Compatibilization of Immiscible Polymer Blends Using in Situ Formed Janus Nanomicelles by Reactive Blending

Reactivity of Joncryl chain extender in PLA/PBAT blends: Effects of processing temperature and PBAT aging on blend performance

This study investigates the effects of incorporating an epoxy-based Joncryl chain extender on the reactivity and performance of amorphous polylactide/poly(butylene-adipate-co-terephthalate)(PLA/PBAT) blends processed at various temperatures. The impact of using freshly provided PBAT versus aged PBAT on Joncryl's reactivity and blend performance is also examined. Joncryl's interactions with PLA, PBAT, and their blends at different temperatures were assessed using rheological analysis. The blends morphology, tensile and impact properties, and dynamic mechanical analysis were examined. Increasing the processing temperature enhances Joncryl's reactivity with PLA more noticeably than that with PBAT but also accelerates PLA degradation. Although PBAT exhibits reactivity with Joncryl, aged PBAT with significantly suppressed melt rheological properties remained largely unaffected by the presence of Joncryl. Overall, the melt rheological properties of blends improved with Joncryl addition at higher processing temperatures, likely due to the increased Joncryl reactivity and enhanced compatibilization. The tensile properties of blends processed at higher temperatures are more adversely affected by bioplastic degradation, although Joncryl addition mitigates these effects. Impact strength increased with higher processing temperatures due to enhanced Joncryl reactivity, more effective interfacial compatibilization, and PBAT phase droplet refinement. Blends prepared with aged PBAT exhibited markedly poorer mechanical performance, attributed to severely suppressed melt properties and resultant non-homogeneous blend morphology.

Enhancing Thermal Insulation Property and Flexibility of Starch/Poly(butylene adipate terephthalate) (PBAT) Blend Foam by Improving Rheological Properties

Starch foam has attracted significant attention as an alternative to expanded styrene (EPS) foam owing to its abundance and biodegradability. Despite these merits, its limited thermal insulation and flexibility compared to EPS have hindered its utilization in packaging. Herein, we report the effect of blending with starch/PBAT on foaming behavior and physical properties during foaming processing. We fabricated a starch/PBAT blend with systematically controlled blending ratios (0, 10, 15, 20, and 25 wt%) to analyze their effect on the interaction and characteristics of blended foam. The blending of starch and PBAT significantly reduced complex viscosity, enhancing resin flow during the foaming process. This improvement in resin flow led to increases in expansion ratio while reducing density and cell wall thickness. The thermo-insulation performance improved to 0.043 W/mK with 20 wt% of PBAT due to the enhanced expansion ratio and cell morphology. Additionally, the flexural strain at break improved significantly from 2.8 ± 0.6% to 9.6 ± 1.0% with increasing PBAT content. Enhanced water resistance was also observed, demonstrated by a reduction in water absorption and an extension of dissolution time. Overall, these findings underscore the potential of starch/PBAT foam to improve the thermal-insulating property, flexibility, and water resistance while maintaining their biodegradability and sustainability.

Super Tough PA6/PP/ABS/SEBS Blends Compatibilized by a Combination of Multi-Phase Compatibilizers

Development of multi-component blends to prepare high-performance polymer materials is still challenging, and is a key technology for mechanical recycling of waste plastics. However, a multi-phase compatibilizer is prerequisite to create high-performance multi-component blends. In this study, POE-g-(MAH-co-St) and SEBS-g-(MAH-co-St) compatibilizers are prepared via melt-grafting of maleic anhydride (MAH) and styrene (St) dual monomers to polyolefin elastomer (POE) and poly [styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), respectively. Subsequently, these compatibilizers are utilized to compatibilize the PA6/PP/ABS/SEBS quaternary blends through melt-blending. When POE-g-(MAH-co-St) and SEBS-g-(MAH-co-St) are added, respectively, both can promote the distribution of the dispersed phases, significantly reducing the dispersed phase size. When adding 10 wt% POE-g-(MAH-co-St) and 10 wt% SEBS-g-(MAH-co-St) together, compared to the non-compatibilized blend, the fracture strength, fracture elongation, and impact strength surprisingly increased by 106%, 593%, and 823%, respectively. It can be attributed to the hierarchical interfacial interactions which facilitate gradual energy dissipation from weak to strong interfaces, resulting in the improvement of mechanical properties. The synergistic effect of the enhanced phase interfacial interactions and toughening effect of elastomer compatibilizer achieved simultaneous growth in strength and toughness.

