Networks Crosslinked by Strained-Ring Precursors

Another approach to the creation of rigid netwoiics containing alkylene-type junctions is by first preparing more or less stiff aromatic segments terminated by 

The three strained-ring end-cap groups most commonly used for forming junctions between stiff aromatic segments are the benzocyclobutene (BCB) [577-586], biphenylene (BP) [586-591] and [2.2] paracyclophane (PCP) [586, 592] groups  

Benzocyclobutene (BCB) Biphenylene (BP) [2.2]Paracyclophane (PCP) More recent additions to the list of strained-ring reactive crosslinking groups are [586] cyclobutaquinoline (CBQ) and benzocyclobutaacenaphthylene (BCBAN)  

The benzocyclobutene end-group was used with a broad variety of segments ranging from wholly aliphatic to wholly aromatic and from very short to relatively long. Segments of interest in the context of this review are, for instance [582,583]  

Polyquinoxaline network segments were also claimed by Arnold et al. [581] but with BCB end-caps instead of BP end-caps. 

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