Recently we reported an unusual multilayered structure in a linear polyethylene containing precisely periodic carboxylic acid groups pendant to every 21st carbon atom (p21AA). Within the ordered domains, p21AA executes tight chain folds at the location of each acid group, and the chain-fold surfaces participate in hydrogen bonds with adjacent fold surfaces to form acid-rich layers. Here, we investigate the bulk morphologies of p21AA after isothermal crystallization and, using X-ray scattering and polarized optical microscopy, find p21AA to be semicrystalline. By analyzing X-ray peak widths, creating real-space models of lamellae, and performing in-situ X-ray scattering during tensile deformation, we find that, contrary to the typical structure of polymer crystallites, the polymer stems lie in the plane of the lamellae such that the acid layers are transverse (within 30° of orthogonal) to the crystallite plane. This surprising structure, not reported before to our knowledge, could be useful for designing semicrystalline membranes because, given the appropriate chemistry, layers of functional groups could provide pathways for small molecule, ion, or proton transport through crystallites. We expect this novel structure to be accessible in similarly designed crystallizable polymers that contain evenly spaced, moderately sized, associating side groups.

中文翻译：

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精密聚合物微晶中酸层的横向取向

最近，我们报道了一种线性聚乙烯中不寻常的多层结构，该线性聚乙烯中的每一个第21个碳原子（p21AA）都带有侧链。在有序域内，p21AA在每个酸基团的位置执行紧密链折叠，并且链折叠表面与相邻折叠表面参与氢键形成富酸层。在这里，我们研究了等温结晶后p21AA的整体形态，并使用X射线散射和偏振光学显微镜发现p21AA是半结晶的。通过分析X射线峰宽，创建薄片的真实空间模型并在拉伸变形过程中执行原位X射线散射，我们发现，与聚合物微晶的典型结构相反，聚合物茎位于薄片的平面内，以使酸层垂直于微晶平面（正交于30°内）。这种令人惊讶的结构（据我们所知尚未报道过）可用于设计半结晶膜，因为在适当的化学作用下，官能团层可为小分子，离子或质子通过微晶的传输提供途径。我们希望这种新颖的结构可在相似设计的可结晶聚合物中使用，该聚合物包含间距均匀，大小适中的缔合侧基。官能团层可以为小分子，离子或质子通过微晶的传输提供途径。我们希望这种新颖的结构可在相似设计的可结晶聚合物中使用，该聚合物包含间距均匀，大小适中的缔合侧基。官能团层可以提供小分子，离子或质子通过微晶传输的途径。我们希望这种新颖的结构可在相似设计的可结晶聚合物中使用，该聚合物包含间距均匀，大小适中的缔合侧基。