Sala Renata L, Venâncio Tiago, Camargo Emerson R
Department of Chemistry, Federal University of São Carlos (UFSCar), Rod. Washington Luis km 235, São Carlos, SP 13565-905, Brazil.
Langmuir. 2021 Feb 2;37(4):1531-1541. doi: 10.1021/acs.langmuir.0c03079. Epub 2021 Jan 22.
Nanocomposite hydrogels have emerged to exhibit multipurpose properties, boosting especially the biomaterial field. However, the development and characterization of these materials can be a challenge, especially stimuli-sensitive materials with dynamic properties in response to external stimuli. By employing UV-vis spectroscopy and NMR relaxation techniques, we could outline the formation and behavior of thermosensitive nanocomposites obtained by polymerization of poly(-vinylcaprolactam) (PNVCL) and mesoporous silica nanofibers under temperature stimuli. For instance, inorganic nanoparticles covalently linked to PNVCL changed the pattern of temperature-induced phase transition despite showing similar critical temperatures to neat PNVCL. Thermodynamic parameters indicated the formation of an interconnected system of silica and polymer chains with reduced enthalpic contribution and mobility. The investigation of water molecule and polymer segment motions also revealed that the absorption and release of water happened in a wider temperature range for the nanocomposites, and the polymer segments respond in different ways during the phase transition in the presence of silica. This set of techniques was essential to reveal the polymer motions and structural features in nanocomposite hydrogels under temperature stimuli, demonstrating its potential use as experimental guideline to study multicomponent nanocomposites with diverse functionalities and dynamic properties.
纳米复合水凝胶已展现出多种用途的特性，尤其推动了生物材料领域的发展。然而，这些材料的开发和表征可能具有挑战性，特别是对于那些在外部刺激下具有动态特性的刺激敏感材料。通过采用紫外可见光谱和核磁共振弛豫技术，我们能够勾勒出在温度刺激下通过聚（乙烯基己内酰胺）（PNVCL）和介孔二氧化硅纳米纤维聚合得到的热敏纳米复合材料的形成和行为。例如，与PNVCL共价连接的无机纳米颗粒尽管显示出与纯PNVCL相似的临界温度，但改变了温度诱导的相变模式。热力学参数表明形成了二氧化硅和聚合物链的相互连接系统，其焓贡献和流动性降低。对水分子和聚合物链段运动的研究还表明，纳米复合材料在更宽的温度范围内发生水的吸收和释放，并且在二氧化硅存在下的相变过程中聚合物链段以不同方式响应。这组技术对于揭示温度刺激下纳米复合水凝胶中的聚合物运动和结构特征至关重要，证明了其作为研究具有多种功能和动态特性的多组分纳米复合材料的实验指南的潜在用途。
