The exclusive location of compatibilizers at the interface of immiscible binary polymer blends to bridge the neighboring phases is the most important issue for fabricating desirable materials with synergistic properties. However, the positional stability of the compatibilizers at the interface remains a challenge in both scientific and technical points of view due to the intrinsic flexibility of compatibilizer molecules against aggressive processing conditions. Herein, taking the typical immiscible poly vinylidene fluoride (PVDF)/polylactic acid (PLLA) blend as an example, we demonstrate a novel approach, termed as the interfacial nanoparticle compatibilization (IPC) mechanism, to overcome the challenges by packing nanoparticles thermodynamically at the interface through melt reactive blending. Specifically, we have first synthesized nanosilica with both reactive epoxide groups and long poly(methyl methacrylate) (PMMA) tails, called reactive PMMA-graft-SiO (Epoxy-MSiO), and then incorporated the Epoxy-MSiO into the PVDF/PLLA (50/50, w/w) blends by melt blending. PLLA was in situ grafted onto SiO by the reaction of the carboxylic acid groups with epoxide groups on the surface of SiO. Therefore, the reacted SiO particles were exclusively located at the interface by the formation of the Janus-faced silica hybrid nanoparticles (JSNp) with pregrafted PMMA tails entangled with PVDF molecular chains in the PVDF phase and the in situ grafted PLLA chains embedded in the PLLA phase. Such JSNp with a distinct hemisphere, functioning as compatibilizer, can not only suppress coalescence of PVDF domains by its steric repulsion but also enhance interfacial adhesion via the selective interactions with the corresponding miscible phase. The interfacial location of JSNp is very stable even under the severe shear field and annealing in the melt. This IPC mechanism paves a new possibility to use the various types of nanoparticles as both effective compatibilizers and functional fillers for immiscible polymer blends.

Exclusive localization of nanofillers at the interface of immiscible polymer blend has been confirmed to be effective in improving compatibility and facilitating the formation of nanofiller-network with very low percolation threshold, while the rheology of such nanofiller compatibilized blends has seldom been investigated. Herein, we present a systematic rheological study on nanosilica-compatibilized PVDF/PLLA (poly­(vinylidene fluoride)/poly­(l-lactide)) blends. The linear viscoelastic properties of the systems are evaluated using small amplitude oscillatory shear (SAOS). It is found that the interfacial jammed Janus grafted silica (JGS) located at the interface increases dynamic moduli at low frequency even with very low filler loadings. The nonterminal effects become more pronounced with increasing JGS loadings. Weighted relaxation spectra inferred from SAOS reveals that the shape relaxation of PVDF-droplets is strongly influenced by addition of JGS. The solid-like behavior of JGS-filled blends has been attributed to both the orderly arrangement of JGS at PVDF–PLLA interface and the molecular entanglement between the grafted long tails of JGS with the molecular chains of the component polymers. In other words, JGS at the interface not only promotes strong interfacial interactions between phases, but also stimulates the formation of unique nanoparticle–polymer hybrid network, termed as “heterogeneous network” with the silica as the junctions.

Physically anchoring carbon nanotubes (CNTs) onto the interface of immiscible polymer blends has been extensively reported; however, enhancement of physical properties of the blends has seldom been achieved. Herein, we used CNTs with reactive epoxide groups and long poly(methyl methacrylate) (PMMA) tails as a thermodynamic compatibilizer for immiscible poly vinylidene fluoride/poly l-lactide (PVDF/PLLA) blends. The CNTs acted as an efficient compatibilizer and bridged the two phases through physical entanglement and chemical reaction. The sea-island structure of the blend transformed into a bicontinuous structure for CNT contents greater than 3 wt %. The mechanical properties, including ductility and tensile strength, thermal properties, and electrical conductivities were all enhanced by the CNTs compatibilizer. This strategy thermodynamically compatibilized by reactive nanofillers paves the way for advanced blend nanocomposites.

Micellization of in situ formed graft copolymers during reactive blending is commonly observed. Numerous studies have been carried out to minimize the formation of micelles and enhance emulsification efficiency. Herein, we investigated the formation of interfacial Janus nanomicelles (JNMs) and their compatibilization effects on immiscible polymer blends when reactive graft copolymers (RGCs) are used as compatibilizers. Poly(styrene-co-glycidyl methacrylate)-graft-poly(methyl methacrylate) RGCs were synthesized and used as compatibilizers for immiscible poly(l-lactide) (PLLA)/poly(vinylidene fluoride) (PVDF) blends. Numerous nanomicelles were formed in situ during melt blending by grafting of PLLA onto the RGCs. The formation and location of JNMs depended not only on the molecular architecture of the RGCs but also on the melt processing sequence and molecular weight of the components. Interfacial JNMs can effectively improve the miscibility of polymer blends, thereby enhancing the performance of immiscible polymer blends.

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