Polymerization-induced Phase Separation Research Articles

Preparation and Characterization of Bilayer Polymer-Dispersed Liquid Crystals Doped with Gd2O3 Nanoparticles and Rhodamine B Base Fluorescent Dye.

Using the polymerization-induced phase separation (PIPS) method, bilayer polymer-dispersed liquid crystal (PDLC) films with a PDLC-PVA-PDLC structure were prepared in this work. It was found that all PDLC performance indexes were affected by polymer mesh size after comparing the microscopic morphology and electro-optical properties of samples with different monomer ratios. Gd2O3 nanoparticles and rhodamine B base fluorescent dyes introduced into the bilayer PDLC optimized the samples' electro-optical properties and developed new functionalities. In addition, the bilayer PDLC doped with Gd2O3 and rhodamine B base held excellent progressive driving functions as well as stable durability properties. Samples doped with Gd2O3 nanoparticles and rhodamine B base also produced excellent anti-counterfeiting effects under UV irradiation at different angles, further exploiting the application potential of PDLC.

Hierarchically Structured Metal-Organic Framework Polymer Composites for Chemical Warfare Agent Degradation.

Metal-organic frameworks (MOFs) have captured the imagination of researchers for their highly tunable properties and many potential applications, including as catalysts for a variety of transformations. Even though MOFs possess significant potential, the challenges associated with processing of these crystalline powders into usable form factors while retaining their functional properties limit their end use applications. Herein, we introduce a new approach to construct MOF-polymer composites via 3D photoprinting to overcome these limitations. We designed photoresin composite formulations that use polymerization-induced phase separation to cause the MOF catalysts to migrate to the surface of the printed material, where they are accessible to substrates such as chemical warfare agents. Using our approach, MOF-polymer composites can be fabricated into nearly any shape or architecture while retaining both the excellent catalytic activity at 10 wt % loading of the MOF components and the flexible, elastomeric mechanical properties of a polymer.

Design Rationale for CO2 Separation Membranes with Micropatterned Surface Structures.

Here, we report the design rationale of CO2 separation membranes with micropatterned surface structures. Thin film composite (TFC) membranes with micropatterned surface structures were fabricated by spray coating amine-containing hydrogel particles on the top of micropatterned porous support membranes, which were synthesized by a polymerization-induced phase separation process in a micromold (PIPsμM). The pore size of the support membranes was optimized by tuning the proportion of good and poor solvents for the polymerization process so that the microgels would be assembled as a defect-free separation layer. The relationship between the size of the micropatterned structures on the surface of the support membrane and the thickness of the separation layer was optimized to maximize the surface area of the separation layer. The rationally designed micropatterned TFC membrane showed a CO2 permeability (835.8 GPU) proportional to the increase in surface area relative to the flat membrane with a high CO2/N2 selectivity of 58.7. The rational design for micropatterned TFC membranes will enable the development of inexpensive and high-performance functional membranes not only for CO2 separation but also for other applications such as water treatment and membrane reactors.

3D-Printed Porous Supramolecular Sorbents for Cobalt Recycling.

Electronic waste recycling is a recognized global challenge that requires new strategies to bind and release critical materials selectively, such as cobalt present in lithium-ion batteries. To address this challenge, hierarchical 3D-printed porous polymer scaffolds bearing supramolecular receptors were prepared using vat photopolymerization and their cobalt binding profiles were examined as a function of matrix polarity. By combining high-resolution digital light processing (DLP) with polymerization-induced phase separation (PIPS), functional acrylic copolymer networks with micrometer-level precision of geometry and nanometer-level pores were generated. Covalent integration of a methacrylate-functionalized bisdicyclohexyl acetamide (BDCA-MA) receptor enabled binding and release of cobalt(II) chloride (CoCl2) via a solvent polarity switch mechanism involving a change in solvent from ethanol to water. The present structures proved reusable as shown by sustained high binding efficiency over five bind and release cycles. This platform represents a "green" and energy conscious method for future electronic waste recycling.

Biowaste-based porous carbon nanoparticle doped polymer dispersed ferroelectric liquid crystal composites: an impact on optical and electrical properties

Bio-waste-based porous carbon nanoparticles (PCNPs) were synthesized using green synthesis and investigated their doping effect on the optical and electrical properties of polymer-dispersed ferroelectric liquid crystals (PDFLCs) composites. Here we employed the polymerization-induced phase separation (PIPS) approach for constructing the PDFLCs. Our results indicate that the dispersion of PCNPs into the PDFLC material results in an alteration to several physical parameters, including morphology, dielectric permittivity, conductivity and optical band gap. A decrease in the ac conductivity of the doped samples was seen. Additionally, UV-Visible study reveals that inclusion of PCNPs resulted in a decrease in the optical band gap of PDFLC, with a value of approximately 3.1 eV. These findings demonstrate the potential of using PCNPs as dopants in PDFLCs for various applications, including sensing, energy storage and optoelectronics.

