Nanoporous crystalline phases preparation

Preparation, Structure, Properties, and Applications of Co-Crystals and Nanoporous Crystalline Phases of Syndiotactic Polystyrene... 

Structure, preparation, properties, and applications of the nanoporous crystalline phases of syndiotactic polystyrene are described in section 3 of this chapter. 

Preparation of the Nanoporous Crystalline Phases By suitable procedures of guest-removal from 8 clathrate and intercalate SPS cocrystalline phases, the nanoporous crystalline 8 phases can be e Jlily obtained. 

Several exciting new material based on co-crystalline and nanoporous crystalline phases of syndiotactic polystyrene have been achieved. In particular, several kinds of polymer co-crystalline phases have been prepared, belonging to three different classes 8- and e-clathrates and intercalates. Polymer cocrystals with active guest molecules show unusual physical properties, hence are promising for several kinds of advanced materials. Moreover, the unprecedented achievement of polymeric nanoporous crystalline phases (8 and e) has given very interesting results in the fields of molecular separations, water/ air purification and sensorics. 

In the section on structure and fundamental properties of SPS, Chapter 9 summarizes the polymorphic behavior of this polymer, the structure of the different forms, and the crystallization and melting behavior. Chapter 10 describes co-crystals and nanoporous crystalline phases of SPS regarding preparation, structure, properties, and new interesting applications, for example, molecular sensors. The section concludes with Chapter 11 on selected topics of crystallization thermodynamics and kinetics of SPS. 

Lee et al. reported the preparation of nanoporous crystalline sheets of penta-p-phenylene using a (oligomeric) block copolymer with a cleavable juncture approach in 2004 [63]. These so-called rod-coil block copolymers of penta-p-phenylene and PPO can self-assemble to give layered phases that contain sheets of perforated crystalline penta-p-phenylene in which the perforations are filled with PPO [64]. The PPO segment is covalently bound to the... 

Mesophases can be locked into a polymer network by making use of polymerizable LCs [59]. These molecules contain moieties such as acryloyl, diacety-lenic, and diene. Self-organization and in situ photopolymerization under UV irradiation will provide ordered nanostmctured polymers maintaining the stable LC order over a wide temperature range. A number of thermotropic liquid crystalline phases, including the nematic and smectic mesophases, have been successfully applied to synthesize polymer networks. Polymerization of reactive lyotropic liquid crystals also have been employed for preparation of nanoporous polymeric materials [58, 60]. For the constmction of nanoporous membranes, lyotropics hexagonal or columnar, lamellar or smectic, and bicontinuous cubic phases have been used, polymerized, and utilized demonstrated in a variety of applications (Fig. 2.11). 

The evidence for the formation of a new crystaUine phase is also reinforced by the XRD patterns shown in Fig. 4.4. As can be verified, the methyl methacrylate spheres exhibit some degree of crystallinity. Furthermore, the titania-covered spheres exhibit the same XRD patterns as the uncovered spheres, indicating that the Ti02 coat is amorphous. On the other hand, the nanoporous thiol-functionalized titania-sifica hybrid exhibits a distinct XRD pattern, showing that a new crystaUine phase was formed. By comparison with previously prepared double oxides [13,16] the diffraction peak at 5.5° observed in Fig. 4.2c could be attributed to the 100 diffraction plane of a hexagonal phase. 

The above-discussed acid retardation and base retardation in the immobiUzed Uquid phase could be compared with the so-called salting-out effects. However, this term is hardly applicable to the case of salt retardation, the first example of which was demonstrated by a successful removal of small amounts of NH4CI from a concentrated brine of (NH4)2S04. This practically important problem arises in the manufacture of caprolactam, where large amounts of sulfuric acid are converted into ammonium sulfate used for the preparation of the crystalline fertilizer. The new process of ISE on nanoporous NN-381 resin allowed an effective purification of very large volumes of concentrated sulfate brine, due to the fact that small ions of NH and Cl are efficiently squeezed into and retained in the finest pores of the sorbent [172]. We consider this salt retardation process as a convincing proof of our interpretation of the mechanisms of the new electrolyte separation process. 

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