In situ Fourier transform infrared spectroscopic study of the conformational changes of nylon‐10,12 during its Brill transition

In Situ microscopic infrared imaging study on deformation‐induced spatial orientation and phase transition distributions of PA12

“…To construct the spatial distributions of crystal and amorphous orientations of PA12 during uniaxial stretching, FTIR spectra with radiation parallel and perpendicular to tensile directions at different drawing ratios are measured. Because the bands at 946, 980, and 1064 cm −1 are associated with the crystalline phase, while the bands at 1026 and 1160 cm −1 are associated with the amorphous phase . As 1064 and 1026 cm −1 show strong dichroism, the vibrational bands at 1064 (CONH in‐plane deformation) and 1026 cm −1 (skeletal motion involving CONH) are assigned as crystalline phase and amorphous phase for analyzing quantitative behaviors of the uniaxial orientation, respectively.…”

“…Because γ phase is the most stable form in the film, and the whole tensile experiments were done at room temperature, the most crystal phase in the sample at first is γ phase, which is verified by the FTIR spectra as shown in Figure . For undeformed PA12 samples, the 946 cm −1 band (CONH in‐plane deformation) in the spectrum belongs to the γ phase while 1160 cm −1 band (Skeletal motion involving CONH deformation) belongs to the amorphous phase . Because there have large numbers of hydrogen bonds and some are perpendicular to the stretching direction, these cause the two bands not showing strong dichroism.…”

Crystalline transition of polyamide‐10,20 investigated by in situ Fourier transform infrared spectroscopy

“…In addition, strong absorbance bands at about 3080 (amide B, overtone of amide II), 1640 (amide I, CO stretch), 1540 (amide II, CN stretch), 1367 (amide III, CN stretch and in‐plane NH deformation), and 940 cm −1 (amide IV, CCO stretch) can be observed for the room‐temperature crystal structure of the polyamide under consideration. Moreover, the characteristic bands around 1276, 1240, and 1211 cm −1 belong to amide III coupled with the out‐of‐plane vibration of methylene units 3, 11, 12, 16, 19…”

“…In FTIR, some bands are related to the Brill transition and disappear abruptly during the crystalline transition. Other bands at 1440, 1352, and 1308 cm −1 are associated with the conformation band of polyamide and reflect the defect of the conformation of the methylene sequences between the amide groups 16…”

Investigation on the Brill transition of polyamide 618

“…In addition, the changes of diffraction spacings are crystalline transition are unclear. Recently, some papers were published to present the conformational change of the methylene moiety during Brill transition of even-even polyamides [16,17].…”