Otero Navas Ivonne, Kamkar Milad, Arjmand Mohammad, Sundararaj Uttandaraman
Department of Chemical and Petroleum Engineering, Schulich School of Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada.
School of Engineering, University of British Columbia, Kelowna, BC V1V 1V7, Canada.
Polymers (Basel). 2021 Jan 11;13(2):230. doi: 10.3390/polym13020230.
This work studied the impact of three types of styrene-butadiene (SB and SBS) block copolymers on the morphology, electrical, and rheological properties of immiscible blends of polypropylene:polystyrene (PP:PS)/multi-walled carbon nanotubes (MWCNT) with a fixed blend ratio of 70:30 vol.%. The addition of block copolymers to PP:PS/MWCNT blend nanocomposites produced a decrease in the droplet size. MWCNTs, known to induce co-continuity in PP:PS blends, did not interfere with the copolymer migration to the interface and, thus, there was morphology refinement upon addition of the copolymers. Interestingly, the addition of the block copolymers decreased the electrical resistivity of the PP:PS/1.0 vol.% MWCNT system by 5 orders of magnitude (i.e., increase in electrical conductivity). This improvement was attributed to PS Droplets-PP-Copolymer-Micelle assemblies, which accumulated MWCNTs, and formed an integrated network for electrical conduction. Molecular simulation and solubility parameters were used to predict the MWCNT localization in the immiscible blend. The simulation results showed that diblock copolymers favorably interact with the nanotubes in comparison to the triblock copolymer, PP, and PS. However, the interaction between the copolymers and PP or PS is stronger than the interaction of the copolymers and MWCNTs. Hence, the addition of copolymer also changed the localization of MWCNT from PS to PS-PP-Micelles-Interface, as observed by TEM images. In addition, in the last step of this work, we investigated the effect of the addition of copolymers on inter- and intra-cycle viscoelastic behavior of the MWCNT incorporated polymer blends. It was found that addition of the copolymers not only affects the linear viscoelasticity (e.g., increase in the value of the storage modulus) but also dramatically impacts the nonlinear viscoelastic behavior under large deformations (e.g., higher distortion of Lissajous-Bowditch plots).].
本研究考察了三种类型的苯乙烯-丁二烯（SB和SBS）嵌段共聚物对聚丙烯与聚苯乙烯（PP:PS）/多壁碳纳米管（MWCNT）不相容共混物（固定共混比为70:30体积%）的形态、电学和流变性能的影响。向PP:PS/MWCNT共混纳米复合材料中添加嵌段共聚物会使液滴尺寸减小。已知MWCNT可诱导PP:PS共混物产生双连续结构，但它不会干扰共聚物向界面的迁移，因此，添加共聚物后形态得到细化。有趣的是，添加嵌段共聚物使PP:PS/1.0体积% MWCNT体系的电阻率降低了5个数量级（即电导率增加）。这种改善归因于PS液滴-PP-共聚物-胶束聚集体，其积累了MWCNT，并形成了用于导电的集成网络。利用分子模拟和溶解度参数预测MWCNT在不相容共混物中的定位。模拟结果表明，与三嵌段共聚物、PP和PS相比，二嵌段共聚物与纳米管的相互作用更有利。然而，共聚物与PP或PS之间的相互作用强于共聚物与MWCNT之间的相互作用。因此，如透射电镜图像所示，添加共聚物也使MWCNT的定位从PS转变为PS-PP-胶束-界面。此外，在本研究的最后一步，我们考察了添加共聚物对含MWCNT的聚合物共混物的周期内和周期间粘弹性行为的影响。结果发现，添加共聚物不仅影响线性粘弹性（如储能模量值增加），而且对大变形下的非线性粘弹性行为也有显著影响（如李萨如图形的更高畸变）。
