The IR laser‐induced degradations of liquid polydimethylsiloxane (PDMS) vapor and of hexamethyldisiloxane vapor have been studied in order to determine whether the high temperature thermal properties of the dimethylsiloxane unit is best represented by SiO bond rearrangement (the conventional pyrolysis mechanism) or SiC bond cleavage (the thermodynamic reaction pathway). The volatile products of these pulsed laser experiments with various viscosities of PDMS are methane, ethane, ethylene, and hydrogen. These results are consistent with SiC bond cleavage to form methyl radicals, which can then recombine to form ethane or abstract a hydrogen atom from a matrix molecule to form methane. The presence of ethylene and hydrogen can be explained by the decomposition of hot ethane molecules. No evidence of SiO bond cleavage was observed. Reaction temperatures are estimated with computer modeling using heat capacity data.

There exists a high correlation between molecular total surface area (TSA) values and diorganotin toxicity towards several distinct types of organisms. This correlation was found for N,a neuroblastoma cells, 3T3 fibroblasts, Daphnia magna Rhithropanopeus harrisii and Ankistrodesmus falcatus. In the case of Rhithvopanopeus harrisii, a high correlation was also found between TSA and toxicity for triorganotins as well. This study suggests that the relationship between TSA and toxicity is a function of the hydrophobicity of the organotin compounds rather than electronic or steric effects.

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Potassium ferrocyanide Is encapsulated In the aqueous cavity of spherical phospholipid bilayer vesicles (liposomes) at concentrations of approximately 104 molecules/llposome. Physical parameters and stability of these structures are determined by electrochemical and spectroscopic methods. The electroactive marker Ions (ferrocyanide) are released from within the liposome by either the addition of surfactant or the complement lysis of the membrane. The classical complement pathway Is an antlgen/antlbody-speclflc reaction that occurs when an antigen-sensitized liposome Immunospeclflcally binds with a corresponding antibody In the presence of certain serum proteins (complement). The release of encapsulated ferrocyanide Is monitored by differential pulse voltammetry. Preliminary Investigations with an Ion-exchange polymer modified electrode demonstrate the ability to preconcentrate the released marker at the electrode surface as well as the necessity of a polymer film to protect the surface from fouling during serum-mediated lysis.

The 'H, I3C and =Si nuclear magnetic resonance spectra of the parent compound and twelve derivatives of 2,8,9-trioxa-5-aza-l-silatri~yclo[3.3.3.O~~~]undecane (silatrane) are discussed. Effective Taft polarity constants for the silatrane snbstituents are proposed. An equation is developed to correlate the "Si NMR chemical shifts of the silatranes with the corresponding organo-triethoxysilanes.