聚乳酸超薄膜结晶行为的掠角反射红外光谱研究

发布时间：2018-06-15 19:58

本文选题：PLLA + 聚乳酸立构复合体　；参考：《青岛科技大学》2015年硕士论文

【摘要】：本文以掠角反射红外光谱(RAIR)、配合掠入射X射线衍射(GIXRD)和差示扫描量热法(DSC)作为聚合物结构表征的主要手段,对不同厚度聚乳酸(PLLA)超薄膜的结晶行为、片晶取向、影响结晶的因素和相转变行为进行了详细的研究,同时,我们还研究了聚乳酸立构复合体本体和超薄膜结晶及相转变的差异。通过对PLLA/CHCL3溶液浓度的控制,制备了不同厚度的PLLA超薄膜,并采集了一系列PLLA超薄膜样品的掠角反射红外光谱数据和掠入射X射线衍射数据。首先我们分析了PLLA超薄膜中的晶体结构,发现在冷结晶过程中α和α晶型是同时存在的；其次我们分析了在升温冷结晶和降温熔融结晶的过程中,PLLA超薄膜中分子链的取向行为,结果表明这两个结晶过程所导致的薄膜晶体中10/7螺旋链在金片基底上取向有明显的不同(即片晶的不同取向：冷结晶片晶采取edge-on的取向,熔融结晶片晶采取flat-on的取向)。该研究表明,PLLA超薄膜的不同片晶取向可由结晶温度和薄膜厚度等因素来进行调控。利用变温掠角反射红外光谱技术我们研究了不同厚度PLLA超薄膜的相转变行为,发现PLLA超薄膜的玻璃化转变温度(Tg)等对PLLA超薄膜的厚度有着明显的依赖性,即随着PLLA超薄膜厚度的降低,玻璃化转变温度(Tg)等呈现逐渐升高的趋势。我们认为产生该现象的原因主要是PLLA聚合物/基底间界面层中分子链的运动受到强烈的抑制,导致PLLA超薄膜的玻璃化转变温度(Tg)等的升高。我们还研究了聚乳酸立构复合体超薄膜非等温结晶过程中结晶和相变行为与其本体的差异。研究发现聚乳酸立构复合体本体在冷结晶和熔融结晶过程中,α、α’和βc三种晶型同时存在,而聚乳酸立构复合体超薄膜在冷结晶和熔融结晶过程中,只有βc晶型的存在。与聚乳酸薄膜均晶取向行为类似,聚乳酸立构复合体超薄膜在冷结晶过程中,片晶采取edge-on的取向,在熔融结晶的过程中,片晶采取flat-on的取向。
[Abstract]:In this paper, the crystallization behavior and lamellar orientation of poly (lactic acid) (PLLA) ultrathin films with different thickness were studied by means of grazing angle reflectance infrared spectroscopy (RAIRI), combined with grazing incident X-ray diffraction (GIXRD) and differential scanning calorimetry (DSC). The factors affecting crystallization and phase transition behavior were studied in detail. At the same time, we also studied the difference of crystallization and phase transition between bulk and ultrathin film of polylactide orthotropic complex. PLLA ultrathin films with different thickness were prepared by controlling the concentration of PLLA / CHCL3 solution. A series of FTIR data and grazing incidence X-ray diffraction data of PLLA ultrathin films were collected. Firstly, we analyzed the crystal structure of PLLA ultrathin films and found that both 伪 and 伪 crystal forms exist in the cold crystallization process, and then we analyzed the orientation behavior of molecular chains in PLLA ultrathin films during the process of cold crystallization and melting crystallization. The results show that the orientation of 10 / 7 helical chain on the gold substrate is obviously different due to these two crystallization processes (that is, the orientation of the sheet is different: the cold crystal takes the orientation of edge-on and the melt crystal takes the orientation of flat-on. The results show that the different crystal orientation of PLLA ultrathin films can be controlled by crystallization temperature and film thickness. The phase transition behavior of PLLA ultrathin films with different thickness has been studied by means of variable temperature sweep angle reflectance infrared spectroscopy. It is found that the glass transition temperature of PLLA ultrathin films is obviously dependent on the thickness of PLLA ultrathin films. As the thickness of PLLA ultrathin films decreases, the glass transition temperature (TG) increases gradually. We believe that this phenomenon is mainly due to the strong inhibition of molecular chain movement in PLLA polymer / substrate interfacial layer, which leads to the increase of glass transition temperature (Tg) of PLLA ultrathin films. We also studied the difference between the crystallization and phase transition behavior of polylactic acid complex ultrathin film and its bulk during non-isothermal crystallization. It is found that the 伪 'and 尾 c crystal forms exist simultaneously in the cold crystallization and melting crystallization process of polylactic acid orthotectic complex, but only 尾 c crystal form exists in the cold crystallization and melting crystallization process of the polylactic acid orthotropic complex ultrathin film. The homocrystalline orientation behavior of polylactic acid thin films is similar to that of polylactic acid thin films. In the process of cold crystallization, the lamellae takes the orientation of edge-on, and the sheet takes the orientation of flat-on in the process of melt crystallization.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ317;TB383.2

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