Macrocyclic PS Combs

Deprotection of the hydroxyl groups of the SiVE sequence can be readily achieved by reaction of the triblock copolymer with tetrabutylammonium fluoride (TBAF) in THE, thus 

Triblock M X 10 Mp X 10- MJM Afpc/MpL. X 10 DpnA (SiVE) DpnB (CEVE) DPnC (CDVE) Estimated 

In a second step the A and C triblock end sequences are reacted in the presence of an acid as catalyst, under highly dilute conditions to favor macrocyclization by intramolecular coupling of the functions of A and C sequences. This is achieved by adding dropwise a solution of the copolymer into a large volume of methylene dichloride containing traces of an acid catalyst. 

Deconvolution of the main SEC peak attributed to cyclic gives as a first estimate a cyclization yield in the range 65 to 70%, Table 21.10. As will be shown latter, these values are higher than those directly measured by AFM imaging on the corresponding cyclic combs. This could be ascribed to the coelution of low molar mass linears with cyclics. 

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Scheme 21.7 Strategy used for the synthesis of large PCEVE rings and of corresponding macrocyclic PS combs. (Reprinted with permission from M. Schappacher and A. Deffieux, Atomic force microscopy imaging and dilute solution properties of cyclic and linear polystyrene combs, Journal of the American Chemical Society, 130, 14684-14689, 2008. 2008 American Chemical Society.)...

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