Multifunctional coupling reagents

The terminal phenolic groups of oligomers of poly(2,6-dimethyl-l,4-phenylene oxide), 1, (1, 2) react efficiently with multifunctional coupling reagents to form polymers with increased molecular weights. 

Many types of mono-, bi-, and multifunctional coupling reagents are available for labeling antibodies or antigens with an enzyme. Glutaraldehyde, carbodiimide, N-succinimidyl-3-(2-pyridyldithio)propionate, and periodate oxidation of carbohydrate moieties to form active dialdehydes are several commonly used approaches in the preparation of enzyme conjugates (104-106). 

The formation of PAA star polymers using the core first method has been demonstrated in the ATRP process by use of multifunctional initiators [111, 112]. In this method, the number of arms in the star polymer can be determined by the number of initiating sites on the initiator. Star-shaped PtBuA was prepared by the arm first method via ATRP, using divinylbenzene, 1,4-butanediol diacrylate, and EGDMA as coupling reagents [113]. 

Purification. Hemoglobin is provided by the red blood cell in highly purified form. However, the red cell contains many enzymes and other proteins, and red cell membranes contain many components that could potentially cause toxicity problems. Furthermore, plasma proteins and other components could cause toxic reactions in recipients of hemoglobin preparations. The chemical modification reactions discussed herein are not specific for hemoglobin and may modify other proteins as well. Indeed, multifunctional reagents could actually couple hemoglobin to nonhemoglobin proteins. 

The cross-linking of R. requires the presence of functional groups, e. g., unsaturated carbon/carbon bonds, hydroxy or isocyanate groups. By means of these groups, the R. molecules can be coupled with each other intermolecularly (cross-linking) on reaction with multifunctional reagents in a process known as vulcanization. 

Telechelic polymers can be used as cross-linkers, chain extenders, and precursors for block and graft copolymers. Moreover, star and hyper-branched or dendric polymers are obtained by coupling reactions of monofunctional and multifunctional telechelics with appropriate reagents. Various macromolecular architectures obtained by the reactions of telechelics are represented in Figure 1. 

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