本研究主要探討高分子在超薄膜內，因分子鏈受拘束於不穩態使性質與塊材的差異。聚苯乙烯(polystyrene, PS)超薄膜(4 - 100 nm)在玻璃轉換溫度(glass transition temperature, 100℃)以上退火(170℃)時，薄膜表面將產生許多除潤孔洞，藉由原子力顯微鏡(atomic force microscopy, AFM)量測孔洞表面形貌，並使用force curve測量楊氏係數，可計算因分子拘束所引起的分子鏈反彈應力(molecular recoiling stress)，實驗中發現楊氏係數將會隨薄膜厚度下降而線性下降，並且有分子量效應；薄膜表面與背面也展現不同之楊氏係數。薄膜愈薄所量測出的分子鏈反彈應力愈大，且比毛細力大二至三個數量級。若改變分子量進行實驗，發現溶劑拘束能力愈強的交纏分子，愈容易殘留較大的分子鏈反彈應力。而若將薄膜於略高於玻璃轉換溫度(110℃)進行時效，則發現此分子鏈反彈力將會先密化使應力上升爾後因鬆弛(relaxation)而逐漸下降。若將少量的共軛高分子，MEH-PPV摻入膜內，則發現分子鏈反彈力在共軛高分子薄膜的光致發光有增益的效果，分子鏈的拉伸將會抑制polaron interaction致使發光效率增加，若薄膜進行退火使除潤反應發生，則強大的剪切力將使共軛高分子鏈被拆散，致使發光效率藍位移並產生巨大增益。

Molecular recoiling stresses in polystyrene ultrathin films (4 -100 nm) were measured through wetting instability at above Tg (100 ℃) to explore the physical state and condensation process. To obtain the molecular recoiling stress, the measurement of Young’s modulus was needed. By measuring the force curve using an indenting AFM tip on the film surface, the Young’s modulus was found to decrease linearly with decreasing film thickness if thickness was lower than about 1μm. The Young’s modulus of thin films with different molecular weight show different dependent on film thickness. Moreover, the face and back of thin films show different Young’s modulus. With the measurement of Young’s modulus, the molecular recoiling stress could be calculated. Molecular recoiling stress emerges when the film thickness is less than the unperturbed molecular diameters. Thin films with better solvent trapping entangle chain would constrain larger molecular recoiling stress. As aging temperature lowered but still above Tg, film stability increased but recoiling stress underwent significant changes by stress relaxation. A small fraction of MEH-PPV added in films manifested photoluminescence (PL) following the same trend as recoiling stress confirming stress-enhanced PL characteristic of conjugated polymers. In dewetting films, the sheared molecules emit light very efficiently, giving rise to the large PL enhancement.

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