Formation Of Interpenetrating Polymer Networks Research Articles

Characterization Methods to Determine Interpenetrating Polymer Network (IPN) in Hydrogels.

Significant developments have been achieved with the invention of hydrogels. They are effective in many fields such as wastewater treatment, food, agriculture, pharmaceutical applications, and drug delivery. Although hydrogels have been used successfully in these areas, there is a need to make them better for future applications. Interpenetrating polymer networks (IPNs) can be created to make hydrogels more adjustable and suitable for a specific purpose. IPN formation is an innovative approach for polymeric systems. It brings two or more polymer networks together with entanglements. The properties of IPNs are controlled by its chemistry, crosslinking density, and morphology. Therefore, it is necessary to understand characterization methods in order to detect the formation of IPN structure and to develop the properties of hydrogels. In recent studies, IPN structure in hydrogels has been determined via chemical, physical, and mechanical methods such as Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X-ray diffraction (XRD), and rheology methods. In this paper, these characterization methods will be explained, recent studies will be scrutinized, and the effectiveness of these methods to confirm IPN formation will be evaluated.

'Donor-acceptor', 'interpenetrating polymer network' and 'electrostatic self-assembly' work in tandem to achieve extraordinary specific shielding effectiveness.

The exploration of 'electrostatic self-assembly' on solid surfaces has garnered significant interest across various fields. With the sophistication of gadgets, managing electromagnetic interference (EMI) from stray signals, especially in stealth applications, necessitates materials that can absorb microwaves. A promising approach involves integrating lightweight self-healing polymeric materials. This study employs electrostatic self-assembly to design a carbon nanotube structure on an interpenetrating polymer network (IPN) made of PVDF and bismaleimide (BMI)-grafted dopamine hydrochloride, enhancing mechanical integrity through well-formed IPNs. Graphene oxide (GO) is introduced before IPN formation to facilitate an 'acceptor-donor' interaction via the Diels-Alder adduct between BMI and GO, which binds with multi-walled carbon nanotubes (MWCNTs). MWCNTs, modified with PQ7 or PDDA for a positive charge, self-assemble onto the IPN-GO construct, creating a lightweight and chemically stable structure capable of absorbing electromagnetic radiation. The 21 μm thick construct exhibits enhanced microwave absorption within the X-band (8.2-12.4 GHz), with a specific shielding effectiveness of 8637 dB cm2 g-1 and a green index (gs ≈ 1.41). The construct is coated with self-healable polyetherimide (PEI) containing exchangeable disulfide bonds to address maintenance challenges, providing heat-triggered self-healing properties. These innovative structures offer solutions for 5G and IoT applications where lightweight, durable, and multifunctional properties are essential for effectively shielding electronic devices from stray signals.

Core-shell structured tow-pregs enabled additive manufacturing of continuously reinforced thermoset composites

One of the major challenges in thermally curable polymer composite additive manufacturing is the slow curing time of thermally curable resins, coupled with a significant drop in thermoset viscosity upon heating, making the formation of complex shapes difficult. To tackle these issues, we have introduced a novel rapid composite preformation strategy called Tow-Preg Cladding (TPC). This technique involves the use of a thin and rapidly curable dual-cure resin, which combines a thermally curable resin (such as epoxy) with a fast photo-curable resin. The dual-cure resin is applied as a coating over a thermally curable resin tow-preg, enabling the formation of a rigid cladding that supports and shapes the tow-pregs into the desired geometries and patterns. The key advantage of this approach lies in the sequential formation of an interpenetrating polymer network (IPN) at the interlayer between laminates, resulting from the curing of the photocurable resin and the thermally curable resin sequentially. This IPN formation enhances interlaminar bonding in the composite, contributing to its overall strength and performance. The composites produced using this technique exhibited impressive mechanical properties, including longitudinal tensile strength of 1058.2 MPa, longitudinal tensile modulus of 74.2 GPa, flexural strength of 1080.4 MPa, and flexural modulus of 41.7 GPa. Overall, our Tow-Preg Cladding approach shows great promise in overcoming the challenges associated with thermally curable polymer composite additive manufacturing. It offers a viable solution to creating strong, shape-specific thermoset composites efficiently with enhanced mechanical properties.

