Potential monomers for

Some compounds of general structures (137) and (138) have hydroxy or carboxy termini, making them potential monomers for the synthesis of energetic polymers (binders) and plasticizers for both explosive and propellant formulations. ... 

On the other hand, the high degree of unsaturation of this type of drying oil has made it a potential monomer for polymerization into useful polymers. More recently, Li and Larock (41) reported the conversion of tung oil to solid polymers by cationic copolymerization with divinylbenzene as a comonomor. The resulting polymers have proven to be thermosetting materials with good mechanical... 

Other Perethynylated Compounds as Potential Monomers for Carbon Networks... 

In Section 13-4, it will be shown that tetraethynylethenes are potential monomers for the construction of all-carbon networks [1]. Other perethynylated compounds have been reported, which could also serve as building blocks for infinite two- and three-dimensional carbon nets [46]. They all represent fascinating small molecules of substantial structural and electronic interest [1, 2, 47]. 

Tetraethynylmethane (39), a potential monomer for a three-dimensional superdiamonoid carbon network [1], was elusive for many years [51, 52], until its synthesis was accomplished in 1993 by Feldman and co-workers [53]. The key step in the synthesis was the acid-mediated Johnson orthoester variant of the Claisen rearrangement, which provided the central quaternary methane C-atom with suitable functional groups for the ultimate transformation into 39 [Scheme 13-9(b)]. Solid 39, like tetraethynylethene (20), decomposes rapidly at room temperature in either the presence or absence of oxygen. The earlier efforts to prepare tetraethynylmethane had yielded the peralkynylated derivatives 40-42 [Scheme 13-9(c, d)] [51, 52]. Tetraethy-nylallene represents another potential precursor for a three-dimensional carbon network [1], but remains elusive of the perethynylated [K]cumulenes, so far only the silyl-protected [3]cumulenes 43a and 43b [Scheme 13-9 (e)] have been prepared [54]. With 44 [Scheme 13-9 (f)], the first transition metal complex of a perethynylated ligand is now available [55]. 

Dimerisation of monounsaturated fatty acids has been exploited to prepare monomers bearing two carboxylic functions and, after reduction, the corresponding diols [2], i.e., potential monomers for the synthesis of polyesters, polyamides, polyethers and polyurethanes incorporating long aliphatic motifs. Scheme 2.7 shows two possible mechanisms associated with this reaction (i.e., ene- or carbonation coupling), which is inevitably accompanied by further additions to give trimers and oligomers, if not carried out under finely controlled conditions. 

On the other hand, compounds that can be described as trapped or masked disilenes can be viewed as potential monomers for polymer synthesis. The trapped or masked disilene can be liberated from its adduct by chemical or photochemical process. However, even if moderately buUq substituents are present on silicon in such compounds, the liberated disilene combines to afford the thermodynamically favorable cyclized products. Thus, the masked disilene containing isopropyl substituents on silicon affords the cyclotetrasilane [zPr2Si]4 (see Eq. 7.7) [49]. 

Phenylglycosyl sulphones also gave C-glycosides under these conditions, but elimination concurrently occurred. Several compounds based on 107 (R=H) which allows alkylation and introduction of groupings with unsaturation within R have been prepared as potential monomers for the preparation of polyvinylsaccharides. Elaboration of 1-cyanoglycals has allowed the... 

Figure 7-15 shows the time evolution of the temperature, total energy, and potential energy for a 300 ps simulation of the tetracycline repressor dimer in its induced (i.e., hgand-bound) form. Starting from the X-ray structure of the monomer in a complex with one molecule of tetracycline and a magnesium ion (protein database... 

Of the individual dimethylnaphthalenes, 2,6-dimethylnaphthalene [28804-88-8] h.a.s been of particular interest as a precursor to 2,6-naphthalenedicarboxyhc acid [1141-38-4] a potentially valuable monomer for polyesters. 

