Morphology Of Interpenetrating Polymer Networks Research Articles

Multimorphic Materials: Spatially Tailoring Mechanical Properties via Selective Initiation of Interpenetrating Polymer Networks.

Access to multimaterial polymers with spatially localized properties and robust interfaces is anticipated to enable new capabilities in soft robotics, such as smooth actuation for advanced medical and manufacturing technologies. Here, orthogonal initiation is used to create interpenetrating polymer networks (IPNs) with spatial control over morphology and mechanical properties. Base catalyzes the formation of a stiff and strong polyurethane, while blue LEDs initiate the formation of a soft and elastic polyacrylate. IPN morphology is controlled by when the LED is turned "on", with large phase separation occurring for short time delays (≈1-2 min) and a mixed morphology for longer time delays (>5min), which is supported by dynamic mechanical analysis, small angle X-ray scattering, and atomic force microscopy. Through tailoring morphology, tensile moduli and fracture toughness can be tuned across ≈1-2 orders of magnitude. Moreover, a simple spring model is used to explain the observed mechanical behavior. Photopatterning produces "multimorphic" materials, where morphology is spatially localized with fine precision (<100µm), while maintaining a uniform chemical composition throughout to mitigate interfacial failure. As a final demonstration, the fabrication of hinges represents a possible use case for multimorphic materials in soft robotics.

Butyl rubber-based interpenetrating polymer networks with side chain crystallinity: Self-healing and shape-memory polymers with tunable thermal and mechanical properties

A self-healing and shape-memory interpenetrating polymer network (IPN) is produced by UV polymerization of n-octadecyl acrylate (C18A) monomer in a toluene solution of butyl rubber (isobutylene-isoprene rubber, IIR) using Irgacure 2959 photoinitiator at ambient temperature. IPNs containing 20–80 wt% IIR have crystalline domains formed by side-by-side packed octadecyl side chains aligned perpendicular to the poly(C18A) (PC18A) backbone. TEM images reveal that the morphology of IPNs consists of crystalline domains dispersed in a continuous amorphous matrix where the size of the dispersed phase could be adjusted between µm and nm level by changing the amount of IIR. Calculations indicate that the effective cross-link density of IPNs is mainly determined by their crystalline domains followed by hydrophobic associations while the chemical cross-links between IIR and PC18A components are negligible. We also show that the crystalline domains acting as sacrificial bonds dissipate energy under strain leading to a significant toughness improvement. IPNs exhibit tunable melting temperature (46–50 °C), crystallinity (1.5–25%), Young’s modulus (0.6–35 MPa), toughness (1.3–12 MPa), and a stretchability of up to 1200% by varying the amount of IIR component. What is more, they also exhibit temperature induced healing behavior with 59–77% efficiency, and an effective shape-memory function. The strategy presented here is applicable for the preparation of IPNs based on various rubbers and poly(n-alkyl(meth)acrylates) with long alkyl side chains.

Transport behaviour of aromatic solvents through styrene butadiene rubber/poly [methyl methacrylate] (SBR/PMMMA) interpenetrating polymer network (IPN) membranes

Sequential polymerization technique has been adopted for the synthesis of a series of full and semi interpenetrating polymer network (IPN) membranes based on styrene butadiene rubber (SBR) and poly [methyl methacrylate] (PMMA). IPN morphology has been tuned by varying the blend composition and extent of cross-linking of both the phases. The dispersed and co-continuous morphologies of IPNs were characterised by AFM, SEM and TEM analysis. The transport behaviour of aromatic hydrocarbons through the membranes has been studied in detail by tracing the solvent uptake up to equilibrium. As the PMMA content in the IPN increases to 60 wt %, the solvent uptake value decreases by about 50% which is in tune with the morphological changes of the system where PMMA phase forms a well interconnected network structure with the SBR phase. The network structure has been compared with the Phantom and the Affine models and also with the theoretical predictions.

Exploring the Effect of Poly(propylene carbonate) Polyol in a Biobased Epoxy Interpenetrating Network.

