Meng Zhao, Löser Lucas, Saalwächter Kay, Gasser Urs, Klok Harm-Anton
Institut des Matériaux and Institut des Sciences et Ingénierie Chimiques, Laboratoire des Polymères, École Polytechnique Fédérale de Lausanne (EPFL), Bâtiment MXD, Station 12, CH-1015 Lausanne, Switzerland.
Swiss National Center for Competence in Research (NCCR) Bio-inspired Materials, University of Fribourg, Chemin des Verdiers 4, CH-1700 Fribourg, Switzerland.
Macromolecules. 2024 Mar 25;57(7):3058-3065. doi: 10.1021/acs.macromol.3c02514. eCollection 2024 Apr 9.
The preparation of polymer gels via cross-linking of four-arm star-shaped poly(ethylene glycol) (Tetra-PEG) precursors is an attractive strategy to prepare networks with relatively well-defined topologies. Typically, Tetra-PEG gels are obtained by cross-linking heterocomplementary reactive Tetra-PEG precursors. This study, in contrast, explores the cross-linking of self-reactive, thiol-end functional Tetra-PEG macromers to form disulfide-cross-linked gels. The structure of the disulfide-cross-linked Tetra-PEG gels was studied with multiple-quantum NMR (MQ-NMR) spectroscopy and small-angle neutron scattering (SANS) experiments. In line with earlier simulation studies, these experiments showed a strong dependence of the relative fractions of the different network connectivities on the concentration of the thiol-end functional Tetra-PEG macromer that was used for the synthesis of the networks. Disulfide-cross-linked Tetra-PEG gels prepared at macromer concentrations below the overlap concentration ( = 0.66*) primarily feature defect connectivity motifs, such as primary loops and dangling ends. For networks prepared at macromer concentrations above the overlap concentration, the fraction of single-link connectivities was found to be similar to that in amide-cross-linked Tetra-PEG gels obtained by heterocomplementary cross-linking of -hydroxysuccinimide ester and amine functional Tetra-PEG macromers. Since disulfide bonds are susceptible to reductive cleavage, these disulfide-cross-linked gels are of interest, e.g., as reduction-sensitive hydrogels for a variety of biomedical applications.
通过四臂星形聚乙二醇（Tetra-PEG）前体的交联制备聚合物凝胶是一种制备拓扑结构相对明确的网络的有吸引力的策略。通常，Tetra-PEG凝胶是通过异互补反应性Tetra-PEG前体的交联获得的。相比之下，本研究探索了自反应性、硫醇末端官能化的Tetra-PEG大分子单体的交联以形成二硫键交联的凝胶。利用多量子核磁共振（MQ-NMR）光谱和小角中子散射（SANS）实验研究了二硫键交联的Tetra-PEG凝胶的结构。与早期的模拟研究一致，这些实验表明不同网络连接性的相对分数强烈依赖于用于合成网络的硫醇末端官能化Tetra-PEG大分子单体的浓度。在大分子单体浓度低于重叠浓度（= 0.66*）时制备的二硫键交联的Tetra-PEG凝胶主要具有缺陷连接基序，如初级环和悬垂端。对于在大分子单体浓度高于重叠浓度时制备的网络，发现单链连接性的分数与通过异羟基琥珀酰亚胺酯和胺官能化Tetra-PEG大分子单体的异互补交联获得的酰胺交联Tetra-PEG凝胶中的分数相似。由于二硫键易于还原裂解，这些二硫键交联的凝胶例如作为对多种生物医学应用具有还原敏感性的水凝胶而受到关注。
