Relative secondary ion yields of polymers

A method has been developed to measure the relative secondary ion yields of polymers. Parameters affecting secondary ion yield include primary ion cur rent, detector efficiency, mole concentrations of oligomers, and the extent of oligomer fragmentation. All of these factors are considered in the meas urement protocol. Two specific homopolymers were investigated: poly(dimethy lsiloxane) and poly(methylphenylsiloxane). The relative secondary ion yield s measured for PMPhS/PDMS were in the range of 0.29-0.35, depending on the polymer ratio. Transformation probabilities also were measured for the two polymers, and the PMPhS/PDMS ratio was 0.57. The results of the study indic ate that the pendant groups on the siloxane side chain have a significant e ffect on polymer ion yield and that measurement of relative ion yields for polymer mixtures represents a valid yield comparison.