Interpenetrating Polymer Network Materials Research Articles

Multiply Interpenetrating Polymer Networks: Preparation, Mechanical Properties, and Applications.

This review summarizes work done on triply, or higher, interpenetrating polymer network materials prepared in order to widen the properties of double polymer network hydrogels (DN), doubly interpenetrating polymer networks with enhanced mechanical properties. The review will show that introduction of a third, or fourth, polymeric component in the DNs would further enhance the mechanical properties of the resulting materials, but may also introduce other useful functionalities, including electrical conductivity, low-friction coefficients, and (bio)degradability.

Composite Cellularized Structures Created from an Interpenetrating Polymer Network Hydrogel Reinforced by a 3D Woven Scaffold.

Biomaterial scaffolds play multiple roles in cartilage tissue engineering, including controlling architecture of newly formed tissue while facilitating growth of embedded cells and simultaneously providing functional properties to withstand the mechanical environment within the native joint. In particular, hydrogels-with high water content and desirable transport properties-while highly conducive to chondrogenesis, often lack functional mechanical properties. In this regard, interpenetrating polymer network (IPN) hydrogels can provide mechanical toughness greatly exceeding that of individual components; however, many IPN materials are not biocompatible for cell encapsulation. In this study, an agarose and poly(ethylene) glycol IPN hydrogel is seeded with human mesenchymal stem cells (MSCs). Results show high viability of MSCs within the IPN hydrogel, with improved mechanical properties compared to constructs comprised of individual components. These properties are further strengthened by integrating the hydrogel with a 3D woven structure. The resulting fiber-reinforced hydrogels display functional macroscopic mechanical properties mimicking those of native articular cartilage, while providing a local microenvironment that supports cellular viability and function. These findings suggest that a fiber-reinforced IPN hydrogel can support stem cell chondrogenesis while allowing for significantly enhanced, complex mechanical properties at multiple scales as compared to individual hydrogel or fiber components.

A detailed experimental study of the validity and applicability of slotted stand-off layer rail dampers in reducing railway vibration and noise

This paper is concerned with an experimental study of improved slotted stand-off layer rail dampers in reducing railway vibration and noise. To achieve the goal, based on the idea of molecular design, polyurethane/vinyl ester resin interpenetrating polymer network damping materials with high damping properties was developed in the laboratory for the material of the damping layer. The effects of vinyl ester resin and organic small molecule hybridization on the damping properties of the polyurethane/vinyl ester resin interpenetrating polymer network material were investigated. The structural style of the damper was improved for ease of installation and removal in situ. Then, these improvements of damping material and structural style were used to make optimized slotted stand-off layer dampers, which were applied in a test section. The measurements indicate that the structural style improvement could improve the application convenience while also maintaining the noise reduction effect. The improved rail dampers could greatly increase the track decay rate at frequencies above 100 Hz and reduce noise levels by up to 6 dB at the speed of 60 km/h.

3D-printable CFR polymer composites with dual-cure sequential IPNs

In this work a sequential interpenetrating polymer network (IPN) obtained by co-formulation of a photocurable acrylic resin with a thermocurable epoxy resin is presented and proposed as matrix for the fabrication of carbon-fiber reinforced (CFR) composite structures by means of 3D-printing technology. This approach combines the advantages of the easy free-form fabrication typical of the 3D-printing technology with the purposely customized features of the newly developed IPN material. Photocalorimetric and dynamic-mechanical analyses were performed in order to investigate the photo- and thermal-crosslinking reactions and their effect on the development of the IPN system. The IPN resin was finally loaded with carbon fibers and successfully ultraviolet-assisted (UV)-3D printed, demonstrating the possibility of fabricating CFR composite materials in 3D with excellent mechanical properties. Being the first example of direct fabrication of IPN-based composites by 3D printing, this study clearly shows the great potential of this additive manufacturing technology for advanced industrial applications.

3D Printed Silicone-Hydrogel Scaffold with Enhanced Physicochemical Properties.

