Effect of Loop/Bridge Conformation Ratio on Elastic Properties of the Sphere-Forming ABA Triblock Copolymers under Uniaxial Elongation

Takahashi, Yoshiaki; Song, Yihu; Nemoto, Norio; Takano, Atsushi; Akazawa, Yoshihiko; Matsushita, Yushu

doi:10.1021/ma050720w

Cited by 43 publications

(44 citation statements)

References 25 publications

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“…97 This result is complementary to the result found for well entangled bridges, the elasticity per bridge much larger than k B T (as quantified by the use of a ring block copolymer as a reference for the loops). 106,107 Thus, the combination of different methods of physical measurements, not only the viscoelastic and dielectric methods but also the dichroism, scattering, and NMR methods, [64][65][66][67] enables us to reveal novel features of flexible polymers. It is of particular scientific interest to explore the universality underlying these features.…”

Section: Discussionmentioning

confidence: 99%

Slow Dynamics in Homopolymer Liquids

Watanabe

2009

Polym. J.

139

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Dynamic physical properties of homopolymer liquids relax through global motion of the polymer chains over their dimension. This motion is affected by a variety of factors. For high molecular weight (M) chains, the entanglement retards the global motion to affect the properties. This entanglement effect changes with the chain architecture as well as the molecular weight distribution. The effect of the chain architecture on the global chain dynamics is found also for non-entangled low-M chains as well. This article gives a very brief summary of the experimental facts and molecular interpretations for these effects.KEY WORDS: Homopolymer Liquid / Relaxation / Slow Dynamics / Entanglement / Viscoelastic Property / Dielectric Property / Type-A Dipole / Needless to say, flexible polymer chains are composed of monomeric units covalently connected in a thread-like structure. In a local length scale, they have their own chemical functionalities such as the polorizability and electron susceptibility to exhibit intrinsic spectroscopic properties, for example, optical and electronic properties. In this sense, chemically different polymers cannot be regarded as the same class of materials. At the same time, however, the threadlike structure of polymer chains allows such chemically different chains to exhibit some universal properties. For example, flexible linear polymer melts exhibit the universal power law dependence of the zero-shear viscosity 0 on the molecular weight M, 0 / M with ¼ $ 1 and ¼ $ 3:5 in low-and high-M regimes, respectively.1 This dependence and related slow viscoelastic relaxation of polymer melts are believed to result from the fundamental thread-like structure of polymer chains irrespective of their chemical details. Scientifically, it is very interesting to explore a relationship(s) between such universal behavior of flexible polymer chains and their slow dynamics and further examine the factors that affect the slow dynamics and properties.This article follows the above viewpoint to give a very brief review of slow viscoelastic and dielectric relaxation behavior of homopolymer liquids. We place our main focus on homopolymer systems where the entanglement resulting from mutual uncrossability of real polymer chains plays the essential role. The entanglement, often modeled as mutual winding/hooking of threads, is equivalent to a topological constraint for thermal motion of the polymer chains that changes its magnitude according to the time and length scales. The linear and nonlinear viscoelastic behavior and related dielectric behavior of homopolymer melts/solutions are summarized on the basis of this molecular understanding. BASICS Molecular Expression of Viscoelastic Relaxation FunctionFor a series of chemically identical linear polymer melts having different molecular weights M, Figure 1 schematically shows the relaxation behavior of shear stress ðtÞ under a small step shear strain :1 The relaxation modulus, GðtÞ ðtÞ=, is double-logarithmically plotted against the time t after imposition of strain. The...

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Section: Discussionmentioning

confidence: 99%

Slow Dynamics in Homopolymer Liquids

Watanabe

2009

Polym. J.