Poly(propylene carbonate) (PPC) polyol derived from carbon dioxide has been used to make a tough biobased interpenetrating polymer network (IPN). PPC polyol (10, 20, and 30 phr) was added to an epoxy/poly(furfuryl alcohol) IPN, and the effect of PPC polyol on the tensile modulus, tensile strength, tensile toughness, and notched Izod impact strength was determined. Dynamic mechanical analysis (DMA) was used to investigate the effect of PPC polyol on the glass-transition temperature. Loss area (LA) as a characteristic of IPN damping properties was evaluated using DMA. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to obtain more information on the morphology of IPNs on the micro- and nanoscale. It was found that the incorporation of PPC polyol improved the notched Izod impact strength and tensile toughness up to 190 and 220%, respectively. The damping factor peak was broadened with the addition of PPC polyol, and the glass-transition temperature was decreased as the amount of PPC polyol increased. The IPN with 20 phr PPC polyol exhibited better damping properties than neat epoxy and the epoxy/PFA IPN. SEM and AFM images revealed that PPC polyol domains were dispersed in the epoxy phase with an average diameter of around 280 nm.

Elastomeric Light Emitting Polymer Enhanced by Interpenetrating Networks.

Conjugated polymers containing long-chain alkyl side groups for solubility are generally unstretchable: large strain induces crack formation, fracture, or plastic deformation. When the polymers are stretched to reorient the conjugated chains along the stretching direction, high dichroic ratio is observed both for absorption of the ground state and radiative decay of the excited state. Here an interpenetrating polymer network (IPN) approach is reported to impart elastomeric deformability to a conjugated polymer. A soluble alkyloxy phenyl substituted poly(1,4-phenylenevinylene) (SY-PPV) with bright yellow fluorescent emission was admixed with an ionically conductive medium containing poly(ethylene oxide), exoxylated trimethylolpropanetriacrylate, and lithium trifluoromethanesulfonate. The spin-cast blend film formed an IPN morphology wherein SY-PPV forms a porous network with pores filled by the ionic medium. PeakForce quantitative nanomechanical mapping showed that the local Young's modulus was high in the SY-PPV phase, while the ionic phase was two-times softer. No global polarization of the SY-PPV chains was observed at strains up to 100% as the dichroic ratio remains close to 1. Light-emitting devices based on the blend sandwiched between two stretchable transparent composite electrodes could be stretched by up to 140% strain. No electroluminescence polarization was observed.

Influence of N-vynilcarbazole on the photopolymerization process and properties of epoxy-acrylate interpenetrating polymer networks

Abstract Photocured simultaneous epoxy-acrylate interpenetrating polymer networks (IPNs) were formed both under irradiation by UV-lamp and natural sunlight. The conversion degrees of functional groups were calculated by using data obtained from Fourier transform infrared (FTIR) spectroscopy. The influence of N-vynilcarbazole (NVC) as a photosensitizer on the kinetics of IPN photopolymerization was investigated. The conversion degrees of epoxy groups were revealed to increase significantly with the addition of NVC to the given systems. The phase morphology of IPNs was analyzed by optical and scanning electronic microscopy as well as by dynamic mechanical analysis (DMA). The data obtained using DMA method, which was used for analyzing the IPN samples with different component ratios, indicate the formation of both phase-separated and single-phase IPNs. The phase separation is occurred only in NVC-containing 50:50 IPN.

Novel anion-conducting interpenetrating polymer network of quaternized polysulfone and poly(vinyl alcohol) for alkaline fuel cells

Chloromethylated polysulfone is firstly converted to cationic groups under the condition of N,N,N′,N′-tetramethylethylenediamine in dimethyl sulfoxide, then blended with poly(vinyl alcohol) (PVA) solution, followed by casting, crosslinking and treatment in trimethylamine solution for constructing anion-conducting interpenetrating polymer networks (IPNs). Fourier transform infrared spectra, thermogravimetric analysis and scanning electron microscopy are employed to characterize the structure and morphology of IPNs. The properties of IPNs including water uptake, mechanical property, thermal stability and ionic conductivity are studied. Compared with the quaternized polysulfone membrane, the IPN derived from 60% CMPSF and 40% PVA shows better balanced properties. It exhibits an ionic conductivity of 1.82 × 10−2 S cm−1 at 60 °C and nearly 80% ionic conductivity of the original value after being treated in 2 M NaOH solution for 120 h at 60 °C.

Interpenetrating polymer networks as innovative drug delivery systems.

