Structure and dynamics of a pentablock copolymer of polystyrene-polybutadiene in a butadiene-selective solvent

Nie, Huiling; Li, Minghai; Bansil, Rama; Koňák, Čestmı́r; Helmstedt, Martin; Lal, Jyotsana

doi:10.1016/j.polymer.2004.10.051

Cited by 10 publications

(10 citation statements)

References 29 publications

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“…For example, DLS has been used to study the random association of hydrophobically modified water-soluble polymers, [174] block copolymers composed of elastin-like and poly(ethylene glycol) (PEG) blocks, [156] and multiblock copolymers. [175] Diffusing-wave spectroscopy (DWS) uses dynamic light scattering in the determination of the viscoelastic behavior of a complex fluid. The time evolution of the mean-square displacement of a suspension of particles, acting as hard spheres in a viscoelastic medium, can be related to the frequency-dependent storage and loss moduli of the medium.…”

Section: Hydrogelsmentioning

confidence: 99%

Smart Self‐Assembled Hybrid Hydrogel Biomaterials

2012

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Hybrid biomaterials are systems created from components of at least two distinct classes of molecules, for example, synthetic macromolecules and proteins or peptide domains. The synergistic combination of two types of structures may produce new materials that possess unprecedented levels of structural organization and novel properties. This Review focuses on biorecognition-driven self-assembly of hybrid macromolecules into functional hydrogel biomaterials. First, basic rules that govern the secondary structure of peptides are discussed, and then approaches to the specific design of hybrid systems with tailor-made properties are evaluated, followed by a discussion on the similarity of design principles of biomaterials and macromolecular therapeutics. Finally, the future of the field is briefly

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Section: Hydrogelsmentioning

confidence: 99%

Smart Self‐Assembled Hybrid Hydrogel Biomaterials

2012

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“…Experiments that investigate the association behavior of multiblock copolymers in dilute, apolar organic solutions are limited. [63][64][65] An example is the work by Nie and et al 65 that studied the structure and dynamics of a polystyrene ͑PS͒polybutadiene ͑PB͒ pentablock copolymer ͑S-B-S-B-S͒ in heptane, a strongly selective solvent for PB and a poor solvent for PS. In dilute solutions, no micellization of the pentablock was detected.…”

Section: A Macro-versus Microphase Separationmentioning

confidence: 99%

“…Only aggregates in the vicinity of N chain multiblock chains in the melt 15,30,69,[81][82][83] and in solutions of selective solvents. 65,75,84 In this work, the qualitative nature of multiblock network formation is examined with respect to the type of thermodynamic phase equilibrium attained in dilute solutions.…”

Section: E Network Formationmentioning

confidence: 99%

Phase behavior and structure formation in linear multiblock copolymer solutions by Monte Carlo simulation

Gindy

Prud'homme²,

Panagiotopoulos³

2008

The Journal of Chemical Physics

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The solution phase behavior of short, strictly alternating multiblock copolymers of type (A(n)B(n))(m) was studied using lattice Monte Carlo simulations. The polymer molecules were modeled as flexible chains in a monomeric solvent selective for block type A. The degree of block polymerization n and the number of diblock units per chain m were treated as variables. We show that within the regime of parameters accessible to our study, the thermodynamic phase transition type is dependent on the ratio of m / n. The simulations show microscopic phase separation into roughly spherical aggregates for m / n ratios less than a critical value and first-order macroscopic precipitation otherwise. In general, increasing m at fixed n, or n at fixed m, promotes the tendency toward macroscopic phase precipitation. The enthalpic driving force of phase change is found to universally scale with chain length for all multiblock systems considered and is independent of the existence of a true phase transition. For aggregate forming systems at low amphiphile concentrations, multiblock chains are shown to self-assemble into intramolecular, multichain clusters. Predictions for microstructural dimensions, including critical micelle concentration, equilibrium size, shape, aggregation parameters, and density distributions, are provided. At increasing amphiphile density, interaggregate bridging is shown to result in the formation of networked structures, leading to an eventual solution-gel transition. The gel is swollen and consists of highly interconnected aggregates of approximately spherical morphology. Qualitative agreement is found between experimentally observed physical property changes and phase transitions predicted by simulations. Thus, a potential application of the simulations is the design of multiblock copolymer systems which can be optimized with regard to solution phase behavior and ultimately physical and mechanical properties.

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“…The relative amplitude of the slow mode is determined by the relative strength of the osmotic and the elastic modulus. A q-independent slow mode has indeed been observed for transient gels formed by entangled semidilute polymer solutions [45,46], self-assembled triblock copolymers [4,[47][48][49][50][51], and emulsions of small droplets connected by triblock copolymers [52][53][54]. However, slow modes with relaxation times inversely proportional to q 2 have also been observed and have been attributed to the diffusion of clusters or large scale heterogeneities [4,49,50].…”

Section: Introductionmentioning

confidence: 87%

Slow dynamics in transient polyelectrolyte hydrogels formed by self-assembly of block copolymers

et al. 2013

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Transient polyelectrolyte hydrogels were formed by self-assembly of triblock copolyelectrolytes with a central hydrophilic block, poly(acrylic acid) (PAA), and two hydrophobic end blocks, poly(n-butyl acrylate(50%)-stat-acrylic acid(50%)) [P(nBA(50%)-stat-AA(50%))]. The relaxation of the concentration fluctuations was investigated by dynamic light scattering as a function of the concentration, the pH, the temperature, and the ionic strength. A relatively fast mode was observed at all polymer concentrations caused by cooperative diffusion of the polymers. Above the critical percolation concentration a second slow relaxation mode was observed caused by a linear displacement of small heterogeneities in the network with constant velocity. The relative amplitude of the slow mode was determined by the strength of the electrostatic repulsion. The velocity of the displacement in the transient network is shown to be directly correlated to the terminal relaxation time of the shear modulus and has the same Arrhenius temperature dependence. Both the velocity of the displacement and the mechanical relaxation strongly slow down with decreasing degree of ionization below 0.7 and increasing ionic strength above 0.5 M. A ballistic relaxation process has been reported earlier for colloidal gels, and the present study shows that it can also occur in polymeric networks.

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Structure and dynamics of a pentablock copolymer of polystyrene-polybutadiene in a butadiene-selective solvent

Cited by 10 publications

References 29 publications

Smart Self‐Assembled Hybrid Hydrogel Biomaterials

Smart Self‐Assembled Hybrid Hydrogel Biomaterials

Phase behavior and structure formation in linear multiblock copolymer solutions by Monte Carlo simulation

Slow dynamics in transient polyelectrolyte hydrogels formed by self-assembly of block copolymers

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