Scaffolds with multiple functionalities have attracted widespread attention in the field of tissue engineering due to their ability to control cell behavior through various cues, including mechanical, chemical, and electrical. Fabrication of such scaffolds from clinically approved materials is currently a huge challenge. The goal of this work was to fabricate a tissue engineering scaffold from clinically approved materials with the capability of delivering biomolecules and direct cell fate. We have used a simple 3D printing approach, that combines polymer casting with supercritical fluid technology to produce 3D interpenetrating polymer network (IPN) scaffold of silicone-poly(2-hydroxyethyl methacrylate)-co-poly(ethylene glycol) methyl ether acrylate (pHEMA-co-PEGMEA). The pHEMA-co-PEGMEA IPN materials were employed to support growth of human mesenchymal stem cells (hMSC), resulting in high cell viability and metabolic activity over a 3 weeks period. In addition, the IPN scaffolds support 3D tissue formation inside the porous scaffold with well spread cell morphology on the surface of the scaffold. As a proof of concept, sustained doxycycline (DOX) release from pHEMA-co-PEGMEA IPN was demonstrated and the biological activity of released drug from IPN was confirmed using a DOX regulated green fluorescent reporter (GFP) gene expression assay with HeLa cells. Given its unique mechanical and drug releasing characteristics, IPN scaffolds may be used for directing stem cell differentiation by releasing various chemicals from its hydrogel network.

Damping properties and the morphology analysis of the polyurethane/epoxy continuous gradient IPN materials

As engineering materials, the gradient polymer with high modulus as well as excellent damping properties are of great interest in aerospace and automotive industries for severe dynamic environment. A new type of continuous gradient polyurethane/epoxy interpenetrating polymer network (IPN) material was realized according to the self-stratification mechanism in this paper. Dynamic mechanical analysis (DMA) tests showed that it undergoes more than 117.69 °C with loss tangent larger than 0.3, much better than the traditional IPN with the same component. Morphological analysis revealed that the polyurethane phase dominated IPN concentrated in one surface of the samples while the epoxy phase in the other, it was continuous gradient shifting from one surface to the other with no obvious phase separation.

Smarter Actuator Design with Complementary and Synergetic Functions.

A general synthetic strategy for multifunctional actuators is presented, by confining desired functions in separate domains of interpenetrating polymer network materials. Specifically, complementary ionic actuator and shape-memory functions are demonstrated by simultaneous, orthogonal reaction pathways. Synergistic effects also allow dynamic programming and two-way linear shape-memory actuation.

Soft hydrogels interpenetrating silicone--A polymer network for drug-releasing medical devices.

Materials for the next generation of medical devices will require not only the mechanical stability of current devices, but must also possess other properties such as sustained release of drugs in a controlled manner over a prolonged period of time. This work focuses on creating such a sophisticated material by forming an interpenetrating polymer network (IPN) material through modification of silicone elastomers with a poly(2-hydroxyethyl methacrylate) (PHEMA)-based hydrogel. IPN materials with a PHEMA content in the range of 13%-38% (w/w) were synthesized by using carbon dioxide-based solvent mixtures under high pressure. These IPNs were characterized with regard to microstructure as well as ability of the hydrogel to form a surface-connected hydrophilic carrier network inside the silicone. A critical limit for hydrogel connectivity was found both via simulation and by visualization of water uptake in approximately 25% (w/w) PHEMA, indicating that entrapment of gel occurs at low gel concentrations. The optimized IPN material was loaded with the antibiotic ciprofloxacin, and the resulting drug release was shown to inhibit bacterial growth when placed on agar, thus demonstrating the potential of this IPN material for future applications in drug-releasing medical devices.

Designed hydrocolloid interpenetrating polymeric networks for clinical applications of novel drug-carrying matrix systems using Tris (6-isocyanatohexyl) isocyanurate and hydroxypropylmethylcellulose.

Hydroxypropyl methylcellulose (HPMC) was employed in this study to design controllable drug release systems because of its non-toxic nature, swelling properties. New interpenetrating polymer networks (IPN) of HPMC / tri-isocyanate crosslinked polyurethane (TCPU) could be prepared on the surfaces of IPN materials. To design "Novel Drug-carrying Matrix Systems", incorporation of novel structure is important to the possible formation of drug-carrying spaces within the material, which was achieved by using Tris (6-isocyanatohexyl) isocyanurate with three soft hexyl arms in this study. A series of novel drug-carrying matrix systems prepared by crosslinking reaction could be candidates for an excellent and smart potential material. When the polymeric networks were established on the surfaces of resulting materials, the developed hydrophilic interpenetrating polymeric structures of HPMC/ polyurethane could provide good wettability to the wound dressings, particularly for moisture healing application. The materials containing HPMC/polyurethane networks using 1% cross-linking agent showed a water uptake value of 5.1% after one hour, which has great potential for use as wound dressings for moisture healing. Furthermore, a new drug delivery system of hydrophilic IPN was successfully designed and established.