139

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“…Small‐angle X‐ray scattering (SAXS) measurement4–11 and transmission electron microscopy (TEM)12–18 have generally been used to study the orientation behavior of microdomains. For instance, cylindrical microdomains inclined to the stretching direction have been quantitatively estimated by analysis of the two‐dimensional SAXS pattern.…”

Section: Introductionmentioning

confidence: 99%

Thermal and microwave‐assisted oxidative degradation of poly(ethylene oxide)

Vijayalakshmi¹,

Chakraborty²,

Madras³

2005

J of Applied Polymer Sci

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ABSTRACT:The kinetics of the thermal and microwaveassisted oxidative degradation of poly(ethylene oxide) were determined with potassium persulfate as the oxidizing agent. Gel permeation chromatography was used to determine the variation of the molecular weight with time. The degradation was studied as a function of the temperature and persulfate concentration, and it was found that the degradation rate increased with the temperature and concentration of persulfate. Continuous distribution kinetics were used to determine the rate coefficients for the degradation process, and the activation energies were obtained. The results indicated that the microwave-assisted process had a lower activation energy of 10.3 kcal/mol, whereas that of the thermal degradation was 25.2 kcal/mol.

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“…1,2 Since the elastomeric deformation properties are directly related to the molecular and phase structures, the deformation properties such as stress-strain [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and stress relaxation behavior [22][23][24][25][26][27][28][29][30][31][32][33][34][35] have been widely studied. Especially, the stress relaxation behavior is closely related to the practical important properties for elastomers, such as tension and compression permanent set.…”

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confidence: 99%

Orientation Relaxation of Triblock Copolymer with Cylindrical Microdomain by in situ Stress-Birefringence Measurements

Shimizu

Saito

2009

Polym. J.

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The orientation relaxation behavior of polystyrene-block-hydrogenated polyisoprene-block-polystyrene (SEPS) with cylindrical microdomains of polystyrene (PS) dispersed in the rubbery segments was investigated by simultaneous measurements of stress and birefringence, and small angel X-ray scattering (SAXS) measurements. At short relaxation time, the stress ' and the birefringence Án decreased at almost constant rate with time and temperature. At long relaxation time, however, the ' and Án decreased steeply with time, and the decrease became larger with increasing time and temperature. The decrease of the Án stopped and large Án remained at high temperature, while the ' was close to zero. Such characteristic relaxation behavior is ascribed to the form birefringence induced by the orientation of the parallel arranged cylindrical microdomains and the conformational change of the phenyl ring side group associating with the orientation relaxation of PS. The analysis of these results suggest that the orientation relaxation of the rubbery segments occurs at short relaxation time during the stress relaxation after the uniaxial stretching, and then the orientation relaxation of the PS segments in the cylindrical PS microdomains occurs associating with the conformational change of the phenyl side group at long relaxation time at high temperature while the orientation of the cylindrical domain is not changed.KEY WORDS: Tribrock Copolymer / Cylindrical Microdomain / Birefringence / Stress / Orientation Relaxation / Triblock copolymers consisting of glassy end blocks and rubbery midblock such as polystyrene-block-polybutadieneblock-polystyrene (SBS) are typical thermoplastic elastomers.1,2 Since the elastomeric deformation properties are directly related to the molecular and phase structures, the deformation properties such as stress-strain 3-21 and stress relaxation behavior [22][23][24][25][26][27][28][29][30][31][32][33][34][35] have been widely studied. Especially, the stress relaxation behavior is closely related to the practical important properties for elastomers, such as tension and compression permanent set.The birefringence method is often used in combination of the deformation studies. 8,15,[19][20][21][29][30][31][32]36,37 It has shown a great advantage to estimate the physical property and molecular structure because 1) birefringence is sensitive to the change of orientation at small deformation, 2) in situ measurement of high-speed deformation processes is possible by fast measurement, and 3) the orientations of microdomain segments and matrix ones can be evaluated separately by using the additive rule for each segment.Recently, we found that the birefringence of polystyreneblock-hydrogenated polyisoprene-block-polystyrene (SEPS) with cylindrical microdomains of glassy polystyrene (PS) dispersed in the rubbery ethylene-propylene matrix changed little below a yield strain, increased sharply with strain above a yield strain up to a strain of 0.5, and then increased gradually during uniaxial stretching, while the s...

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Effect of Loop/Bridge Conformation Ratio on Elastic Properties of the Sphere-Forming ABA Triblock Copolymers under Uniaxial Elongation

Cited by 43 publications

References 25 publications

Slow Dynamics in Homopolymer Liquids

Slow Dynamics in Homopolymer Liquids

Thermal and microwave‐assisted oxidative degradation of poly(ethylene oxide)

Orientation Relaxation of Triblock Copolymer with Cylindrical Microdomain by in situ Stress-Birefringence Measurements

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