In Situ Ceramization of Nanoscale Interface Enables Aerogel with Thermal Protection at 1950 °C.

Conventional carbon fiber felt-reinforced aerogel composites are often used as lightweight thermal protection systems (TPSs) for aerospace craft. However, due to their poor oxidation resistance, they have gradually failed to handle increasingly harsh thermal environments. In this work, a nanoscale composite coating interface of SiC-ZrC ceramic precursor is first constructed on the fiber surface. Subsequently, using the coated fiber felt as a three-dimensional skeleton and through polymerization-induced phase separation, an aerogel composite with excellent thermal protection in extreme thermal environments is prepared. Owing to the in situ ceramization of this nanoscale interface at ultrahigh temperatures, the back temperature of the 12 mm thick aerogel is only 147 °C after exposure to an oxyacetylene flame at 1950 °C for 70 s. Meanwhile, the central region of the aerogel recedes by only 7%. Not only does this work provide a way to enhance aerogels by constructing a self-ceramizable nanoscale interface it is also expected that the developed aerogel composite can be applied in the ultrahigh-temperature thermal protection of future aerospace craft.

Modeling the competition between phase separation and polymerization under explicit polydispersity.

The dynamics of phase separation for polymer blends is important in determining the final morphology and properties of polymer materials; in practical applications, this phase separation can be controlled by coupling to polymerization reaction kinetics via a process called 'polymerization-induced phase separation'. We develop a phase-field model for a polymer melt blend using a polymerizing Cahn-Hilliard (pCH) formalism to understand the fundamental processes underlying phase separation behavior of a mixture of two species independently undergoing linear step-growth polymerization. In our method, we explicitly model polydispersity in these systems to consider different molecular-weight components that will diffuse at different rates. We first show that this pCH model predicts results consistent with the Carothers predictions for step-growth polymerization kinetics, the Flory-Huggins theory of polymer mixing, and the classical predictions of spinodal decomposition in symmetric polymer blends. The model is then used to characterize (i) the competition between phase separation dynamics and polymerization kinetics, and (ii) the effect of unequal reaction rates between species. For large incompatibility between the species (i.e. high χ), our pCH model demonstrates that the strength for phase separation directly corresponds to the kinetics of phase separation. We find that increasing the reaction rate k̃, first induces faster phase separation but this trend reverses as we further increase k̃ due to the competition between molecular diffusion and polymerization. In this case, phase separation is delayed for faster polymerization rates due to the rapid accumulation of slow-moving, high molecular weight components.

3D printing of reactive macroporous polymers via thiol-ene chemistry and polymerization-induced phase separation.

Using thiol-ene chemistry, polymerization-induced phase separation, and DLP 3D printing, we present a method for manufacturing reactive macroporous 3D structures. This approach enables the fabrication of structures with tunable physicochemical properties and compressibility. Moreover, it facilitates post-functionalization through thiol-Michael addition reactions, thereby expanding performance and application potential.

DLP 3D printing of electrically conductive hybrid hydrogels via polymerization-induced phase separation and subsequent in situ assembly of polypyrrole

A porous hydrogel was constructed through polymerization-induced phase separation and DLP 3D printing. After in situ formation of an interconnected polypyrrole network, the hybrid hydrogel shows an exceptional electrical conductivity of 264 S m−1.

Rheological Properties Study of Polymer Dispersed Liquid Crystals Doped by SiO2 Nanoparticles

The present report discusses the development of a novel nano-composite using a polymer dispersed liquid crystal (PDLC) and inorganic silicon dioxide (SiO2) nanoparticles. The aim of this work was to investigate the effect of the SiO2 nanoparticles on the rheological properties of the PDLC films. In our research described in this paper SiO2 nanoparticle-doped polymer dispersed liquid crystal films were made from a mixture of ethylene glycol phenyl ether methacrylate (EGPEMA) pre-polymer, 4-Cyano-4′-pentylbiphenyl (5CB) liquid crystals (LC) and SiO2 nanoparticles by the polymerization induced phase separation (PIPS) process. Doping the PDLC systems with SiO2 improved the rheological properties of these materials; the percolation (network formation) observed reflected the good interfacial adhesion between the nanoparticles, the polymer matrix and the LC. On the other hand, a decrease in the storage modulus (G′) and loss modulus (G″) of the PDLC systems after addition of the SiO2 nanoparticles confirmed their high flexibility and low crystallinity. A slight increase in G′ at 0.05 wt.% SiO2 resulted in the good mechanical strength of the doped PDLC. The viscoelastic behavior of the doped and undoped PDLC systems was confirmed at high frequencies. Thermal characterization by differential scanning calorimetry (DSC) showed a decrease in the glass transition temperature (Tg) of the PDLC with 0.05 wt.% of SiO2 nanoparticles, which showed that we had a more flexible material.

