Crystal structure transition of polyrotaxanes attributable to competing rings and backbone induced by in situ modification of the backbone
Crystal structure transition of polyrotaxanes attributable to competing rings and backbone induced by in situ modification of the backbone
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DOI：
10.1016/j.polymer.2014.01.044
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发表时间：
2014-03
期刊：
影响因子：
4.6
通讯作者：
Kazuaki Kato;Tomoya Ise;K. Ito
中科院分区：
文献类型：
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作者：
Kazuaki Kato;Tomoya Ise;K. Ito
聚丁二烯基聚轮烷（BPR）的20%主链被γ-环糊精部分覆盖，其原位催化氢化诱导归因于主链和环的竞争晶体形成的晶体结构转变。温度和时间控制的乳化BPR与十二烷基硫酸钠（SDS）的反应产生氢化BPR（H-PRs）与不同程度的氢化;均相反应导致较低程度的氢化。BPR的加氢速率高于聚丁二烯本身，表明具有亲水环和疏水主链的两亲性聚轮烷有利于乳液反应。通过差示扫描量热法检测H-PR主链的结晶，并且产生的热量随着氢化度的增加而增加。粉末X-射线衍射分析表明，其晶体结构类似于正交聚乙烯，且环组分的晶体随着氢化而减少。这表明BPR的原位氢化赋予主链足够的结晶度以与通常通过独立于主链的有效氢键网络控制聚轮烷的整个晶体结构的结晶环竞争。
In situ catalytic hydrogenation of polybutadiene-based polyrotaxane (BPR) that has 20% of its backbone covered withγ-cyclodextrin moieties induced a crystal structure transition attributed to competing crystal formations of the backbone and rings. Temperature- and time-controlled reactions of emulsified BPR with sodium dodecyl sulphate (SDS) yielded hydrogenated BPRs (H-PRs) with different degrees of hydrogenation; homogeneous reactions resulted in lower degrees of hydrogenation. The hydrogenation rate of BPR was higher than that of polybutadiene itself, indicating that the amphiphilic polyrotaxane with hydrophilic rings and a hydrophobic backbone is advantageous for the emulsion reaction. Crystallization of the H-PR backbones was detected by differential scanning calorimetry and the amount of heat generated increased with increasing degree of hydrogenation. Powder X-ray diffraction revealed that the crystal structures resemble orthorhombic polyethylene and the crystals of the ring components decreased with hydrogenation. This demonstrates that in situ hydrogenation of BPR endows the backbone with sufficient crystallinity to compete with the crystalline rings that generally govern the entire crystal structures of polyrotaxanes through efficient hydrogen-bonding networks that are independent of the backbones.