Viscoelastic Properties and Shock Response of Coarse-Grained Models of Multiblock versus Diblock Copolymers: Insights into Dissipative Properties of Polyurea

Abstract

We compare and contrast the microstructure, viscoelastic properties, and shock response of coarse-grained models of multiblock copolymer and diblock copolymers using molecular dynamics simulations. This study is motivated by the excellent dissipative and shock-mitigating properties of polyurea, speculated to arise from its multiblock chain architecture. Our microstructural analyses reveal that the multiblock copolymer microphase-separates into small, interconnected, rod-shaped, hard domains surrounded by a soft matrix, whereas the diblock copolymer forms larger, unconnected, hard domains. Our viscoelastic analyses indicate that compared with the diblock copolymer, the multiblock copolymer is not only more elastic but also more dissipative, as signified by its larger storage and loss modulus at low to intermediate frequencies. Our shock simulations and slip analyses reveal that shock waves propagate slower in the multiblock copolymer in comparison with the diblock copolymer, most likely due to the more deformable hard domains in the former system. These results suggest that the multiblock architecture of polyurea might impart polyurea with smaller, more deformable, and interconnected hard domains that lead to improved energy dissipation and lower shock speeds.

Polymer Engineering Science and Viscoelasticity

“…In this case, the backbone consists of two different polymers in a block copolymer arrangement (see Chap. 4 for more details) which phase segregate into hard and soft domains (Das et al 2007;Arman et al 2012). The hard domains form by hydrogen bonding (secondary bonds) between of one of the polymer segments with itself which then aggregate into dispersed crystalline domains, 10's of nanometers in size.…”

Regulation of crystalline morphologies and mechanical properties of olefin multiblock copolymers by blending polymer with similar architecture of constituent blocks

“…Owing to the larger number of chemical restrictions imposed on the domains of multiblock copolymer, the shape and size of domains are less stable, [6] and the crystalline morphologies can be diversiform. Consequently, the mechanical properties are quite distinct compared to conventional polymers with simple architectures, generating an expanding range of practical applications such as elastomers, [7,8] compatibilizers for blends of immiscible homopolymers, [9,10] as well as pressure-sensitive adhesives.…”

Elastomer-metal laminate armor

“…The elastomeric material had a calorimetric glass transition temperature equal to −60°C. The application of the polymer for ballistic armor is described in several publications [39,40,41,42]. The metal for the laminate was either aluminum (2024-T3 alloy) or titanium (grade 2).…”