Multifunctional Separator for Li-Ion Batteries Enabling Acid Scavenging and Long Cyclability

The membrane separator is indispensable in lithium-ion batteries (LIBs), electrically isolating the electrodes while hosting liquid electrolyte for facile ion transport. Microporous polyolefin materials, consisting of polyethylene (PE) and/or polypropylene (PP), represent the state-of-the art in separator technology. They offer sufficient mechanical properties, chemical inertness, effective pore sizes <100 nm, porosity ranging from 30-78%, and relatively low costs. However, safety issues associated with thermal shrinkage above 70℃ and poor electrolyte wettability are significant limitations. Replacing these conventional polyolefin separators with multifunctional microporous membranes provides opportunities to address these limitations and other challenges in lithium ion batteries. LiMn2O4 cathodes, for example, attract widespread interest due to the abundance and low cost of Mn, especially in comparison to Co, and reasonable energy densities. However, these cathodes do not provide the calendar and cycle life of the layered oxide cathodes, especially at elevated temperatures (>50°C), due to dissolution of Mn and structural instabilities.1 One of the underlying reasons is the presence of HF in commercial LiPF6-carbonate electrolytes; HF will attack and dissolve the Mn, leading to severe capacity decay, as shown in Figure 1.2 Chemically active multifunctional separator can scavenge HF from the electrolyte, improving the stability of LiMn2O4, but they must be fabricated by low cost, scalable processes without compromising other separator properties.Herein, a multifunctional separator will be described, wherein poly(4-vinylpyridine) (P4VP) is incorporated into separators prepared by polymerization induced phase separation (PIPS). In PIPS, a homogenous solution of difunctional monomers and porogen is polymerized; the difunctional monomers polymerize and crosslink while the porogen phase separates into nanoscale domains. Our previous study employed PIPS to prepare highly porous and thermally stable separators, exhibiting comparable ion transport to conventional Celgard 2500 Polypropylene (PP) separators and negligible thermal shrinkage at 150 °C (digital images in Figure 1).3 Moreover, when incorporated into LIB half cells, these separators enable better electrochemical performance than Celgard 2500 separators due to their reduced thicknesses and superior electrolyte uptake. In the study, P4VP is integrated with the PIPS process to scavenge both HF and PF5 (precursor to HF) through acid-base interactions. A thin layer of P4VP coating was fabricated via initiated chemical vapor deposition (iCVD) process and makes full use of high porosity of separators due to the conformal nature of the coating, increasing the surface area to scavenge the acids. The P4VP-coated PIPS separator enables better capacity retention in Mn-based cathode materials, relative to cells using inert polyolefin separators. The scavenged concentration of HF and transition metal will be compared to validate the HF scavenging property. Post-mortem analysis of the Li anode also confirms the suppression of Mn dissolution and deposition on the anode at elevated temperatures (50°C).

Integrating radical polymerization and non-solvent induced phase inversion strategy for functionalized ultrafiltration membrane fabrication

The facile fabrication of high-performance membranes with attractive water permeability, retention ability, and fouling resistance holds a significant interest within the realm of membrane technology advancement. In this study, we developed an integrated radical polymerization and non-solvent induced phase separation strategy for functionalized ultrafiltration membrane fabrication. This innovative approach enabled the compositive of membrane preparation and functionalization by introducing a radical initiator into the casting solution and incorporating functional monomers into the coagulation bath. We demonstrated the effectiveness of this integrated membrane fabrication method by using zwitterionic sulfobetaine methacrylate (SBMA) as a classic test case. By optimizing radical polymerization time, the SBMA/PVDF membrane achieved simultaneous enhancements in water flux (187.6 L m−1 h−1), retention ability (99.0 % rejection for BSA protein), and antifouling property (9.8 % improvement) compared with the pristine PVDF membrane. Additionally, the microstructure, hydrophilicity, and zeta potential of SBMA/PVDF membranes were deliberately controlled by regulating the radical polymerization time. Furthermore, we demonstrated the universal applicability of the integrated membrane fabrication method by replacing SBMA with antimicrobial agent monomers in the coagulation bath. Our research contributes to the field of functionalized ultrafiltration membrane fabrication by developing the integration strategy of radical polymerization and non-solvent induced phase separation.

