title: Hierarchical assembly of nanostructured organosilicate networks via stereocomplexation of block copolymers.
abstract: The effect of the stereochemistry of polylactide (PLA)-based block copolymers on templated inorganic nanostructures has been investigated from the self-assembly of a stereoisomer pair/organosilicate mixture followed by organosilicate vitrification and copolymer thermolysis. Isomeric PLA homopolymers, block copolymers, and a stereoblock copolymer were prepared by ring-opening polymerization of D-, L-, or rac-lactide using an organocatalytic catalyst. Both differential scanning calorimetry and atomic force microscopy showed the formation of a stereocomplex between enantiomeric stereoisomers, that is, block copolymer/block copolymer and block copolymer/homopolymer mixtures as well as a stereoblock copolymer. The unique noncovalent interactions driven by stereocomplexation of D- and L-lactide provided supramolecular structures with a hierarchical order as characterized by distinctive vertical and horizontal growth of toroidal nanostructured inorganic features. This study demonstrates the potential of hierarchically assembling suprastructures that bridge the nano- to mesoscale feature sizes in the design of tunable functional nanomaterials suitable for future applications of microelectronics, material science, and bioengineering.
authors: IBM Almaden Research Center, 650 Harry Road, San Jose, California 95120, USA.
authors: Sung Ho
authors: SH
authors: Kim
authors: Fredrik
authors: F
authors: Nederberg
authors: Lei
authors: L
authors: Zhang
authors: Charles G
authors: CG
authors: Wade
authors: Robert M
authors: RM
authors: Waymouth
authors: James L
authors: JL
authors: Hedrick