Partially Crystalline States

The intention of this brief survey has been to demonstrate that besides the "classical" aspects of isotropic polymer solutions and the amorphous or partially crystalline state of polymers, a broad variety of anisotropic structures exist, which can be induced by definable primary structures of the macromolecules. Rigid rod-like macromolecules give rise to nematic or smectic organization, while amphiphilic monomer units or amphiphilic and incompatible chain segments cause ordered micellar-like aggregation in solution or bulk. The outstanding features of these systems are determined by their super-molecular structure rather than by the chemistry of the macromolecules. The anisotropic phase structures or ordered incompatible microphases offer new properties and aspects for application. 

Unique nanocrystalline microstructures can be produced by controlled crystallization of the fully amorphous product, including nanocrystalline precipitates homogeneously distributed in an amorphous alloy matrix. In some systems, both the strength and ductility increase in this partially crystalline state [24], Other alloys produce nanocrystalline intermetallic or quasicrystalline precipitates, providing a credible path for increasing the specific stiffness. Thus, a significant effort is required to study the kinetics of crystallization, the devitrification pathways and the microstructures and properties that may be produced upon devitrification. The potential for exploration of novel compositions and microstructures in this class of materials is clearly promising. 

The polymers II and III were in partially crystalline state at room temperature irrespective from the method of production. 

The process of crystallization may be considered in three stages crystal nucleation, crystal growth, and the equilibrium partially crystalline state. Embryo nuclei may continuously form and grow even in amorphous rubber. However, below a certain critical size they are unstable enough to disappear due to random thermal motions of the molecular chain and may not have measurable macroscopic consequences. 

The polymer I was synthesized by means of high-temperature acceptor-free polycondensation from dichloranhydride of terephthaloyl-bis( -oxybenzoic) acid and 2-methylhexa-methylene-l, 5-diol in inert dissolvent (bisphenyloxide at 200 °C). The phase state of polymer I at room temperature was found to depend on the way of sample preparation. The samples obtained from pol5uner immediately after synthesis and those cooled from melt were in mesomorphic state, but dried from the solutions in trifluoroacetic acid were in partially crystalline state. 

Liquid crystals do not lend themselves to electron microscopy, as a liquid phase cannot be easily handled within a vacuum column unless cumbersome wet stages are employed. However, the fact that polymeric liquid crystals can be quenched to the glassy or partially crystalline states without any apparent disturbance of the local orientation characteristic of the liquid mesophase means that the electron microscope becomes a most useful tool. It is now providing new insights into the local molecular orientation in some liquid crystal polymer systems. 

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