Intermolecular cross-linked macromolecule

The formation of intermolecular cross-links, i.e. covalent bonds between different polymer chains, causes an increase in the average molar mass and eventually combines all of the macromolecules into a three-dimensional insoluble network. Cross-linking can be accomplished in various ways. Several methods rely on reactions of electronically excited pendant groups on the polymer chains, others on reactions of various kinds of reactive species in the ground state that are photogenerated in polymeric systems. Typical of the former reaction type are [2-f-2] cycloadditions that occur in the case of linear polymers bear-... 

This feature can be explained by intermolecular chain transfer, giving branched macromolecules with high molecular weight or by the occurrence of dehydrocoupling cross-linking reactions, such as described previously for polyborazylene (scheme 1). 

The periphery of convergently synthesized den-drimers has also been modified to allow the assembly of monolayers,494 to support dendritic catalysts,495 to control the intermolecular assembly of porphyrin dendrimers,246 to probe the effect of photo isomerization,319 and to enable cross-linking of the periphery followed by removal of the core.496 These studies in peripheral modification highlight the versatility of the convergent synthesis. In particular, the ability to selectively modify the periphery and focal functionalities of a dendron enables the design of complex macromolecules that involve the interaction between multiple functional components. 

For an example of the application of Radziszewski reaction for intra- and intermolecular polymer coupling, see K.-S. Krannig, D. Esposito, M. Antonietti, Macromolecules 2014, 47, 2350-2353. Highly efficient transfer of amino groups to imidazolium entities for polymer coupling and cross-linking. 

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