The synergistic impacts of hybrid nanofillers of graphene nanoplatelets/carbon nanotubes on curing behavior of an epoxy‐vinyl ester interpenetrating polymer network nanocomposite coating

AbstractThis study investigated the synergistic effects of hybrid graphene nanoplatelet (GnP)/multi walled carbon nanotube (MWCNT) nanofillers at various loadings on the kinetics of curing of the epoxy (EP)/vinyl ester (VE) interpenetrating polymer network (IPN) system, with a mass ratio of 1:1. Fourier transform infrared spectroscopy (FTIR), dynamic mechanical thermal analyzer (DMTA) and differential scanning calorimetry (DSC) were used to monitor the interpenetration process of EP and VE and likely interactions between the components of the different resin systems in IPN. The curing behavior of all prepared samples under non‐isothermal conditions was studied using DSC at four heating rates. Two different isoconversional approaches were applied to evaluate the reaction kinetics, that is, the Friedman and the advanced Vyazovkin methods. The obtained activation energy curves for all samples revealed a complex curing behavior involving three stages; early IPN stage, IPN growth stage, and late IPN stage. Then, the activation energy values for each reaction step were determined based on the Friedman method. The presence of GnP/MWCNT nanoparticles showed no catalytic effect on the reaction of VE with methyl ethyl ketone peroxide (MEKP). In contrast, incorporating GnP/MWCNT nanoparticles significantly decreases the activation energy values of the reaction of ring opening of epoxides with methyl tetrahydrophthalic anhydride (MTHPA) 1‐methyl imidazole (‐Mi) and the reaction of esterification of the hydroxyl groups of VE with MTHPA.Highlights Model‐free methods used to curing study of epoxy‐vinyl ester IPN nanocomposites FTIR, DSC and DMTA used for evaluation IPN formation of EP/VE It showed that the improvement of dispersion and compatibility by using of GnP/MWCNT hybrid Frideman and Vyazovkin methods used to calculate Ea of nanocomposites DSC thermograms were deconvoluted into three individual peaks.

Construction of starch-sodium alginate interpenetrating polymer network and its effects on structure, cooking quality and in vitro starch digestibility of extruded whole buckwheat noodles

The effects of different concentrations and crosslinking methods of sodium alginate (SA) on the structure, cooking quality and in vitro starch digestibility of extruded whole buckwheat noodles were investigated. The results showed that SA could interact with starch through hydrogen bonding, resulting in decrease of the relative crystallinity of starch and improvement of thermal stability. Addition of 1% SA significantly decreased the cooking loss from 15.33% to 8.64%, predicted glycemic index (pGI) from 84.76 to 78.92, and increased the noodle hardness from 2260.16 g to 2809.34 g，as well as the content of resistant starch (RS) from 37.25 to 45.47. Two different crosslinking methods, dynamic blending crosslinking (DBC) and in-situ polymerization crosslinking (ISPC) of SA at 1% induced by CaCl2 were attempted to further improve the properties of extruded buckwheat noodle. SEM showed that both starch gel network and SA gel network existed. DBC induced fast gelation of SA molecules, and the aggregated SA gels disrupted the continuity of the starch gel network. As a comparison, SA network was evenly distributed in starch network when ISPC was applied, indicating Starch-SA interpenetrating polymer network (IPN) was successfully constructed. The resultant cooking loss, surface adhesion and pGI value significantly decreased to 6.58%, −19.59 g s, 69.25, while the noodle hardness and content of RS increased to 6220.90 g, 61.03%, respectively. In a word, the formation of Starch-SA IPN enhanced cooking quality and reduced starch digestibility of extruded whole buckwheat noodles.

Preparation and Performance Evaluation of a Plugging Agent with an Interpenetrating Polymer Network.

