FUMED SILICA PARTICLES POLYDIMETHYLSILOXANE OLIGOMERS INTERFACE - I -QUANTUM-CHEMICAL MODELING OF PARTICLE SURFACE - CUBIC PACKING/

The paper opens a series of publications devoted to a microscopic appr oach to the intermolecular interaction between fumed silica particles and polydimethylsiloxanes of different structure. The paper presents r esults on atomic characterization of the surface of both hydroxylated and silylated particles in a supercluster approach. A rhomb-like-four- layer supercluster containing 222 atoms is proposed as the basic unit simulating an individual surface facet of the hydroxylated silica part icle with a (111)-like packing of the siloxane elements. The total-ene rgy-minimization procedure for obtaining equilibrated cluster structur es has been performed at the level of semiempirical quantum-chemical c onsiderations by using the AM1 method. The optimized basic cluster ser ved as a basis for a microscopic examination of the silylation process . The supercluster characteristics are presented by distribution funct ions related to atomic charges, bond lengths, and bond angles.