Dynamics of solutions of triblock copolymers in a selective solvent: Effect of varying copolymer concentration

Koňák, Čestmı́r; Fleischer, G.; Tuzar, Zdeněk; Bansil, Rama

doi:10.1002/(sici)1099-0488(20000515)38:10<1312::aid-polb70>3.0.co;2-g

Cited by 29 publications

(34 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The data for the LC gels qualitatively resemble those observed from previous light-scattering studies of associating polymers, [23][24][25][26][27][28][29] with the appearance of slow relaxation modes above a critical concentration and highly stretched intensityautocorrelation functions with a strong q-dependence. However, in the present study, the scattered light arises primarily from fluctuations in the orientation of the nematic director, not density fluctuations as in the previous lightscattering studies of gelled systems [23][24][25][26][27][28][29] .…”

Section: Discussionsupporting

confidence: 80%

“…However, in the present study, the scattered light arises primarily from fluctuations in the orientation of the nematic director, not density fluctuations as in the previous lightscattering studies of gelled systems [23][24][25][26][27][28][29] . Therefore, structural changes such as micellar diffusion or concentration fluctuations in the polymer network are revealed indirectly by their effect on the nematic-director dynamics.…”

Section: Discussionmentioning

confidence: 47%

“…Indeed, the q-dependence of the slow relaxation appears to be stronger than q 2 (or sin 2 h s /2) for small wavevectors (or low h s ), and it is reminiscent of hindered relaxational dynamics in colloidal glasses and associative polymers. [23][24][25][26]28,30 We propose that the nematic director is coupled to the associated gel structure, yielding long-lived orientational fluctuations. The nematic director can relax via the fast relaxation mode only to a certain extent, due to a coupling to the polymer-gel structure.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Director dynamics in liquid-crystal physical gels

et al. 2007

View full text Add to dashboard Cite

Nematic liquid-crystal (LC) elastomers and gels have a rubbery polymer network coupled to the nematic director. While LC elastomers show a single, non-hydrodynamic relaxation mode, dynamic light-scattering studies of self-assembled liquid-crystal gels reveal orientational fluctuations that relax over a broad time scale. At short times, the relaxation dynamics exhibit hydrodynamic behavior. In contrast, the relaxation dynamics at long times are nonhydrodynamic, highly anisotropic, and increase in amplitude at small scattering angles. We argue that the slower dynamics arise from coupling between the director and the physically associated network, which prevents director orientational fluctuations from decaying completely at short times. At long enough times the network restructures, allowing the orientational fluctuations to fully decay. Director dynamics in the self-assembled gels are thus quite distinct from those observed in LC elastomers in two respects: they display soft orientational fluctuations at short times, and they exhibit at least two qualitatively distinct relaxation processes.

show abstract

Section: Discussionsupporting

confidence: 80%

Section: Discussionmentioning

confidence: 47%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Director dynamics in liquid-crystal physical gels

et al. 2007

View full text Add to dashboard Cite

show abstract

“…Therefore, in comparison with dynamics in homopolymers, the results of block copolymer chains in semidilute solution were more controversial and diversified. [123][124][125][126][127][128][129][130][131][132][133][134][135][136][137][138][139][140][141] The system of poly(ethylene oxide)-poly(propylene oxide)-poly (ethylene oxide) (PEO-PPO-PEO) in H 2 O was also selected to investiage the solution dynamics because of the well-known fact that it can exhibit temperature-induced micellization phenomenon at a certain concentration range. Figure 12a shows typical plots of intensity-intensity correlation function for the PEO-PPO-PEO/H 2 O system in both the dilute and semidilute regimes, and Figure 12b shows the corresponding plots of characteristic relaxation time distribution analyzed by the CONTIN method.…”

Section: The Slow Mode In Peo-ppo-peo/h 2 O Systemmentioning

confidence: 99%

The slow relaxation mode: from solutions to gel networks

Ngai

2010

Polym J

View full text Add to dashboard Cite

In the past, many laser light-scattering experimental results revealed that besides the fast relaxation mode, there existed an additional slow mode in semidilute solutions. This slow mode has been assigned to a variety of origins, but there has been no clear and well-accepted explanation. As the polymer concentration increases, the slow relaxation mode persists in the concentrated region, in melts and in gels in which polymer chains are crosslinked instead of entangled. The slow relaxation mode has also been reported for charged macromolecules in aqueous and nonaqueous solutions. However, it is generally thought to be different in nature from that observed in semidilute neutral polymer solution. In recent years, armed with novel solution preparation methods and some specially designed polymers, we have reexamined the dynamics of polymer chains, especially the slow mode, in semidilute neutral polymer solutions, dilute polyelectrolyte solutions and gels, which are reviewed here. Our results suggest that the slow mode can be qualitatively considered as hindered motions of interacting chains even though the nature of interaction can be very different; namely, from the weak segment-segment interaction in a less good solvent to strong electrostatic interaction among polyelectrolyte chains, and even to chemical crosslinking inside gel networks.

show abstract

“…In dilute solution flowerlike micelles are formed consisting of solvophobic cores of B blocks surrounded by a solvated corona of A blocks. A further increase of the concentration leads to bridging of flower-like micelles into larger aggregates [1][2][3][4][5][6]. The aggregates grow in size with increasing concentration until at the critical percolation concentration (C p ) a system spanning transient network is formed [7][8][9]; see Fig.…”

Section: Introductionmentioning

confidence: 97%

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

et al. 2013

View full text Add to dashboard Cite

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.

show abstract

Dynamics of solutions of triblock copolymers in a selective solvent: Effect of varying copolymer concentration

Cited by 29 publications

References 50 publications

Director dynamics in liquid-crystal physical gels

Director dynamics in liquid-crystal physical gels

The slow relaxation mode: from solutions to gel networks

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

Contact Info

Product

Resources

About