利用多體耗散粒子動力學研究同源高分子共混物之奈米薄膜、液滴的尺寸效應，一般而言我們會認為同源高分子彼此會完美地均勻混合，然而，事實上會發現短鏈高分子會傾向聚集在表面。首先我們先研究不同長鏈的高分子的液氣、液固表面張力，結果發現兩種不同的表面張力皆會隨著鏈段長度增加而增加，但鏈段長度達一定程度之後增加的趨勢會減緩，我們可以用實驗上使用的半經驗式來表示高分子的分子量與兩種表面張力的關係。兩種不同長度混合而成的高分子同源共混物可以發現液氣界面的表面張力與短鏈的表面過量程度會隨著膜厚不同而改變，隨著共混物的膜厚減少，液氣表面張力越大但短鏈在表面聚集的程度越不明顯，另外，我們還探討了不同尺寸的奈米共混物液滴，發現接觸角會隨著液滴尺寸的減少而增加，從共混物之奈米薄膜和奈米液滴的實驗結果，可以發現短鏈在表面聚集程度與尺寸效應相關。;The size-dependent behavior of nanofilms and nanodroplets of homologous polymer blends was explored by many-body dissipative particle dynamics. Although a homologous blend can be regarded as a completely miscible and athermal system, enrichment of the surface in short polymers always take place. First, liquid-gas and solid-liquid interfacial tensions of polymer melts were acquired. It is found that they grow and approach asymptotes with increasing chain lengths. The molecular weight dependence can be depicted by the two semi-empirical expressions. Second, the variation of surface tension and surface excess of polymer blend nanofilms with the thickness was observed. Surface tension of the blend is observed to increase but the extent of surface segregation decreases with increasing the film thickness. Finally, the wetting phenomenon of nanodroplets of homologous blends was examined. The contact angle is found to rise as the droplets size is reduced. Our simulation results indicate that the size-dependence of nanofilms and nanodroplets is closely related to surface segregation in homologous blends.
