Physical Characterization of Hierarchically Structured Nanocomposites

In this contribution we present various aspects of the thermodynamics of self assembly in block copolymer / layered silicate nanocomposites (BCPLSs). Hierarchically structured BCPLSs were prepared using an \textit{in situ} atom transfer radical polymerization (ATRP) approach. The three part synthesis of the materials included an ion exchange functionalization of the clays, sonication during styrene (St) polymerization, and a block copolymer \textit{tert}-butyl acrylate (tBA) synthesis. Highly organized lamellar structures were formed with a periodicity of $\sim $200 nm, much larger than the $\sim $35 nm periods of bulk block copolymers of comparable molecular weights. The final material had two distinct glass transitions (Tg) 69\r{ }C for the tBA and 103\r{ }C for the St. This is a significant Tg enhancement for atactic tBA (Tg = 42\r{ }C) and is attributed to the chain extension which occurs in the confined geometry of the silicate sheets.