In view of the problems of polymer cross-linked elastic particle plugging agents commonly used in oilfields, including easy shear, poor temperature resistance, and weak plugging strength for large pores, the introduction of particles with certain rigidity and network structure, and cross-linking with a polymer monomer can improve the structural stability, temperature resistance, and plugging effect, and the preparation method is simple and low-cost. An interpenetrating polymer network (IPN) gel was prepared in a stepwise manner. The conditions of IPN synthesis were optimized. The IPN gel micromorphology was analyzed by SEM and the viscoelasticity, temperature resistance, and plugging performance were also evaluated. The optimal polymerization conditions included a temperature of 60 °C, a monomer concentration of 10.0-15.0%, a cross-linker concentration of 1.0-2.0% of monomer content, and a first network concentration of 20%. The IPN showed good fusion degree with no phase separation, which was the prerequisite for the formation of high-strength IPN, whereas particle aggregates reduced the strength. The IPN had better cross-linking strength and structural stability, with a 20-70% increase in the elastic modulus and a 25% increase in temperature resistance. It showed better plugging ability and erosion resistance, with the plugging rate reaching 98.9%. The stability of the plugging pressure after erosion was 3.8 times that of a conventional PAM-gel plugging agent. The IPN plugging agent improved the structural stability, temperature resistance, and plugging effect of the plugging agent. This paper provides a new method for improving the performance of a plugging agent in an oilfield.

Simulation of mass transfer and kinetics during double‐network formation using a heterogeneous model

AbstractA detailed heterogeneous model considering the thermodynamic incompatibility was developed to simulate polyurethane/poly(methyl methacrylate) (PU/PMMA) interpenetrating polymer network (IPN) formation. The Gibbs free energy was calculated to predict the phase separation point and a two‐film theory was used to quantify the mass transfer between the PU‐rich phase and the PMMA‐rich phase. Compared with the homogeneous model, the cross‐linking density of PMMA increases rapidly during the network formation, because the monomer dispersion in two phases improves the possibility of free radical cross‐linking reaction, whereas the cross‐linking density of PU is unaffected. Simulations show that the partitioning of monomer significantly affects the PMMA network structure. The phase separation is strongly dependent on the onset of MMA polymerization. The proposed model allows visualizing of the IPN formation process and provides direction for reducing the extent of phase separation. Moreover, the structural information derived from the simulations can be further related to the properties.

CuAAC-methacrylate interpenetrating polymer network (IPN) properties modulated by visible-light photoinitiation.

Interpenetrating polymer networks (IPNs) are a class of materials with interwoven polymers that exhibit unique blended or enhanced properties useful to a variety of applications, ranging from restorative protective materials to conductive membranes and hydrophobic adhesives. The IPN formation kinetics can play a critical role in the development of the underlying morphology and in turn the properties of the material. Dual photoinitiation of copper-catalyzed azide-alkyne (CuAAC) and radical mediated methacrylate polymerization chemistries enable the manipulation of IPN microstructure and properties by controlling the kinetics of IPN formation via the intensity of the initiating light. Specifically, azide and alkyne-based polyethylene glycol monomers and tetraethylene glycol dimethacrylate (TEGDMA) were polymerized in a single pot to form IPNs and the properties were evaluated as a function of the photoinitiating light intensity. Morphological differences as a function of intensity were observed in the IPNs as determined by thermomechanical properties and phase-contrast imaging in tapping mode atomic force microscopy (AFM). At moderate intensities (20 mW/cm2) of visible light (470 nm), the TEGDMA polymerization gels first and therefore forms the underlying network scaffold. At low intensities (0.2 mW/cm2), the CuAAC polymerization can gel first. The ability to switch sequence of gelation and IPN trajectory (simultaneous vs. sequential), affords control over phase separation behavior. Thus, light not only allows for spatial and temporal control over the IPN formation but also provides control over their thermomechanical properties, representing a route for facile IPNs design, synthesis, and application.

Multifunctional Surface Modification of PDMS for Antibacterial Contact Killing and Drug-Delivery of Polar, Nonpolar, and Amphiphilic Drugs.

Medical device-associated infections pose major clinical challenges that emphasize the need for improved anti-infective biomaterials. Polydimethylsiloxane (PDMS), a frequently used elastomeric biomaterial in medical devices, is inherently prone to bacterial attachment and associated infection formation. Here, PDMS surface modification strategy is presented consisting of a cross-linked lyotropic liquid crystal hydrogel microparticle coating with antibacterial functionality. The microparticle coating composed of cross-linked triblock copolymers (diacrylated Pluronic F127) was deposited on PDMS by physical immobilization via interpenetrating polymer network formation. The formed coating served as a substrate for covalent immobilization of a potent antimicrobial peptide (AMP), RRPRPRPRPWWWW-NH2, yielding high contact-killing antibacterial effect against Staphylococcus epidermidis and Staphylococcus aureus. Additionally, the coating was assessed for its ability to selectively host polar, amphiphilic, and nonpolar drugs, resulting in sustained release profiles. The results of this study put forward a versatile PDMS modification strategy for both contact-killing antibacterial surface properties and drug-delivery capabilities, offering a solution for medical device-associated infection prevention.

