Multinetwork (MN) is a common topological structure in polymerization related manufacturing and artificial high-performance polymers. Currently the experimental and theoretical researches of MNs are generally focused on the deformation and failure mechanism of self-dissimilar tough hydrogels or tough elastomers, in which the topological structures of each sub network are significantly different. In naturally formed MNs the networks are highly entangled and the interactions between the self-similar sub networks dominate the overall mechanical behaviors. Examples of such self-similar MNs include the case when monomers diffuse into the polymer network during nonuniform polymerization and forms additional interpenetrating chains. In this paper we present the experiment results for a series of self-similar MNs. The networks were created by sequentially immersing the MNs in the same monomers, during which the base network gradually expanded until saturation. Different from tough hydrogels or tough elastomers, here all of the compositional networks deformed simultaneously without obvious damage of any individual network before ultimate breaking. With the increase of interpenetration cycle, the MN was gradually stiffened until the introduction of interpenetrating chains exerted no effect on the mechanical behaviors. With the gradual hydrostatic stretching of each sub network, the viscoelasticity of the MN decreased in the sequential interpenetration process. By introducing the idea of equivalent network, we developed a theoretical model incorporating both the phenomenological treatment and the micromechanical description of MNs, with special attention payed to the interactions of different sub networks in the self-similar MN, the extensibility of chain segments during interpenetration, as well as the alteration of network viscoelasticity. The sequential stiffening phenomenon, the saturation of network elasticity and the disappearance of viscoelasticity could be well captured by the theoretical model.

多网络（MN）是聚合相关制造和人造高性能聚合物中常见的拓扑结构。目前MNs的实验和理论研究普遍集中在自不同的坚韧水凝胶或坚韧弹性体的变形和破坏机制上，其中每个子网络的拓扑结构存在显着差异。在自然形成的 MN 中，网络高度纠缠，自相似子网络之间的相互作用主导着整体机械行为。这种自相似 MN 的例子包括单体在非均匀聚合过程中扩散到聚合物网络中并形成额外的互穿链的情况。在本文中，我们展示了一系列自相似 MN 的实验结果。这些网络是通过将 MN 依次浸入相同的单体中而创建的，在此期间基础网络逐渐扩展直至饱和。与坚韧的水凝胶或坚韧的弹性体不同，这里所有的组成网络同时变形，在最终断裂之前没有任何单个网络的明显损坏。随着互穿周期的增加，MN逐渐变硬，直到引入互穿链对力学行为没有影响。随着每个子网络的逐渐静水拉伸，MN的粘弹性在顺序互穿过程中下降。通过引入等效网络的思想，我们开发了一个理论模型，该模型结合了 MN 的现象学处理和微观力学描述，特别关注自相似MN中不同子网络的相互作用，互穿过程中链段的可扩展性，以及网络粘弹性的改变。理论模型可以很好地捕捉到连续硬化现象、网络弹性饱和和粘弹性消失。