Self-Organization in Solution

Like the artist, the chemist engraves into matter the products of creative imagination. The stone, the sounds, the words do not contain the works that the sculptor, the composer, the writer express from them. Similarly, the chemist creates original molecules, new materials and novel properties from the elements provided by nature, indeed entire new worlds, that did not exist before they were shaped at the hands of the chemist, like matter is shaped by the hands of the artist, as so powerfully rendered by Auguste Rodin. 

Indeed chemistry possesses the creative power as stated by Marcelin Berthelot La chimie cree son objet ( Chemistry creates its object ).  

The convection currents in a liquid can best be made visible by making use of patterns caused by a color change. This effect can be achieved very simply when a slightly alkaline aqueous surface which is colored by means of an indicator is exposed to an atmosphere of HCl. The convection is set in motion by the warmth provided by the lamp of an overhead projector. A variety of patterns can be obtained by changing the starting conditions slightly. 

Overhead projector, glass dish (diameter 10 cm, height 1.5 cm), glass dish (diameter 15 cm), filter paper (diameter 14 cm), paper towels, 250-mL beaker, 1-mL pipette, safety glasses, protective gloves. 

1 % bromocresol green indicator in ethanol solution, half-concentrated HCl, 0.005 mol/L sodium hydroxide solution (100 mL). 

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Fig. 10.6 (A) Stick representation of the packing of 3 in the crystal, showing the formation of directional tubular conduction pathways (B) schematic representation ofthe hierarchically organized system 3 (top) self-organization in solution and (bottom) sol-gel transcription of encoded molecular features into a hybrid heteropolysiloxane matrix [18].

Molecular self-organization in solution depends critically on molecular structural features and on concentration. Molecular self-organization or aggregation in solution occurs at the critical saturation concentration when the solvency of the medium is reduced. This can be achieved by solvent evaporation, reduced temperature, addition of a nonsolvent, or a combination of all these factors. Solvato-chromism and thermochromism of conjugated polymers such as regioregular polythiophenes are two illustrative examples, respectively, of solubility and temperature effects [43-45]. It should therefore be possible to use these solution phenomena to pre-establish desirable molecular organization in the semiconductor materials before deposition. Our studies of the molecular self-assembly behavior of PQT-12, which leads to the preparation of structurally ordered semiconductor nanopartides [46], will be described. These PQT-12 nanopartides have consistently provided excellent FETcharacteristics for solution-processed OTFTs, irrespective of deposition methods. 

Synthesis of Model Block Copolymers and Self-Organization in Solution and in Bulk... 

The choice of the particular monomers is based on the fact that PI is a nonpolar low Tg polymer, P2VP is a relatively more polar material with a coordinating ability, due to the presence of nitrogen in the side phenyl ring, with high Tg and the potential to be transformed into a water-soluble polyelectrolyte by postpolymerization reaction. On the other hand, PEO is a semicrystalline polymer, water-soluble (polar), and biocompatible. The incorporation of all these diverse properties in the same molecule makes these materials very interesting in terms of their self-organization in solution, bulk, and thin films. 

Intermolecular interactions between Pc moieties and electron-donor or electron-acceptor units other than Pcs have also been exploited in order to promote the organization in Pc-based systems. One of the examples has been reported by Amabilino, Rowan, and Nolte, who prepared a TTF-crown ether-substituted Pc 8 (Figure 6a), which was able to self-organize in solution mainly because of intermolecular interactions between the TTF and the Pc moieties as inferred from UV-vis studies. TEM analysis of the gel... 

Recent advances in polymerization techniques have made possible the synthesis of complex, including hierarchically branched, maaomolecules with perfectly controlled architecture. Analysis of interplay between complex maaomolecular topology and multiple competing interactions on conformations, routes of self-organization in solutions and at interfaces, and properties of resulting supramolecular stractures presents a major cuuent and future challenge for polymer theory. 

Figure 7-29. (a) Schematic representation of the hierarchicalgeneration of a hybrid membrane material self-organization in solution (i) and sol-gel transcription of encoded molecuUtr features into a hybrid heteropolysUoxane material (ii) (b) crystal packing of the macrocyclic superstructure. 

Figure 10. Dynamic self-organization in solution of the heteroditoplc macrocyclic receptors...

Reduced Surface Tension. Just as surfactants self-organize in the bulk solution as a result of their hydrophilic and hydrophobic segments, they also preferentially adsorb and organize at the solution—vapor interface. In the case of aqueous surfactant solutions, the hydrophobic tails protrude into the vapor and leave only (he hydrophilic head groups in contact with the solution. The favorable energetics of the arrangement can be seen by the reduction in Ihe interracial free energy per unit area, nr surface tension, it. 

This self-organization in reverse micelles interacting through a sticky potential is actually general in extractant solutions for extractant concentrations typically between 0.2 and 1 M, namely for the concentration ranges usually used in industrial processes. 

The poly(3, 4 -alkylterthiophene), PTT (2) used in our studies is prepared by FeCl3-mediated oxidative coupling polymerization [39]. PTT with a long alkyl side-chain (R > C6) for example PTT-10 (2, R = n-Ci0H2i) has an ability to self-organize in the solid state as reflected by a bathochromic shift in its UV-visible absorption spectra from solution to thin film (Fig. 4.1a). The solution spectrum of PTT-10 also has a progressive bathochromic shift with concomitant appearance of a longer-... 

We used our experience with reversible encapsulation to arrive at a rule regarding the proper filling of space, the 55% solution [87]. The filling of space probably drives other recognition phenomena, even in those synthetic receptors that do not completely surround their targets [88]. Some of the earliest, finite self-assemblies in solution based on melamine/cyanuric acid recognition [89] had no other function than to fill space. However unconventional, the departure from mainstream physical organic chemistry [90] is familiar to us and may offer rewards. 

Since CDs are highly biocompatible, readily available, and easy to functionalize, and since they self-organize in a rather predictable way in aqueous solutions, they will become one of the most important supramolecular building blocks of the future. 

Self-organization in many solution-processed, semiconducting conjugated polymers results in complex microstructures in which ordered microcrystaUine domains are embedded in an amorphous matrix [20,21]. This has important consequences for electrical properties of these materials Charge transport is usually limited by the most difficult hopping processes and is therefore dominated by the disordered matrix, resulting in low charge-carrier mobilities (<10 cm V s ) [22]. 

Preorganization is not a prerequisite for hydrogen-bonded co-crystal formation. It appears that the directing forces of hydrogen bonds are so powerful that many simple organic hydrogen-bond donors and acceptors will self-associate in solution and... 

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