Tensile properties and deformation by different compatibilizers in bio-based polylactide/poly(4-hydroxybutyrate) blends

Blending chemically synthesized poly(4-hydroxybutyrate) (P4HB) with polylactide (PLLA) can overcome PLLA's brittleness, offering fully biobased blends. However, due to low compatibility between PLLA and P4HB, the influence of compatibilizers on the morphology, structure and tensile deformation of PLLA/P4HB blends remains to be unresolved. This article introduces reactive poly(methyl methacrylate-co-styrene-glycidyl methacrylate) (MSG) and non-reactive polyformaldehyde (POM) compatibilizers to improve the compatibility between P4HB and PLLA, achieving the maximal elongation at break exceeding 300 % at 2 wt% MSG or 3 wt% POM. MSG inhibits PLLA crystallization, extending stress stability in the silver streak stage, while POM enhances crystallization, prolonging the strain-hardening stage. Small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) analysis show that pristine PLLA forms voids before fracture, and PLLA/P4HB blends cavitate at the yield point and develop crazes in the silver streak stage. MSG effectively transmits stress and delays cavitation, extending the silver streak stage, whereas POM forms a microcrystalline network, lowering the energy barrier for stretching-induced recrystallization. These findings could provide theoretical guidelines on selecting compatibilizers for different PLLA based blends.

Toughening Immiscible Polymer Blends: The Role of Interface-Crystallization-Induced Compatibilization Explored Through Nanoscale Visualization

This study explores the novel approach of interface-crystallization-induced compatibilization (ICIC) via stereocomplexation as a promising method to improve the interfacial strength in thermodynamically immiscible polymers. Herein, two distinct reactive interfacial compatibilizers, poly(styrene-co-glycidyl methacrylate)-graft-poly(l-lactic acid) (SAL) and poly(styrene-co-glycidyl methacrylate)-graft-poly(d-lactic acid) (SAD) are synthesized via reactive melt blending in an integrated grafting and blending process. This approach is demonstrated to enhance the interfacial strength of immiscible polyvinylidene fluoride/poly l-lactic acid (PVDF/PLLA) 50/50 blends via ICIC. IR nanoimaging indicates a cocontinuous morphology in the blends. The blend compatibilized with SAD exhibits a higher storage modulus, as unveiled by small amplitude oscillatory shear (SAOS) in the melt state at a temperature below the melting temperature of the stereocomplex (SC) crystals and by DMTA measurements in the solid state. This increase is attributed to the formation of a 200-300 nm thick rigid interfacial SC crystalline layer that is directly visible using AFM imaging and chemically characterized via IR nanospectroscopy. This ICIC also results in a significant toughening of the blend, with the elongation at break increasing more than 20-fold. Moreover, the fracture toughness factor obtained from single edge-notch bending (SENB) tests is doubled with ICIC as compared to the uncompatibilized blend, indicating the strong crack-resistance capability as a result of ICIC. This improvement is also evident in SEM images, where thinner and longer fibrillation is observed on the fractured surface in the presence of ICIC.

Interfacial Activity of Janus Particle: Unity of Molecular Surfactant and Homogeneous Particle

Janus particles with different compositions and properties segmented to different regions on the surface of one objector provide more opportunities for interfacial engineering. As a novel interfacial active material, Janus particles integrate the amphiphilic properties of molecular surfactants and the Pickering effect of homogeneous particles. In this research, the outstanding properties of Janus particles on various interfaces are examined from both theoretical and practical perspectives, and the advantages of Janus particles over molecular surfactants and homogeneous particle surfactants are analyzed. We believe that Janus particles are ideal tools for interface regulation and functionalization in the future.

Interfacial Engineering with Rigid Nanoplatelets in Immiscible Polymer Blends: Interface Strengthening and Interfacial Curvature Controlling

The interfacial nanoparticle compatibilization (INC) strategy has opened up a promising avenue toward simultaneous functionalization and interfacial engineering of immiscible polymer blends. While the INC mechanism has been well developed recently, few investigations have focused on rigid nanoplatelets because of the inherent steric hindrance of the surface-grafted polymer chains. Herein, surface-modified rigid nanoplatelets have been incorporated into an immiscible poly(l-lactide) (PLLA)/poly(butylene succinate) (PBSU) blend. It is demonstrated that the strong interfacial adhesion between PLLA and PBSU phases is promoted via molecular entanglements of the grafted chains on the surface of nanoplatelets with the individual components. A refined phase morphology with improved mechanical properties can be achieved with the addition of 5 wt % modified Gibbsite nanoplatelets. It was further found that the stiffness of nanoplatelets can change the geometry of the interface significantly. It is, therefore, indicated that the simultaneous interface strengthening and interfacial curvature controlling of rigid nanoplatelets originate from the selective swelling/collapse of the in situ-formed PLLA and PBSU grafts within the corresponding phase at the interface. Such a mechanism is confirmed by the Monte Carlo simulations. This work provides new opportunities for the fabrication of advanced polymer blend nanocomposites.