Formulation, optimization, and in-vitro-ex-vivo evaluation of dual-crosslinked zinc pectinate-neem gum-interpenetrating polymer network mediated lansoprazole loaded floating microbeads

Low methoxy pectin (LM pectin) suffers from burst release owing to its high swellability and solubility in water. Consequently, in ways to design an ideal drug delivery system, these obstacles must be surmounted. Therefore, the work aimed to design dual crosslinked LM pectin -neem gum (NG) mediated interpenetrating polymer network (IPN) floating mucoadhesive microbeads for lansoprazole (LNZ) gastro-retentive delivery. In short, LNZ-loaded floating microbeads were achieved by using the ionic gelation method wherein zinc acetate was preferred as a crosslinking agent. The optimization of IPN microbeads was performed employing a 32factorial design wherein concentration of pectin and NG was considered as independent factors whereas dependant factors are entrapment efficiency and drug release. Importantly, carboxylic functionality of low methoxy (LM) pectin and hydroxylic functionality NG cross-linked with Zn+2 forms a 3D network. Diffractogram and thermogram revealed that conversion of drug from crystalline to amorphous form because of entrapment of drug within polymeric network. Anticipated floating microbeads showed that polymer concentration had considerable effect on drug encapsulation efficiency and drug release. Briefly, optimizing floating microbeads (Batch B:5) showed maximum drug entrapment (87.47 %) with a delayed drug release (69.20 %, at 8 h) due to formation of strong IPN. Moreover, it showed good mucoadhesive aptitude with goat stomach mucosa because of entanglement between gum and mucus layer. In addition, use of calcium silicate assists to modulate floating profile of IPN microbeads. Therefore, designing dual crosslinked zinc-pectinate-NG mediated IPN floating mucoadhesive microbeads will offer a new substitute for floating delivery.

Kinetic modeling of simultaneous polycondensation and free radical polymerization for polyurethane/poly(methyl methacrylate) interpenetrating polymer network

AbstractA comprehensive kinetic Monte Carlo algorithm has been developed to investigate the formation process of a polyurethane/poly(methyl methacrylate) (PU/PMMA) interpenetrating polymer network (IPN), in which a component independent strategy is proposed to perform the simulation of simultaneous polycondensation and free radical polymerization. An empiric diffusion model based on the mass fraction of polymer is used to quantify the effect of diffusional limitations on MMA polymerization. Results show that the presence of acrylic monomers has little impact on the formation rate of PU, but the presence of the PU network can accelerate the polymerization of MMA. In addition, the effects of component mass ratio, acrylic cross‐linker concentration, and [NCO]/[OH] ratio on the IPN formation kinetics are investigated based on the kinetic model. It is believed that the as‐developed modeling strategy can be extended to other IPN systems and provide a better understanding of the interactions between chemically independent networks.

POLY (N-VINYLCARBAZOLE) AND (α-POLMETHYLSTYRENE) BASED SEMI INTERPENETRATING POLYMER NETWORK: SYNTHESIS AND CHARACTERIZATION

