一种高拉伸离子导体的设计与制备
摘 要
离子凝胶是一种新型功能材料，其应用范围可涵盖到传感设备、电子器件等多个领域。但是当前的离子凝胶还存在不可拉伸、力学性能差等不足之处。本论文使用“一锅法”进行制备，将1-乙基-3-甲基咪唑四氟化硼盐（C2mimBF4）作为溶剂，加入单体丙烯酸（AA）、丙烯酰胺（AM）、交联剂PEGDA及光引发剂，在紫外线照射下固化。此凝胶体系将类离子液体引入凝胶网络中，形成单网络双交联结构，其中物理交联为各组分之间的氢键作用，化学交联为PEGDA形成的共价交联。所制得的凝胶主要用于制备柔性传感器件。本文通过在C2mimBF4体系中调节丙烯酸（AA）和丙烯酰胺（AM）单体的不同配比并考量了不同配比下凝胶的机械性能与导电性能。研究发现，在P(AA-co-AM)/C2mimBF4中，当AA和AM的摩尔比为1:2时，所制得的离子凝胶拉伸强度和弹性模量较大，分别为28.56kPa和17.80kPa，断裂伸长率为894.55%，且导电性能较好，电导率为3.4S/m。
关键词：离子凝胶 氢键 高拉伸 电导率
The design and preparation of a high tensile ionic gel Abstract
Ionic gel is a new type of functional material, which has a wide application prospect in many fields, such as sensors and electronic devices. However, the current ionic gels still have some shortcomings, such as unstretchability and poor mechanical properties. In this paper, the preparation was carried out by 'one-pot method'. C2mimBF4 were used as solvent. Monomer acrylic acid (AA), acrylamide (AM), crosslinking agent (PEGDA) and photoinitiator were added to form gel through light initiated polymerization. The gel system introduced ionic liquid into the gel network to form a single network and double cross-linked structure, in which physical cross-linking was hydrogen bonding between components and chemical cross-linking was covalent cross-linking formed by PEGDA. The obtained gel is mainly used to prepare flexible sensor parts. In this paper, the mechanical properties and electrical properties of acrylamide (AM) and acrylic acid (AA) monomers were adjusted in the system of C2mimBF4. It was found that in P(AA-co-AM)/C2mimBF4, when the molar ratio of AA and AM was 1:2, the tensile strength and elastic modulus of the prepared ionic gel were relatively large (28.56 kPa and 17.80 kPa, respectively), the elongation at break rate was 894.55%, and the conductivity was relatively good (3.4S/m).
Key Words: Ionic gel; Hydrogen bond; Self-healing; High tensile strength; Conductivity
1.1 离子凝胶概述
离子凝胶是一种固体混合物。分子链间缠结作用构成的聚合物网络成为它的基本骨架，此网络可被电解质溶液或离子液体溶胀。盐类电解质电解出的离子作为分散介质，填充在聚合物网络的空隙中。它们虽然采用导电固体形式，但具有很大的可拉伸性和透明度，在可拉伸设备中具有巨大的潜力[2]。近年来，由于其机械适形性[3]，良好的透明度和生物相容性[4]而备受关注。
根据聚合物网络中溶剂的类型，离子导体可分为水性离子凝胶和非水性离子凝胶[5]。水离子凝胶的制备可以通过在交联剂和引发剂的存在下在电解质溶液中使乙烯基单体聚合来实现，例如水凝胶。最突出的例子之一是基于聚丙烯酰胺（PAM）的水凝胶[6]，它是通过在电解质溶液（如NaCl，KCl和LiCl）中丙烯酰胺（AM）单体进行原位聚合交联形成的。过去的研究表明，基于PAM的水凝胶可用于透明扬声器，皮肤状和自愈式触觉传感器[7]，执行器[8]，和触摸面板[9]。水凝胶会减少装备的使用年限以及破坏它的稳定性，这样就会使它们的应用受阻。非水离子凝胶通常是通过在有机电解质溶液中溶胀聚合物网络并在聚合物网络中由物理相互作用来制备的，如制备由离子液体物理组装而成的离子凝胶。其中，离子液体是一类室温熔融盐，具有出色的离子传导性[22]。在一般情况下不挥发，而且在电场力作用下，也不易发生化学反应。传统的离子液体凝胶也存在一些不足，如结构不匀称、机械性能不好、溶胀能力较差及应对环境变化时灵敏度不高等。仅仅通过提高交联度的手段，并不能实现凝胶体系综合性能的提高。虽然离子液体凝胶的力学强度有所提升，但是其弹性变差，呈现出一定的脆性。
