Wilk Jeffrey T, Furner Carl T, Kent Ethan W, Kelly Michael T, Zhao Bin, Li Christopher Y
Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States.
Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States.
Macromolecules. 2024 Aug 20;57(17):8487-8497. doi: 10.1021/acs.macromol.4c00752. eCollection 2024 Sep 10.
A unique case of sterically constrained crystallization arises in bottlebrush polymers bearing semicrystalline side chains. Bottlebrushes with grafted side chains can form crystalline structures governed by the complex interplay between side chain packing and backbone confinement. The confinement effect can be readily tuned by varying the side chain grafting density, thus affording control over the crystallization behavior of these systems. In this work, the grafting density effect on the crystallization behavior of molecular bottlebrushes comprising poly(ethylene oxide) (PEO) side chains grafted to a methacrylate backbone was systematically studied. Thermal analysis using differential scanning calorimetry showed that the bottlebrush polymers displayed suppressed crystallization temperatures, lower melting temperatures, and reduced crystallinities compared to linear homopolymer PEO. The crystalline morphology was investigated using polarized light, atomic force, and scanning electron microscopy. Isothermal crystallization experiments revealed a nonmonotonous dependence of the nucleation density on the side chain grafting density. The grafting density effect was also investigated using self-seeding experiments, revealing an increased clearing temperature and memory retention at higher grafting densities. This work highlights how grafting density influences the crystallization behavior of semicrystalline bottlebrushes, providing information for the processing and application of these unique polymers.
在带有半结晶侧链的刷状聚合物中出现了一种独特的空间受限结晶情况。带有接枝侧链的刷状聚合物能够形成由侧链堆积和主链限制之间复杂相互作用所支配的晶体结构。通过改变侧链接枝密度，可以很容易地调节限制效应，从而实现对这些体系结晶行为的控制。在这项工作中，系统研究了接枝密度对由接枝到甲基丙烯酸酯主链上的聚环氧乙烷（PEO）侧链组成的分子刷状聚合物结晶行为的影响。使用差示扫描量热法进行的热分析表明，与线性均聚物PEO相比，刷状聚合物的结晶温度受到抑制，熔点降低，结晶度减小。使用偏光、原子力和扫描电子显微镜研究了晶体形态。等温结晶实验揭示了成核密度对接枝密度的非单调依赖性。还使用自晶种实验研究了接枝密度效应，结果表明在较高接枝密度下，清亮点温度升高且记忆保留增强。这项工作突出了接枝密度如何影响半结晶刷状聚合物的结晶行为，为这些独特聚合物的加工和应用提供了信息。
