Surface and Interface Spectroscopy of High Explosives and Binders:HMX and Estane

摘要

Vibrational sum-frequency generation spectroscopy (SFG) is used to characterize the surfaces of P-HMX single crystals and Estane polymer binder,as well as the HMX-Estane interface.SFG is a nonlinear vibrational spectroscopy that selectively probes vibrational transitions at surfaces and interfaces.On the HMX {011} surface,both CH- and NO_2-stretching transitions are observed.Compared to bulk HMX,the surface transitions are blueshifted and the splittings are larger.This effect is explained by surface HMX molecules having partially buried and partially free CH_2 and NO_2 groups.Estane is a diblock copolymer with both soft and hard segments.Comparison of Estane spectra with polymers having only the soft unit and with polymers having predominantly hard units indicate there is a preference for the hard unit on the surface.SFG spectra of the HMX-Estane interface show smaller splittings of the HMX CH-stretch transitions than at the HMX-air interface,because the partially free surface groups are buried in Estane.