Vapor phase infiltration (VPI) for transforming polymers into organic–inorganic hybrid materials: a critical review of current progress and future challenges

Abstract

This review critically assesses the state-of-knowledge for vapor phase infiltration (VPI) processing science, an emerging gas phase processing scheme for producing organic–inorganic hybrid materials. In VPI, vapor phase metalorganic precursors are diffused into and subsequently reacted with organic polymers to transform them into organic–inorganic hybrid materials. While this processing technique originates from the atomic layer deposition (ALD) research community, and its processing conditions are similar to ALD, the fundamental phenomenological mechanisms of VPI and ALD are significantly different. In fact, the kinetics of VPI more closely parallel processes in gas membrane separations and solvent vapor annealing than ALD. This review clarifies the nomenclature and taxonomy of VPI within the greater family of chemical vapor phase processing techniques. The current understanding of VPI's atomic-scale processing phenomenology is reviewed, and a basic framework for understanding the processing kinetics is presented. Characterization methods for studying the processing dynamics and final material structure are summarized along with some current applications for the unique materials that are created. Most importantly, this article aims to unify the research field and identify several scientific challenges that must be overcome to advance this processing technology towards broad commercial acceptance.