Preparation of a new lightly cross-linked liquid crystalline polyamide by interfacial polymerization. Application to the obtainment of microcapsules with photo-triggered release
Preparation of a new lightly cross-linked liquid crystalline polyamide by interfacial polymerization. Application to the obtainment of microcapsules with photo-triggered release
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DOI：
10.1016/j.eurpolymj.2009.02.008
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发表时间：
2009-05
影响因子：
6
通讯作者：
B. Tylkowski;Malgorzata Pregowska;Emilia Jamowska;R. García-Valls;M. Giamberini
中科院分区：
文献类型：
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作者：
B. Tylkowski;Malgorzata Pregowska;Emilia Jamowska;R. García-Valls;M. Giamberini
基于一种新的液晶轻交联聚酰胺，其中的有序状态可以触发通过外部刺激，如温度和光，通过界面聚合制备微胶囊。该聚酰胺在高达166°C时表现出结晶相，并且在340°C时开始分解;通过扫描电子显微镜观察到膜的形态变化与澄清温度相对应;此外，通过在室温下用UV光连续照射，聚合物经历E-Z光异构化。制备的微胶囊含有甲苯或萘或β-胡萝卜素的浓缩溶液作为核心;在所有情况下，它们的外表面看起来光滑致密，而内表面上可以看到不均匀性。胶囊直径在30-120μm范围内，取决于封装的材料，具有相当窄的尺寸分布。据作者所知，这是其壳完全由液晶轻度交联聚合物构成的微胶囊的第一个例子。在水和四氢呋喃中进行β-胡萝卜素的释放实验。在20°C下，β-胡萝卜素在水中的释放受到UV照射的强烈影响：在没有照射的情况下，其几乎可以忽略不计，而当微胶囊经受UV光的连续照射时，β-胡萝卜素快速释放并且在5分钟后达到100%释放。还进行了关于温度和溶胀溶剂（如THF）对释放的影响的初步实验。
Microcapsules based on a new liquid crystalline lightly cross-linked polyamide, in which the state of order can be triggered by means of external stimuli, such as temperature and light, were prepared by interfacial polymerization. This polyamide exhibited a nematic phase up to 166°C and it started to decompose at 340°C; morphological variations of the film were observed by Scanning Electron Microscopy in correspondence to the clearing temperature; moreover, by continuous irradiation with UV light at room temperature, the polymer underwent E–Z photoisomerization. The prepared microcapsules contained either toluene, or concentrated solutions of naphthalene or β-carotene, as the core; in all cases, their outer surface appeared smooth and dense, while heterogeneities could be seen on the inner face. Capsule diameter lay in the range 30–120μm, depending on the encapsulated material, with quite narrow size distributions. To the authors’ knowledge, this is the first example of microcapsules whose shell is completely constituted by a liquid crystalline lightly cross-linked polymer. Release experiments of β-carotene were performed in water and in tetrahydrofuran. β-Carotene release in water at 20°C was strongly influenced by UV irradiation: in the absence of irradiation, it was practically negligible while, when microcapsules were submitted to continuous irradiation with UV light, β-carotene was quickly released and reached 100% release after 5min. Preliminary experiments concerning the effect of temperature and of a swelling solvent, such as THF, on release, were also performed.