been found that, only one common α-relaxation process has been observed for all measured samples, its dynamics and broadness were found to be composition dependent. The existence of only one common α-relaxation process located at a temperature range between those of the pure polymer components was taking as a strong evidence for the miscibility of the blend over the entire range of composition. The miscibility was also confirmed by measuring the glass transition temperatures of the blends, T g s, calorimetrically using DSC and dielectrically from the activation curves of the α-relaxation processes of the blends. The T g s of the blends were found to follow Fox-equation. The composition dependence of the dielectric relaxation strength, ∆ε has been also examined for α and β-relaxation processes. In addition, the blending was found to have no effect on the kinetics and broadness of the β-relaxation processes of the PMMA, indicating that blending does not change the local environment of each component in the blend. This also led to in turn that the mixing of the two polymer components should take place on a structure level bigger than the segmental level to keep the local environment unchanged and small enough to have the same volume as the cooperative dipoles, which are related to the single T g of the miscible blend. KEY WORDS Poly(methyl methacrylate)/Poly(α-methyl styrene-co-acrylonitrile) (PMMA/ PαMSAN) / Miscibility / Molecular Dynamics / Physical or chemical combination of two structurally different polymers can be used to obtain materials with properties which differ from those of the constituent components and which can be optimized to meet specific needs, like chemical resistance, impact strength, flexibility or weatherability. The final properties of the blend depend on the properties of the pure polymer components, miscibility and adhesion between the phases as well as the size and uniformity of the phase texture or morphology. Many techniques have been extensively used to investigate the miscibility and molecular dynamics of polymer blends, such as, differential scanning calorimetry (DSC), 1, 2 NMR, 3-6 dielectric spectroscopy, 7-12 and mechanical measurements. [13][14][15][16][17] The dielectric relaxation spectroscopy is a powerful tool cable of providing information about the molecular dynamics and the nature of the interactions in blends by monitoring the motion of dipolar groups attached to molecular chains. The dielectric spectroscopy has been widely used in polymer relaxation analysis and has the advan...

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Section: Resultssupporting

confidence: 94%

Section: Molecular Dynamics Of β-Relaxation Processsupporting

confidence: 92%

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Broadband Dielectric Spectroscopy for Poly(methyl methacrylate)/Poly(α-methyl styrene-co-acrylonitrile) Blend

Madbouly

2002

Polym J

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“…The most important parameter determining the quality of the blends is the degree of compatibility. It is still not clear whether the components in a blend are mixed on a segmental level or on a scale somewhere between segmental and molecular [1,2]. Furthermore, different methods used in the detection of phase separation could yield different results [3,4].…”

Section: Introductionmentioning

confidence: 95%

Detection of compatibility of some rubber blends by DSC

Yehia

Mansour

Stoll³

1997

Journal of Thermal Analysis

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The compatibility of some technically important polymer blends, namely BR/NR, NR/NBR and CR/NBR, has been investigated using the DSC method. In addition, dynamic mechanical measurements have been carried out for the NR/NBR blends over the frequency range of 10 -4 Hz -200 Hz and temperatures ranging from -70 to +70~The results obtained show that the three rubber blends are not compatible over the entire composition range as proven by the DSC and mechanical measurements. By analyzing the heat capacity increases at the glass transitions of the separate phases in the NR/BR blend, it was possible to suggest the presence of a limited compatibility at the boundaries of the two phases.By comparing this work with prior measurements, it was possible to conclude that the calorimetric method is a more efficient tool for the study of compatibility of polymer blends when compared to ultrasonic and viscosity methods.Furthermore, it was found that polymers that show compatibility when measured with an ultrasonic method could behave compatible, semicompatible or incompatible when analyzed by DSC. On the other hand, blends that show incompatibility by the ultrasonic method are always incompatible by the DSC method.

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“…It can be seen that in addition to the ThermX homopolymer possessing a greater relaxation strength than that of PC, it varies smoothly between the two homopolymers. The dielectric relaxation strength is a function of factors such as temperature, density, the number of dipoles per unit volume, and chain conformation and interaction (both intra-and intermolecular), the latter parameter being expressed in terms of g, the dipolar correlation ~oefficient.~ Katana et al3R and Mansour et al 73 found a linear change in the strength of the a relaxation of a miscible polycarbonate pair and this was ascribed to a change in the volume of cooperativity of the a relaxation as composition was altered-with a lower relaxation strength accompanying a greater cooperative motion. Naito et al39 also noted a linear variation in a miscible poly(methy1 methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (PS-co-AN) and ascribed it to the intimacy of mixing and cooperativity of motion between the component homopolymers.…”

Section: Resultsmentioning

confidence: 99%

Molecular dynamics in a miscible polyester blend

Spall

Goodwin

Zipper

et al. 1996

J. Polym. Sci. B Polym. Phys.

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The dynamic mechanical and dielectric spectra of a miscible polyester and polycarbonate blend are investigated with emphasis on the latter technique. It was found that relaxation spectra for the blends from both techniques are broader than those of the constituent homopolymers. This is ascribed to greater intermolecular coupling and concentration fluctuations within the blends. The composition at which the greatest coupling occurs is dependent on the relaxation technique used and is skewed towards the component which shows the highest degree of intermolecular coupling. A number of parameters, such as relaxation time of the polymer molecules in the blend and relaxation strength, are compared as a function of reduced temperature (experimental temperature scaled by the glass transition temperature). Whereas blend behavior is generally intermediate between that of the homopolymers, it appears as though mobility of compositions with low polyester content have a greater relaxation time and possess a higher activation energy when compared to a simple, weighted average of the corresponding homopolymer values. © 1996 John Wiley & Sons, Inc.

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Dielectric investigation of the molecular dynamics in blends: polymers with similar molecular architecture (TMPC/PC blend)

Cited by 24 publications

References 17 publications

Broadband Dielectric Spectroscopy for Poly(methyl methacrylate)/Poly(α-methyl styrene-co-acrylonitrile) Blend

Broadband Dielectric Spectroscopy for Poly(methyl methacrylate)/Poly(α-methyl styrene-co-acrylonitrile) Blend

Detection of compatibility of some rubber blends by DSC

Molecular dynamics in a miscible polyester blend

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