Helium Ion Microscopy with Secondary Ion Mass Spectrometry (HIM-SIMS) for the analysis and quantitation of polyolefins

Abstract

Petroleum based polyolefin plastics makeup a large part of the multicomponent/multiphase plastics we use in our daily lives. Multiple plastics are often compounded, laminated or coextruded in these multicomponent systems creating multiple phases and interfaces of varying strengths. Significant opportunity exists in developing strategies for enhancing interfacial properties as well as facilitating disposal of polyolefin plastics by upcycling of polymeric products for reuse. Thus, interfaces and chemically distinct phases in these materials need to be probed structurally and chemically at the relevant length scales. To date, chemical imaging of polymer and polymer blends has been primarily accomplished using time-of-flight secondary ion mass spectrometry (ToF-SIMS) to directly visualize the distribution of components in a complex material with spatial resolution ranging from 100 nm to 5μm. However, in many cases this resolution falls far short of visualizing interfaces directly. To overcome these limitations recent work has focused on developing a SIMS detection system based on the helium ion microscope (HIM) enabling chemical imaging to ~14 nm. Here, we utilize the HIM-SIMS for quantitative differentiation between the olefin-based polymers of polyethylene (PE) and polypropylene (PP). We illustrate both quantitative analysis for separating PE and PP using specific mass fragment ratios as well as demonstrate spatially resolved imaging of phase separated domains within PE thin films with ~14 nm chemical and ~2 nm morphological spatial resolutions. Overall, we demonstrate HIM-SIMS as a multimodal chemical technique for imaging and quantification of polyolefin interfaces, that could be more broadly applied to the analysis of multicomponent/multiphase polymeric systems.

Highest resolution chemical imaging based on secondary ion mass spectrometry performed on the helium ion microscope

“…However, it can be observed in the literature, and especially at numerous lectures given at electron and analytical microscopy conferences, that a wide variety of topics are being addressed in materials science and they should soon give rise to future publications. For example, these include studies on, petroleum based polyolefin plastics [225], the distribution of rare earths in optical fibres, which directly influences the performance of optical fibres, or the precipitation of doping elements in the grain boundaries of super alloys, which can weaken the structure, and which could be harmful for aeronautical applications. Also, some preliminary results on polymers used for photo resist patterning produced by lithographic interference with a pitch of 400 nm have been presented.…”