Stabilizing Polymeric Interface by Janus Nanosheet

A strategy is proposed to stabilize the polymeric interface by using the irregular Janus nanosheet (JNS). The poly(vinylidene fluoride) (PVDF)/poly(l-lactic acid) (PLLA) at 60/40 (wt/wt) with a bi-continuous structure is selected as the model melt blend, and the PMMA/epoxy JNS is synthesized and used as the compatibilizer. The JNS is preferentially located at the interface. The interfacial coverage by the JNS reaches a saturated state forming the interconnected jamming structure at 0.5 wt% of the JNS. The interface is thus stabilized which is well preserved after annealing at high temperature. After selectively etching PLLA, the robust PVDF porous material is derived with the JNS armored at the pore skeleton surface. The porous material provides a universal scaffold to achieve stable functional materials after filling the pores.

Supertough and Transparent Poly(lactic acid) Nanostructure Blends with Minimal Stiffness Loss

This contribution is an attempt to explore the effectiveness of a series of newly obtained thermoplastic elastomers (TPEs) as a toughening agent for modifying poly(lactic acid) (PLA). The TPEs, including ionically modified isotactic polypropylene-graft-PLA (iPP-g-PLA) copolymers with explicit graft length, graft density, and ionic group content, and an iPP-g-PLA copolymer with a very high molecular weight and explicit graft density, were elaborately designed and synthesized. The semicrystal or rubbery copolymer backbone originated from iPP was designed to improve the toughness and maintain a relatively high strength, while the grafted PLA side chain was to ensure a high level of compatibility with the PLA matrix. To obtain further enhancement in interfacial reinforcement, the imidazolium-based ionic group was also added during graft onto reaction. All of these graft copolymers were identified with randomly distributed PLA branches, bearing a very high molecular weight ((33-398) × 10⁴) and very high PLA content (57.3-89.3 wt %). Unprecedentedly, with a very small amount of newly designed TPE, the modified PLA blends exhibited a significantly increased elongation at break (up to about 190%) and simultaneously retained the very high stiffness and excellent transparency. The nanometer-scale phase-separated particles with good compatibility and refractive index matching to the PLA matrix were demonstrated to play a crucial role in the excellent performance. The findings suggested that the newly designed iPP-g-PLA copolymers are very economic, promising, and effective modifying agents for developing highly transparent and tough PLA-based sustainable materials.

Distinctive Morphology Modifiers for Polymer Blends: Roles of Asymmetric Janus Nanoparticles during Phase Separation

Janus nanoparticles (JPs), which are anisotropic nanoparticles with multiple constituting parts, have been recognized as superior compatibilizers for polymer-blend-based nanocomposites. However, so far, most studies focused on the effects of symmetric JPs on the phase separation dynamics of polymer blends, while the roles of asymmetric JPs during phase separation remain unclear. In this work, the phase separation dynamics of symmetric blends compatibilized by JPs with various compositions was studied by using dissipative particle dynamics (DPD) simulations. It was found that the blends compatibilized by asymmetric JPs tend to undergo morphological transitions from bicontinuous networks to droplets-in-matrix structures at the late stage of phase separation, which is due to the influence of asymmetric JPs on the energetically favored curvature of the interfaces between polymer domains. Such a mechanism is absent for symmetric JPs and other compatibilizers (e.g., triblock copolymers and homogeneous particles) because they lack the unique combination of chemical asymmetry with the particulate nature like the asymmetric JPs. Moreover, it was observed that the asymmetric JPs can stably localize at the interfaces and act as efficient compatibilizers only when the fraction of the minor constituent part exceeds a critical value. These findings not only shed light upon the roles of asymmetric JPs as compatibilizers but also indicate a promising strategy for designing polymer-blend-based nanocomposites with tailor-made structures.

