Novel Thermotropic Behavior of (Diphenyl/Phenyl- o-Tolyl)Phosphazene RandomCopolymer

摘要

Ph2PN 0,76(Ph(o-tolyl)PN)0.24 random copolymer (Ph: phenyl) was synthesized bythe reaction of Ph2POCH2CF3 and Ph(o-tolyl)POCH2CF3 with trimethylsilyl azide. Differential scanning calorimetry (DSC) measurements showed that this copolymer has a single glass transition at approx. 80 deg C and transforms into a mesophase at 162 approx. 189 deg C depending upon the thermal history of the specimens. Lath shaped crystals with unit cell dimensions a = 1,30 nm, b = 1,13 nm and y = 87 deg (Form-I) were obtained from mixed dilute monochlorobenzene and p-xylene solution of the copolymer. Upon heating the specimens to 140 deg C, the 'a' parameter of Form-I changes to a = 2,21 nm and the 'b', 'gamma' remain unaltered (Form-II). When the specimens are cooled (10 deg C/min) from above T(1), the mesophase (delta-form) is 'frozen in' and the delta-form specimens transform into Form-II by heating to 140 deg C. Another structure change (Form-III) occurs after the delta-form specimens were heated to 180 deg C followed by cooling below the glass transition temperature Tg. However, upon cooling the specimens slowly (0,2 deg C/min) from above T(1), Form-III results.