应用化学 ›› 2021, Vol. 38 ›› Issue (10): 1226-1237.DOI: 10.19894/j.issn.1000-0518.210381
收稿日期:
2021-07-30
接受日期:
2021-08-26
出版日期:
2021-10-01
发布日期:
2021-10-15
通讯作者:
于海峰
基金资助:
Yu-Fan JI, Feng CAI, Hai-Feng YU()
Received:
2021-07-30
Accepted:
2021-08-26
Published:
2021-10-01
Online:
2021-10-15
Contact:
Hai-Feng YU
About author:
yuhaifeng@pku.edu.cnSupported by:
摘要:
光响应液晶聚合物具有良好的自组装特性与光调控性能,被广泛地应用于表面微纳结构的研究中。通过改变液晶分子的取向方式和有序参数,可以得到复杂多样的表面形貌,这在光学、生物学和机械控制等领域有较高的研究价值与应用前景。表面形貌调控的关键在于对其机理的深刻理解与把握:从液晶分子指向矢的角度来说,当液晶分子的有序参数减小时,会沿指向矢方向收缩,垂直指向矢方向膨胀,利用相邻域之间分子取向差异产生的侧向剪应力,可以构建具有表面起伏的微纳结构;从液晶聚合物产生自由体积的角度来说,紫外光照射时产生的自由体积会使薄膜密度下降,在偶氮苯可逆的反-顺-反异构化的动态过程中,会形成宏观表面起伏;从光诱导聚合物质量迁移的角度来说,光场的光强分布、偏振态以及光束的波前均会对材料的定向质量迁移产生影响;从光照使薄膜表面稳定性改变的角度来说,可以利用光聚合时薄膜的各向异性收缩产生褶皱,也可以通过应力释放对薄膜的表面褶皱形貌进行调控。因此,基于光诱导产生表面形貌变化的4种不同机理,对光控表面形貌的相关研究进展进行了回顾和总结,并展望了未来可能的发展方向,为后续进一步研究液晶聚合物的表面形貌调控及其功能化提供了参考。
中图分类号:
纪宇帆, 蔡锋, 于海峰. 液晶聚合物的表面形貌光调控研究进展[J]. 应用化学, 2021, 38(10): 1226-1237.
Yu-Fan JI, Feng CAI, Hai-Feng YU. Research Progress on Photoswitchable Surface Topography of Liquid Crystalline Polymer[J]. Chinese Journal of Applied Chemistry, 2021, 38(10): 1226-1237.
图 1 (A)液晶分子有序参数降低引起的变化; (B)偶氮苯的光致异构化转变; (C)表面起伏光栅的形成过程; (D)双层膜的两种失稳模式
Fig.1 (A) The change induced by the decreased order parameter; (B) Photo-isomerization of azobenzene; (C) The formation process of surface relief gratings; (D) Two instability modes of bilayer membrane
图 2 (A)平面取向和垂直取向交替排列的LCN涂层。紫外光照射后,平面取向的分子在垂直平面方向膨胀,垂直取向的分子在垂直平面方向收缩;(B)包含指纹图案的LCN涂层。紫外线照射前和照射时表面形貌的干涉仪测量图像[40];玻璃基底(C)和柔性聚合物基底(D)的LCN涂层表面形貌变化[41]
Fig.2 (A) LCN containing chiral nematic and homeotropic orientation. After ultraviolet (UV) illumination, the chiral nematic areas expand perpendicular to the plane of the film while the homeotropic areas contract in the perpendicular direction; (B) LCN including fingerprint patterns. Images from interferometer measurements showing the surface topography before and during UV irradiation[40]; Topographical deformation of LCN coatings with (C) rigid glass and (D) a compliant polymer layer as the substrate[41]
图 3 (A)利用掩模进行紫外光照射后,自由体积的产生导致LCN密度降低的示意图;(B)在365和 455 nm双波长照射时,表面变形增加[21];(C)在任意波长的两束光照射下实现光机械响应最大化的设计模型[45]
Fig.3 (A) Illustration of the reduced LCN density after UV illumination with photomasks due to the generation of free volume; (B) Under the illumination of 365 and 455 nm light, surface topographical deformation is increased[21]; (C) Design box for maximizing the optomechanical response under two-light illumination with arbitrary wavelengths[45]
图 4 线偏振光(A) 和圆偏振光(B)产生的表面起伏[49];(C)q值对螺旋图案的影响的示意图,q=10(D)和q=-10(E)L-G光束所得图案的光学显微照片和原子力显微镜(AFM)图像(所有比例尺均为1 μm[51]);聚合过程中利用二向色性染料(F)和二向色性引发剂(G)调控表面形貌