Reactive Comb Polymer Compatibilized Immiscible PVDF/PLLA Blends: Effects of the Main Chain Structure of Compatibilizer

The compatibilizer with double comb structure has a superior compatibilizing effect for immiscible polymer blends due to the symmetrical structure on both sides of main chains. Extensive study related to the architectural effects of compatibilizer on the compatibilization has mainly focused on the side chains. We investigated the influence of the compatibilizer-main-chain structure on the compatibilizing effect for immiscible poly(vinylidene fluoride)/poly(L-lactic acid) (PVDF/PLLA) blends. Two reactive-comb compatibilizers with polystyrene (PS) and polymethylmethacrylate (PMMA) as main chains and PMMA as the side chains have been synthesized. PS is immiscible with both PLLA and PVDF, while PMMA is miscible with PVDF. It was found that both compatibilizers can improve the compatibility between the PLLA and PVDF, with different compatibilization effects. In the PVDF/PLLA (50/50) blends, 1 wt.% poly(styrene-co-glycidyl methacrylate)-graft-poly(methyl methacrylate) (RC-SG) tuned the morphology from the droplet-in-matrix structure to the co-continuous structure, while the blends with poly(methyl methacrylate-co-glycidyl methacrylate)-graft-poly(methyl methacrylate) (RC-MMG) kept the sea-island structure with even 3 wt.% loading. Moreover, RC-SG induces a wider co-continuous interval range than RC-MMG. The co-continuous structure obtained by RC-SG was also more stable than that by RC-MMG. It was further found that RC-SG-compatibilized PVDF/PLLA blends exhibit higher mechanical properties than the RC-MMG-compatibilized blends.

Physical and Rheological Properties of Maleic Anhydride-Incorporated PVDF: Does MAH Act as a Physical Crosslinking Point for PVDF Molecular Chains?

The miscibility and physical and rheological properties of binary poly(vinylidene fluoride)/maleic anhydride (PVDF/MAH) blends have been systematically investigated. MAH was found to be miscible with PVDF by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Fourier transform infrared (FTIR) investigations provided positive evidence for the specific interaction between the carbonyl groups of MAH and the methylene groups of PVDF. Rheological measurements showed that both the storage modulus and the melt viscosity of PVDF increase with the addition of MAH, followed by a decrease with excess MAH. In addition, the elongation of the PVDF/MAH blend with 10 wt % MAH is 589.7%, which is almost 5 times that of neat PVDF. It is concluded that MAH small molecules act as physical "crosslinking" points for the neighboring PVDF molecule chains due to this specific interaction between PVDF and MAH. Such a physical crosslinking function enhances the storage modulus, viscosity, and mechanical properties of PVDF.

Molecular Engineering of the Cellulose-Poly(Caprolactone) Bio-Nanocomposite Interface by Reactive Amphiphilic Copolymer Nanoparticles

A molecularly engineered water-borne reactive compatibilizer is designed for tuning of the interface in melt-processed thermoplastic poly(caprolactone) (PCL)-cellulose nanocomposites. The mechanical properties of the nanocomposites are studied by tensile testing and dynamic mechanical analysis. The reactive compatibilizer is a statistical copolymer of 2-(dimethylamino)ethyl methacrylate and 2-hydroxy methacrylate, which is subsequently esterified and quaternized. Quaternized ammonium groups in the reactive compatibilizer electrostatically match the negative surface charge of cellulose nanofibrils (CNFs). This results in core-shell CNFs with a thin uniform coating of the compatibilizer. This promotes the dispersion of CNFs in the PCL matrix, as concluded from high-resolution scanning electron microscopy and atomic force microscopy. Moreover, the compatibilizer "shell" has methacrylate functionalities, which allow for radical reactions during processing and links covalently with PCL. Compared to the bio-nanocomposite reference, the reactive compatibilizer (<4 wt %) increased Young's modulus by about 80% and work to fracture 10 times. Doubling the amount of peroxide caused further improved mechanical properties, in support of effects from higher cross-link density at the interface. Further studies of interfacial design in specific nanocellulose-based composite materials are warranted since the detrimental effects from CNFs agglomeration may have been underestimated.

A brief review on carbon selective membranes from polymer blends for gas separation performance

The development of carbon membranes for the separation of various gases has gained interest among researchers due to their superior performance in gas separation. The preparation of carbon membranes by blending materials has many advantages including time and cost effectiveness for tuning the properties of the membranes. Here we review the recent research progress that has been made in the context of breakthroughs and challenges in the development of carbon membrane materials. In addition, we provide information regarding carbon membrane fabrication in terms of the selection of precursors and additives, carbon membrane process conditions, and coating conditions that influence the performance of gas separation of the resulting carbon membranes. The perspectives and future research directions for carbon membranes are also presented.

