Fig. 3

Non-rigid precursors form network terminations and reduce the elastic properties. a The predicted bulk modulus, K, as a function of the predicted mass density, ρ, for model organosilicate glasses: a hyperconnected flexible silane architecture with various side chain lengths (R₂, R₄, and R₆, where R = CH₂), a 1,3,5-benzene-bridged hyperconnected architecture, and an ethylene-bridge architecture (ethylene) with a fraction of the total precursors, Φ, containing a terminal phenyl group (ethylene-phenyl), where Φ = 0, 0.5, and 0.75. The circles and squares represent hyperconnected and non-hyperconnected architectures, respectively. The condensation degree, q, for all models is q = 0.8. The arrow between dashed and solid line shows the difference in the elastic properties between molecular architectures. b The fraction of flexible silane precursors, β, that form a network termination through a Si–O–Si bond with respect to the side chain length, L, of the precursor (R₂, R₄, and R₆, where R = CH₂), as represented by the circles and solid line. The ratio of the relative condensation degree to the condensation degree, q _rel /q, with respect to the side chain length, as represented by the squares and dashed line. The inset is a visualization⁶⁷ of a flexible silane precursor that forms a network termination through a Si–O–Si bond. The error bars denote one standard deviation of the mean of three trials per condition in a, b