The structure of amino-functionalized polyhedral oligomeric silsesquioxanes (POSS) studied by molecular dynamics simulations

• Published in: Computational materials science Vol. 62; pp. 258 - 265
• Main Authors: Neyertz, S., Brachet, P., Brown, D., Männle, F.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2012; Elsevier
• Subjects: Amino-functionalized; Applied sciences; Cohesion; Computer simulation; Density; Dynamical systems; Exact sciences and technology; Hydroxyl groups; Mathematical models; Molecular dynamics; Molecular dynamics (MD); Organic chains; Organic polymers; Physicochemistry of polymers; Polyhedral oligomeric silsesquioxane; POSS; Properties and characterization; Structure; Structure, morphology and analysis; Organic chains; Molecular dynamics (MD); POSS; Structure; Amino-functionalized; Molecular structure; Molecular dynamics method; X ray diffraction; Intermolecular interaction; Chemical modification; Radial distribution function; Cohesive energy; Intramolecular interaction; Hydrogen bond; Long range order
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2012.05.057

[Display omitted] ► We modelled three amino-functionalized polyhedral oligomeric silsesquioxanes (POSS). ► Their bulk amorphous structure was studied using molecular dynamics (MD) simulations. ► The organic pendant arms are intertwined, the inorganic siloxane cages are dispersed. ► An hydroxyl group on a phenyl ring increases cohesion through additional H-bonds. ► Replacing an aromatic by a cyclohexyl ring leads to molecular disorder. Molecular models of three amino-functionalized cubic polyhedral oligomeric silsesquioxanes (POSS) have been studied at 293K using classical molecular dynamics (MD) simulations. These hybrid organic/inorganic systems were all based on the T8R8 form, but they differed by the end-groups of their organic pendant chains, i.e. either R=–(CH2)3–NH–CO–C6H5OH, R=–(CH2)3–NH–CO–C6H6 or R=–(CH2)3–NH–CO–C6H11. Model densities, volumes, cohesive energies, void spaces, X-ray diffractograms and intermolecular as well as intramolecular interactions were analysed. The differences in bulk and structural properties between both aromatic-based organic chains are fairly small, although the added hydroxyl groups bring additional cohesion by modifying the amide⋯amide H-bonding network. On the other hand, replacing an aromatic by a cyclohexyl ring leads to molecular disorder, larger POSS⋯POSS separations and a lower density. The pendant arms of the three POSS under study were found to be intertwined with a preference for intermolecular interactions because of steric considerations. Such an interdigitation also allowed for the parallel stacking of the ring end-groups at short distances, thus bringing extra cohesion to the systems. However, there was no evidence of long-range crystalline order.