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.
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).
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.
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.
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.
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.
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.
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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