Interfacial molecular structure and orientation evolution of the polystyrene under confinement during annealing revealed by sum frequency generation vibrational spectroscopy

IF 2.1 4区化学 Q3 CHEMISTRY, PHYSICAL

Surface Science Pub Date : 2024-05-07 DOI:10.1016/j.susc.2024.122506

Mingfeng Zhang , Xintong Hu , Ziyun Wang , De Hou , Linhua Hu , Bolin Li , Ganhong Zheng , Zhigao Sheng

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Abstract

The geometrical confinement directly affects many crucial properties of polymer thin films by interfacial interactions. A key to understanding the role of these interfacial interactions is to specifically probe the confined interface at the molecular level and in situ. However, the direct and nondestructive detection of interfacial polymer structures under confinement is very difficult. In this study, specific interface-sensitive sum frequency generation (SFG) spectroscopy was applied to study the deuterated PS (d₈-PS) film confined between hydrogenated poly (methyl methacrylate) (PMMA) films at the molecular level and in situ. The results showed that the ordering/orientation of the PS chain (backbone and phenyl group) evolved at the buried d₈-PS/PMMA interface during annealing. The tilt angle of the PS phenyl group increased while the twist angle decreased with elevated annealing temperature. Both overall SFG ssp and ppp intensities decreased after annealing at 433 K for 24 h, indicating that PS chains entangled with or penetrated the PMMA chains at the confined interface. This study qualitatively and quantitatively revealed the interfacial structure and structural evolution of the PS chain confined between PMMA films in situ during annealing, which is beneficial to the molecular-level understanding of the interfacial chain conformational relaxation of polymers under confinement.

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通过和频发生振动光谱揭示退火过程中受限聚苯乙烯的界面分子结构和取向演变

几何约束通过界面相互作用直接影响聚合物薄膜的许多关键特性。要了解这些界面相互作用的作用，关键在于在分子水平和原位对约束界面进行专门探测。然而，要直接无损地探测约束下的聚合物界面结构非常困难。本研究采用特定界面敏感的和频发生（SFG）光谱法，从分子水平和原位研究了封闭在氢化聚甲基丙烯酸甲酯（PMMA）薄膜之间的氚代 PS（d8-PS）薄膜。结果表明，在退火过程中，PS 链（主干和苯基）的有序/定向在埋藏的 d8-PS/PMMA 界面发生了演变。随着退火温度的升高，PS苯基的倾斜角增大，而扭曲角减小。在 433 K 下退火 24 小时后，整体 SFG ssp 和 ppp 强度均有所下降，这表明 PS 链与 PMMA 链缠结或穿透了封闭界面。该研究定性和定量地揭示了退火过程中PMMA薄膜间原位密闭的PS链的界面结构和结构演变，有助于从分子水平理解密闭条件下聚合物界面链构象弛豫。

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来源期刊

Surface Science 化学-物理：凝聚态物理

CiteScore

3.30

自引率

5.30%

发文量

137

审稿时长

25 days

期刊介绍： Surface Science is devoted to elucidating the fundamental aspects of chemistry and physics occurring at a wide range of surfaces and interfaces and to disseminating this knowledge fast. The journal welcomes a broad spectrum of topics, including but not limited to: • model systems (e.g. in Ultra High Vacuum) under well-controlled reactive conditions • nanoscale science and engineering, including manipulation of matter at the atomic/molecular scale and assembly phenomena • reactivity of surfaces as related to various applied areas including heterogeneous catalysis, chemistry at electrified interfaces, and semiconductors functionalization • phenomena at interfaces relevant to energy storage and conversion, and fuels production and utilization • surface reactivity for environmental protection and pollution remediation • interactions at surfaces of soft matter, including polymers and biomaterials. Both experimental and theoretical work, including modeling, is within the scope of the journal. Work published in Surface Science reaches a wide readership, from chemistry and physics to biology and materials science and engineering, providing an excellent forum for cross-fertilization of ideas and broad dissemination of scientific discoveries.