A study of molecular mobility and relaxation properties of epoxy-allyl interpenetrating polymer networks with a high degree of interpenetration

Features of the formation of the epoxy-allyl polymers are considered during simultaneous and consecutive curing of epoxy and allyl polymers. Study of their molecular mobility and relaxation properties shows the high interpenetration degree of the epoxy-allyl interpenetrating polymer networks.     

A study of molecular mobility and relaxation properties of epoxy-allyl polymers during formation of interpenetrating polymer networks under conditions of the phase separation of the networks

Molecular mobility and relaxation properties of epoxy-allyl polymers (EAPs) and features of the formation of interpenetrating polymer networks under conditions of the phase separation of the network have been studied. The presence of the extensive interphase zone between the individual epoxy and allyl component networks has been established. The segregation degree has been calculated taking into account the volume fractions of the components of the polymer mixture. The interrelation between the features of the structure of the obtained EAP with a high level of adhesion and deformation-strength characteristics of polymers in glassy and highly elastic states has been demonstrated.     

Structural parameters of the network formed first in in-situ sequential interpenetrating polymer networks

As part of a study concerning poly(propylene glycol)-based polyurethane / poly(methyl methacrylate) interpenetrating polymer networks, polyurethane networks were synthesized at various dilutions of the reaction medium and at different values of the [NCO]/[OH] ratio. The network defects arising in such materials were evaluated by three independent experimental approaches: solvent extraction, swelling behaviour, and compression measurements. It was found that the networks with the least defects are formed at high precursor concentration, with a [NCO] over [OH] excess of about 7%.     

Structure of interpenetrating polymer networks

A possible model for the formation of interpenetrating polymer networks is suggested. Phase separation is assumed to be faster than gelation. This implies that domains rich in either component grow first until late stages of spinodal decomposition. In these domains, short linear chains are crosslinked, leading to large branched macromolecules. Growth of the domains is slowed down by the presence of crosslinked polymers. It is assumed that it is stopped when the sizes of the domains and of the branched macromolecules are comparable. The resulting domains are significantly larger than the average distance between crosslinks. These results are supported by recent neutron scattering results on a poly(carbonate-urethane)/polyvinyl pyridine interpenetrating network. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1507–1512, 1998     

Swelling of interpenetrating polymer networks

We have studied the densities, kinetics, and equilibrium degree of swelling in a number of different solvents of poly(carbonate urethane)/poly(methyl methacrylate) and poly(carbonate urethane)/poly(vinyl pyridine) interpenetrating polymer networks (IPN's). The kinetics of solvent uptake are often anomalous. The equilibrium extent of swelling reflects, among other factors, the number of phases present. © 1993 John Wiley & Sons, Inc.     

Power law relaxation in an interpenetrating polymer network

Emulsion polymerized interpenetratingpolymer networks (IPN) of polyacrylate and polystyrene exhibit a power law relaxation over a wide frequency range. The response of the material to oscillatory shear, step sheaf strain and a constant stress can be described with a two parameter constitutive equation. The power law behavior was previously found in polymers at their critical state where molecular motions were correlated over large distances without intrinsic size or time scale.The effect of composition and crosslink density on the behavior of the material is studied. The behavior might be explained with the granular structure of the material.     

The current status of interpenetrating polymer networks

An interpenetrating polymer network, IPN, is defined as a combination of two or more polymers in network form, at least one of which is polymerized and/or crosslinked in the immediate presence of the other(s). The synthesis, morphology and mechanical properties of recent works are reviewed, with special emphasis on dual phase continuity, and the number of physical entanglements that arise in homo-IPNs. The concepts of phase diagrams are applied, especially to simultaneous interpenetrating network phase separations and gelations. Recent engineering applications are discussed.     

On microphase segregation of interpenetrating polymer networks

The topological entanglements between subchains of two interpenetrating polymer networks are described in the simplest approximation supposing that the primitive path of each subchain is influenced due to the shift of one network relatively to the other. The entanglement contribution to the free energy of the networks is shown to behave as 1/q² for the state with deviation from uniform densities with the wave vector of order q. This contribution is shown to cause the microphase type of segregation.     