An Elastomeric Poly(Thiophene‐EDOT) Composite with a Dynamically Variable Permeability Towards Organic and Water Vapors

AbstractAn interpenetrating polymer network (IPN) material with controllable nanoporosity is developed for applications such as chemical protection. The IPN material is based on a conducting polymer backbone consisting of thiophene and 3,4 ethylenedioxythiophene (EDOT) repeat units–poly(thiophene‐EDOT)–formed within a soft polyurethane support. The IPN demonstrates reversible, electrochemically switchable nanoporosity in the absence of standard liquid electrolyte, with the oxidized state being the open (high porosity) state and the reduced state being the closed (low porosity) state. The switching of the IPN between its oxidized (open) and reduced (closed) states is actuated using application of ±1.0 V. The variability in the IPN porosity, induced by the electrochemical switching, is revealed by large changes in water vapor diffusivity, as well as changes in the diffusivities of the chemical agent simulants chloroethyl ethyl sulfide (CEES) and methyl salicylate (MeS). The closed state of the IPN is able to decrease CEES diffusivity by ≈99% compared to expanded Teflon (ePTFE), while the open state allows high MVT rates comparable to ePTFE. The IPN's ability to allow high MVT under non‐threat conditions (open state) and high protection from agents under threat conditions (closed state) is a unique and desirable characteristic of this novel IPN material.

Dielectric properties and AC conductivity studies of novel NR/PVA full-interpenetrating polymer networks

Fully interpenetrating polymer networks (IPN) based on natural rubber (NR) and polyvinyl alcohol (PVA) were prepared by using Glutaraldehyde as the common crosslinking agent. Crosslinking reactions were confirmed by Fourier Transform Infra-red Spectroscopy. The electrical properties of full-IPN have been studied in the frequency range of 102–106Hz. The dielectric constant, dielectric loss and ac conductivity were analyzed as a function of frequency, temperature and blend composition. It was found that the dielectric constant and dielectric loss increased with the addition of PVA into NR. Interpenetrated system showed a significant reduction in dielectric constant and dielectric loss and almost frequency independent. The dielectric constant and dielectric loss were increased with increase in temperature. The change in these parameters with temperature in the IPN system was found too low as compared to the pure blends. The ac conductivity study revealed that the IPN materials exhibited a considerable reduction in conductivity.

Visualizing phase separation in polystyrene/polystyrene homo‐IPNs via sulfonation

AbstractBACKGROUND: Polystyrene/polystyrene (PS/PS) interpenetrating polymer networks (IPNs) represent ideal homo‐IPNs. Whether phase separation occurs in this system has been a long‐standing problem, which is closely related to the self‐organization mechanism in IPN formation and is important to the exploration of new polymer morphologies and properties by topological isomerism.RESULTS: A series of bead samples of PS/PS sequential IPNs with the same nominal divinylbenzene contents were synthesized by suspension polymerization, followed by sulfonation. Scanning electron micrographs and energy‐dispersive X‐ray mapping show unique distinctive topography on both surfaces and fractured surfaces and large heterogeneity in sulfonation of the PS/PS IPN beads, which for the first time provide visual evidence for dual‐phase continuity in PS/PS IPNs.CONCLUSION: The phase separation behavior is proposed to be due to hydrodynamic screening, architectural asymmetry and excluded volume interactions between network I and the precursor chains of network II. This is considered to represent pure IPN effects in sequential formation and may shed light on the general constitution mechanism and molecular design of IPN materials. Copyright © 2009 Society of Chemical Industry

Structure and Properties of PVA/SiO2 Interpenetrating Polymer Network Materials Prepared by the Sol–Gel Method

Organic–inorganic interpenetrating polymer network (IPN) materials were prepared by hydrolysis and condensation of tetraethoxysilane (TEOS) in poly(vinyl alcohol) (PVA) solution. The structure and morphology of the IPNs were investigated by infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The thermal properties were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). FTIR spectroscopy showed the formation of Si–O–C and Si–O–Si bonds in the system. TEM demonstrated a homogeneous dispersion of silica in the PVA matrix when the amount of TEOS added was appropriate. DSC and TGA revealed that, compared with pure PVA films, the hybrid films exhibited a higher glass transition temperature (Tg) and high thermal stability.

