Understanding interfacial segregation in polymer blend films with random and mixed side chain bottlebrush copolymer additives
Understanding interfacial segregation in polymer blend films with random and mixed side chain bottlebrush copolymer additives
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DOI：
10.1039/d1sm01146d
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发表时间：
2021-09-08
期刊：
影响因子：
3.4
通讯作者：
Verduzco, Rafael
中科院分区：
文献类型：
--
作者：
Mei, Hao;Mahalik, Jyoti P.;Verduzco, Rafael
瓶刷聚合物是一种复杂的大分子，其物理性质取决于侧链和主链的化学性质和结构。先前的工作已经证明，瓶刷聚合物添加剂可用于控制与线性聚合物的共混物的界面性质，但尚未具体解决瓶刷侧链微观结构的影响。在这里，使用实验和自洽场理论（SCFT）模拟的组合，我们研究了侧链微观结构的影响，通过比较瓶刷添加剂具有无规共聚物侧链与瓶刷添加剂具有两种不同的均聚物侧链化学的混合物的偏析。具体而言，我们合成了瓶刷聚合物与聚（苯乙烯-然-甲基丙烯酸甲酯）侧链或与聚苯乙烯（PS）和聚（甲基丙烯酸甲酯）（PMMA）侧链的混合物。瓶刷添加剂在PS和PMMA组合物方面相匹配，并且它们与长度范围从比瓶刷侧链短到长的线性PS或PMMA链共混。实验表明，两种类型的瓶刷的类似行为，与混合侧链瓶刷在膜表面的轻微偏好。SCFT模拟定性与实验观察一致，预测只有轻微的差异，侧链微观结构驱动的瓶刷添加剂的偏析。具体而言，这些微小的差异是由瓶刷聚合物接头和侧链端基的化学性质驱动的，它们分别被熵排斥和吸引到界面。使用SCFT，我们还表明，界面行为的熵效应占主导地位的高分子量的线性聚合物，导致富集的瓶刷界面附近。令人惊讶的是，SCFT模拟表明，与侧链端基相比，连接瓶刷主链和侧链的接头的化学性质在影响具有随机和混合侧链的瓶刷的表面过量差异方面发挥了更重要的作用。这项工作提供了新的见解，侧链微观结构的影响，瓶刷聚合物添加剂的偏析。
Bottlebrush polymers are complex macromolecules with tunable physical properties dependent on the chemistry and architecture of both the side chains and the backbone. Prior work has demonstrated that bottlebrush polymer additives can be used to control the interfacial properties of blends with linear polymers but has not specifically addressed the effects of bottlebrush side chain microstructures. Here, using a combination of experiments and self-consistent field theory (SCFT) simulations, we investigated the effects of side chain microstructures by comparing the segregation of bottlebrush additives having random copolymer side chains with bottlebrush additives having a mixture of two different homopolymer side chain chemistries. Specifically, we synthesized bottlebrush polymers with either poly(styrene-ran-methyl methacrylate) side chains or with a mixture of polystyrene (PS) and poly(methyl methacrylate) (PMMA) side chains. The bottlebrush additives were matched in terms of PS and PMMA compositions, and they were blended with linear PS or PMMA chains that ranged in length from shorter to longer than the bottlebrush side chains. Experiments revealed similar behaviors of the two types of bottlebrushes, with a slight preference for mixed side-chain bottlebrushes at the film surface. SCFT simulations were qualitatively consistent with experimental observations, predicting only slight differences in the segregation of bottlebrush additives driven by side chain microstructures. Specifically, these slight differences were driven by the chemistries of the bottlebrush polymer joints and side chain end-groups, which were entropically repelled and attracted to interfaces, respectively. Using SCFT, we also demonstrated that the interfacial behaviors were dominated by entropic effects with high molecular weight linear polymers, leading to enrichment of bottlebrush near interfaces. Surprisingly, the SCFT simulations showed that the chemistry of the joints connecting the bottlebrush backbones and side chains played a more significant role compared with the side chain end groups in affecting differences in surface excess of bottlebrushes with random and mixed side chains. This work provides new insights into the effects of side chain microstructure on segregation of bottlebrush polymer additives.