| 摘要: | 本研究探討利用PS次微米球(PS球)與不同含量之奈米球來建構光子晶體，以及光子晶體之成膜性質。
首先利用無乳化劑乳化聚合法在沸騰狀態下製備PS球(185.4 nm)以及不同硬軟奈米球。硬軟奈米球是以苯乙烯(St)、甲基丙烯酸正丁酯﹙BMA﹚、 丙烯酸丁酯(BA)，為單一單體或兩種單體，在不同含量之共單體對-苯乙烯磺酸鈉鹽(Nass)存在下，聚合成六種硬軟奈米球，即可依據玻璃轉移溫度(Tg)，區分為成兩種硬奈米球(H100與H58)與四種軟奈米球(S26、S06、S-17與S-54)。並利用動態光散射粒徑分析儀(DLS)與折射率偵檢器來量測硬軟奈米球粒徑、均一度與折射率，結果顯示六種硬軟奈米球均一性好且粒徑約30nm，其折射率分佈於1.4至1.6之間。
接下來將上述硬軟奈米球以不同添加含量，分別與PS球混合後，自組裝形成光子晶體，得到硬或軟奈米球存在下之光子晶體建構，並利用掃描式電子顯微鏡(SEM)、有效折射率公式、修飾布拉格公式(Modified Bragg’s law) 與紫外-可見光光譜儀(UV-Vis)，探討其表面形態、粒徑大小分佈以及光子晶體行為，同時也利用DLS探討軟奈米球在次微米球溶液中的穩定性。
PS球在硬奈米球存在下之光子晶體建構，由SEM結果顯示硬奈米球規則排列於PS球間，且些許撐開PS球間距，造成數目平均粒徑(Dn)隨之上升。經由有效折射率公式與修飾布拉格公式，計算得到隨著硬奈米球添加量的增加，有效折射率(neff)隨之上升，且反射波長(λ)也隨之上升而產生紅位移現象，此光子晶體行為與UV-Vis量測反射波長(λmax)相符合。
PS球在軟奈米球存在下之光子晶體建構，由SEM結果顯示軟奈米球軟化成膜於PS球間，具有規則性排列，造成Dn隨之上升。經由有效折射率公式與修飾布拉格公式，計算得知隨著軟奈米球添加量的增加， neff不變，而λ上升產生紅位移現象，此光子晶體行為與UV-Vis量測λmax有相同趨勢。
將上述之光子晶體膜，利用鉛筆硬度計探討膜性質，結果顯示結果顯示當使用Tg越低且添加含量最多的奈米球其成膜性質最好，也就是S-54存在20 wt.%之光子晶體膜，鉛筆硬度值從原本小於6B可提升至H。
最後利用二氧化矽前驅物製備反光子晶體模板，可以證實光子晶體在硬奈米球存在下分散於PS球，而在軟奈米球存在下，則塗佈於PS球上。
In this study, photonic crystals were fabricated by self-assembled polystyrene submicrosphere (PS sphere) with different amount of nanospheres and their opal and mechanic properties were investigated.
First, PS sphere (185.4nm) and nanospheres were prepared by soap-free emulsion polymerization at boiling condition. Styrene, n-butyl methacrylate, and butyl acrylate were used as monomers in the presence of sodium p-styrenesulfonate to prepare nanospheres. According to glass transition temperature (Tg), nanospheres were divided into hard nanospheres (H100 and H58) and soft nanospheres (S26, S06, S-17 and S-54). The particle size, polydispersity index (PDI) and refractive index of nanospheres was measured by dynamic particle size analysis (DLS) and refractive index detector (RI). The results showed that nanospheres had narrow PDI, about 30nm diameter and 1.4 to 1.6 RIs.
Surface morphology, particle size (Dn), and wavelength (λ) of photonic crystals were determined from scanning electron microscope (SEM), effective refractive index equation and modified Bragg's law. The reflection wavelength (λmax) was measured from ultraviolet-visible spectroscopy (UV-Vis). In addition, stability of soft nanospheres in PS sphere solution was measured by DLS.
SEM results showed that hard nanospheres were distributed around PS spheres in their photonic crystals. On the other hand, soft nanopheres were coated onto PS spheres in their photonic crystals. With increasing weight fraction of hard or soft nanospheres in the photonic crystals, Dn and λ were increased. The value of λmax was corresponding to that of λ.
The mechanical property of the photonic crystals was measured by the pencil hardness test. The result showed with increasing Tg and the weight fraction of nanospheres, the pencil hardness was increased. The opal film prepared by PS sphere with 20% S-54 nanpsphere had the highest pencil hardness, H.
Finally, inverse opal templates were fabricated by adding silica precursor into photonic crystals, then calcinated. SEM results showed that hard nanospheres were distributed around PS spheres and soft nanospheres were coated onto PS spheres in their photonic crystals, respectively. |
