本研究利用傅立葉轉換紅外線光譜儀及掠角X光小角／廣角散射臨場觀察消光旋聚乳酸（即等比例左／右旋聚乳酸混摻）在旋轉塗佈薄膜中的結晶行為，其中薄膜厚度以塗佈時的溶液濃度來控制，實驗中膜厚從厚到薄約為630、200、65、16奈米。在完成旋轉塗佈時並薄膜中沒有結晶產生，需透過升溫程序才在X光廣角散射圖譜中觀察到結晶峰，此現象與冷結晶的過程相同，並發現在630和200奈米的薄膜中，結晶過程α相及βc相都會產生；而在65和16奈米的薄膜中則只有βc相產生。透過設計好的實驗，將兩種可能造成較薄的膜中α相無法形成的原因排除：「α相本身無法在較薄的膜中形成」以及「旋轉塗佈時在基材上產生βc相的晶核，而導致膜較薄時偏向產生βc相」。另外，在一開始觀察到α相 (110)/(200) 結晶峰時，即以近40奈米的晶面大小出現，而同時βc相的 (110) 晶面大小則大約為10奈米，可以推論出α相比βc相有較大的晶核；並且若仔細觀察結晶前期的X光廣角散射圖譜，可發現βc相的結晶峰比α相早出現。在薄膜小於100奈米時，βc相10奈米的晶面相較來說占了許多空間。因此α相在65和16奈米的薄膜中無法形成的原因可能是βc相在結晶過程中先形成，使自由空間被限制住，而需要較大自由空間來形成的α相便無法形成。
此外，利用X光廣角散射圖譜的量化分析可得知結晶晶面大小會隨膜厚變薄而較小。在630奈米薄膜中，結晶熔融前βc相的結晶晶面可大至30奈米；然而在16奈米膜中，βc相熔融前的晶面大小則約為16奈米。在X光廣角散射圖譜的方向性分析中，發現630奈米薄膜的方向性較其他三者為差，也得知βc相在薄膜中可能以三方晶格的方式排列，並且高分子鏈多數傾向躺平於基材上。同時，X光小角散射圖譜可以利用圓盤排列模型來擬合，且數據與模型間有高相似性。擬合的結果顯示，在630奈米薄膜中的結晶圓盤半徑較16奈米薄膜的大兩倍，但在圓盤陣列之間能維持同方向的長度（平行於基材方向）則是較16奈米的薄膜短了兩倍。最後綜合以上實驗分析，提出βc相在薄膜中的結晶結構，並比較了630和16奈米薄膜間βc相結晶結構的差異。

The crystallization behavior of racemic polylactide (equimolar PLLA/PDLA) blend spin-cast on thin film was investigated using FTIR and in-situ GISAXS/GIWAXS. The film thicknesses were controlled by coating with different solution concentration, which gives the film thicknesses equal to 630, 200, 65, and 16 nm. There is no crystalline found right after spin-coating, but crystalline peak would emerge during heating (from 40 °C to 250 °C at 3 °C/min) of thin films, which is same as cold crystallization process. It is discovered that racemic PLA blend will form into α and βc phase in 630 and 200 nm thick films, yet only form into βc phase in the films of 65 and 16 nm during cold-crystallization process. By practicing designed experiment, two possibilities are excluded to be responsible for the suppression in 65 and 16 nm thin film. For one hand, α phase is proved be able to form with only optically pure polylactide in 83 and 24 nm thin film. On the other hand, the spin-coating effect which may produce βc phase nuclei near substrate was erased by melt-quench process, but the same suppression of α phase in 65 and 16 nm result are still observed. From the observation of coherence length of α crystals that emerges in large size from the beginning of the GIWAXS peak becoming discernible, which may suggest that α phase have larger nuclei than βc phase. Moreover, when examine GIWAXS characteristic peaks carefully, the reflections of βc phase will emerge earlier than α phase, implying that formation of βc phase is earlier than α phase. The nanograin size of βc phase is ca. 10 nm initially, which is comparatively large in films under 100 nm. Therefore, earlier formation of βc phase will make formation of α phase is restricted by confined free space. The larger space which α phase required to form and the earlier formation of βc phase may be responsible for the suppression of α phase formation in 65 and 16 nm films.
Besides, quantitative analysis for GIWAXS reveals that coherence length of crystalline reduced with decreasing film thickness. While the coherence length can be up to ca. 30 nm in the 630 nm thin film before melting, the coherence length in 16 nm thin film was only ca. 16 nm. Moreover, the orientation analysis from GIWAXS points out that the orientation in 630 nm film is worse than others, while 200, 65 and 16 nm thin film give apparent edge-on packing by thickness confinement. The orientation analysis also gives the idea that βc crystals may form in trigonal unit cell, and has its chain backbones lying on substrate. With model fitting analysis in GISAXS, the nanograins of βc phase can be well described with arrayed disks model. According to the fitting results, the radius of disk-like nanograins in 16 nm thin film is 2 times smaller than the one in 630 nm thin film, while the correlation between disks is two times better in 16 nm film than in 630 nm. Finally, by combining the GISAXS/GIWAXS results, a comparison crystal model for βc phase between 630 and 16 nm thin film was proposed.

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