Universality in eight-arm star polystyrene and methylcyclohexane mixtures near the critical point

Jacobs, D. T.; Braganza, Clinton; Brinck, Andy P.; Cohen, Adam B.; Lightfoot, Mark; Locke, Christopher J.; Suddendorf, Sarah J.; Timmers, Henry; Triplett, Angela L.; Venkataraman, Nithya; Wellons, Mark

doi:10.1063/1.2771161

Cited by 8 publications

(12 citation statements)

References 46 publications

(77 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In other words, the solubility of star polymers becomes better with increasing arm number if the total molecular weight is the same. We note that, if Â=T c is plotted against M w À1=2 , the literature data for eight-arm star PS in methylcyclohexane 6,8 come much higher than the present data.…”

Section: Phase Diagramcontrasting

confidence: 47%

See 1 more Smart Citation

Light Scattering and Phase Separation Studies on Cyclohexane Solutions of Six-Arm Star Polystyrene†

Tasaka

Okumoto

Nakamura

et al. 2008

Polym J

View full text Add to dashboard Cite

Light scattering and phase separation experiments were performed for four six-arm star polystyrene (6SPS) samples with weight-average molecular weights M w of 9:62 Â 10 4 to 1:16 Â 10 6 in cyclohexane below the theta temperature (34.5 C). From the former experiment, the apparent second virial coefficient J was obtained as functions of the polymer volume fraction and temperature T, along with the spinodals. In the latter experiment, the concentrations of coexisting two phases were determined as functions of T. The critical point T c determined from the coexisting curve was lower than that for fourarm star polystyrene (4SPS) when compared at the same M w . As was the case for 4SPS and linear polystyrene in cyclohexane, J for 6SPS at each T in a region of large was represented by a universal function of =P 0:1 regardless of P (the volume of the polymer chain relative to that of the solvent molecule), although it differed from the common function previously found for the other two types of polystyrene. It was concluded that the solubility of 6SPS higher than that of 4SPS in cyclohexane as indicated by the lower critical point is attributable to the chain-end effect.KEY WORDS: Star Polymer / Phase Separation / Chemical Potential / Binodal / Spinodal / Critical Point / Polystyrene / It is known that the phase separation temperature for star polymers in poor solvents are lower than that for the corresponding linear polymer with the same molecular weight and the same chemical structure. [1][2][3][4][5][6] This cannot be explained by theories invoking the Flory-Huggins type 7 mean-field approximation, but at present, there exists no molecular theory that explains the phase behavior of branched molecules. Recent Monte Carlo simulation results also fail to describe the experimental data. 8,9 In this situation, a phenomenological approach to the problem may be useful as an alternate. [10][11][12] In our previous work, Terao et al.4 carried out light scattering and phase separation experiments on four-arm star polystyrene (PS) in cyclohexane below the theta point Â (34.5 C). Their light scattering data showed that the apparent second virial coefficient J at a fixed temperature T in a region of high polymer volume fraction can be represented by a universal function of =P 0:1 regardless of molecular weight and that the same function is also applicable to linear PS in cyclohexane, where P is the relative chain length (the volume of the polymer chain relative to that of the solvent molecule). The difference in J between four-arm star and linear PS's appeared only at low . Thus, it was concluded that the difference in the chemical potential of the solvent in the low region is responsible for the difference in phase separation behavior between the two polymers.The present study was undertaken as an extension of the previous work to six-arm star PS in cyclohexane below Â to examine the J function behavior and the phase diagrams in relation to four-arm star and linear PS's. Light scattering and phase separation data obtained as func...

show abstract

Section: Phase Diagramcontrasting

confidence: 47%

“…[1][2][3][4][5][6] This cannot be explained by theories invoking the Flory-Huggins type 7 mean-field approximation, but at present, there exists no molecular theory that explains the phase behavior of branched molecules. Recent Monte Carlo simulation results also fail to describe the experimental data.…”

mentioning

confidence: 99%

Light Scattering and Phase Separation Studies on Cyclohexane Solutions of Six-Arm Star Polystyrene†

Tasaka

Okumoto

Nakamura

et al. 2008

Polym J

View full text Add to dashboard Cite

show abstract

“…It is important to note that, for polydisperse micelles that form coexisting liquid phases, the cloud points and the coexistence curves do not coincide. Koningsveld , has shown that for polydisperse systems: “As a rule, it is not allowed to identify a cloud-point curve with a bimodal (coexistence curve), nor the maximum in a cloud-point curve with a critical point.” This differs from a monodisperse system such as methanol and cyclohexane or even from a polymer of narrow polydispersity in a solvent, where the onset of phase separationthe “cloud point”, where the system is opalescent as a second phase formscoincides with the coexistence curve. For monodisperse systems with an upper critical solution temperature (UCST) [or a lower critical solution point (LCST)], the maximum of the cloud point curve is also the maximum [or minimum] of the coexistence curve and is the critical point …”

