Self-oriented structures

The HT-HT PATs undergo a solid-state macromolecular self-assembly and give self-oriented structures, as determined by X-ray diffraction studies. PDDT induces the formation of planar main chain structures and has the greatest effective conjugation length, followed by HT-HT POT, HT-HT PHT and HT-HT PBuT [99]. 

Fig. 1 Phase diagram of self-assembled structures in AB diblock copolymer melt, predicted by self-consistent mean field theory [31] and confirmed experimentally [33]. The MesoDyn simulations [34, 35] demonstrate morphologies that are predicted theoretically and observed experimentally in thin films of cylinder-forming block copolymers under surface fields or thickness constraints dis disordered phase with no distinct morphology, C perpendicular-oriented and Cy parallel-oriented cylinders, L lamella, PS polystyrene, PL hexagonally perforated lamella phase. Dots with related labels within the areal of the cylinder phase indicate the bulk parameters of the model AB and ABA block copolymers discussed in this work (Table 1). Reprinted from [36], with permission. Copyright 2008 American Chemical Society...

As discussed in Section 2.2, surfactant has a tendency to adsorb at interfaces since the polar head group has a strong preference for remaining in water while the hydrocarbon tail prefers to avoid water. The surfactant concentration affects the adsorption of surfactants at interfaces. Surfactant molecules lie flat on the surface at very low concentration. Surfactant molecules on the surface increase with increasing surfactant concentration in the bulk and surfactant tails start to orient towards gas or non-polar liquid since there is not enough space for the surfactant molecules to lie flat on the surface. Surfactant molecules adsorb at the interface and form monolayer until the surface is occupied at which point surfactant molecules start forming self-assembled structures in the liquid (Section 2.3). 

Figure 1.6. Carbon nanotube structures obtained by chemical vapor deposition synthesis, (a) SEM image of self-oriented MWNT arrays. Each tower-like structure is formed by many closely packed multiwalled nanotubes, (b) SEM top view of a hexagonal network of SWNTs (line-like structures) suspended on top of silicon posts (bright dots), (c) SEM top view of a square network of suspended SWNTs, (d) Side view of a suspended SWNT power line on silicon posts (bright) and (e) SWNTs suspended by silicon structures (bright regions). Reproduced from reference 3 with permission from American Chemical Society.

Oriented structures of self-organized ionic liquids can be preserved in solid films... 

Figure 25.3 Polarizing optical microscopic images and schematic illustrations of the oriented and self-assembled structures of 10b in the hexagonal columnar state (a) Before shearing (b) after shearing the material along the direction perpendicular to the Au electrodes. Directions of A analyzer P polarizer S shearing. (Reproduced with permission from J. Am. Chem. Soc., 126, 994-995 (2004). Copyright 2004 American Chemical Society)...

In addition to lipid-like molecules, polymers can also form self-assembling particulates [8]. As expected, the amphiphilic polymers do form polymeric micelles with polar part orienting towards the surface of the particle and the hydrophobic part orienting towards the core of the particle. Also, in this case, different complicated self-assembled structures can be tailored by using block copolymers with regular blocks of monomer units but, only the simpler ones have been investigated so far in the context of drug delivery. 

McCullough, R.D. et al.. Self-orienting head-to-tail poly(3-alkylthiophenes) New insights on structure-property relationships in conducting polymers, J. Am. Chem. Soc. 115, 4910 911, 1993. 

Bertini et have studied the question of whether reliable models for a protein of unknown structure can be constructed from that of a protein of known structure if the sequence homology is greater than 30%. They modeled the structure of cytochrome c556 on that oT cyt c and validated the model using paramagnetic structure constraints (pseudocontact shifts and self-orientation residual dipolar couplings) without determining the full solution structure. 

Fig. 1 (a) Schematic representation of the mechanically induced transformation of a disordered semicrystalline polymer comprising small aggregates of self-assembled ehromophores (small-molecule or polymeric) into an oriented structure in which the guest moleeules are well dispersed, (b) Stmcture of EHO-OPPE, a poly(p-phenylene ethynylene) derivative... 

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