Hwang Uijung, Moon HoYeon, Park Junyoung, Jung Hyun Wook
Department of Chemical and Biological Engineering, Korea University, Seoul 02841, Republic of Korea.
Polymers (Basel). 2024 Jul 29;16(15):2149. doi: 10.3390/polym16152149.
This study investigates the crosslinking dynamics and swelling properties of pH-responsive poly(ethylene glycol) (PEG)/poly(acrylic acid) (PAA) interpenetrating polymer network (IPN) hydrogels. These hydrogels feature denser crosslinked networks compared to PEG single network (SN) hydrogels. Fabrication involved a two-step UV curing process: First, forming PEG-SN hydrogels using poly(ethylene glycol) diacrylate (PEGDA) through UV-induced free radical polymerization and crosslinking reactions, then immersing them in PAA solutions with two different molar ratios of acrylic acid (AA) monomer and poly(ethylene glycol) dimethacrylate (PEGDMA) crosslinker. A subsequent UV curing step created PAA networks within the pre-fabricated PEG hydrogels. The incorporation of AA with ionizable functional groups imparted pH sensitivity to the hydrogels, allowing the swelling ratio to respond to environmental pH changes. Rheological analysis showed that PEG/PAA IPN hydrogels had a higher storage modulus (') than PEG-SN hydrogels, with PEG/PAA-IPN5 exhibiting the highest modulus. Thermal analysis via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated increased thermal stability for PEG/PAA-IPN5 compared to PEG/PAA-IPN1, due to higher crosslinking density from increased PEGDMA content. Consistent with the storage modulus trend, PEG/PAA-IPN hydrogels demonstrated superior mechanical properties compared to PEG-SN hydrogels. The tighter network structure led to reduced water uptake and a higher gel modulus in swollen IPN hydrogels, attributed to the increased density of active network strands. Below the p (4.3) of acrylic acid, hydrogen bonds between PEG and PAA chains caused the IPN hydrogels to contract. Above the p, ionization of PAA chains induced electrostatic repulsion and osmotic forces, increasing water absorption. Adjusting the crosslinking density of the PAA network enabled fine-tuning of the IPN hydrogels' properties, allowing comprehensive comparison of single network and IPN characteristics.
本研究考察了pH响应性聚乙二醇（PEG）/聚丙烯酸（PAA）互穿聚合物网络（IPN）水凝胶的交联动力学和溶胀性能。与PEG单网络（SN）水凝胶相比，这些水凝胶具有更致密的交联网络。制备过程包括两步紫外光固化工艺：首先，通过紫外诱导自由基聚合和交联反应，使用聚乙二醇二丙烯酸酯（PEGDA）形成PEG-SN水凝胶，然后将其浸入含有两种不同摩尔比丙烯酸（AA）单体和聚乙二醇二甲基丙烯酸酯（PEGDMA）交联剂的PAA溶液中。随后的紫外光固化步骤在预制的PEG水凝胶中形成PAA网络。含有可电离官能团的AA的引入赋予水凝胶pH敏感性，使溶胀比能够响应环境pH变化。流变学分析表明，PEG/PAA IPN水凝胶的储能模量（G'）高于PEG-SN水凝胶，其中PEG/PAA-IPN5表现出最高的模量。通过热重分析（TGA）和差示扫描量热法（DSC）进行的热分析表明，与PEG/PAA-IPN1相比，PEG/PAA-IPN5的热稳定性有所提高，这是由于PEGDMA含量增加导致交联密度更高。与储能模量趋势一致，PEG/PAA-IPN水凝胶与PEG-SN水凝胶相比表现出优异的力学性能。更紧密的网络结构导致溶胀的IPN水凝胶吸水率降低和凝胶模量更高，这归因于活性网络链密度的增加。在丙烯酸的pKa（4.3）以下，PEG和PAA链之间的氢键导致IPN水凝胶收缩。在pKa以上，PAA链的电离诱导静电排斥和渗透压，增加吸水率。调节PAA网络的交联密度能够对IPN水凝胶的性能进行微调，从而可以全面比较单网络和IPN的特性。
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