Self-assembly dissolved polymers

Another nice example of nanostructuring an MIP layer is the work published by Wu et al. [138, 139] who developed a label-free optical sensor based on molecularly imprinted photonic polymers. Photonic crystals were prepared by self-assembly of silica nanospheres. The space between the spheres was then filled with MIP precursor solution. After polymerization, the silica was dissolved, leaving an MIP in the form of a 3D-ordered interconnected macroporous inverse polymer opal (Fig. 15). The authors were able to detect traces of the herbicide atrazine at low concentrations in aqueous solution [139]. Analyte adsorption into the binding sites resulted in a change in Bragg diffraction of the polymer characterized by a color modification (Fig. 15). 

Finally, we will consider briefly the formation of multilayer thin films by layer-by-layer deposition of hydrogen-bonded polymer pairs [51,52]. In this way a multilayer structure is obtained from potentially miscible polymer pairs. The stability of these films very much depends on the presence of hydrogen bonds, and pH may be used as an external trigger to erase the layered structure [53,54] and selectively dissolve one of the components [25-27]. This procedure allows for the preparation of microporous films not unlike the nanoporous films obtained by dissolution of the hydrogen-bonded side groups from self-assembled block copolymer-based comb-shaped supramo-lecules [15,17,18]. 

SUPRAMOLECULAR ORDERING AND SELF-ASSEMBLY OF DISSOLVED POLYMERS... 

Ringsdorf showed a nice example of confinement of supramolecular polymers.192 In cyclohexane, hexa-cinnamoyl azacrown 37 self-assembles to form supramolecular columnar polymers. The periphery of photopolymerizable groups forms cross-links via photocycloaddition and allows the pre-assembled supramolecular polymer to be transferred into a rodlike covalent polymer (Figure 21). Performing the reaction on molecularly dissolved molecules gives rise to a randomly cross-linked polymer with a lower DP. 

The cosolvent method, also known as solvent injection method permits vesicle formation for glassy or crystalline block copolymers. As a rule, the amphiphilic copolymer is dissolved in an appropriate organic solvent or solvent mixture, the role of which is to lower the Tg below room temperature next the solution is added dropwise to an aqueous buffer under vigorous stirring. Originally this method has been employed for PS-PAA and PS-PEO copolymers that self-assembled in vesicular structures by adding water to DMF or dioxane polymer solution [61,105] and then further applied to many other polymer systems [165],... 

Supramolecular approaches [5,7,20-22] are also effective for ion conduction in polymers. Ikkala and ten Brinke prepared the complex of polystyrene-frZock-poly(4-vinylpyridine) (PS-fr-PVP) and oligo(ethylene oxide)sulfonic acid 11 [71,72]. The polymer self-assembles into lamellar nanostructures consisting of glassy hydrophobic polystyrene and hydrophilic PEO layers, as shown in Fig. 11. When LiCl04 is dissolved in the polymer composites, lithium ions are complexed and transported in the hydrophilic PEO layers, resulting in high ionic conductivities on the order of 10-6 S cm-1 at ambient temperature. 

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