Strain-Adaptive Self-Assembled Networks of Linear-Bottlebrush-Linear Copolymers*

We study the strain-adaptive behavior of the self-assembled networks of linear-bottlebrush-linear (LBL) triblock copolymers using a combination of analytical calculations and molecular dynamics simulations. Interactions between immiscible blocks result in microphase separation and formation of soft and strain-adaptive composite networks. Such unique network properties are manifestations of the architectural asymmetry of two blocks: (i) flexible linear chains that aggregate into domains and (ii) bottlebrush strands that form a soft matrix. The mechanical response of the networks is a two-stage process, which starts with the extension of the bottlebrush network strands (elastic regime) followed by the pulling out of the linear chains from L-domains (yielding regime). The two-stage network deformation process is incorporated into a unifying model of strain-adaptive network deformation. The model predictions are confirmed by molecular dynamics simulations of uniaxial deformation of self-assembled LBL copolymer networks and by experimental results for copolymers consisting of poly(dimethyl siloxane) bottlebrush block and two poly(methyl methacrylate) linear chain blocks with different compositions and block lengths.