One-step green construction of granular composite hydrogels for ammonia nitrogen recovery from wastewater for crop growth promotion

The great application potential of hydrogel adsorbent in water treatment has been widely reported in recent years. However, practical application is severely restricted due to the tedious preparation procedures, high energy consumption, and potential environmental threat of spent adsorbent after adsorption. To address these challenges, a new method was proposed in this study to prepare granular hydrogel composites through one-step polymerization induced phase separation (PIPS), initiated via a redox reaction consisting with calcined oil shale semi-coke (COSSC) and active ingredients of in green tea (GT) at 40 °C. Then granular hydrogel was applied to remove NH4-N in wastewater, and the spent adsorbent after adsorbing was used as the medium for plant growth. The granular hydrogel exhibited a favorable swelling capacity of 205 g/g and excellent adsorption capacity of 40.2 mg/g for NH4-N. Remarkably, the adsorption process achieved equilibrium only within 30 min. To avoid the influence of soil and other factors, we conducted a soilless cultivation experiment, and the results showed that the total seed biomass of mung bean increased by 33.69% with adding 1% of spent hydrogels into the culture medium. Based on above excellent performance, this study presented a feasible idea for the green preparation granular hydrogel composites and offered a promising strategy for the sustainable utilization of spent adsorbent.

A novel low-voltage fast-response electrically controlled dimming film based on fluorinated PDLC for smart window applications

A fluorinated polymer dispersed liquid crystal (PDLC) film with low operating voltage and high contrast ratio was successfully fabricated via the ultraviolet-initiated polymerization induced phase separation method. Effects of chemical structure and weight ratio of fluorinated monomers on the properties of PDLC films were systematically investigated through characterization of electro-optical response, micro morphology, optical spectrum and thermal analysis. Compared with the primitive sample, the addition of fluorinated monomers effectively improves the electro-optical properties of the film. The threshold voltage (Vth) is decreased by 39.7 % from 6.3 V to 3.8 V and the saturation voltage is reduced by 30 % from 15.8 V to 11.8 V for a 20 μm-thick film. Besides, the contrast ratio is improved to 110. Meanwhile, its thermal stability and hydrophobic property are also improved. Additionally, due to the abundance of C-O and C-F bonds in these compounds and the porous structure, the prepared film allows for transmittance modulation of sunlight. This research is anticipated to provide an innovative approach to optimize the performance of PDLC films for practical applications.

Preparation of triple-layer polymer dispersed liquid crystal films with progressive driving functionality

ABSTRACT In this paper, three single-layer polymer dispersed liquid crystal (PDLC) films with different electro-optical properties were prepared by the polymerisation-induced phase separation (PIPS) method firstly. The triple-layer PDLC film with progressive drive function was obtained by integrating three single-layer PDLC films. In contrast to the single-layer PDLC film, it is possible to make the triple-layer PDLC film enter the intermediate state between the on-state and off-state, while its transmittance can be controlled in low voltage by adjusting the applied voltage. It was found that the polymerisation temperature, time and UV intensity had significant effects on the electro-optical properties of the triple-layer PDLC films by comparing the electro-optical curves at various temperatures, times and UV intensities. The sample obtained under the optimal polymerisation condition showed a 31% reduction in threshold voltage, a 56% reduction in saturation voltage, a 20% reduction in off-state response time, and a 21% increase in contrast ratio than the original condition. The possibility to broaden the application area of PDLC is offered.

Facile fabrication of hollow molecularly imprinted polymer microspheres via pickering emulsion polymerization stabilized with TiO2 nanoparticles

