Influence of rheology and morphology on foaming of PS-b-PMMA diblock copolymers and their composites with modified silica nanoparticles
Influence of rheology and morphology on foaming of PS-b-PMMA diblock copolymers and their composites with modified silica nanoparticles
复制标题
DOI：
10.1016/j.polymer.2013.05.025
复制
发表时间：
2013-07
期刊：
影响因子：
4.6
通讯作者：
G. L. Chakkalakal;C. Abetz;U. Vainio;U. A. Handge;V. Abetz
中科院分区：
文献类型：
--
作者：
G. L. Chakkalakal;C. Abetz;U. Vainio;U. A. Handge;V. Abetz
在这项研究中，聚苯乙烯-嵌段-聚（甲基丙烯酸甲酯）（PS-b-PMMA）二嵌段共聚物及其复合材料与PMMA改性的二氧化硅纳米粒子的发泡行为的流变学和形态学性能的影响进行了讨论。发泡剂是二氧化碳。圆柱形和层状类型的PS-b-PMMA两嵌段共聚物具有不同的分子量被选择，以阐明形态和分子量的发泡行为的影响。通过小角X射线散射和显微镜研究了两嵌段共聚物的微相分离形态。剪切下的材料的流变行为进行了分析，使用线性粘弹性剪切振荡和蠕变实验，以探测在不同的时间尺度的微观结构。高压差示扫描量热法测量表明，发泡剂二氧化碳溶解在PS和PMMA域。一般来说，我们研究的具有圆柱形形态的二嵌段共聚物导致泡沫的密度低于具有层状形态的泡沫。这种效应表明，在泡沫泡孔的成核和膨胀过程中，大的应力是使层状结构变形所必需的。以聚苯乙烯为基体的圆柱形嵌段共聚物在低频剪切振荡下出现一个与ω无关的平台。发泡后，泡沫的PS-b-PMMA二嵌段共聚物与聚苯乙烯基体的泡孔壁和表面描绘的微相分离结构的圆柱形形态。
In this study, the influence of rheological and morphological properties on the foaming behaviour of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymers and their composites with PMMA modified silica nanoparticles is discussed. The blowing agent was carbon dioxide. Cylindrical and lamellar types of PS-b-PMMA diblock copolymers with different molecular weights were chosen in order to elucidate the influence of morphology and molecular weight on the foaming behaviour. The microphase-separated morphology of the diblock copolymers was studied by small-angle x-ray scattering and microscopic investigations. The rheological behaviour of the materials under shear was analysed using linear viscoelastic shear oscillations and creep experiments in order to probe the microstructure at different time scales. High pressure differential scanning calorimetry measurements indicate that the blowing agent carbon dioxide was dissolved in the PS and in the PMMA domains. Generally, the diblock copolymers of our study with a cylindrical morphology led to foams with a lower density than the ones with a lamellar morphology. This effect indicates that large stresses are necessary to deform lamellar structures during nucleation and expansion of foam cells. The diblock copolymer with a cylindrical morphology and polystyrene as the matrix was associated with an ω-independent plateau at low frequencies of the shear oscillations. After foaming, the cell walls and the surface of the foamed PS-b-PMMA diblock copolymer with the polystyrene matrix depicted the cylindrical morphology of the microphase-separated structure.