Understanding and Controlling Polymer-Organometallic Precursor Interactions in Sequential Infiltration Synthesis

Sequential infiltration synthesis (SIS) is an emerging method for vapor-phase growth of inorganic materials within polymers that is utilized for hybrid organic-inorganic and inorganic nanostructure fabrication. The range of SIS applications has been continuously expanding for the past decade. A fundamental understanding of precursor-polymer interactions is, however, essential to expand the use of SIS to additional chemistries and move beyond thin film polymer templates. This work utilizes density functional theory (DFT) calculations and in situ gravimetric analysis to probe the growth mechanism of trimethylaluminum (TMA) within poly(methyl methacrylate) (PMMA) and poly(2-vinylpyridine) (P2VP). The theoretical and experimental analyses reveal that each precursor-polymer pair is characterized by a balance point temperature at which rates of forward and reverse precursor-polymer binding enable maximum mass gain at thermodynamic equilibrium. At short exposure times, mass gain is significantly influenced by the pressure profile of the process chamber. Mechanism comprehension enabled nanopatterning of a previously unsuitable block copolymer (BCP), polystyrene-block-P2VP (PS-b-P2VP), at elevated temperatures. It was proven possible to grow significant mass while maintaining the pattern by stabilizing the morphology via a single cycle at low-temperature SIS, thus overcoming self-assembly sensitivity to temperature.