Fig.4 (A,B) Surface reliefs resulting from linearly (A) and circularly (B) polarized beams[49]; (C) Scheme of the influence of q value on spiral pattern; (D,E) Optical micrograph and AFM image of the pattern of q=10 (D) and q= -10 (E) L-G beam. All the scale bars are 1 μm[51]; (F,G) Manipulation of surface topography using dichroic dye (F) and dichroic initiator (G) during polymerization
图 5 无(A)和有(B)436 nm 线偏振光照射时表面形貌的光学显微照片;(C)含有偶氮苯光引发剂的紫外光固化 LCP 薄膜在 PDMS 表面形成宏观褶皱的示意图[56] ,单轴压缩方向平行(D)和垂直(E)条纹图案时,紫外光照射下褶皱形貌的光学显微照片[57]; (F)多循环系统中刺激诱导的褶皱产生、光诱导的褶皱调控和擦除[58]
Fig.5 Optical microscopic images of the surface topography without (A) and with (B) 436 nm linearly polarized light irradiation; (C) Scheme of the macroscopic wrinkle formation of the PDMS surface by the UV-curable LCP film containing azobenzene-containing photoinitiator[56]; Optical microscopic images of wrinkle topography under UV illumination when uniaxial compression is parallel (D) and perpendicular (E) to the line pattern[57]; (F) Multiple cycles of stimulus-induced wrinkling, light-induced tuning and erasing in the optically wrinkling system[58]
图 6 (A)制造复杂的分层多级结构的过程示意图; (B)压印图案的结构色照片[65]; (C)光响应LCE涂层的表面形貌变化示意图和NIH-3T3细胞在有呈六边形排列的0.2 μm高的柱子和0.3 μm高的圆形图案的LCN表面的相衬度图像(比例尺为50 μm)[67]; (D)在pDR1m表面图案上的细胞取向,包括沿边、顶点、同心圆环和点阵列4种图案(比例尺为10 μm[68]); (E)HH-垂直结构处于紫外光稳态并局部照射绿光时的表面形貌的AFM图像以及表面波可发生在持续的紫外光与绿光交替照射下[69]; (F)通过光触发的表面形貌变化,粘接状态发生改变的示意图以及光刺激过程中表面起伏反转的三维数字全息显微镜照片[70]
Fig.6 (A) Schematic illustration of the fabrication of complex hierarchical multilevel structures; (B) Structural color images of imprinted nanopatterns[65]; (C) Schematic process of the surface topography change on the light-responsive LCE coatings and phase contrast images of NIH-3T3 cells on patterned LCN in hexagonally arranged pillars of 0.2 μm height and a circular pattern with a height of 0.3 μm. Scale bars are 50 μm[67]; (D) Cell orientation on confocal-induced pDR1m patterns including the geometry along the sides, on the vertex, on concentric rings and on array of dots. Scale bars are 10 μm[68] ; (E) AFM images of surface topography of the HH-perpendicular structure which is UV photostationary state and locally exposed to green light. Surface waving happens under the continuous UV illumination and alternative green light[69] ; (F) Schematic illustration of the switch of adhesion via light-triggered topographical deformation and 3D digital holographic microscopic images of the surface topographical inversion during the light stimulation process[70]
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