Cyclic acetals of fluorinated polyether macrodiols

Telechelic hydroxy terminated perfluoropolyethers were derivatized with dih alomethanes (CH2Cl2;CH2Br2;CH2BrCl) in different stoichiometric ratios. The GPC analysis of the raw reaction product showed a general bimodal molecula r weight distribution. Separation of the different fractions was carried ou t by solvent-non-solvent fractionation procedure or by vacuum distillation. Pt was proved that the lowest molecular weight product (about 50% of the w hole polymer) corresponded to a fluorinated, cyclic monoacetal structure, w hile the higher MW fractions consisted predominantly of linear, polyacetal polymers. The tendency of fluorinated macrodiols to yield cyclic, instead of linear a cetals, is discussed, even in comparison with the behavior of their non-flu orinated analogs. Some physical properties of the new cyclic fluoropolyethe rs are briefly reported. (C) 1999 Elsevier Science S.A. All rights reserved .