Influence of polymer network-metal ion complexation on the swelling behaviour of new gels with incorporated α-amino acid groups
作者:Marcin Karbarz、Jan Romanski、Kamila Michniewicz、Janusz Jurczak、Zbigniew Stojek
DOI:10.1039/b920809g
日期:——
New gels based on N-isopropylacrylamide and amino acid L-ornithine were prepared by free radical polymerization in aqueous solutions. To make the amino acid attachable to the polymer chain the acrylic group was added to the δ-amino group of ornithine, to obtain N-δ-acrylic ornithine. After the polymerization process the α-amino acid groups were unbound. The relative content of amino acid incorporated into the polymeric network of the gels was estimated from 1HNMR spectra, then compared with the molar fraction used for the polymerization process. The presence of free α-amino acid groups attached to the polymeric network of the gels enabled the complexation of some di- and trivalent metal cations. Copper ions, which can form two complexes of different stoichiometry (1â:â1 and 1â:â2) with amino acids, were used to investigate the influence of the complexation process on the swelling behavior of the gels. The influence of amino acid content, temperature and copper ion concentration on the swelling process was also examined. The gels were found to be most sensitive to concentrations of copper ions in the range 10â6â10â5 M. As the amount of amino acid in the polymer network increases the gels gradually lose their temperature-sensitivity and become more sensitive to copper ion concentration. The volume-phase-transition temperature decreases significantly after the addition of copper ions. Analysis of the UV-Vis spectra and the swelling behavior indicates that both 1â:â1 and 1â:â2 complexes are present in the swollen state of the gels, whereas the latter complex is more dominant in the shrunken state.
基于N-异丙基丙烯酰胺和氨基酸L-鸟氨酸的新型凝胶通过自由基聚合在水溶液中制备。为了使氨基酸附着在聚合物链上,将丙烯酸基团添加到鸟氨酸的γ-氨基上,得到N-γ-丙烯酸鸟氨酸。聚合过程结束后,α-氨基被解离。通过1HNMR光谱估计氨基酸掺入凝胶聚合网络的相对含量,然后与聚合过程中使用的摩尔分数进行比较。自由α-氨基附着在凝胶的聚合网络上,能够与一些二价和三价金属阳离子形成络合物。铜离子可以与氨基酸形成两种不同化学计量比的络合物(1∶1和1∶2),用于研究络合过程对凝胶溶胀行为的影响。还研究了氨基酸含量、温度和铜离子浓度对溶胀过程的影响。凝胶对10⁻⁶-10⁻⁵ M范围内的铜离子浓度最为敏感。随着聚合物网络中氨基酸含量的增加,凝胶逐渐失去对温度的敏感性,而对铜离子浓度变得更加敏感。加入铜离子后,体积相变温度显著降低。对紫外-可见光谱和溶胀行为进行分析表明,凝胶溶胀状态下存在1∶1和1∶2络合物,而后者在收缩状态下更占主导地位。