Laser Scanning Confocal Microscopy Versus Scanning Electron Microscopy for Characterization of Polymer Morphology: Sample Preparation Drastically Distorts Morphologies of Poly(2-hydroxyethyl methacrylate)-Based Hydrogels

Abstract

The internal morphologies for a series of heterogeneous PHEMA and P[HEMA-co-MeO-PEGMA] [PHEMA = poly(2-hydroxyethyl methacrylate), MeO-PEGMA = poly(ethylene glycol) methyl ether methacrylate] hydrogels were characterized by scanning electron microscopy (SEM) in conjunction with a sample drying procedure, and by laser scanning confocal microscopy (LSCM) without prior drying. Compared to SEM, LSCM was far simpler and more rapid technique for imaging hydrogels. LSCM also allowed the native hydrated morphology of the hydrogels to be characterized, whereas SEM could only characterize the morphology of samples in their dehydrated state. No dehydration method used in this study preserved the true native morphology, but plunge freezing/freeze drying was the most suitable method that best preserved the native morphology for all hydrogel compositions. Refrigeratedfreezing/freeze-drying and critical point drying introduced significant morphological artifacts, the severity of the artifacts being dependant on the sample’s composition and Tg.