Multifunctional linking agents

Cross-linking agents or oligomers with multifunctional unsaturation sites include the following ... 

Multifunctional Hydroxy, Mercapto, and Amino Compounds. These are used to cross-link halogenated polymers. Depending on the labihty of the halogen, the cross-linking agents can be capped to reduce reactivity or used in combination with accelerators to increase the rate of reaction. Benzoyl capping is common with hydroxy and mercapto compounds forming the carbamate by reaction with one equivalent of carbon dioxide is used with diamines. 

Crosslinking may occur during the polymerization reaction when multifunctional groups are present (as in phenol-formaldehyde resins) or through outside linking agents (as in the vulcanization of rubber with sulfur). 

With the multifunctional linking strategy either homo- or heterofunctional linking agents can be employed. The homo-approach was widely used in the past for the synthesis of well-defined //-stars with predetermined number and molecular characteristics of arms [163]. New applications of these approaches have been recently reported for the synthesis of A2B, A3B and A2B2 type //-stars. 

Star polymers may be synthesized in several ways. The arm-first method joins preformed arms together using a linking agent, and the core-first method utilizes a multifunctional initiator to grow the... 

Figure 387 Polyaldehyde dextran may be used as a multifunctional cross-linking agent for the coupling of amine-containing molecules. Reductive amination creates secondary amine linkages.

Cross-linking Using Multifunctional Reagents Water-insoluble enzymes can be prepared by using multifunctional agents that are all bifunctional in nature and have low molecular weight, such as glutaraldehyde. 

Cationic synthesis of block copolymers with non-linear architectures has been reviewed recently [72]. These block copolymers have served as model materials for systematic studies on architecture/property relationships of macromolecules. (AB)n type star-block copolymers, where n represents the number of arms, have been prepared by the living cationic polymerization using three different methods (i) via multifunctional initiators, (ii) via multifunctional coupling agents, and (iii) via linking agents. 

Po fraction of reactive groups in a copolymerization which are part of a multifunctional cross-linking agent (Chapter 8)... 

---