Sequential Interpenetrating Polymer Networks Produced from Vegetable Oil Based Polyurethane and Poly(methyl methacrylate)

Sequential interpenetrating polymer networks (IPNs) were prepared using polyurethane produced from a canola oil based polyol with primary terminal functional groups and poly(methyl methacrylate) (PMMA). The properties of the material were studied and compared to the IPNs made from commercial castor oil using dynamic mechanical analysis, differential scanning calorimetry, as well as tensile measurements. The morphology of the IPNs was investigated using scanning electron microscopy and transmission electron microscopy. The chemical diversity of the starting materials allowed the evaluation of the effects of dangling chains and graftings on the properties of the IPNs. The polymerization process of canola oil based IPNs was accelerated because of the utilization of polyol with primary functional groups, which efficiently lessened the effect of dangling chains and yielded a higher degree of phase mixing. The mechanical properties of canola oil based IPNs containing more than 75 wt % PMMA were comparable to the corresponding castor oil based IPNs; both were superior to those of the constituent polymers due to the finely divided rubber and plastic combination structures in these IPNs. However, when PMMA content was less than 65 wt %, canola oil based IPNs exhibited a typical mechanical behavior of rigid plastics, whereas castor oil based IPNs showed a typical mechanical behavior of soft rubber. It is proposed that these new IPN materials with high performance prepared from alternative renewable resources can prove to be valuable substitutes for existing materials in various applications.

Differences in curing behavior of cocured and IPN materials

AbstractThis study addressed the blending and cocuring of resole and epoxy, using NaOH and 4,4′‐diaminodiphenylmethane as curing agents. IR band shifts regarding the molecular interactions were investigated with FTIR. Exothermic peak shifts during cocuring reactions were studied with dynamic DSC. Viscosity increases were measured with a Brookfield LVT viscometer at 100°C. The dynamic mechanical properties of the cocured samples were investigated using rheometric dynamic spectroscopy (RDS). Experimental results revealed that the molecular interactions between resole and epoxy resulted in good compatibility as shown by the single damping peak in the RDS curve and the single glass transition for each cocured sample. Also apparent were accelerated curing rates, leading to shifts of the exothermic peaks to lower temperature and faster viscosity increases. Nevertheless, enhanced gel fractions and increased glass‐transition temperatures (Tg) of the samples were generally observed for this cocured system. The average molecular weight between crosslinked points calculated for the cocured materials also showed much less than the two components. These curing behaviors were quite different from those of the Interpenetrating Polymer Network (IPN) materials, which usually indicated lowered gel fractions, decreased Tg, and higher average molecular weight between crosslinkings than for components. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 963–969, 2001

Toughened interpenetrating polymer network materials based on unsaturated polyester and epoxy

Simultaneous interpenetrating polymer networks (IPNs) based on epoxy (diglycidyl ether of bisphenol A) and unsaturated polyester (UP) were prepared by using m-xylenediamine and benzoyl peroxide as curing agents. A single glass transition temperature for each IPN was observed with differential scanning calorimetry, which suggests good compatibility of epoxy and UP. This compatibility was further confirmed by the single damping peak of the rheometric dynamic spectroscopy. Curing behaviors were studied with dynamic differential scanning calorimetry, and the curing rates were measured with a Brookfield RTV viscometer. It was noted that an interlock between the two growing networks did exist and led to a retarded viscosity increase. However, the hydroxyl end groups in UP catalyzed the curing reaction of epoxy; in some IPNs where the hydroxyl concentration was high enough, such catalytic effect predominated the network interlock effect, leading to fast viscosity increases. In addition, the entanglement of the two interlocked networks played an important role in cracking energy absorption and reflected in a toughness improvement. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 585–592, 1999

Toughened interpenetrating polymer network materials based on unsaturated polyester and epoxy

