Miniaturized triblock copolymers have been found to self-assemble into nanostructures that are highly regular in size and shape. Mushroom-shaped supramolecular structures of about 200 kilodaltons form by crystallization of the chemically identical blocks and self-organize into films containing 100 or more layers stacked in a polar arrangement. The polar supramolecular material exhibits spontaneous second-harmonic generation from infrared to green photons and has an adhesive tape-like character with nonadhesive-hydrophobic and hydrophilic-sticky opposite surfaces. The films also have reasonable shear strength and adhere tenaciously to glass surfaces on one side only. The regular and finite size of the supramolecular units is believed to be mediated by repulsive forces among some of the segments in the triblock molecules. A large diversity of multifunctional materials could be formed from regular supramolecular units weighing hundreds of kilodaltons.

This manuscript describes the bulk synthesis of shape persistent two-dimensional (2D) polymers using the self-assembly of rigid precursor molecules into bilayers. A precursor was synthesized with a structure that encodes for the necessary molecular recognition events to form bilayers with intemal orientational order. These events include homochiral interactions and confine reactive functions to planes leading to covalent stitching of flat polymers. The resulting molecular objects have a monodisperse thickness of 5 nm and polydisperse planar dimensions on the order of hundreds or thousands of nanometers. One of the stiching reactions, the oligomerization of acrylate groups to form an all-carbon backbone, is catalyzed by the presence of dipolar stereocenters 13 atoms away from the double bond. These enantiomerically enriched stereocenters are substituted by nitrile groups which react to generate the second stitching backbone of the plate-shaped molecules. A computer simulation indicates that 2D polymers of molar mass in the range of millions can be formed with extremely short stitching backbones provided planar confinement of functions is achieved by molecular recognition events. "Bulk" syntheses of shape persistent 2D polymers which do not require extemal boundaries to confine monomers into 2D spaces may lead to many interesting advanced materials.

A mesogen-substituted polydiacetylene which self-assembles into stacks of bilayered twodimensional structures was investigated by X-ray and electron diffraction as well as electron microscopy. The multilayered stacks of bilayers were found to organize into single crystals with an orthorhombic unit cell. Within each two-dimensional structure, the polyconjugated backbones are oriented along either of the two ab plane face diagonal directions, and the substituted side chains are oriented parallel to the layer normal (c-axis direction). The layered single-crystal structures form blue solids at room temperature but undergo the well-known thermochromic and solvatochromic transitions which produce red, orange, and yellow solids. In this work we have established links among chromic transitions, molecular organization, and morphology of these two-dimensional assemblies. Their thermochromic transition from blue to red solids at elevated temperature was found to be accompanied by reversible fracturing of the large single crystals. However, the red to orange transition at even higher temperatures was found to be associated with the irreversible twisting of fractured crystals and the lengthening of the chemical repeat. Based on electron diffraction, this twisting is accompanied by rotations of mesogenic side chains substituting the polydiacetylene backbone. On the other hand, our studies suggest that conformational changes do not play a role in the reversible blue to red transitions of these two-dimensional assemblies. Electronic delocalization perpendicular to the backbone may be a factor in these reversible changes linked to the fracturing of crystals.

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