Behavioral Synthesis Concepts

In this section, we briefly introduce certain basic concepts which help understand behavioral synthesis better. 

---

With the details associated with ADMET chemistry reasonably well understood, we have embarked on a study of the synthesis of well-controlled polymer structures via metathesis polycondensation chemistry [37]. A series of well-defined polyolefins have been designed to model the crystallization behavior of polyethylene and its related copolymers, including new materials synthesized by metallocene-based catalysts. This synthesis concept has been reduced to practice, and polymers that will aid in the understanding of branching within polyethylene itself have been produced. 

Behavioral synthesis chains operations within a cycle based on the clock period. The following VHDL design example illustrates the concept of chaining. 

Catalano et al. reported the synthesis and characterization of a new series of Pd°-based metallocrypates that bind Tl1 ion in the absence of attractive ligand interactions through metal-lophilic connections. The cationic species have been characterized by a variety of methods and have considerable stability. From the solid-state structural data it is apparent that interaction of the metal atoms with one another is the dominant bonding interaction within the metallocryptate cavity. The characterization of complexes supports the concept of metallophilic behavior as a fundamental component of bonding in closed-shell systems. These materials may ultimately serve as prototypical systems for detection of closed-shell ions 946... 

Particular attention is now given to the characterization of the supported species, and to the control of stability and recycling of the catalyst. The behavior of the supported catalyst under the reaction conditions (temperature, pressure, and nature of reactants and products) is certainly a less well-developed area, even though these data are valuable for the conception and development of a fully recyclable catalyst. Very few chemical engineering studies have been so far reported they will become crucial if the objective is the synthesis of an industrial catalyst. 

It should be also noted that the field of smart polymer surfaces is not limited to the macromolecular structures presented in the first part of this chapter. Although some classic stimuli-responsive polymers such as PNIPAM or poly(acrylic acid) have been studied for several years, new exciting options are reported every week in the polymer literature. For instance, the synthesis of chemo- and bioresponsive polymers is a topic in full expansion [9], Thus, new developments in the fields of bioassays and biosensors may be expected in the near future. For instance, more advanced surface concepts (e.g., multiresponsive behaviors, signal cascades) can be anticipated with reasonable certainty. 

Parallel kinetic resolution (PKR), a concept that has been introduced for reactions where starting from a racemic mixture can allow the preparation of two different compounds at the same reaction rate [31], has been appHed for the separation of a mixture of P-D/L-deoxynucleosides. A practical synthesis of P-t-3 - and P-L-5 -0-levuHnyl-2 -deoxynucleosides has been described for the first time [32] through enzymatic acylation and/or hydrolysis processes. It is remarkable that the different behavior exhibited by PSL in the acylation of D- and L-nucleosides allows the parallel kinetic resolution of D/L nucleoside racemic mixtures. Scheme 10.12 shows a PKR of a 1 1 mixture of D and L nucleosides via an acylation reaction for furnishing easily separable compounds. This methodology would have tremendous potential for both research and industrial applications in the nucleic acid field. 

This chapter will not belabor in great detail the synthesis and structure-property behavior of those systems that have been prepared within our laboratory. Rather, some of the basic concepts involved in preparing these hybrid sol-gel materials will be reviewed. An overview of methods, including those routes taken by other researchers, will be presented. However, greater emphasis will be given to those materials that we have prepared, primarily because only limited structure-property studies have been carried out by other workers in the field. Further details of our studies on many of the hybrid materials (initially denoted as ceramers ) can be found elsewhere (i-9). 

Systematic studies of the processes occurring during freeze-drying synthesis demonstrated that the actual situation in a majority of multicomponent systems is better described by the second concept, although the actual component distribution depends on a number of processing variables and the chemical features of the components. In order to forecast the behavior of a particular multicomponent system in the course of synthesis, several general physicochemical aspects of synthesis processes should be taken into account. 

Thus this book presents current developments and concepts in the chemical techniques for production and characterization of state-of-the-art ceramic materials in a truly interdisciplinary fashion. The 27 chapters are divided into five parts reflecting topical groups. The first part discusses the starting materials—how to prepare and modify them in the nanoscale range. Powders are the most heavily used form of starting ceramic materials. The synthesis, characterization, and behavior of ceramic powders are presented in parts I and II. In the third part, processing of ceramic films via the sol-gel technique is discussed. Fabrication of... 

---