During this early period, a very ingenious free-radical route to polyesters was used to introduce weak linkages into the backbones of hydrocarbon polymers and render them susceptible to bio degradabihty (128—131). Copolymerization of ketene acetals with vinyl monomers incorporates an ester linkage into the polymer backbone by rearrangement of the ketene acetal radical as illustrated in equation 13. The ester is a potential site for biological attack. The chemistry has been demonstrated with ethylene (128—131), acryhc acid (132), and styrene (133). 

There exists a large number of natural monomers that needs further studies for their exploitation Pillai and Manjula have reviewed [25] the subject and a comprehensive list of potential monomers and their source is given in Table 18. 

Butadiene is not only the most important monomer for synthetic ruh-her production, hut also a chemical intermediate with a high potential for producing useful compounds such as sulfolane hy reaction with SO2, 1,4-hutanediol hy acetoxylation-hydrogenation, and chloroprene hy chlori-nation-dehydrochlorination. 

If R and Z, A or X arc connected to form a ring structure the result is a potential ring opening monomer. For many of the transfer agents in this section there are analogous ring-opening monomers described in Section 4.4.2. 

The hydrogenation of 3-hydroxy propan al (HPA) to 1,3-propanediol (PD) over Ni/SiOi/AEO, catalyst powder was studied by Professor Hoffman s group at the Friedrich-Alexander University in Erlagen, Germany (Zhu et al., 1997). PD is a potentially attractive monomer for polymers like polypropylene terephthalate. They used a batch stirred autoclave. The experimental data were kindly provided by Professor Hoffman and consist of measurements of the concentration of HPA and PD (Chpa< Cpd) versus time at various operating temperatures and pressures. 

In an attempt to identify more biocompatible diphenols for the design of degradable biomaterials, we studied derivatives of tyrosine dipeptide as potential monomers. After protection of the amino terminus and the carboxylic acid terminus, the reactivity of tyrosine dipeptide (Figure 1) could be expected to be similar to the reactivity of industrial diphenols. Thus, derivatives of tyrosine dipeptide could be suitable replacements for BPA in the synthesis of a variety of new polymers that had heretofore not been accessible as biomaterials due to the lack of diphenolic monomers with good biocompatibility. 

In an attempt to identify new, biocompatible diphenols for the synthesis of polyiminocarbonates and polycarbonates, we considered derivatives of tyrosine dipeptide as potential monomers. Our experimental rationale was based on the assumption that a diphenol derived from natural amino acids may be less toxic than many of the industrial diphenols. After protection of the amino and carboxylic acid groups, we expected the dipeptide to be chemically equivalent to conventional diphenols. In preliminary studies (14) this hypothesis was confirmed by the successful preparation of poly(Z-Tyr-Tyr-Et iminocarbonate) from the protected tyrosine dipeptide Z-Tyr-Tyr-Et (Figure 3). Unfortunately, poly (Z-Tyr-Tyr-Et iminocarbonate) was an insoluble, nonprocessible material for which no practical applications could be identified. This result illustrated the difficulty of balancing the requirement for biocompatibility with the need to obtain a material with suitable "engineering" properties. 

The ideal electropolymerization scheme (Eq. (5.5.39)) is further complicated by the fact that lower oligomers can react with nucleophilic substances (impurities, electrolyte anions, and solvent) and are thus deactivated for subsequent polymerization. The rate of these undesired side reactions apparently increases with increasing oxidation potential of the monomer, for example, in the series ... 

Potential Non-Cvcllc Precursors of Preceramic Polymers. Boranes such as bis(trimethylsilyl(aminotrimethylsilylaminochloroboranes can be viewed as monomers for preceramic polymer and, ultimately, boron nitride production. Intermolecular dehydrohalogenation of this borane would be thus expected to yield either the dimer or the polymeric system. 

The electrochemical reduction reactions of the central metallotetraphenylporphyrin moieties are, fortunately, much more straightforwardly analyzed (1,2). With few exceptions, when transferred to a fresh supporting electrolyte solution, films formed from ECP reactions like Fig. 2A exhibit electrochemical reduction waves at or very near the potentials observed for reductions of the corresponding monomers dissolved in solutions. For example, a film formed oxidatively as in Fig. 2A gives in fresh electrolyte the reductive gyclic voltammogram of Fig. 2B. 

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