Cross-Polymerization of Hard Blocks in Segmented Copoly(ether urea)s
Koevoets, Rolf A Karthikeyan, S Magusin, Pieter Meijer, E. W Sijbesma, Rint P # ×
American Chemical Society
Macromolecules vol:42 issue:7 pages:2609-2617
Diacetylene-containing segmented copoly(ether urea) 1 was prepared via a polycondensation of 1,10-diisocyanato-deca-4,6-diyne with bis(3-aminopropyl)poly(tetrahydrofuran) (Mn ≈ 2300 g/mol). The reactive diacetylene spacer, which resides within the hard domains of the segmented elastomer, was cross-polymerized topochemically by means of UV radiation, without disrupting the flexible nature of the material, resulting in an intensely blue insoluble material. The extent of cross-polymerization was determined using solid-state 13C NMR and was found to be 10%. The optical properties of the cross-polymerized material could be modified mechanically and thermally as well as by changing the solvent. A study into the mechanochromic behavior—a color change from blue to yellow upon elongation—showed that the color changes are irreversible at strain levels greater than 80%. Polarized UV spectroscopy indicated that upon deformation the polydiacetylene chains orient parallel to the deformation axis. Thermochromic and solvatochromic behavior of 1 was completely irreversible.