Limits...
Unlocking Chain Exchange in Highly Amphiphilic Block Polymer Micellar Systems: Influence of Agitation.

Murphy RP, Kelley EG, Rogers SA, Sullivan MO, Epps TH - ACS Macro Lett (2014)

Bottom Line: Subsequently, the extent of chain exchange between micelles was quantified using small angle neutron scattering.Rapid vortex mixing induced chain exchange within minutes, as evidenced by a monotonic decrease in scattered intensity, whereas Couette flow and sparging did not lead to measurable chain exchange over the examined time scale of hours.These findings demonstrate the strong influence of processing conditions on block polymer solution assemblies.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biomolecular Engineering, University of Delaware , 150 Academy Street, Newark, Delaware 19716, United States.

ABSTRACT

Chain exchange between block polymer micelles in highly selective solvents, such as water, is well-known to be arrested under quiescent conditions, yet this work demonstrates that simple agitation methods can induce rapid chain exchange in these solvents. Aqueous solutions containing either pure poly(butadiene-b-ethylene oxide) or pure poly(butadiene-b-ethylene oxide-d 4) micelles were combined and then subjected to agitation by vortex mixing, concentric cylinder Couette flow, or nitrogen gas sparging. Subsequently, the extent of chain exchange between micelles was quantified using small angle neutron scattering. Rapid vortex mixing induced chain exchange within minutes, as evidenced by a monotonic decrease in scattered intensity, whereas Couette flow and sparging did not lead to measurable chain exchange over the examined time scale of hours. The linear kinetics with respect to agitation time suggested a surface-limited exchange process at the air-water interface. These findings demonstrate the strong influence of processing conditions on block polymer solution assemblies.

No MeSH data available.


Related in: MedlinePlus

Concentrationseries for chain exchange induced by rapid vortexmixing. Scattered intensities from SANS were normalized by polymerconcentration for (a) 2.4, (b) 7.5, (c) 10.0, and (d) 15.0 mg mL–1 micelle solutions at each given mix time (0 min upto 90 min). The 5.0 mg mL–1 data are presented inFigure 2. The normalized maximum (0 min) andminimum (premixed) scattering curves shown in (a–d) are theaverage curves obtained from samples at three different concentrations.Error bars represent the standard deviation in measured scatteredintensity.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4307907&req=5

fig3: Concentrationseries for chain exchange induced by rapid vortexmixing. Scattered intensities from SANS were normalized by polymerconcentration for (a) 2.4, (b) 7.5, (c) 10.0, and (d) 15.0 mg mL–1 micelle solutions at each given mix time (0 min upto 90 min). The 5.0 mg mL–1 data are presented inFigure 2. The normalized maximum (0 min) andminimum (premixed) scattering curves shown in (a–d) are theaverage curves obtained from samples at three different concentrations.Error bars represent the standard deviation in measured scatteredintensity.

Mentions: SANS experiments were conducted at various polymer concentrationsto examine the reproducibility of the linear chain exchange rate andto gain additional insight into the underlying exchange mechanisms.Figure 3 shows similar decreases in scatteredintensity for micelle solutions exposed to rapid vortex mixing atpolymer concentrations ranging from 2 to 15 mg mL–1. Higher polymer concentrations required longer mix times to achievemicelles with randomly mixed chains. For example, randomly mixed micelleswere obtained at tmix ∼ 10 minfor the 2.4 mg mL–1 sample (Figure 3a), whereas the same degree of mixing took tmix ∼ 60 min for the 10.0 mg mL–1 sample (Figure 3c). The corresponding R(tmix) for the different polymerconcentrations decreased linearly with mix time (Figure 4a), further supporting a surface-limited exchange process.


Unlocking Chain Exchange in Highly Amphiphilic Block Polymer Micellar Systems: Influence of Agitation.

Murphy RP, Kelley EG, Rogers SA, Sullivan MO, Epps TH - ACS Macro Lett (2014)

Concentrationseries for chain exchange induced by rapid vortexmixing. Scattered intensities from SANS were normalized by polymerconcentration for (a) 2.4, (b) 7.5, (c) 10.0, and (d) 15.0 mg mL–1 micelle solutions at each given mix time (0 min upto 90 min). The 5.0 mg mL–1 data are presented inFigure 2. The normalized maximum (0 min) andminimum (premixed) scattering curves shown in (a–d) are theaverage curves obtained from samples at three different concentrations.Error bars represent the standard deviation in measured scatteredintensity.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4307907&req=5

fig3: Concentrationseries for chain exchange induced by rapid vortexmixing. Scattered intensities from SANS were normalized by polymerconcentration for (a) 2.4, (b) 7.5, (c) 10.0, and (d) 15.0 mg mL–1 micelle solutions at each given mix time (0 min upto 90 min). The 5.0 mg mL–1 data are presented inFigure 2. The normalized maximum (0 min) andminimum (premixed) scattering curves shown in (a–d) are theaverage curves obtained from samples at three different concentrations.Error bars represent the standard deviation in measured scatteredintensity.
Mentions: SANS experiments were conducted at various polymer concentrationsto examine the reproducibility of the linear chain exchange rate andto gain additional insight into the underlying exchange mechanisms.Figure 3 shows similar decreases in scatteredintensity for micelle solutions exposed to rapid vortex mixing atpolymer concentrations ranging from 2 to 15 mg mL–1. Higher polymer concentrations required longer mix times to achievemicelles with randomly mixed chains. For example, randomly mixed micelleswere obtained at tmix ∼ 10 minfor the 2.4 mg mL–1 sample (Figure 3a), whereas the same degree of mixing took tmix ∼ 60 min for the 10.0 mg mL–1 sample (Figure 3c). The corresponding R(tmix) for the different polymerconcentrations decreased linearly with mix time (Figure 4a), further supporting a surface-limited exchange process.

Bottom Line: Subsequently, the extent of chain exchange between micelles was quantified using small angle neutron scattering.Rapid vortex mixing induced chain exchange within minutes, as evidenced by a monotonic decrease in scattered intensity, whereas Couette flow and sparging did not lead to measurable chain exchange over the examined time scale of hours.These findings demonstrate the strong influence of processing conditions on block polymer solution assemblies.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biomolecular Engineering, University of Delaware , 150 Academy Street, Newark, Delaware 19716, United States.

ABSTRACT

Chain exchange between block polymer micelles in highly selective solvents, such as water, is well-known to be arrested under quiescent conditions, yet this work demonstrates that simple agitation methods can induce rapid chain exchange in these solvents. Aqueous solutions containing either pure poly(butadiene-b-ethylene oxide) or pure poly(butadiene-b-ethylene oxide-d 4) micelles were combined and then subjected to agitation by vortex mixing, concentric cylinder Couette flow, or nitrogen gas sparging. Subsequently, the extent of chain exchange between micelles was quantified using small angle neutron scattering. Rapid vortex mixing induced chain exchange within minutes, as evidenced by a monotonic decrease in scattered intensity, whereas Couette flow and sparging did not lead to measurable chain exchange over the examined time scale of hours. The linear kinetics with respect to agitation time suggested a surface-limited exchange process at the air-water interface. These findings demonstrate the strong influence of processing conditions on block polymer solution assemblies.

No MeSH data available.


Related in: MedlinePlus