Distinctive phase separation dynamics of polymer blends: roles of Janus nanoparticles

The present work demonstrates that Janus nanoparticles uniquely promote the phase separation of polymer blends at the early stage of spinodal decomposition, but impede it at the late stage.

Amphiphilic Janus nanosheets by grafting reactive rubber brushes for reinforced rubber materials

An amphiphilic Janus nanosheet with different reactive rubber brushes on two opposite sides can simultaneously strengthen and toughen rubber blends.

Rheology⁻Microstructure Relationships in Melt-Processed Polylactide/Poly(vinylidene Fluoride) Blends

In this study, small amplitude oscillatory shear tests are applied to investigate the rheological responses of polylactide/poly(vinylidene fluoride) (PLA/PVDF) blends and to correlate their viscoelastic properties with the morphological evolutions during processing. Although the analysis of the elastic moduli reveals some changes as a function of blend composition and processing time, the weighted relaxation spectra are shown to be more useful in detecting changes. The analysis demonstrates that when PVDF, i.e., the more viscous phase, is the matrix, the blend relaxes cooperatively and only a single relaxation peak is observed. By contrast, blends with highly concentrated morphologies do not fully relax, showing instead an upward increasing trend at longer times. This outcome is attributed to the broad distribution of highly concentrated droplets with a high probability of droplet⁻droplet contacts. Dynamic mechanical analysis (DMA) reveals that crystalline segmental motions attributed to the α-relaxation of PVDF at around 100 °C are restricted by the highly concentrated morphology of the 50/50 PLA/PVDF blend processed for 10 min. Relaxation analyses of the blends via dynamic oscillatory shear tests and DMA are shown to be powerful tools for investigating small microstructural changes in immiscible polymer blends.

Reactive Compatibilization: Formation of Double-Grafted Copolymers by In Situ Binary Grafting and Their Compatibilization Effect

Reactive compatibilizers are usually used to enhance the compatibility of immiscible polymer blends. However, reactive linear compatibilizers containing reactive groups on the main chains form graft copolymers during reactive blending, and such graft copolymers with an asymmetric molecular structure are often "pulled in" or "pulled out" under mechanical shear. Double-grafted compatibilizers have a symmetric structure, and they usually exhibit higher compatibilizing efficiency. In this work, we propose a binary grafting strategy during melt blending to form compatibilizers located at the interface of an immiscible polymer blend. Specifically, poly(methyl methacrylate) (PMMA) oligomer with carboxylic end groups (PMMA-COOH) and poly(styrene-co-glycidyl methacrylate) (SG) copolymer were simultaneously incorporated into immiscible poly(vinylidene fluoride)/poly(l-lactic acid) (PVDF/PLLA) blends. The carboxylic acid groups of both the PMMA oligomer and PLLA can react with the epoxide groups on the SG main chains. Therefore, novel compatibilizing polymers with both PMMA and PLLA chains grafted onto the SG main chains form in situ. The grafted PMMA chains can entangle with PVDF, and the grafted PLLA chains are embedded in the PLLA phase, so the double-grafted copolymers act as effective compatibilizers for the PVDF/PLLA blends. Moreover, the effects of the PMMA molecular weight and PMMA loading (number of grafted PMMA side chains) on the compatibilization efficiency were investigated. The compatibilizing efficiency increases with increasing molecular weight and number of side chains in the ranges considered in this study. This one-pot synthesis of double-grafted compatibilizers by in situ grafting provides a new and simple method to prepare double-comb compatibilizers, and it offers the possibility of high-efficiency compatibilization.

Reactive Nanoparticles Compatibilized Immiscible Polymer Blends: Synthesis of Reactive SiO2 with Long Poly(methyl methacrylate) Chains and the in Situ Formation of Janus SiO2 Nanoparticles Anchored Exclusively at the Interface

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-SiO₂ (Epoxy-MSiO₂), and then incorporated the Epoxy-MSiO₂ into the PVDF/PLLA (50/50, w/w) blends by melt blending. PLLA was in situ grafted onto SiO₂ by the reaction of the carboxylic acid groups with epoxide groups on the surface of SiO₂. Therefore, the reacted SiO₂ 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.