Formation of mesomorphic domains associated with dimer aggregates of phenyl rings in cold crystallization of poly(trimethylene terephthalate)

Studies on conformational changes of poly(trimethylene terephthalate) chains during uniaxially cold drawing using time-resolved polarized infrared analysis

“…In region iii, the G(t) started to increase and then the band positions shifted from 933 to 936 and 874 to 872 cm À1 , which the results were similar as our previous studies on the cold crystallization of PTT [27]. We have observed that the rigid segments composed of parallel aligned dimers with trans conformer clustered into nanograins accompanying the conformational changes from trans to gauche in the nucleation stage II to serve as embryos of primary nucleation of PTT crystals [27]. The IR results indicate that the nucleation of PTT chains may occur in the region iii of SHD.…”

“…On the other hand, for CC spectra, the bands at 936 and 872 cm À1 showed an increase in the absorbance, while the band at 818 cm À1 showed a decrease after cold crystallization. According to previous studies on cold crystallized PTT [19,27], 872 cm À1 band was assigned to the separated phenylene rings in crystal lattice unit, while 933 and 936 cm À1 bands were assigned respectively to amorphous gauche and crystalline gauche. Based on previous experimental results, we suggest that the position shifting from 933 to 936 cm À1 and 874 to 872 cm À1 can be an indicator for examining the onset of cold crystallization for PTT.…”

“…Quenched amorphous (QA) specimens were prepared by melt-pressing at 270 C for 5 min before quenching into ice water [26,27]. The prepared PTT films with a thickness of 30 mm were cut into dog-bone shape with dimensions of 3 Â 1 cm 2 for cold drawing under draw rates ( _ g) of 6.6 Â 10 À3 and 0.13 s À1 at 30, 45 and 50 C using Linkam TST350 hot stage.…”

“…On the other hand, the band at 874 cm À1 , which was assigned to the CH out-of-plane bending mode of the phenylene ring unit of PTT chains [19,31,32], showed a slight absorbance decrease after cold drawing. In our previous work, 874 cm À1 band has been used to monitor the formation of ground-state dimers resulting from the phenylene rings of PTT chains via pep interactions in supercooled amorphous liquids [27]. The decreased absorbance of 874 cm À1 band implies that few dimers was destroyed by chain sliding after cold drawing.…”

“…5. The relative crystallinity, W c,IR , was evaluated from the absorbance of band at 936 cm À1 (A 936 ), which was assigned to the crystalline gauche [19,27,32], as:…”