Synthetic polymers from coordination polymerization

PHB is a polymer obtained from many strains of bacteria. Von Korsatko claimed that PHB of various MW can be readily manufactured depending on the extraction method [162]. Grassie et ai and Tanahashi et al. described how PHB can be prepared synthetically [163-164]. Bleoembergen et al. reported the synthesis of HB/HV copolymers by coordination polymerization of )9-lactones [165]. HB/HV copolymers from 0 to 30% HV contents are available as Biopol on the market. 

An example of a nontrivial polyrotaxane formed using a similar synthetic approach is shown in Figure 21(b). In this case, rotaxane ligands bridge cadmium ions into 2D (4,4) sheets, and the wheels (in this case dibenzo-24-crown-8) can no longer be separated from the polymeric network. Indeed, while the previous example contained only rotaxane motifs, in this nontrivial example one can also define catenane-type interactions between the wheels and M4L4 rings formed by the coordination polymer. 

In new synthetic work, Mallon and Kantor have used coordination polymerization to prepare stereoregular hydrocarbon combs (65-90% isotactic) from monomers that are 4,4 -dialkyIbiphenyls containing a terminal double bond in the longer alkyl chain." The resulting polymers exhibit smectic B and smectic E mesophases that are uncommon in comb LCPs. "... 

MOFs/CPs, as the majority of these materials are based on transition metal, and more recently, lanthanide chemistry, yet a review of polymeric materials containing uranium (from more of a polymer chemistry perspective) has appeared recently. We will compare and contrast some uranium specific issues to those of the transition elements as we feel that the unique coordination geometries of the actinides (in particular U(VI)) result in a number of stmctural features, synthetic challenges, relevance to environmental issues, and opportunities for development of functional materials. 

Considerable gains have recently been made in the research of polymer catalysis which has emerged from the interaction of the fields of macromolecular, coordination and catalytic chemistry. Using synthetic macromolecules one can create polymeric catalysts which function like enzymes and almost simulate their activity and selectivity. Consequently, polymer catalysis could enable the high-yield manufacture of industrially important products at low-reaction volumes involving minimal energy consumption. 

The potential synthetic possibilities for the creation of coordination polymers are enormous. A variety of other types of coordination bonds have been used to create polymeric materials. In most cases, the bonds formed are sufficiently labile for depolymerization to occur in solution. For example, by layering a solution of one equivalent of bipyridine with a diborylferrocene, the coordination polymer 7.52 is formed as an insoluble black crystalline solid. Addition of picoline leads to chain cleavage and the formation of the monomeric adduct 7.53 (Eq. 7.13) [97]. Materials analogous to 7.52 have been prepared with pyrazine as the linker, and these dark-green materials show charge-transfer transitions from the iron to the electron-poor heteroaromatic ligand [98, 99]. 

Many different polymers of conjugated dienes are prepared conunercially by a variety of processes, depending upon the need. They are formed by free-radical, ionic, and coordinated anionic polymerizations. In addition, various molecular weight homopolymers and copolymers, ranging from a few thousand for liquid polymers to high molecular weight ones for synthetic rubbers, are on the market. 

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