A series of interpenetrating polymer network (IPN) based on poly(N-vinylcarbazole) and poly(α-methylstyrene) were synthesized using benzoylperoxide (BPO) as initiator and divinyl benzene as crosslinker. The IPNs were characterized using infrared spectroscopic technique, differential scanning calorimetric analysis, thermal gravimetric analysis and scanning electron microscope techniques. FTIR spectra of the synthesized polymeric network revealed the band positions for poly(N-vinylcarbazole), at 2923 cm-1, 1600 cm-1 and 1629 cm-1, and for poly(α-methylstyrene) at 3019 cm-1, 1484 cm-1, 707 cm-1 and 1451 cm-1. The relatively shortened peak value (1595 cm-1 CH-CH2-) of vinyl group in poly(α- methylsytrene) justify the disappearance of double bond which is a clear indication of bonding between the two polymer networks leading to IPN formation. The differential scanning calorimetry (DSC) graph showed glass transition temperature (Tg) at 449ºC, which indicate crystalline nature of synthesized IPN. Thermogravimetric analysis (TGA) graph showed thermal stability of IPN upto 395ºC. Fluorescence spectra of IPN at the visual range near 450 nanometer also predicts its good optical properties. The SEM image showed a transparent and dual morphology of the synthesized polymeric network. The properties like percentage swelling, average molecular weight (Mc) between crosslinker are in direct function of initiator (benzoyl peroxide) and poly(N-vinyl carbazole) but inverse function of monomer (α- methylsytrene) and crosslinker (divinyl benzene).

A polymer hybrid film based on poly(vinyl cinnamate) and poly(2-hydroxy ethyl methacrylate) for controlled flurbiprofen release

A crosslinked polymer hybrid film, ipn-poly(vinyl cinnamate-graft-2-hydroxy ethyl methacrylate)-v-poly(ethylene glycol dimethacrylate) was synthesized by UV initiation using poly(vinyl cinnamate) (polyVCi), 2-hydroxy ethyl methacrylate (HEMA) monomer and ethylene glycol dimethacrylate (EGDMA) crosslinker. Benzophenone (Ph2CO), was used as the photoinitiator. The synthesis was optimized by changing the concentration of HEMA, Ph2CO, EGDMA, and UV irradiation time. PolyVCi undergoes photocrosslinking by 2 + 2 photocylo addition while the monomer/crosslinker couple, HEMA/EGDMA, undergoes free radical polymerization and crosslinking to form EGDMA crosslinked polyHEMA. Hence, simultaneous interpenetrating polymer network (IPN) formation occurs. The IPN consists of dual network of photocrosslinked polyVCi and EGDMA crosslinked polyHEMA chains. Grafting of HEMA/EGDMA chains on the polyVCi backbone also occur during network formation. The chemical functionalities present in the polyVCi/polyHEMA/polyEGDMA IPN films obtained were characterized by FTIR and SEM analysis. The contact angle measurements show enhanced wettability of the IPN film compared to polyVCi surface. TGA analysis confirms thermal stability of the films. Swelling behavior of the films examined in water and in ethanol reveals the effects of the chemical natures of polyVCi and polyHEMA as well as that of crosslinking on the hydrophilicity of the film. The films were tested as drug release matrices using flurbiprofen. The drug was loaded into the film matrix during IPN formation under UV irradiation. PolyVCi/polyHEMA/polyEGDMA IPN proved to be a suitable release matrix for flurbiprofen demonstrating controlled release behavior and zero-order release kinetics. The release mechanism was confirmed by its Ritger-Peppas “n” value (1.00 to 1.42), which indicates super case II release.

Poly 4-Vinylpyridine and Polystyrene Based Interpenetrating Polymer Networks (IPNs): Synthesis and Characterization

A study on synthesis of thin film of interpenetrating polymer network (IPN), of poly(4-vinylpyridine) (PVP) and polystyrene was carried out. A series of IPN was synthesized, using divinyl benzene (as cross linker) and benzoyl peroxide (as an initiator) and characterized using FT-IR spectroscopy, scanning electron microscopy (SEM), thermal (DSC, TGA) and fluorescent techniques. FTIR spectra revealed the presence of PVP at 1584 cm–1 and polystyrene at 1609 cm–1. Shifting in band positions depicts formation of IPN. SEM images show a clear dual phase morphology. DSC thermogram reveals glass transition temperature (Tg) value of the polymer network at 350 ºC. TGA graph depicts thermal stability of IPN upto 400 °C. The XRD pattern of IPN indicates semi crystalline nature. The properties such as average molecular weight between crosslinks (Mc), percentage swelling is found to be the direct function of initiator (BPO) and inverse function of concentration of cross linker (DVB) and styrene. Fluorescence spectra of IPN observed in visual range of 506 nm.