Polymers have always been valuable excipients in conventional dosage forms, also have shown excellent performance into the parenteral arena, and are now capable of offering advanced and sophisticated functions such as controlled drug release and drug targeting. Advances in polymer science have led to the development of several novel drug delivery systems. Interpenetrating polymer networks (IPNs) have shown superior performances over the conventional individual polymers and, consequently, the ranges of applications have grown rapidly for such class of materials. The advanced properties of IPNs like swelling capacity, stability, biocompatibility, nontoxicity and biodegradability have attracted considerable attention in pharmaceutical field especially in delivering bioactive molecules to the target site. In the past few years various research reports on the IPN based delivery systems showed that these carriers have emerged as a novel carrier in controlled drug delivery. The present review encompasses IPNs, their types, method of synthesis, factors which affects the morphology of IPNs, extensively studied IPN based drug delivery systems, and some natural polymers widely used for IPNs.

Influence of the poly(ethylene oxide)/polybutadiene IPN morphology on the ionic conductivity of ionic liquid

Solid polymer electrolytes (SPEs) were prepared by incorporating either aqueous LiClO4 or 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI) ionic liquid into Poly(ethylene oxide) (PEO)/polybutadiene (PB) Interpenetrating Polymer Networks (IPNs). With a given PEO/PB ratio, either transparent or translucent films depending on the synthesis route of these IPNs, have been investigated. TEM observations confirm that the morphology of these IPN films depends also on the PEO weight proportion whereas mechanical properties measured by DMA are only slightly modified. Measurements of ionic conductivity of SPEs are also very dependent on the IPNs morphology. For instance, EMITFSI ionic conductivity increases over four orders of magnitude from 2.2×10−7 to 2.5×10−3Scm−1 at 30°C.

The Influence Factors Analysis to Improve the Compatibility and the Mechanical Behavior of IPN, Gradient IPN and BaTiO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; Filled IPN

Interpenetrating polymer network (IPN), gradient IPN and BaTiO3 filled IPN, composed of poly(ethylene glycol urethane) (PEGPU) and unsaturated polyester resin (UP) curing at room temperatures were prepared. Then the effect of soft/hard segment ratio in polyurethane (PU), component ratio of PU to UP in IPN, adding amount of BaTiO3 in filled IPN, the component sequences and interval times between each IPN for gradient IPN, on morphology and mechanical behavior of IPN and BaTiO3/IPN nanocomposites with different molecular weight of PU were studied systematically. Moreover, the investigation on the relationship between the morphologies and the mechanical properties indicated that the IPN with finer morphology exhibited an excellent consistency of the higher strengths and elongations.

Curing kinetics and morphology of IPNs from a flexible dimethacrylate and a rigid epoxy via sequential photo and thermal polymerization

The curing kinetics and morphology of Interpenetrating polymer networks (IPNs) formed from a rigid epoxy resin thermally cured by an anhydride, and a photocured flexible dimethacrylate resin, have been studied by temperature ramping differential scanning calorimetry (DSC), near-infrared (NIR), and dynamic mechanical thermal analyzer (DMTA). This combination of cross-linkable resins permits the partial or complete cure of each component independent of the other. Also, since the monomers are polar but chemically dissimilar thermosetting resins, their IPNs should offer considerable variation in properties. DSC studies showed that the possible interactions between each component in the IPN could be minimized, but that the curing rate and conversion of the second polymerizing component was affected by vitrification, network topology, or phase separation in the IPN. NIR was also used to confirm that virtually independent cure was achievable by the combination of the thermal and photochemical methods. Dynamical mechanical thermal analysis was used to investigate the effect of curing one or both components and of order of curing on the phase morphology of the IPN. The modulus in the rubbery region also provided information on loop formation and co-continuity of each network component through the polymer matrix. The modulus and tan δ curves showed large differences in the glass transition region of the IPNs with different curing schedules, however phase separation occurred in all fully cured IPNs. These observations conflict with a previously advanced hypothesis that rapid polymerization and gelation of the last-cured component interlocks the two networks into a single phase structure and leads to the inclusion of a caveat that the components require sufficient attraction for interlocking of the networks to occur.