Simultaneous interpenetrating polymer networks (IPNs) based on epoxy (diglycidyl ether of bisphenol A) and unsaturated polyester (UP) were prepared by using m-xylenediamine and benzoyl peroxide as curing agents. A single glass transition temperature for each IPN was observed with differential scanning calorimetry, which suggests good compatibility of epoxy and UP. This compatibility was further confirmed by the single damping peak of the rheometric dynamic spectroscopy. Curing behaviors were studied with dynamic differential scanning calorimetry, and the curing rates were measured with a Brookfield RTV viscometer. It was noted that an interlock between the two growing networks did exist and led to a retarded viscosity increase. However, the hydroxyl end groups in UP catalyzed the curing reaction of epoxy; in some IPNs where the hydroxyl concentration was high enough, such catalytic effect predominated the network interlock effect, leading to fast viscosity increases. In addition, the entanglement of the two interlocked networks played an important role in cracking energy absorption and reflected in a toughness improvement. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 585–592, 1999

Curing behaviour of compatible interpenetrating polymer networks based on epoxy and methacrylated epoxy

Compatible interpenetrating polymer networks (IPNs) based on digly- cidyl ether of bisphenol A (DGEBA) and methacrylated diglycidyl ether of bisp- henol A (MADGEBA) in weight ratios of 100/0, 75/25, 50/50, 25/75 and 0/100 were blended and cured simultaneously by using dicumyl peroxide (DICUP) and hexahydrophthalic anhydride (HHPA) as curing agents. Fourier transform infra- red spectroscopy (FTIR) was employed to investigate the intermolecular inter- actions and functional group changes. Viscosity increases during crosslinking were examined with a Brook-eld viscometer. Curing exothermic peaks were studied with di†erential scanning calorimetry (DSC). The gel fractions of various IPN compositions were measured with a Soxhlet extractor. Samples thus pre- pared were checked for their compatibility by measuring glass transitions with DSC and damping peaks with rheometric dynamic spectroscopy (RDS). Experi- mental results revealed that good compatibility between components induced a network interlock, which subsequently resulted in incomplete cure of the IPN materials.

Curing behaviour of compatible interpenetrating polymer networks based on epoxy and methacrylated epoxy

Compatible interpenetrating polymer networks (IPNs) based on diglycidyl ether of bisphenol A (DGEBA) and methacrylated diglycidyl ether of bisphenol A (MADGEBA) in weight ratios of 100/0, 75/25, 50/50, 25/75 and 0/100 were blended and cured simultaneously by using dicumyl peroxide (DICUP) and hexahydrophthalic anhydride (HHPA) as curing agents. Fourier transform infrared spectroscopy (FTIR) was employed to investigate the intermolecular interactions and functional group changes. Viscosity increases during crosslinking were examined with a Brookfield viscometer. Curing exothermic peaks were studied with differential scanning calorimetry (DSC). The gel fractions of various IPN compositions were measured with a Soxhlet extractor. Samples thus prepared were checked for their compatibility by measuring glass transitions with DSC and damping peaks with rheometric dynamic spectroscopy (RDS). Experimental results revealed that good compatibility between components induced a network interlock, which subsequently resulted in incomplete cure of the IPN materials. ©1997 SCI

Multicomponent latex IPN materials: 2. Damping and mechanical behavior

The integrals of the linear loss shear modulus vs. temperature (loss area, LA) and linear tan δ vs. temperature (tan δ area, TA) were characterized for various core/shell latex particles with synthetic rubber, poly(butadiene-stat-styrene) [P (Bd/S), 90/10], and interpenetrating polymer networks (IPN) as the cores. The IPN cores were composed of P(Bd/S) (Tg ≃ − 70°C) and an acrylate based copolymer (Tg around 10°C) for potential impact and damping improvement in thermoplastics. Poly(styrene-stat-acrylonitrile) (SAN, 72/28) was the shell polymer for all these polymers. Under the same loading, for both toughening and damping controls, among the IPN core/shell, blend of separate core/shell, and multilayered core/shell polymers, the IPN core/shell polymers were the best dampers. However, the other core/shell polymers also showed higher LA values than P(Bd/S)/SAN core/shell polymer. A comparison of LA values via a group contribution analysis method was made, the effect of particle morphology and phase continuity on damping being studied. Inverted core/shell latex particles (glassy polymer SAN was synthesized first) showed much higher LA and TA values than normal core/shell ones (rubbery polymer was synthesized first). Models for maximum LA and TA behavior are proposed. The damping property was essentially controlled by the phase miscibility and morphology of the core/shell latex particles. The LA values for each peak in these multiphase materials provided some indication of the several fractional phase volumes. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1501–1514, 1997