ABA Type Amphiphiles with Poly(2-benzhydryl-2-oxazine) Moieties: Synthesis, Characterization and Inverse Thermogelation,Macromolecular Chemistry and Physics

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ABA Type Amphiphiles with Poly(2-benzhydryl-2-oxazine) Moieties: Synthesis, Characterization and Inverse Thermogelation
Macromolecular Chemistry and Physics ( IF 2.5 ) Pub Date : 2021-08-02 , DOI: 10.1002/macp.202100114
Lukas Hahn ₁ , Larissa Keßler _{1,

2} , Lando Polzin ₁ , Lars Fritze ₃ , Stefan Forster ₁ , Holger Helten ₃ , Robert Luxenhofer _{1,

2}

Affiliation

Thermoresponsive polymers are frequently involved in the development of materials for various applications. Here, polymers containing poly(2- benzhydryl-2-oxazine) (pBhOzi) repeating units are described for the first time. The homopolymer pBhOzi and an ABA type amphiphile comprising two flanking hydrophilic A blocks of poly(2-methyl-2-oxazoline) (pMeOx) and the hydrophobic aromatic pBhOzi central B block (pMeOx-b-pBhOzi-b-pMeOx) are synthesized and the latter is shown to exhibit inverse thermogelling properties at concentrations of 20 wt.% in water. This behavior stands in contrast to a homologue ABA amphiphile consisting of a central poly(2-benzhydryl-2-oxazoline) block (pMeOx-b-pBhOx-b-pMeOx). No inverse thermogelling is observed with this polymer even at 25 wt.%. For 25 wt.% pMeOx-b-pBhOzi-b-pMeOx, a surprisingly high storage modulus of ≈22 kPa and high values for the yield and flow points of 480 Pa and 1.3 kPa are obtained. Exceeding the yield point, pronounced shear thinning is observed. Interestingly, only little difference between self-assemblies of pMeOx-b-pBhOzi-b-pMeOx and pMeOx-b-pBhOx-b-pMeOx is observed by dynamic light scattering while transmission electron microscopy images suggest that the micelles of pMeOx-b-pBhOzi-b-pMeOx interact through their hydrophilic coronas, which is probably decisive for the gel formation. Overall, this study introduces new building blocks for poly(2-oxazoline) and poly(2-oxazine)-based self-assemblies, but additional studies will be needed to unravel the exact mechanism.

中文翻译：

具有聚（2-二苯甲基-2-恶嗪）部分的 ABA 型两亲物：合成、表征和逆热凝胶化

热敏聚合物经常参与各种应用材料的开发。在这里，首次描述了含有聚（2-二苯甲基-2-恶嗪）（pBhOzi）重复单元的聚合物。合成了均聚物 pBhOzi 和包含两个侧翼亲水性 A 嵌段聚（2-甲基-2-恶唑啉）（pMeOx）和疏水性芳香族 pBhOzi 中心 B 嵌段（pMeOx- b -pBhOzi- b -pMeOx）的 ABA 型两亲物，并后者在水中浓度为 20 重量％时显示出逆热凝胶特性。这种行为与由中心聚（2-二苯甲基-2-恶唑啉）嵌段（pMeOx- b -pBhOx- b-pMeOx)。即使在 25 重量％的情况下，也没有观察到这种聚合物的逆热凝胶化。对于 25 wt.% pMeOx- b -pBhOzi- b -pMeOx，获得了令人惊讶的 ≈22 kPa 的高储能模量和 480 Pa 和 1.3 kPa 的高屈服点和流点值。超过屈服点，观察到明显的剪切变稀。有趣的是，通过动态光散射观察到pMeOx- b -pBhOzi- b -pMeOx 和 pMeOx- b -pBhOx- b -pMeOx 的自组装之间只有很小的差异，而透射电子显微镜图像表明 pMeOx- b -pBhOzi的胶束-乙-pMeOx 通过它们的亲水冠相互作用，这可能是凝胶形成的决定性因素。总体而言，这项研究为基于聚（2-恶唑啉）和聚（2-恶嗪）的自组装引入了新的构建模块，但需要更多的研究来阐明确切的机制。

更新日期：2021-09-07

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