Section: Introductionmentioning

confidence: 99%

Micellization and Phase Separation for Triblock Copolymer 17R4 in H₂O and in D₂O

et al. 2011

View full text Add to dashboard Cite

The reverse Pluronic triblock copolymer 17R4 is formed from poly(propylene oxide) (PPO) and poly(ethylene oxide) (PEO): PPO(14)-PEO(24)-PPO(14), where the subscripts denote the number of monomers in each block. In water, 17R4 shows both a transition to aggregated micellar species at lower temperatures and a separation into copolymer-rich and copolymer-poor liquid phases at higher temperatures. For 17R4 in H(2)O and in D(2)O, we have determined (1) the phase boundaries corresponding to the micellization line, (2) the cloud point curves marking the onset of phase separation at various compositions, and (3) the coexistence curves for the phase separation (the compositions of coexisting phases). In both H(2)O and in D(2)O, 17R4 exhibits coexistence curves with lower consolute temperatures and compositions that differ from the minima in the cloud point curves; we take this as an indication of the polydispersity of the micellar species. The coexistence curves for compositions near the critical composition are described well by an Ising model. For 17R4 in both H(2)O and D(2)O, the critical composition is 0.22 ± 0.01 in volume fraction. The critical temperatures differ: 44.8 °C in H(2)O and 43.6 °C in D(2)O. The cloud point curve for the 17R4/D(2)O is as much as 9 °C lower than in H(2)O.

show abstract

“…1,5 Because of the polydispersity of the copolymer, the cloud point curve is not the same as the coexistence curve in this system. 5,13 This differs from a monodisperse system such as a polymer of narrow polydispersity in a solvent, 14 or methanol and cyclohexane, 15 in which the opalescence due to the onset of phase separationthe "cloud point"-coincides with the coexistence curve. This distinction is discussed in some detail by Huff et al, 5 who measured the micellization line, coexistence curves, and the cloud point curve in 17R4/H 2 O as shown in Fig.…”

Section: Phase Boundaries and Critical Pointmentioning

confidence: 99%

“…The cloudy and clear regions can be measured by the turbidity τ, which is an extinction coefficient for a transmitted beam of light that enters the sample of length L with an intensity I 0 and exits with an intensity I t : τ = −(1/L) ln(I t /I 0 ). 14 Using a measurement technique described previously, 14 we can illustrate the cloudiness for one composition of 17R4 and water in Fig. 2.…”

Section: E Turbiditymentioning

confidence: 99%

Heat capacity anomaly in a self-aggregating system: Triblock copolymer 17R4 in water

Dumancas

Simpson

Jacobs

2015

The Journal of Chemical Physics

Self Cite

View full text Add to dashboard Cite

The reverse Pluronic, triblock copolymer 17R4 is formed from poly(propylene oxide) (PPO) and poly(ethylene oxide) (PEO): PPO14 - PEO24 - PPO14, where the number of monomers in each block is denoted by the subscripts. In water, 17R4 has a micellization line marking the transition from a unimer network to self-aggregated spherical micelles which is quite near a cloud point curve above which the system separates into copolymer-rich and copolymer-poor liquid phases. The phase separation has an Ising-like, lower consolute critical point with a well-determined critical temperature and composition. We have measured the heat capacity as a function of temperature using an adiabatic calorimeter for three compositions: (1) the critical composition where the anomaly at the critical point is analyzed, (2) a composition much less than the critical composition with a much smaller spike when the cloud point curve is crossed, and (3) a composition near where the micellization line intersects the cloud point curve that only shows micellization. For the critical composition, the heat capacity anomaly very near the critical point is observed for the first time in a Pluronic/water system and is described well as a second-order phase transition resulting from the copolymer-water interaction. For all compositions, the onset of micellization is clear, but the formation of micelles occurs over a broad range of temperatures and never becomes complete because micelles form differently in each phase above the cloud point curve. The integrated heat capacity gives an enthalpy that is smaller than the standard state enthalpy of micellization given by a van't Hoff plot, a typical result for Pluronic systems.

show abstract

Universality in eight-arm star polystyrene and methylcyclohexane mixtures near the critical point

Cited by 8 publications

References 46 publications

Light Scattering and Phase Separation Studies on Cyclohexane Solutions of Six-Arm Star Polystyrene†

Light Scattering and Phase Separation Studies on Cyclohexane Solutions of Six-Arm Star Polystyrene†

Micellization and Phase Separation for Triblock Copolymer 17R4 in H₂O and in D₂O

Heat capacity anomaly in a self-aggregating system: Triblock copolymer 17R4 in water

Contact Info

Product

Resources

About

Universality in eight-arm star polystyrene and methylcyclohexane mixtures near the critical point

Cited by 8 publications

References 46 publications

Light Scattering and Phase Separation Studies on Cyclohexane Solutions of Six-Arm Star Polystyrene†

Light Scattering and Phase Separation Studies on Cyclohexane Solutions of Six-Arm Star Polystyrene†

Micellization and Phase Separation for Triblock Copolymer 17R4 in H2O and in D2O

Heat capacity anomaly in a self-aggregating system: Triblock copolymer 17R4 in water

Contact Info

Product

Resources

About

Micellization and Phase Separation for Triblock Copolymer 17R4 in H₂O and in D₂O