Haldar Ujjal, Bauri Kamal, Li Ren, Faust Rudolf, De Priyadarsi
†Polymer Research Centre, Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur-741246, Nadia, West Bengal India.
‡Polymer Science Program, Department of Chemistry, University of Massachusetts Lowell, One University Avenue, Lowell, Massachusetts 01854, United States.
ACS Appl Mater Interfaces. 2015 Apr 29;7(16):8779-88. doi: 10.1021/acsami.5b01272. Epub 2015 Apr 14.
This work demonstrates the successful application of dynamic covalent chemistry for the construction of self-healing gels from side-chain primary amine leucine pendant diblock copolymers of polyisobutylene (PIB) ((P(H2N-Leu-HEMA)-b-PIB)) in the presence of PIB based dialdehyde functionalized cross-linker (HOC-PIB-CHO) through imine (-HC═N-) bond formation without aiding any external stimuli. Gels were synthesized in 1,4-dioxane at room temperature at varied wt % of gelator concentration, [H2N]/[CHO] ratios and molecular weight of the block segments. The mechanical property of gels was examined by rheological measurements. We observed higher value of storage modulus (G') than the loss modulus (G″) within the linearity limits of deformation, indicating the rheological behavior in the gel is dominated by an elastic property rather than a viscous property. The G' values significantly depend upon the extent of cross-linking in the gel network. To establish self-healing property of the gels, rheology analysis through step-strain measurements (strain = 0.1 to 200%) at 25 °C was performed. The polymeric gel network shows reversible sol-gel transition for several cycles by adjusting the pH of the medium with the help of hydrochloric acid (HCl) and triethylamine (Et3N) triggers. FT-IR spectroscopy established formation of imine bonds in the gel network and these gels showed poor swelling behavior in various organic solvents because of the small interstitial porosity, confirmed by field emission-scanning electron microscopy (FE-SEM).
这项工作展示了动态共价化学在由聚异丁烯（PIB）的侧链伯胺亮氨酸侧基二嵌段共聚物（P（H2N-Leu-HEMA）-b-PIB）构建自愈合凝胶中的成功应用，该凝胶在基于PIB的二醛官能化交联剂（HOC-PIB-CHO）存在下通过亚胺（-HC═N-）键形成，无需任何外部刺激。凝胶在1,4 - 二氧六环中于室温下合成，改变了凝胶剂浓度的重量百分比、[H2N]/[CHO]比例以及嵌段链段的分子量。通过流变学测量来检查凝胶的力学性能。我们观察到在变形的线性范围内储能模量（G'）的值高于损耗模量（G″），这表明凝胶中的流变行为主要由弹性性质而非粘性性质主导。G'值显著取决于凝胶网络中的交联程度。为了确定凝胶的自愈合性能，在25℃下通过阶跃应变测量（应变 = 0.1至200%）进行流变学分析。借助盐酸（HCl）和三乙胺（Et3N）引发剂调节介质的pH值，聚合物凝胶网络显示出几个循环的可逆溶胶 - 凝胶转变。傅里叶变换红外光谱证实了凝胶网络中亚胺键的形成，并且由于间隙孔隙率小，这些凝胶在各种有机溶剂中表现出较差的溶胀行为，场发射扫描电子显微镜（FE - SEM）证实了这一点。