Phase separation in polystyrene latex interpenetrating polymer networks

Polystyrene/polystyrene latex interpenetrating polymer networks (IPNs) were prepared by seeded emulsion polymerzation of styrene–divinylbenzene mixtures in crosslinked monodisperse polystyrene seed latexes. The resulting latexes comprised uniform nonspherical particles, which were formed by separation of the second-stage monomer from the crosslinked seed network during swelling and polymerization. The kinetics of phase separation were investigated by examining the changes in particle morphology using optical microscopy, which revealed that the phase separation was induced by the relaxation of the polymer chains before polymerization began and was enhanced by increased conversion. The thermodynamics of phase separation were investigated by analysis of the free-energy changes during swelling and polymerization, and the phase separation was described by a nucleation-and-growth mechanism. The results of this study have been applied to the design and synthesis of a series of uniform nonspherical particles of different morphology.     

Reactive compatibilization in phase separated interpenetrating polymer networks

The effects of compatibilizing additives (monomethacrylic ester of ethylene glycol (MEG) and oligo-urethane-dimethacrylate (OUDM)) on the kinetics of interpenetrating polymer network (IPN) formation based on cross-linked polyurethane and linear polystyrene and its influence on the microphase separation, viscoelastic and thermophysical properties have been investigated. It was established, that various amounts (3-10 mass%) of the additive MEG and 20 mass% OUDM introduced into the initial reaction system prevent microphase separation in the IPN. In the course of the reaction the system undergoes no phase separation up to the end of reaction, as follows from the light scattering data. The viscoelastic properties of modified IPN are changed in such a way that instead of two relaxation maxima characteristic of phase-separated system, only one relaxation maximum is observed, what is result of the formation of compatible IPN system. The position of this relaxation transition depends on the system composition and on the reaction conditions.     

Pseudo interpenetrating polymer networks and interpenetrating polymer networks of zeolite 13 X and polystyrene and poly(ethyl acrylate)

Free-radical polymerization of liquid styrene and ethyl acrylate with or without ethylene dimethacrylate crosslinker in the presence of zeolite 13 X produces interpenetrating polymer networks (IPN's) or pseudo IPN's in which polymer chains have grown and filled internal pores of the zeolite. A variety of methods of characterization including, solubility studies, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), ¹³C solid-state nuclear magnetic resonance (NMR) and small-angle X-ray scattering (SAXS) provide supporting evidence for this. The polymer chains within the internal pores do not exhibit a bulk glass transition. This is part of a larger study of the glass transition of polymers confined to cavities or pores of various sizes.     

Synthesis and characterization of interpenetrating polymer networks with nonlinear optical properties

We report the synthesis and characterization of interpenetrating polymer networks (IPNs) exhibiting nonlinear optical (NLO) properties. The network consists of aliphatic polycarbonate urethane (PCU) and poly(methyl methacrylate-co-N,N-disubstituted urea), with a nonlinear optical (NLO) chromophore incorporated into N,N-disubstituted urea. The full IPNs have only one T_g, as determined by differential scanning calorimetry (DSC), together with scanning electron microscopy (SEM) observations, suggest a single phase morphology. The thin films of IPNs are transparent and the unpoled samples produced second harmonic generation (SHG) signals at room temperature. This result indicates that the NLO chromophore is oriented noncentrosymmetrically during the IPN formation process and is tightly held between the permanent entanglements of the two component networks of the IPN. © 1996 John Wiley & Sons, Inc.     

Synthesis and light scattering study of microgels with interpenetrating polymer networks

Monodispersed microgels composed of poly(acrylic acid) (PAAc) and poly(N-isopropylacrylamide) (PNIPAM) interpenetrating polymer networks (IPN) were synthesized by a two-step method, first preparing PNIPAM microgel and then polymerizing acrylic acid that interpenetrates into the PNIPAM network. The growth kinetics of the IPN particle formation was obtained by measuring the turbidity and particle hydrodynamic radius (Rh) as a function of reaction time. IPN and PNIPAM microgels were characterized and compared by dynamic and static light scattering techniques. The concentrated aqueous solutions of the PNIPAM-PAAc IPN microgels exhibit an inverse thermoreversible gelation. In contrast to polymer solutions of poly(NIPAM-co-AAc) that have the inverse thermoreversible gelation, our system can self-assemble into an ordered structure, displaying bright colors. Furthermore, IPN microgels undergo the reversible volume phase transitions in response to both pH and temperature changes associated with PAAc and PNIPAM networks, respectively.     

