Polyrotaxanes Subject

Whereas the directed synthesis was an isolated adventure, the statistical technique was subjected to scrutiny from time to time [33-39] and was finally borrowed by polymer chemists for making polyrotaxanes [22, 40, 41]. 

In 1992, Harada etal. prepared a compound in which many CDs were threaded onto a single PEG chain and were trapped by end-capping groups at both termini of the PEG chain (Scheme 2). The formation of pseudopolyrotaxane form PEG bisamine (Mn 3350) took place in water, from which a large excess of P-CD was isolated and then subjected to end-capping reaction with 2,4-dinitrofluorobenzene in DMF to yield polyrotaxane. The average molecular weight of the polyrotaxane was estimated to be about 25 000. Approximately 20-23 CDs were threaded in one PEG molecnle. This is the first example of polyrotaxane, which was referred to as a molecular necklace by Harada et al. 

Subjecting inclusion compounds, isolated beforehand, to y-irradiation, Maciejewski et al. 21.100.104) managed to obtain stable polymeric adducts with a polyrotaxane structure only when adducts of P-cyclodextrin with vinylidene chloride or allyl chloride served as initial adducts. Polymerization of the rest of the monomeric adducts resulted in unstable compounds, dissociating into a homopolymer and the initial P-cyclodextrin in hot water. 

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