The polymer microspheres with hollow structure are of technological importance in the removal of pollutants because of the large specific surface area and low mass transfer resistance. In this work, we employ the Pickering emulsion polymerization stabilized with TiO2 nanoparticles to build the molecularly imprinted polymers microspheres with hollow structure (H-MIPs) for the precise recognition of dibutyl phthalate (DBP), which would influence the biological reproductive system and endocrine system as a typical endocrine disrupting compound. The polymerization induced phase separation occurring within Pickering emulsion droplets plays a significant role in the formation of hollow structure. The morphology and structure of H-MIPs were observed via optical microscope and field emission scanning electron microscope, respectively. The results indicate that H-MIPs microspheres are of irregular spherical form with sunken surface and perfect hollow structure. The forming process of the hollow structure was analyzed in detail. Besides, the chemical structure and thermal stability of H-MIPs and H-NIPs were characterized by fourier transform infrared spectroscopy and thermal gravimetric analysis, respectively. The binding performance of H-MIPs and H-NIPs was investigated through a series of binding experiments, which consist of the binding kinetics, binding isotherm, selective test and reusability experiment. The results show that H-MIPs microspheres exhibit remarkable binding kinetics towards DBP, and the saturated adsorption time is not more than 30 min. Apart from the fast binding rate, H-MIPs also show considerable binding amount, accurate binding selectivity and good regenerability. The imprinting factor could reach to 2.56, and the binding amount towards DBP remains at a relatively high level within 3 cycles. The prepared H-MIPs microspheres have broad application prospects in environmental and analytical field involved DBP, and the study also offers an alternative method for the facile building of H-MIPs microspheres.

In-situ polymerization induced phase separation to develop high-performance self-healable polymeric electrolytes for lithium metal battery

In-situ polymerization induced phase separation to develop high-performance self-healable polymeric electrolytes for lithium metal battery

Energy saving phase change energy storage thermochromic liquid crystal display

Phase change energy storage microcapsules (PCESM) improve energy utilization by controlling the temperature of the surrounding environment of the phase change material to store and release heat. In this paper, a phase change energy storage thermochromic liquid crystal display (PCES-TC-LCD) is designed and prepared for the first time. The as-prepared PCES-TC-LCD has a stable bilayer structure, where the lower layer is a thermochromic LC layer produced by centrifugal spin coating and high temperature curing, and the upper layer is a polymer-stabilized liquid crystal (PSLC) film with phase change energy storage properties obtained by polymerization-induced phase separation method. The prepared PCES-TC-LCD can realize the functions of triple-field driven and phase change energy storage, which has strong research value. In the performance experiments, the electro-optical properties of PCES-TC-LCD were analyzed and optimized by three sets of experiments on liquid crystal content, polymerization time, and PCESM content. In the film formation study, PCES-TC-LCD based on rigid/flexible substrates were prepared, respectively. The phase change energy storage function of PCES-TC-LCD was performed by differential scanning calorimetry (DSC) and infrared thermography. The devices formed on rigid or flexible substrates with stable phase change energy storage performance, which has great application value by reducing the external energy input, prolonging the thermochromic time and achieving energy saving effects.

Controlling Nano-to-Microscale Multilevel Architecture in Polymeric Microfibers through Polymerization-Induced Spontaneous Phase Separation.

Hierarchically structured polymeric fibers, composed of structural nanoscale motifs that assemble into a microscale fiber are frequently found in natural fibers including cellulose and silk. The creation of synthetic fibers with nano-to-microscale hierarchical structures represents a promising avenue for the development of novel fabrics with distinctive physical, chemical, and mechanical characteristics. In this work, we introduce a novel approach for creating polyamine-based core-sheath microfibers with controlled hierarchical architectures. This approach involves a polymerization-induced spontaneous phase separation and subsequent chemical fixation. Through the use of various polyamines, the phase separation process can be manipulated to produce fibers with diverse porous core architectures, ranging from densely packed nanospheres to segmented "bamboo-stem" morphology. Moreover, the nitrogen-rich surface of the core enables both the chemisorption of heavy metals and the physisorption of proteins and enzymes. Our method offers a new set of tools for the production of polymeric fibers with novel hierarchical morphologies, which has a high potential for a wide range of applications such as filtering, separation, and catalysis.

Fluorescent Dye-Doped Brightening Polymer-Stabilized Bistable Cholesteric Liquid Crystal Films.

Brightening polymer-stabilized bistable cholesteric liquid crystal (PSBCLC) films with doped fluorescent dyes were prepared using the polymerization-induced phase separation (PIPS) method. The transmittance performance behavior of these films in both states (focal conic and planar) and absorbance change in multiple dye concentrations were studied using a UV/VIS/NIR spectrophotometer. The change occurring in dye dispersion morphology with different concentrations was obtained by means of the polarizing optical microscope. The maximum fluorescence intensity of different dye-doped PSBCLC films was measured using a fluorescence spectrophotometer. Moreover, the contrast ratios and driving voltages of these films were calculated and recorded to demonstrate film performance. Finally, the optimal concentration of dye-doped PSBCLC films with a high contrast ratio and a relatively low drive voltage was found. This is expected to have great potential applications in cholesteric liquid crystal reflective displays.