EFFECT OF SCISSION OF HYDROGEN-BONDS BY PHENOL ON PHASE-BEHAVIOR AND PHYSICAL-PROPERTIES OF POLYDIACETYLENE GELS - P(3BCMU) AND P(4BCMU)

We report the effect of phenol on the phase behaviour and physical pro perties of polydiacetylene gels. Specifically, they are o-dichlorobenz ene (o-DCB) solution of ne-1,10-diol-bis(n-butoxycarbonylmethylurethan e)], abbreviated as P(3BCMU), and toluene (Tol) solution of ne-1,12-di ol-bis(n-butoxycarbonylmethylurethane)], abbreviated as P(4BCMU). The polymer concentration was 0. 1 to 2 wt%, and the molar ratio z of phen ol to the monomer unit of the polydiacetylenes was regulated within 20 . The gel-to-sol transition temperatures T(t) were determined by measu rements of shear modulus for the P(3BCMU)/o-DCB system and by a fallin g ball method for the P(4BCMU)/Tol systems. T(t) decreased with increa sing z and the systems with polymer concentration of 1 wt% turned into a sol at room temperature in the range of z greater than or similar t o 10. The temperature dependence of alternating-current (a.c.) conduct ivity sigma(ac) at 1 kHz exhibited a maximum at a temperature ca. 20 K below the transition temperature. The value of sigma(ac) decreased st eeply at the electrical transition temperature T(sigma), which also de creased with increasing z. Ultra-violet and visible-light spectra for the P(3BCMU)/o-DCB and P(4BCMU)/Tol systems shifted to the short-wavel ength side with increasing z. The infra-red spectra indicate that the intramolecular hydrogen bonds between the N-H and C=O groups of the si de groups are cleaved by phenol. These results indicate that the conju gated rod-like conformation is made unstable by phenol. To clarify the mechanism of crosslinks of the gel network, the crystallinity of conc entrated P(3BCMU) gels was determined by wide-angle X-ray diffraction. No crystallinity was observed in the gels of C less than 30 wt%.