PNIPAAM/SA pH-responsive microcapsules based on chemical and non-covalent crosslinking

Abstract A triple interpenetrating polymer network (IPN) with dual responses to temperature and pH was constructed based on chemical crosslinking and electrostatic interaction. In this IPN, CaCO3 microspheres were used as the kernel and PNIPAAM/sodium alginate microcapsules were prepared by the inverse emulsion polymerization method. Research results demonstrated that CaCO3 kernels were decomposed into Ca2+ and CO2 at pH 1.2. Such decomposition facilitated the formation of triple IPN of Ca2+ crosslinking. Moreover, microcapsules were expanded by tension of CO2 and the volume increased to 3.55 × 105 times that of the original microcapsules, with capsules remaining an intact morphology. These microcapsules loading doxorubicin hydrochloride (DOX) stability and responses to environment were investigated. No drug overflow was observed at pH 7.4, indicating the high stability of microcapsules. However, DOX was released gradually in the simulated human stomach acid with a weak solution of hydrochloric acid (pH 1.2, 37 °C). This showed that the prepared microcapsules were feasible for drug-loaded capsules and the controlled drug release behavior could relieve side effects of drugs to human body. Moreover, it will help to increase the drug utilization and realize accurate treatment.

EFFECT OF AZOINITIATORS OF METHYL METHACRYLATE POLYMERIZATION ON THE FORMATION PROCESS AND MORFOLOGY OF POLYURETHANE /POLYMETHYL METHACRYLATE INTERPENETRATING POLYMER NETWORKS

Interpenetrating polymer networks (IPN) are mixtures of two cross-linked polymers formed as a result of chemical reactions of in situ synthesis of components from single-phase initial mixtures. As a rule, due to the incompatibility of the components, a physical process of phase separation takes place with the formation of heterogeneous systems with insignificant interphase adhesion, which can have a negative effect on the physicochemical properties. To increase the compatibility of the components and to stabilize the systems, compatibilizers are introduced into the reaction mixtures. In this work the kinetics of the in situ formation of the components of polyurethane/poly(methyl methacrylate) interpenetrating polymer networks and the phase separation induced by chemical reactions in the presence of methyl methacrylate polymerization oligoazoinitiators in the reaction mixture were studied. Oligoazoinitiators contained fragments of a polyurethane chain also. It has been shown that the introduction of oligoazoinitiators of various chemical natures can control the process of IPN formation due to the formation of block copolymers during synthesis, which are compatibilizers of the mixture. They slow down the phase separation process and favor the formation of a finer IPN structure.

2D Fabrication of Tunable Responsive Interpenetrating Polymer Networks from a Single Photoresist

AbstractLight‐induced curing of photoresists is a well‐established technique to fabricate polymer networks with precise control over the material properties. Herein, control is exerted over network material properties of a single polymer blend through the spatiotemporally controlled incorporation of secondary polymer networks resulting in interpenetrating polymer networks (IPNs). Light gated control over materials properties of IPNs is assessed theoretically by applying the general rule of mixture and experimentally by using a multifunctional polymer resist. The full IPNs are formed through covalent bonds, based on photocuring of the complementary photoreactive groups o‐methyl benzaldehyde (UV light) and styrylpyrene (visible light). Applied to a spin coated polymer blend of UV light curable responsive poly(4‐vinylpyridine) (P4VP) and visible light curable poly(methyl methacrylate) (PMMA), the developed platform technology not only affords spatial control over the curing of the pH‐swellable P4VP component from the polymer blend, but also allows adjustment of the extent of swelling by forming an IPN through subsequent curing of the PMMA component. Gated only by light irradiation of a polymer blend, it is possible to control IPN formation in 2D structures, which precisely adjusts the swelling behavior of the respective materials segments.

