Highly ordered morphology

Mobilities up to 1.5 cm2 V-1 s 1 have been obtained for films deposited on hcale substrates [94—96]. As in the case of oligothiophenes, this has been attributed to a highly ordered morphology, close to that of a single crystal [94]. However, high values are only obtained under very acute deposition parameters (in particular an opti... 

A remarkable property of polymer systems is their ability to self-assemble, driven by thermodynamic incompatibilities of the different monomers, which will be discussed in more detail in Chap. 4. The resulting repulsive forces make homopolymer blends to separate into macrostructures. In contrast, being covalently bonded, the thermodynamically incompatible blocks of copolymers are prevented from separating on a macroscopic level. Even for the most simple copolymer architecture, namely diblocks, this gives rise to the formation of a variety of highly ordered morphologies with nanoscale periodicities [3]. 

A highly ordered morphology for polyelectrolyte/surfactant complexes has been found by Antonietti et al. [35]. Polyacrylic acid (PAA) was complexed with dodecyltrimethylammonium chloride (DMAC) with 1 1 ratio of DMAC to acrylic units. Thus the high coverage limit is achieved for PAA/DMAC complexes. Dry complexes are birefringent, highly elastic, deformable materials. They are noncrystalline the wide-angle diffraction data show an amorphous structure. 

In view of the problems associated with the expanding 2 1 clays, the smectites and vermiculites, it seemed desirable to use a different clay mineral system, one in which the interactions of surface adsorbed water are more easily studied. An obvious candidate is the hydrated form of halloysite, but studies of this mineral have shown that halloysites also suffer from an equally intractable set of difficulties (JO.). These are principally the poor crystallinity, the necessity to maintain the clay in liquid water in order to prevent loss of the surface adsorbed (intercalated) water, and the highly variable morphology of the crystallites. It seemed to us preferable to start with a chemically pure, well-crystallized, and well-known clay mineral (kaolinite) and to increase the normally small surface area by inserting water molecules between the layers through chemical treatment. Thus, the water would be in contact with both surfaces of every clay layer in the crystallites resulting in an effective surface area for water adsorption of approximately 1000 tor g. The synthetic kaolinite hydrates that resulted from this work are nearly ideal materials for studies of water adsorbed on silicate surfaces. 

As previously stated, the rigid polyimides meet many of the requirements for microelectronics applications however, the presence of an ordered morphology, coupled with the lack of a softening transition results in extremely poor self-adhesion. Alternatively, thermally stable thermoplastics exhibit excellent self-adhesion, but often lack sufficiently high temperature dimensional stability and/or solubility and processability from common organic solvents. For instance, po-ly(phenylquinoxaline) (PPQ) has a T in the 370 °C range, thereby overcoming... 

Starting with basic physical concepts and synthetic techniques, the book describes how molecules assemble into highly ordered structures as single crystals and thin films, with examples of characterization, morphology and properties. Special emphasis is placed on the importance of surfaces and interfaces. The final chapter gives a personal view on future possibilities in the field. 

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