Small-angle x-ray diffraction study of thermal transition in styrene-butadiene block copolymers

Roe, Ryong‐Joon; Fishkis, M.; Chang, Jiaying

doi:10.1021/ma50005a040

Cited by 140 publications

(109 citation statements)

References 14 publications

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“…The change in SAXS profile accompanying the thermal transition was first discussed by Roe et a/. 8 and extensively so in our previous papers. 4 • 5 • 9 The scattering from the disordered phase was analyzed on the basis of Leibler's theory.…”

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confidence: 74%

Structure and Properties of Tapered Block Polymers of Styrene and Isoprene II. Dynamic Mechanical Responses and Their Structural Interpretations

Hashimoto

Tsukahara

Kawai

1983

Polym J

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The dynamic mechanical properties of "tapered" block polymers consisting of styrene and isoprene were studied in relation to the unique microdomain structure of these polymers. It was found from morphological observations that considerable mixing of the two monomers occurs in the primary structure, giving rise to a class of block polymers consisting approximately of "styrene-rich" and "isoprene-rich" block chains. Microphase-separated domain structures existed in the tapered block polymers prepared by sequential living anionic polymerization. Each domain, however, contained a substantial amount of dissimilar monomeric units, thus having an order-to-disorder transition temperature T, (the temperature at which the microdomains are dissolved into a homogeneous mixture) lower than that of the ideal block. This lowering in T, should have a substantial influence on flow behavior. The tapered block polymers gave essentially a single broad primary dispersion. This dispersion is related to the microbrownian motion of segments with a relaxation time between those of the parent homopolymers. The temperature dependence of the shift factor aT obeyed the WLF equation, in spite of the heterophase structure. The mechanical behavior was interpreted using a model in which two incompatible units undergo extensive mixing in each domain, leading to an increase in the interfacial volume fraction.KEY Tapered block polymers of styrene and isoprene were prepared by a simultaneous copolymerization of the two monomers containing trace amounts of tetrahydrofuran, with s-BuLi as the initiator and benzene as the polymerization solvent. The sequence distribution of the two monomers and the supermolecular structure were investigated in our previous paper. 1 The results obtained may be summarized as follows. Pyrolysis gaschromatography and proton NMR spectroscopy indicated that the two monomers in the tapered block polymer chains are considerably mixed with each other and give, at least from a phenomenological view point, a block polymer consisting of a "styrene-rich block sequence" and an "isoprene-rich block sequence."Owing to the mixing of the two monomers in the primary structure, the repulsive interaction between the two block sequences (i.e., styrene-rich and isoprene-rich sequences) is much weaker than that between the pure polystyrene and polyisoprene block chains in ideal block polymers (i.e., conventional block polymers prepared by sequential polymerization). This effect leads to an enhanced mixing of the two block sequences in phase-• Present Address:

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mentioning

confidence: 74%

Structure and Properties of Tapered Block Polymers of Styrene and Isoprene II. Dynamic Mechanical Responses and Their Structural Interpretations

Hashimoto

Tsukahara

Kawai

1983

Polym J

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“…In recent years the theoretical and experimental aspects of the determination of the width of domain boundaries have been studied by several authors [4][5][6][7], especially in connexion with studies of semicrystalline polymers and blockcopolymers. In the latter case there is a considerable interest in accurate measurements of *) Dedicated to Prof. Dr. Dr. h. c. O. Kratky on the occasion of his 80th birthday.…”

Section: Introductionmentioning

confidence: 99%

Determination of the width of the domain boundaries in polymer two-phase systems by X-ray small-angle scattering

Siemann

Ruland

1982

Colloid & Polymer Sci

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An accurate determination of the width of domain boundaries presupposes an unambigous elimination of the intensity component due to density fluctuations within the domains. The theoretical aspects of this problem are discussed and an application is demonstrated in an SAXS study of a styrene-isoprene-styrene blockcopolymer. The widths of the domain boundaries depend on the history of the sample, its values are, in general, smaller than theoretically predicted. The domain sizes correspond to the theoretical values, its variance is of the same order as the variance of the molecular weight of the domain-building blocks.

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“…4 Diffuse boundaries are evidence that the phase separation is a gradual phase-demixing, the reverse of which-gradual intermixing upon phase homogenization-has been reported. 5 Upon heating the non-equilibrated F41 l to 212°C (Figure 16), we see more of the circular domains and less-diffuse domain boundaries. In Figure 16a, the sample has been heated for 15 min.…”

Section: Modification Of the Doolittle Equation 39 Yields R( = A(t) Ementioning

confidence: 92%

Microstructural Response of SiIm and SBS Block Copolymers to Heat Treatment

Spontak

Williams

1988

Polym J

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ABSTRACT:Using dynamic transmission electron microscopy, we have studied in-situ the effects of thermal curing/annealing on microstructural elements within films of unstained siloxaneimide (Silm) and stained styrene-butadiene-styrene (SBS) block copolymers. Samples of the Silm multiblock copolymer, only partially cured, were heated to I00°C and 212' C, with the appearance of siloxane domains increasing with curing time. Microstructural coalescence was observed at 324°C, suggesting the presence of a phase transition. SBS transition kinetics are prefaced by theoretical predictions of the equilibrium separation temperature T, as a function of molecular weight and composition, leading to T,oc.M/ 8 • Since the presence of a stain alters all kinetic phenomena, a model based on free-volume theory was devised to estimate how the stain concentration affects local viscosity. Annealing of initially non-equilibrated SBS sample films was observed to cause increased ordering of styrene domains as temperature increased, with phase inversion at elevated temperatures. Lamellar development was found to occur by coarsening in areas where some lamellae initially formed; structure bands, measuring 110 nm across and separated by 280 nm, were observed to form in initially homogeneous regions.KEY WORDS Block Copolymer / Dynamic TEM / Heat Treatment / Microphase Separation / Microstructural Evolution / Multiblock Copolymer/ Transmission Electron Microscopy/ Microphase separation in block copolymers, due to thermodynamic incompatibility between the blocks, results in microstructures, or domains, which are on the size scale of the end-to-end distance of the polymer molecules. These microstructures and their corresponding interphase regions are responsible for thermal and mechanical properties that are unlike those of either homopolymer or those of a random copolymer of equal composition. Direct studies of these microstructures are restricted by the small size of the domains (typically on the order of tens of nanometers); consequently, only some experimental methods-e.g., transmission electron microscopy (TEM), 1 -4 small-angle X-ray scattering (SAXS), 5 -7 and small-angle neutron scattering (SANS) 8 -10 -have proven useful in accurately characterizing the microstructures of block copolymers.

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Small-angle x-ray diffraction study of thermal transition in styrene-butadiene block copolymers

Cited by 140 publications

References 14 publications

Structure and Properties of Tapered Block Polymers of Styrene and Isoprene II. Dynamic Mechanical Responses and Their Structural Interpretations

Structure and Properties of Tapered Block Polymers of Styrene and Isoprene II. Dynamic Mechanical Responses and Their Structural Interpretations

Determination of the width of the domain boundaries in polymer two-phase systems by X-ray small-angle scattering

Microstructural Response of SiIm and SBS Block Copolymers to Heat Treatment

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