聚（N-异丙基丙烯酰胺）接枝甲基纤维素溶液中链构象和原纤维形成的温度依赖性,Macromolecules

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聚（N-异丙基丙烯酰胺）接枝甲基纤维素溶液中链构象和原纤维形成的温度依赖性
Macromolecules ( IF 5.1 ) Pub Date : 2022-01-09 , DOI: 10.1021/acs.macromol.1c02206
McKenzie L. Coughlin ₁ , Jerrick Edmund ₁ , Frank S. Bates ₁ , Timothy P. Lodge _{1,

2}

Affiliation

作为一种水溶性纤维素醚，甲基纤维素 (MC) 用于利用其热可逆凝胶化的各种应用。最近的研究表明，MC 凝胶化是由于形成了具有相对均匀直径（约15 nm）的纳米原纤维，并且可以通过添加低分子量聚（乙二醇）作为接枝物来抑制凝胶化和原纤维的形成沿着脊椎。在这项工作中，我们用硫醇封端的聚（N-异丙基丙烯酰胺）（PNIPAm，M _w≈ 3 kg/mol) 使用硫醇-烯点击化学并研究由此产生的对 MC 水溶液性质的影响。从静态和动态光散射来看，很明显线圈尺寸随着接枝密度（高达 0.11 个接枝/脱水葡萄糖重复单元）而增加，这导致从 Kratky-Porod 蠕虫状链模型推断的持续长度增加。数据与基于移植物-移植物和移植物-骨干排除体积相互作用的模型一致。有趣的是，接枝 PNIPAm 会导致 theta 温度升高，尽管 PNIPAm 通常具有低于裸 MC 的较低临界溶解温度 (LCST)。小角度 X 射线散射和低温透射电子显微镜显示，接枝链在高温下仍会形成原纤维。

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Temperature Dependence of Chain Conformations and Fibril Formation in Solutions of Poly(N-isopropylacrylamide)-Grafted Methylcellulose

As a water-soluble cellulose ether, methylcellulose (MC) is used in a variety of applications that take advantage of its thermoreversible gelation. Recent work has shown that MC gelation is due to the formation of nanofibrils with a relatively uniform diameter (ca. 15 nm) and that gelation and fibril formation can be suppressed through the addition of low-molecular-weight poly(ethylene glycol) as grafts along the backbone. In this work, we modify MC similarly with thiol-terminated poly(N-isopropylacrylamide) (PNIPAm, M_w ≈ 3 kg/mol) using thiol–ene click chemistry and investigate the resulting influence on aqueous MC solution properties. From static and dynamic light scattering, it is apparent that the coil dimensions increase with grafting density (up to 0.11 grafts/anhydroglucose repeat unit), which leads to an increase in the persistence length inferred from the Kratky–Porod wormlike chain model. The data are consistent with a model based on the incorporation of graft–graft and graft–backbone excluded volume interactions. Interestingly, grafting PNIPAm leads to an increase in the theta temperature, even though PNIPAm typically has a lower critical solution temperature (LCST) that is lower than bare MC. Small-angle X-ray scattering and cryogenic transmission electron microscopy reveal that fibril formation still occurs at high temperature for the grafted chains.

更新日期：2022-01-25

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