Network toughening of additively manufactured, high glass transition temperature materials via sequentially cured, interpenetrating polymers

AbstractVinyl ester and epoxy–amine resins are used to produce polymeric materials for numerous commercial and military applications due to their relatively high moduli (>2 GPa), glass transition temperatures (Tgs) (≥120 °C) and adequate fracture toughness (G1C ≈ 200–250 J m−2). Most commercially available vinyl ester and epoxy–amine resins are typically cured into polymeric materials via traditional manufacturing techniques, such as resin transfer molding and thermal curing. However, additive manufacturing (AM) has gained significant traction as a favorable manufacturing technique over traditional methods due to the ability to create customizable parts with complex geometries on‐demand. Manipulation of polymer network connectivity using a dual‐cure mechanism of methacrylate free radical cure via stereolithography (SLA) and epoxy–amine thermal cure for the in situ creation of interpenetrating polymer networks (IPNs) for AM was investigated. Resins and formulations of individual monomers bearing both vinyl ester and epoxy functionality were either synthesized or formulated to elucidate the effect of interconnecting the two networks at the molecular level. The formation of a multi‐mechanistic, interconnected, sequentially cured IPN via SLA yielded polymeric materials with glass transition temperatures that exceeded 120 °C. Polymer network connectivity was shown to have a minimal impact on thermomechanical and thermogravimetric properties. IPN formation was shown to afford materials with high storage moduli (E′ values as high as 3.2 GPa), tensile strengths (as high as 51 MPa), Young's moduli (exceeding 3.5 GPa) and fracture energies (as high as 790 J m−2). © 2020 Society of Industrial Chemistry

The role of an interfacial interpenetrating polymer network formation on the adhesion of resin composite layers in immediate dentin sealing

The aim of this study was to evaluate the influence of chemical and physical processes at the resin-composite and composite-cement interface as a function of the resin composite's water exposure on the bond strength (BS) between these two components. The free-radical concentration was studied using electron paramagnetic resonance (EPR), while the chemical changes at the resin composite's surface were studied using attenuated total-reflection FTIR spectroscopy (ATR-FTIR). The free-radical concentration in the studied samples dropped to 10% in 24 h, indicating that prolonged BS values do not correlate with the free-radical concentration. An alternative bonding mechanism between the resin composite and the composite cement was proposed, based on the formation of an interpenetrating polymer network (IPN) layer at the interface. As proven using ATR-FTIR spectroscopy, changes occurred at the resin composite's surface as a consequence of water exposure, comprising the diffusion of water molecules into the resin composite. These changes reduced the diffusion rate of the composite cement's phosphorus-containing monomers into the resin composite, as shown by the linescan SEM-EDS analysis of phosphorus, thus reducing the thickness of the IPN layer at the interface and consequently reducing the BS between both components.This study reveals that the concentration of free radicals at the surface of the resin composite is only relevant immediately after the polymerisation to the bond strength between the resin composite and the composite cement. Therefore, an alternative explanation is given by applying the theory of the formation of a gradient IPN at the interface between the resin composite and the adhesive cement by changes in the rate of diffusion of the adhesive cement's monomers into the resin composite as a function of the resin composite's exposure to water.

Cell-laden interpenetrating network hydrogels formed from methacrylated gelatin and silk fibroin via a combination of sonication and photocrosslinking approaches

The regeneration of load-bearing soft tissues has long driven the research and development of bioactive hydrogels. A major challenge facing the application of hydrogels to load-bearing tissues is the development of hydrogels with appropriate biological functionality and biomechanical stability that closely mimic the host tissue. In this paper, we describe a newly synthesized cell-laden interpenetrating polymer network (IPN) hydrogel based on gelatin methacrylate (GelMA) and silk fibroin (SF) that was formed via sequential sonication and photocrosslinking. The experimental results revealed that SF-GelMA IPN hydrogels exhibited high swelling ratios, excellent mechanical properties, resistance to enzymatic degradation by collagenase, and porous internal microstructures. Moreover, these properties could be tailored by changing the prepolymer components. MC3T3-E1 pre-osteoblasts attached to and subsequently proliferated on the IPN hydrogels, as demonstrated by fluorescein diacetate/propidium iodide (FDA/PI) staining and Cell Counting Kit-8 (CCK-8) analysis. In addition, the encapsulation of MC3T3-E1 pre-osteoblasts and a subsequent cell viability assay demonstrated that the entire IPN formation process was compatible with cells and that the growth of encapsulated cells could be tuned by adjusting the GelMA concentration, underlining their versatility for various load-bearing soft tissue engineering. Overall, this study introduces a class of mechanically robust and tunable cell-laden IPN hydrogels which have great potential as load-bearing soft tissue engineering scaffold.