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Structured water in polyelectrolyte dendrimers: Understanding small angle neutron scattering results through atomistic simulation
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10.1063/1.3697479
/content/aip/journal/jcp/136/14/10.1063/1.3697479
http://aip.metastore.ingenta.com/content/aip/journal/jcp/136/14/10.1063/1.3697479
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

The pair distribution function of oxygen-oxygen distance g oo(r) for TIP3P water around the vicinity of a G4 PAMAM dendrimer of different molecular protonation level: (a) neutral (α = 0), (b) protonated primary amines (α = 1), and (c) protonated primary and tertiary amines (α = 2). It is important to point out that all the reported g oo(r) reach the asymptotic value of 1 when r > 15 Å.

Image of FIG. 2.
FIG. 2.

The snapshot of G4 PAMAM dendrimer of α = 2 created using visual molecular dynamics.40,63 Selectively chosen atoms from simulation system are shown. Panel (a) illustrates polymeric part of dendrimer as well as counterions. The light blue, white, blue, red, and yellow spheres represent carbon, hydrogen, nitrogen, oxygen, and chloride atoms, respectively. In addition to the atoms present in panel (a), panel (b) incorporates interfacial water which should be recognized as part of the scatterer. The virtual sphere used for calculation of P(Q) are shown in panel (c).

Image of FIG. 3.
FIG. 3.

Comparison of the form factor P(Q) of G4 PAMAM dendrimer obtained from MD simulation and SANS model fitting as a function of molecular protonation in semi-log plots (Figures 3(a)–3(c)) and logarithmic plots (Figures 3(d)–3(f)). A better quantitative agreement is reached with the incorporation of the scattering contributions from the density fluctuations introduced by confined water structuring and voids.

Image of FIG. 4.
FIG. 4.

Comparison of the pair distance distribution function (PDDF) p(r) of G4 PAMAM dendrimer obtained from MD simulation (red curves) and indirect Fourier transform (IFT) of experimental model fitting data (black curves) at different molecular protonation levels.

Image of FIG. 5.
FIG. 5.

The excess neutron scattering length density profiles Δρ(r) of G4 PAMAM dendrimers obtained from MD simulation as a function of molecular protonation. The experimental Δρ(r) (Ref. 35) determined from contrast variation SANS study is given in the inset.

Image of FIG. 6.
FIG. 6.

The radial SLD distributions of polymer ρ(r) of G4 PAMAM dendrimers obtained from MD simulation at three different levels of molecular protonation. The experimental ρ(r) is given in the inset.

Image of FIG. 7.
FIG. 7.

The angularly averaged number density of invasive water per unit volume H(r) obtained MD simulation as a function of molecular protonation. The experimentally determined H(r) is given in the inset.

Image of FIG. 8.
FIG. 8.

The total number of invasive water n water(r) obtained from MD simulation as a function of molecular protonation. The SANS determined values are presented in the inset.

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/content/aip/journal/jcp/136/14/10.1063/1.3697479
2012-04-11
2014-04-25
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Structured water in polyelectrolyte dendrimers: Understanding small angle neutron scattering results through atomistic simulation
http://aip.metastore.ingenta.com/content/aip/journal/jcp/136/14/10.1063/1.3697479
10.1063/1.3697479
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