激光诱导聚酰亚胺纳米微结构中分子链取向排列的研究

通过Nd:YAG偏振脉冲激光辐射聚酰亚胺薄膜,在其表面制得大面积纳米级周期性微线条,线条的周期性为200nm,线条方向始终平行于偏振激光束电场方向,线条横截面为圆形或椭圆形柱状结构.采用偏振反射红外光谱分别在平行与垂直纳米线条的方向上测试聚合物表面分子IR吸收光谱,结果发现,1722和1231cm^-1处的吸收有明显的二向色性,表明微线条内聚合物分子链部分呈现取向排列,且聚酰亚胺分子链方向与微线条方向垂直.

Polyimide Molecular Chains Alignment in Polarized Pulsed Laser-Induced Periodic Surface Structures

Periodic nano-lines in a large area have been formed on polyimide surface using polarized pulsed laser-inducing of the fourth harmonic Nd:YAG laser. The linear direction is parallel to the polarization direction and the periodical width of these lines is 200 nm.The dichroism due to the alignments of functional group in periodic nano-structure has been studied by recording polarized reflected FTIR spectra at 0° polarization parallel to the polymer lines and 90 °polarization lines. We found that C=Ostretching at 1722 cm^-1in the irradiated area has a stronger response than in the nonirradiated area when the IR polarization direction is parallel to the lines, while the band at 1231 cm^-1assigned to C-C-Cbetween phenylenes and the methylene groups has a stronger response when the polarized IRdirection is perpendicular to the lines. The dichroic spectrum indicates that in the irradiated area polyimide molecular chains are preferentially oriented perpendicular to the nano line direction. The orientation is caused by the directional electric field associated with the polarized laser beam during the melting and cooling process, while the polar carbonyl groups are subjected to the orientation in the electric field direction.