Effects of Primary Structure of Reactive Polymers on Network Structure and Mechanical Properties of Gels

Abstract

The effects of the primary structure of multifunctional reactive polymers on the network structure and the mechanical properties of gels formed by crosslinking the reactive polymers with crosslinkers are studied by a coarse‐grained molecular dynamics simulation. When functional groups are randomly arranged on the polymers, the network structure, such as the number densities of elastically effective chains and entanglements, and the mechanical properties depend on the number average molecular weight of the polymers; however, these properties are almost independent of the molecular weight distribution and the functional group number distribution of the polymers. The control of the arrangement of functional groups on the polymers improves the uniformity and the mechanical properties. By changing the arrangement from a random one to a periodic one, the number of elastically effective chains and the shear modulus increase, and the occurrence of entanglement is suppressed. The detailed analysis of the network structure reveals that the improvement of the mechanical properties is mainly due to the reduction of intramolecular crosslinking.

Comparison of gels synthesized by controlled radical copolymerization and free radical copolymerization: molecular dynamics simulation

“…Since M n,p is almost the same in all the gels, the number of dangling ends rarely varies. 43 The differences in the cross-linked structure between the gels with almost the same composition are caused by kinetic effects. 33 The increase in ν x due to the change in the synthesis method from the FRP to the CRP is attributed to the change of the network strands from the loop, which is a defect in the cross-linked structure, into the bridge.…”

“…Although the molecular weight distribution of the primary chains differs between the CRP gel and the FRP gel, we have confirmed that the difference in the molecular weight distribution does not significantly affect the network structure. 43…”

“…We adjusted n p–x in the CRP and n i in the FRP so that the number average molecular weights M n,p of the primary chains in the corresponding systems were almost equal, because the network structure and physical properties significantly depend on M n,p . 43 Here, the primary chains are the polymers obtained by the scission of the cross-linkers in the network. The volume V of the simulation box was set so that the monomer volume fraction ϕ m = n m σ 3 π/6 V was ϕ m = 0.1.…”