Time-of-Flight-Secondary Ion Mass Spectrometry and Principal Component Analysis: Determination of Structures of Lamellar Surfaces

In this article, we addressed the applicability of time-of-flight secondary ion mass spectrometry (TOF-SIMS) to examine the effects of molecular weight and of flexible-segment length on the polymer chain arrangement at the folding surfaces of the lamellae. Poly(bisphenol A-etheralkane) (Cn) contains both rigid aromatic and flexible aliphatic CH2 segments. The number of CH2 units per flexible segment, n, varies from 8 to 12. Principal component analysis (PCA) of TOF-SIMS data revealed the chemical and structural variations of the folding surfaces of these polymers and identified the ion peaks contributing to these variations. We highlighted the discriminating power of PCA to distinguish the structural conformations of the amorphous and flat-on lamellar surfaces of these polymers. PCA loadings analyses showed that relatively more flexible structures were deposited on the folding surfaces when the flexible-segment length increased from 8 to 10 CH2 units. The concentration of short loops at folding surfaces and the disorder of folding surfaces increased when the molecular weight increased. All these results led us to conclude that TOF-SIMS has great potential for probing the chemical composition of the folding surfaces of polymers