The molecular conformation, hydrodynamic and mechanical properties of a 4:5 block copolymer of styrene and isoprene

Бреслер, С. Е.; Pyrkov, L.M.; Frenkel, S.Ya.; Laius, L. A.; Klenin, S.I.

doi:10.1016/0032-3950(63)90548-3

Cited by 14 publications

(9 citation statements)

References 3 publications

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“…There are no accurate data with which to compare predicted distribution widths for the present system, but in any case such a comparison would not be straightforward since account would need to be taken of the finite size distribution of the block copolymer sample. An average association number has been determined experimentally for SI(1) in hexadecane by light scattering,35 but not for SI (2). It was found that SI(1) had an average association number of 33. This experimental value was arrived at by fitting the lightscattering data in the region of the critical micelle concentration (cmc) to a model which assumed there were just two sizes of species present in solution, unassociated chains and micelles with a particular association number.…”

Section: Statementioning

confidence: 96%

“…The molar concentration of copolymer chains to be found in the form of micelles with a given association number m is mpm. Comparison between Experiment and Theory Calculations were carried out for two polystyrene-6/ocApolyisoprene copolymers, designated SI(1) and SI (2). The weight-average and number-average molecular weights, Mw and M", and the polydispersity ratio, Mw/fifa, for the copolymers in the unassociated state are give at the top of Table I.…”

Section: Statementioning

confidence: 99%

“…However, for the SI/hexadecane system considered in this study, which is characterized by strongly segregated polystyrene blocks, the SCF calculations predict the association number of prominent micellar species is very dependent on the block length of the least soluble block. It is the difference in the molar masses of the polystyrene block lengths (7000:13 000) which is largely responsible for the large difference in the association numbers (41:128) of SI (1) and SI (2). It may be noted that for SI block copolymers in the microphase separated bulk state, there is an even stronger dependence of association number (in that case of the polystyrene blocks in spherical domains) on block length:37-38 the domain radius R\ Ma2/3 and hence m ~Ma2.…”

Section: Statementioning

confidence: 99%

“…^p{lL~l](2) If we choose an ideally dilute standard state of unit molar0024-9297/92/2225-6876103.00i v i d u a l n o t d i r e c t l y a s s o c i a t e d w i t h s c i t e i s p r o h i b i t e d .…”

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confidence: 99%

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Self-consistent field theory of micelle formation by block copolymers

Yuan¹,

Masters

Price³

1992

Macromolecules

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A self-consistent field theory was developed to account for the micellization of block copolymers in selective solvents. The mean-field expression used successfully by Edwards in treating the polymer excludedvolume problem was modified to enable it to be applied to chains in bad solvents without the generation of unrealistically high segment densities. Full consideration was given to the issue of standard states so that a meaningful comparison could be made between theoretical and experimental results. The theory was able to account in a consistent and satisfactory manner for the thermodynamics of micellization of two polystyreneblock-polyisoprene copolymers in n-hexadecane which is a selectively bad solvent for polystyrene.

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Section: Statementioning

confidence: 96%

Section: Statementioning

confidence: 99%

Section: Statementioning

confidence: 99%

mentioning

confidence: 99%

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Self-consistent field theory of micelle formation by block copolymers

Yuan¹,

Masters

Price³

1992

Macromolecules

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“…It is supposed that monomolecutar micelles can exist only on the assumption that they are strongly protected by dissolved solvated subchains which sterically prevent a direct mutual contact between the undissolved regions. This applies to a grafted copolymer with rather a large number of branches or to multi block copolymer [2,3]. The two and threeblock copolymers with a lower number of branches yield in selective solvents micelles which are rather polymolecular [4,5].…”

Section: Introductionmentioning

confidence: 95%

Micellization of styrene/butadiene/styrene block copolymers in mixed solvents

Ahmad

Kaleem

Noor

1983

Colloid & Polymer Sci

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Dilute solutions of three block copolymers, styrene/butadiene/styrene in the mixed selective solvents dioxane/different alcohols is studied at different temperatures. The molecular weight, second virial coefficient and radius of gyration in all selective solvents are also determined. From these measurements it is concluded that a maximum in the dissymmetry of the system for all the selective solvents used is observed. This maximum is observed at higher temperatures for concentrated solutions. Similarly, this maximum is also shifted to lower temperature by using strong precipitants in selective solvents. The milky opalescence is observed for all the selective solvents either by lowering the temperature of the system or by increasing the ratio of the precipitant in the selective solvent.

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Thermoplastic elastomers

Holden

Bishop

Legge

1969

J. polym. sci., C Polym. symp.

252

130

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An important new class of polymers, the thermoplastic elastomers, was announced by the Shell Chemical Company (U.S.A.) in 1965. These new products may be formed into useful articles by modern rapid thermoplastics processing techniques, such as injection molding, and without any chemical vulcanization step provide most of the useful physical properties of vulcanized rubber. High resilience, high tensile strength, highly reversible elongation, and abrasion resistance are obtained. The thermoplastic elastomers consist of ordered, block copolymers of the general structure A‐B‐A, where A is a thermoplastic block polymer and B is an elastomeric block polymer. Choice of monomers, block length, and the weight fractions of A and B are crucial in achieving elastomeric performance. An example is the polystyrene–polybutadiene–polystyrene block copolymer (S‐B‐S) where the molecular weights of S and B and the weight fraction of S are restricted. A two‐phase system is formed, with the middle‐block phase constituting a continuous three‐dimensional elastomeric network and the dispersed end‐block phase serving as multijunction points for the ends of the middle blocks. These systems, without vulcanization, have rubber‐like properties similar to those of conventional rubber vulcanizates but flow as thermoplastics at temperatures above the glass transition of the end block. The behavior is fully temperature reversible. Melt viscosity behavior, measured as a function of shear and temperature, is similar to that of conventional thermoplastics. Activation energies obtained at constant shear stress vary with temperature: at high temperatures they are between those of the pure homopolymers and at low temperatures they approach that of the thermoplastic part of the molecule. Melt viscosities, however, are very much higher than those of either homopolymer of the same total molecular weight. An additional energy term is indicated in the flow process which arises from the transfer of the end block from one aggregate to another, in the process being forced to pass through the elastomeric matrix with which it is thermodynamically incompatible. The classical kinetic theory of rubber elasticity can be applied to these polymers, treating the end‐block phase as hard discrete particles which do not contribute to the elastic network For example, equilibrium modulus or swelling measurements are used to calculate the concentration of elastically effective chains or effective crosslink density. The resulting effective elastic chain length (Mc) is thus identified, not with the middle‐block segment length, but with the normal entanglement length. Hence, normal entanglement junctions in the elastomeric matrix behave as strong effective crosslinks because the ends of the middle block are securely anchored in the end‐block aggregates. High tensile strengths, in the absence of reinforcing fillers or crystallization, may be attributed to a highly perfected network (Case theory) or to the inertial masses of the discrete end‐block aggregates (Bueche the...

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The molecular conformation, hydrodynamic and mechanical properties of a 4:5 block copolymer of styrene and isoprene

Cited by 14 publications

References 3 publications

Self-consistent field theory of micelle formation by block copolymers

Self-consistent field theory of micelle formation by block copolymers

Micellization of styrene/butadiene/styrene block copolymers in mixed solvents

Thermoplastic elastomers

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