Polybutadiene/poly(ethylene oxide) based IPNs, Part II: Mechanical modelling and LiClO4 loading as tools for IPN morphology investigation

Interpenetrating polymer networks (IPNs) combining polybutadiene (PB) and poly(ethylene oxide) (PEO) show very close α relaxations leading to a partially resolved signal as determined by DMA. Nevertheless it is shown in this paper, in complement to part I, that it is still possible to get a better insight into the material morphology through two different approaches. First DMA experimental data are compared with theoretical predictions obtained from mechanical coupling models (Christensen and Lo and Budiansky approaches). Second, it is shown that full splitting of DMA signals can be induced providing that LiClO4 is introduced in polybutadiene/poly(ethylene oxide) IPNs. Indeed the Li+ cation has a particular affinity for the ethylene oxide segments in the PEO network. IPN morphologies are then discussed much more accurately according to LiClO4 loaded IPN mechanical behaviour. This concept could be usefully generalized to other types of polymers IPN associations as long as a selective complexation agent for one of the partner networks can be found that selectively modifies one particular property of this partner network.

Hydrogel-elastomer composite biomaterials: 3. Effects of gelatin molecular weight and type on the preparation and physical properties of interpenetrating polymer networks

To optimize the preparation of a gelatin-HydroThane Interpenetrating Polymer Network (IPN) and obtain optimum physical properties for its use as a wound dressing, we studied IPN films prepared with two types of gelatin having different molecular weights. The effects of the gelatin molecular weight and type on the IPN film's structure, morphology, swelling and mechanical properties were determined. While FTIR did not reveal any noticeable differences between the IPNs prepared using different gelatin, light microscopy showed a lesser phase separation of the film prepared with a high-molecular-weight type A gelatin. Furthermore, these films displayed slightly less swelling, higher strength and lower strain, compared to the IPNs prepared with either low-molecular-weight type A or type B gelatin. The IPN prepared with type B gelatin showed higher swelling in serum-containing medium than those prepared with type A gelatin, because of its ionic charges under the condition. Increases in viscosity were observed with increasing molecular weight, type A being more viscous than type B gelatin despite having a lower bloom number. The viscosity of the high-molecular-weight gelatin was in the same magnitude as that of HydroThane, which might lead to less phase separation. A better understanding of the effects of alterations in the gelatin molecular weight and type on the formation and properties of the gelatin-HydroThane IPN should facilitate the development of promising composite biomaterials for wound dressing applications.

Poly(ethylene oxide)/polybutadiene based IPNs synthesis and characterization

Interpenetrating polymer networks (IPNs) were prepared from hydroxytelechelic polybutadiene (HTPB) and poly(ethylene oxide) (PEO) via an in situ process. The PEO network was obtained by free radical copolymerization of poly(ethylene glycol) methacrylate and dimethacrylate. Addition reactions between HTPB and a pluri-isocyanate cross-linker (Desmodur ® N3300) led to the HTPB network. Polymerization kinetics were followed by Fourier transform spectroscopy in the near and middle infrared. Mechanical properties and the IPN morphology were investigated by dynamic mechanical analysis and transmission electron microscopy. The relation between the formation rates of the two networks and the IPN final morphology is discussed.

Synthesis and characterization of conducting interpenetrating polymer networks for new actuators

The synthesis of conducting interpenetrating polymer networks (IPNs) for actuator applications is described. The IPNs are synthesized from poly(ethylene oxide) and polybutadiene networks in which the conducting polymer (poly(3,4-ethylenedioxythiophene)), PEDOT, is gradually dispersed, i.e. its content decreases from the outside towards the centre of the film. The conducting IPN morphology was investigated by electrical resistance measurements and DMA. For actuation experiments, aqueous or organic electrolyte solutions were used but the best results were obtained with a room temperature ionic liquid, 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide (EMITFSI).

PH dependence of PDMS–PMAA IPN morphology and transport properties

The objectives of this study are to probe the pH responsiveness of polydimethyl siloxane (PDMS)/polymethacrylic acid (PMAA) interpenetrating polymer networks (IPNs), and to relate pH-dependent changes in permeation to morphological changes. PDMS/PMAA IPNs of 70:30 mass ratio on a dry basis were prepared using a monomer immersion method [Macromolecules 33 (10) (2000) 3714]. IPNs made by this method have previously been shown to exhibit a bicontinuous morphology at pH 7 with PMAA structural features of 10–200 nm in dimension [Macromolecules 36 (6) (2003) 1962]. Equilibrium hydration, morphology and diffusion characteristics of the IPNs were investigated at different pH. Equilibrium hydration was gravimetrically determined to be in the range of 0.77–0.9 at pH 7 and 0.42–0.5 at pH 3, corresponding to average hydrations of 0.93 and 0.74 of the PMAA component, respectively. Morphology imaged using laser scanning confocal microscopy (LSCM) showed that the area fraction of fluorescein isothiocyanate labelled dextran (FITC-dextran) accessible regions decreased from pH 7 to 3, consistent with hydration data. Additionally at pH 3, the hydrogel domain appeared to be disconnected. Vitamin B 12 (VB 12) permeability through the IPN was found to be 1.7 × 10 −7 cm 2/s at pH 7, and below detection (<10 −13 cm 2/s) at pH 3, consistent with the observed morphology. Dynamic responses in hydration and permeation to pH changes suggests a surface driven phenomenon with response times that are expected to be thickness-dependent.

