Detection of the glass relaxation process of the PS-phase in block copolymers

Mohammady, Sayed Z.; Mansour, Ahmed S.; Knoll, Konrad; Stoll, B.

doi:10.1016/s0032-3861(01)00798-4

Cited by 21 publications

(25 citation statements)

References 35 publications

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“…A great deal of research effort has been expended over the years in quantitatively describing the cooperative nature of the glass process 15–23. It is well established now that there is a domain in which cooperative particle motion can take place and its size decreases as the temperature increases.…”

Section: Resultsmentioning

confidence: 99%

“…It is well established now that there is a domain in which cooperative particle motion can take place and its size decreases as the temperature increases. This domain is named the cooperative rearranging region (CRR) 17, 19, 23. Based on the literature, the CRR can take values between 2 and 25 nm, depending on the method of data treatment 15–23…”

Section: Resultsmentioning

confidence: 99%

“…5 can be fitted by means of the well‐known William–Landel–Ferry (WLF) equation (Eqn (2)) or its mathematical equivalent, the Vogel–Fulcher–Tammann (VFT) equation:11 where C 1 and C 2 are fitting parameters and T 0 is a constant value normally taken at the vicinity of T g . In fact, these equations cannot give any idea about CRR values, but researchers15, 16, 18, 21–23 have suggested a ‘dislocation concept’ for bundles of polymer chain molecules, where the smallest isotropic arrangements of such bundles (so‐called meander cubes) may be taken as cooperatively rearranging units 15, 16. The authors were able to calculate the diameter ( r ) of the molecular bundles by thermodynamic treatments.…”

Section: Resultsmentioning

confidence: 99%

“…This r in turn, through the suggested superfolding mechanism in the meander model, is related to the length of the cube ( L ) by L = 3 r . Moreover, the following equation has been suggested15, 16, 18, 21–23 for the temperature dependence of the relaxation frequency of the maximum of the glass process: where the first term on the right‐hand side is the Arrhenius factor and the second term is the cooperative factor. L is the length of the cooperative rearranging structural unit (the length of the side of the meander cube), f 0 is the local vibrational frequency, d is the interchain distance, s is the segment length, ε s is the dislocation energy and Q γ is the local activation energy of the segment.…”

Section: Resultsmentioning

confidence: 99%

“…This domain is named the cooperative rearranging region (CRR). 17,19,23 Based on the literature, the CRR can take values between 2 and 25 nm, depending on the method of data treatment. 15 -23 Unfortunately, the available dielectric and dynamic mechanical spectrometers in our laboratory possess relatively narrow frequency windows.…”

Section: Activation Curves and The Cooperative Rearranging Regions Ofmentioning

confidence: 99%

See 4 more Smart Citations

Investigation of the relaxation behavior of novel terpolymers of acrylonitrile, methyl methacylate and indene

Mohammady¹,

Elkholy²,

Elsabeé³

2006

Polymer International

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Terpolymer samples were prepared by free radical polymerization of methyl methacrylate (MMA), indene (In) and acrylonitrile (AN) in bulk. The samples were chosen so that the molar ratio of AN to MMA varied from 1.00:4.39 to 1.00:0.83, while the molar ratio of In was kept almost unchanged. The glass transition temperatures (T g ) of the samples were determined using differential scanning calorimetry. Moreover, isochronal dynamic mechanical measurements of the complex bending modulus as well as the complex dielectric permittivity were carried out over wide temperature ranges, namely from 50 to 190• C, depending on the material investigated. All samples exhibited a single common T g value, which increased to higher temperature upon increasing the content of AN. In addition, the results were investigated quantitatively in the framework of a molecular model.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Activation Curves and The Cooperative Rearranging Regions Ofmentioning

confidence: 99%

See 3 more Smart Citations

Investigation of the relaxation behavior of novel terpolymers of acrylonitrile, methyl methacylate and indene

Mohammady¹,

Elkholy²,

Elsabeé³

2006

Polymer International

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Optical transparency, thermal resistance, intermolecular interaction, and mechanical properties of poly(styrene‐butadiene‐styrene) copolymer‐based thermoplastic elastomers

Tsai

et al. 2009

J of Applied Polymer Sci

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ABSTRACT:The optical transparency, thermal resistance, intermolecular interaction, and mechanical properties of poly(styrene-block-butadiene-block-styrene) (SBS), which were modified by blending with crystalline polypropylene (PP) or amorphous polystyrene (PS), were analyzed. The dynamic mechanical test indicated that the PP exhibited an intermolecular interaction with SBS and PS was compatible with SBS. The optical properties indicated that the direction of the light was changed due to the difference between the refractive indices of SBS and the added modifiers. Additionally, refraction and reflection occurred at the interface, reducing the transparency of SBS. The thermal resistance of SBS clearly improved upon modification by the addition of crystalline PP polymer. The thermal treatment increased the tensile strength and the elongation at breakage of modified SBS by reducing the internal stress, which was generated during the blending process.

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Viscoelastic relaxation of styrene–butadiene–styrene block copolymers with different topological structures

Liang

et al. 2011

J of Applied Polymer Sci

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The viscoelastic relaxation of linear styrenebutadiene-styrene triblock copolymer (l-SBS) and star styrene-butadiene-styrene triblock copolymer (s-SBS) with four arms were investigated with differential scanning calorimetry and dynamic rheological measurements. Three characteristic viscoelastic responses of l-SBS and s-SBS in the plot of the loss tangent (tan d) and temperature at different frequencies (x's), which corresponded to the relaxation of the polybutadiene (PB) block (peak I), the glass transition of the polystyrene (PS) phase (peak II), and the mutual diffusion between the PB blocks and PS blocks (peak III), respectively, were observed in the experimental range. Although x was 0.1 rad/s, a noticeable peak III was gained for both l-SBS and s-SBS. The dynamic storage modulus (G 0 ) of l-SBS showed two distinct types of behavior, depending on the temperature. At temperature (T) < T 2 (where T 2 is the temperature corresponding to peak II), G 0 of l-SBS displayed a very weak x dependency. In contrast, at T > T 2 , G 0 decayed much more rapidly. However, G 0 of s-SBS displayed a very weak x dependency at both T < T 2 and T > T 2 . Only near T 2 did s-SBS decay with x a little sharply. These indicated, in contrast to l-SBS, that s-SBS still exhibited more elasticity even at T > T 2 because of its crosslinking point between the PB blocks (the star structure). In the lower x range, l-SBS exhibited a stronger peak III than s-SBS despite the same styrene content for l-SBS and s-SBS. The high tan d value of peak III for l-SBS was considered to be related to the internal friction among the PB blocks or the whole l-SBS chain, not the PS blocks.

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Detection of the glass relaxation process of the PS-phase in block copolymers

Cited by 21 publications

References 35 publications

Investigation of the relaxation behavior of novel terpolymers of acrylonitrile, methyl methacylate and indene

Investigation of the relaxation behavior of novel terpolymers of acrylonitrile, methyl methacylate and indene

Optical transparency, thermal resistance, intermolecular interaction, and mechanical properties of poly(styrene‐butadiene‐styrene) copolymer‐based thermoplastic elastomers

Viscoelastic relaxation of styrene–butadiene–styrene block copolymers with different topological structures

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