三嵌段共聚物PS-b-PEG-b-PS与聚苯乙烯共混薄膜的表面形貌与性能研究

Surface Properties and Morphology of PS-b-PEG-b-PS/PS Blend Films

使用原子转移自由基聚合(ATRP)制备三嵌段共聚物PS-b-PEG-b-PS。通过红外光谱、核磁共振氢谱(1H-NMR)和凝胶渗透色谱(GPC)对嵌段共聚物结构及分子量进行表征。将嵌段共聚物与聚苯乙烯溶液共混成膜,使用原子力显微镜(AFM)和接触角测试仪(CA)对不同含量嵌段共聚物共混膜的表面形貌和性能进行了分析表征。PEG链段与PS链段在共混膜中发生了微相分离,由于PEG链段对PS链段的热力学排斥作用以及PS的硬链段特性,PS不能在PEG微区上方形成覆盖,因而在薄膜表面形成大量孔洞,PEG微相区位于孔洞底部。随嵌段共聚物含量增加,孔洞(PEG微区)尺寸增大。当嵌段共聚物含量增加10%以后,孔洞内出现PS微相区,导致形成"胞状"结构。嵌段共聚物含量增加使得共混薄膜的亲水性和表面张力增大。

Triblock copolymer of styrene and ethylene glycol （PS-b-PEG-b-PS） was synthesized by using ATRP technique. FT-IR, NMR and GPC were used to characterize the molecular structure of the synthesized copolymer. The films of PS-b-PEG-b-PS/PS blends were prepared from their CHCl3 solution by spin coating. The relationships between PS-b-PEG-b-PS content and the surface properties and morphologies of the films were investigated by using the atomic force microscopy （AFM） and measuring the static contact angle （CA） of the blending films. It was observed from the AFM phase contrast images that the microphase separation of PEG segments and PS segments occurs in the blending films. Due to the thermodynamical repulsion between PEG segments and PS segments and the rigid nature of PS segments, PS segments could not spread over the microdomains occupied by PEG in the blending film, which leads to form a large number of holes on the surface of the films with PEG microdomains in the bottom of the holes. It was found that, with the increase of triblock content in the film, the size of the holes （PEG microdomains） increases, and the PS microdomains were observed inside the holes when the PS-b-PEG-b-PS content in the blending film is over 10%, which form the cellular domain structure. The increase of PS-b-PEG-b-PS content also results in the improving hydrophilicity and increasing surface tension of the blending films.