Morphology of the transparent IPN‐like system PE: (BMA‐co‐S)

AbstractIn the study of interpenetrating polymer networks (IPN)‐like systems consisting of polyethylene (PE) and butyl methacrylate (BMA)–styrene (S) copolymer PE/(BMA‐co‐S), the effect of the crosslinker on the morphology of IPN by using electron microscopy and atomic force microscopy (AFM) was investigated. The IPN‐like system PE/(BMA‐co‐S) represents a two‐phase system with finely dispersed domains of crosslinked PE matrix. The interphase between dispersed domains and PE matrix is inhomogeneous and is considered the most interpenetrated part of this IPN‐like system. The size of the domains decreases with the content of crosslinker used. The AFM micrographs allowed the observation of PE lamellae with lengths of about 25 nm. © 2001 John Wiley &amp; Sons, Inc. J Appl Polym Sci 81: 2615–2620, 2001

Volume Phase Transition in Interpenetrating Networks of Poly(N-isopropylacrylamide) with Gelatin

Fully interpenetrating polymer networks (IPNs) of gelatin and poly(N-isopropylacrylamide) (PNIPA) are synthesized. The IPNs exhibit volume phase transition in aqueous medium and re-entrant type behavior in mixed solvent systems similar to pure PNIPA hydrogels. Neither the hydrophilic ambience of the gelatin network nor the additional topological constraints imposed by the IPN morphology restrain the characteristic features of PNIPA suggesting short-range interactions are responsible for the volume phase transition (VPT) phenomenon. Thus it could very well be that the conditions of the planarity of the amide group together with the directionality of the H bonds with the solvent decide the phenomenon of lower critical solution temperature (LCST)/VPT in PNIPA polymers.

Energy Transfer Studies of Interpenetrating Polymer Networks: Characterizing the Interface in Polyacrylate−Polyurethane IPNs

Interpenetrating polymer networks (IPNs) of polyurethane (PU) and polyacrylate (PA) were prepared to give very small domains (ca. 20 nm) of PA dispersed in a PU matrix. In these samples the PU phase is labeled with phenanthrene, a donor for energy transfer experiments, and the PA phase is labeled with anthracene, the corresponding acceptor. Direct nonradiative energy transfer from phenanthrene to anthracene was used to study the IPN morphology. The interface and mixing between the microphases were analyzed in terms of a Helfand and Tagami (H−T) profile, which is commonly used to describe the interface in polymer blend systems. Exact fluorescence theoretical decay profiles were calculated according to the H−T profiles in a restricted geometry. Experimental fluorescence decays were compared to the theoretical decays, and the interface thickness was recovered. At the level of the model we used in our analysis, we found strong similarities between these IPNs and traditional polymer blends.

Modulated differential scanning calorimetry: XVI. Degree of mixing in interpenetrating polymer networks

Quantitative analysis using the differential of heat capacity with temperature, d C p/d T, signal from modulated-temperature differential scanning calorimetry (M-TDSC) allows the extent of phase mixing to be calculated for interpenetrating polymer networks (IPNs). As an example, the extents of phase mixing of polyurethane–polystyrene (PUR/PS) (60/40, wt/wt) IPNs with different levels of grafting agent, benzene-1-(1-isocyanato-1-methyl ethyl)-3-(1-methylethenyl) (TMI) have been analysed. At lower TMI contents, the d C p/d T with temperature signal shows two significant glass-transition temperatures. With increasing TMI contents, a broad transition peak appears in the d C p/d T with temperature signal. This indicates that with increasing TMI contents, the degree of phase mixing increases. It is believed that the d C p/d T vs. temperature signal will become a useful tool and a powerful complement to solid-state NMR, scattering and direct non-radiative energy-transfer methods in analysing the morphology of IPNs.