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

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.