Compatibilization of Immiscible Polymer Blends by Reactive Polymer Grafted Graphene with Interfacial Crosslinking

We investigate reactive compatibilization by applying two multifunctional polymers grafted on a graphene surface, which leads to crosslinked interphase at immiscible polymer blends. Reactive compatibilizer-grafted graphene (RCG) nanoparticles were synthesized through esterification and amidation reactions between oxidative groups of graphene oxide and reactive multifunctional groups of polymers. Polymer blends of polyisoprene (PI) and polydimethysiloxane (PDMS) with PI:PDMS ratio of 30:70 or 70:30 and RCG nanoparticle loadings from 0.1 and 1 wt% were evaluated by optical microscopy and rheometry. The results indicated that the blend with 0.1 wt% RCG showed unusual characteristics including nonspherical and bridged droplets, while those containing 1 wt% RCG showed usual droplet-matrix morphology. The rheological results are also asymmetric: the blend with 0.1 wt% RCG displayed gel-like behavior in the dynamic oscillatory tests, high viscosity, slow interfacial relaxation during startup shear flow, and divergence in the transient stress response due to coalesced and bridged droplets. However, the latter blend containing 1 wt% RCG reveals liquid-like behavior, low viscosity, and convergence in the transient stress response due to stabilized droplet-matrix morphology. Overall, it was suggested that these asymmetries are attributable to interfacial crosslinked interphase formed through an in-situ reaction between multifunctional polymers grafted on graphene sheets.