聚偏氟乙烯C—H伸缩振动模式三级中红外光谱研究

Three-step MIR Spectroscopy of Polyvinylidene Difluoride C—H Stretch Vibration MODE

采用中红外(MIR)光谱开展聚偏氟乙烯分子结构的研究。试验发现:聚偏氟乙烯分子的红外吸收模式主要包括ν_(asCH2)、ν_(sCH2)、δ_(CH2)、ν_(asCF2)和ν_(sCF2)。进一步开展了聚偏氟乙烯分子的变温中红外(TD-MIR)光谱研究。试验发现:随着测定温度升高,聚偏氟乙烯分子ν_(asCH2)和ν_(sCH2)对应的红外吸收频率及强度均有明显的改变。采用二维中红外(2D-MIR)光谱开展了聚偏氟乙烯的热老化性研究。试验发现:相变前,聚偏氟乙烯分子ν_(CH2-二维-相变前)吸收峰变化快慢信息为:3012 cm^(-1)(ν_(asCH2-二维-2-相变前))>2980 cm^(-1)(ν_(sCH2-二维-4-晶体-相变前))>2970 cm^(-1)(ν_(sCH2-二维-5-晶体-相变前))>2990 cm^(-1)(ν_(asCH2-二维-3-晶体-相变前))>3033 cm^(-1)(ν_(asCH2-二维-1-晶体-相变前))。相变过程中,聚偏氟乙烯分子ν_(CH2-二维-相变过程中)吸收峰变化快慢信息为:3015 cm^(-1)(ν_(asCH2-二维-2-相变过程中))>2980 cm^(-1)(ν_(sCH2-二维-4-晶体-相变过程中))>3030 cm^(-1)(ν_(asCH2-二维-1-晶体-相变过程中))>2990 cm^(-1)(ν_(asCH2-二维-3-晶体-相变过程中))>2970 cm^(-1)(ν_(sCH2-二维-5-晶体-相变过程中))。相变后,聚偏氟乙烯分子ν_(CH2-二维-相变后)吸收峰变化快慢信息为:2980 cm^(-1)(ν_(sCH2-二维-3-晶体-相变后))>2970 cm^(-1)(ν_(sCH2-二维-4-晶体-相变后))>3026 cm^(-1)(ν_(asCH2-二维-1-晶体-相变后))>3012 cm^(-1)(ν_(asCH2-二维-2-相变后))。研究发现:聚偏氟乙烯的红外吸收峰(ν_(asCH2)和ν_(sCH2))对热敏感程度及变化顺序均存在着较大的差异性。研究拓展了三级MIR光谱对聚偏氟乙烯结构及热老化性的研究范围。

The molecular structure of polyvinylidene difluoride(PVDF)was studied by infrared(MIR)spectroscopy.The infrared absorption modes of PVDF molecules includedν_(asCH2),ν_(sCH2),δ_(CH2),ν_(asCF2) andν_(sCF2).Temperature-dependent infrared(TD-MIR)spectroscopy of PVDF were also studied.With the increase of temperature,the corresponding frequency and absorption intensity of PVDF(νasCH2 andνsCH2)changed obviously.The thermal aging of PVDF was considered by the two dimensional infrared(2D-MIR)spectroscopy.Before phase transition,the sequence of PVDF/ν_(CH2-2D-before phase transition)infrared absorption peak changes were:3012 cm^(-1)(ν_(asCH2-2D-2-before phase transition))>2980 cm^(-1)(ν_(sCH2-2D-4-crystal-before phase transition))>2970 cm^(-1)(ν_(sCH2-2D-5-crystal-before phase transition))>2990 cm^(-1)(ν_(asCH2-2D-3-crystal-before phase transition))>3033 cm^(-1)(ν_(asCH2-2D-1-crystal-before phase transition)).During phase transition,PVDF/ν_(CH2-2D-during phase transition)infrared absorption peak changes were:3015 cm^(-1)(ν_(asCH2-2D-2-during phase transition))>2980 cm^(-1)(ν_(sCH2-2D-4-crystal-during phase transition))>3030 cm^(-1)(ν_(asCH2-2D-1-crystal-during phase transition))>2990 cm^(-1)(ν_(asCH2-2D-3-crystal-during phase transition))>2970 cm^(-1)(ν_(sCH2-2D-5-crystal-during phase transition)).After phase transition,PVDF/ν_(CH2-2D-after phase transition)infrared absorption peak changes were:2980 cm^(-1)(ν_(sCH2-2D-3-crystal-after phase transition))>2970 cm^(-1)(ν_(sCH2-2D-4-crystal-after phase transition))>3026 cm^(-1)(ν_(asCH2-2D-1-crystal-after phase transition))>3012 cm^(-1)(ν_(asCH2-2D-2-after phase transition)).The main functional group of PVDF(ν_(asCH2)andν_(sCH2))showed different sensitivity and order to the heat.The paper demonstrated the key roles of three-step MIR spectroscopy in the analysis of structure and thermal aging of the important polymers materials PVDF.