Thermal history and enthalpy relaxation of an interpenetrating network polymer with exceptionally broad relaxation time distribution

Differential scanning calorimetry (DSC) of an interpenetrating network polymer of composition 25% polyurethane–75% poly(methyl methacrylate) shows a slowly increasing heat capacity, instead of the usual glass transition endotherm, whose onset temperature is not clearly discernible. On aging of the polymer at several temperatures between 193 and 333 K, an endothermic peak is observed whose onset is in the vicinity of the respective temperature of aging. The area under these peaks increases with increasing aging time at a fixed temperature. The effects are attributed to a very broad distribution of relaxation times, which may be represented by either a sum of discrete structural relaxation times of local network arrangement or by a nonexponential relaxation function which is equivalent to a distribution of relaxation times. In either view the vitrified state of the polymer can be envisaged as containing local structures whose own T_gs extend over a wide range of temperature. Aging decreases the enthalpy and produces an endothermic region which resembles an increase in C_p on heating because of relaxation of that local structure. The interpretation is supported by simulation of DSC scans in which the distribution of relaxation times is assumed to be exceptionally broad and in which aging introduced at several temperatures over a wide range produces endothermic effects (or regions of DSC scans) qualitatively similar to those observed for the interpenetrating network polymer. © 1994 John Wiley & Sons, Inc.     

Strain effects on the microphase separation in interpenetrating polymer networks and cross-linked polymer mixtures

We study the microphase separation in cross-linked polymer mixtures and interpenetrating polymer networks by taking into account the coupling between the fluctuations of the order parameter and the strain tensor. We predict that thermal fluctuations of the order parameter decrease the compression and shear moduli and that compression of the sample decreases the critical temperature of microphase separation. We also compute the scattering function in the case of shear and uniaxial deformations.     

Electrical conductivity of iodine doped pseudo interpenetrating polymer networks

The iodine doped pseudo interpenetrating polymer networks (PIPN's) of both conjugated and non-conjugated linear polymers in less conducting crosslinked polymer networks may possess modest DC conductivities, σ, of the order of the iodine doped bulk polymers. There is evidence that critical percolation occurs in PIPN's and that these materials possess a quasi-one dimensional character unlike the iodine doped bulk polymers, e.g. the σ of the iodine doped PIPN's increases from about 120 K to 4 K with decreasing temperature. We provide a simple partial (near and somewhat below room temperature) theory and summarize conductivity and resonance Raman spectroscopic studies.     

聚氨酯/环氧树脂互穿网络聚合物的性能研究

互穿聚合物网络（Interpenetrating polymer net-work,简称IPN）广泛应用的为聚氨酯基的互穿网络聚合物。其合成多集中在弹性体方面。本文用同步法合成的聚氨酯／环氧树脂互穿网络硬质泡沫塑料材料（简称PU／ERIPNF）,机械性能较好,并研究了其动态力学性能及形态变化。     

Analysis of interpenetrating polymer networks via quartz crystal microbalance with dissipation monitoring

A quartz crystal microbalance with dissipation monitoring (QCM-D) was used to assess the physical properties of interpenetrating polymer networks (IPNs) through swelling experiments in ambient humidity and in phosphate-buffered saline (PBS), pH 7.4. The IPNs, based on acrylamide (AAm) and poly(ethylene glycol) (pEG), swell from thin, rigid films when dry (16.7 +/- 5.2 nm on Si/SiO(2)) to expanded, viscoelastic films when hydrated (107 +/- 24.2 nm on Si/SiO2). The dry IPNs could be analyzed using the Sauerbrey relationship, but for the hydrated films it was necessary to interpret QCM-D data with a Kelvin-Voigt viscoelastic model. A complex modulus |G| of 116 +/- 38.1 kPa for the swollen IPN surface on Si/SiO2 was defined by the model. The QCM-D was also employed to quantify the adsorption of human fibrinogen, a protein important in thrombus formation, onto the IPNs. Fibrinogen adsorption studies demonstrated the sensitivity of the QCM-D, as well as confirmed the nonfouling nature of the IPN surface, where less than 5 ng/cm2 of fibrinogen was adsorbed.     

Modification of aqueous polyurethanes by forming latex interpenetrating polymer networks with polystyrene

A series of latex particles with interpenetrating polymer network structure have been synthesized from waterborne polyurethane (PU) and polystyrene (PS). The effect of PU/PS composition, cross-linking density in the PS domain as well as in PU have been studied in terms of dispersion size, transmission electron microscopy morphology, mechanical and dynamic mechanical properties in addition to swellability in water and toluene of the dispersion cast film. It was found that inverted core (PS)–shell (PU) morphology was well defined and that the domain size as well as the film properties were well controlled by the latex composition and cross-linking density of both phases. Received: 15 March 2000 Accepted: 21 February 2001