Interpenetrating polymer networks with controllable intermolecular hydrogen bonding: Swelling behavior

Summary The swelling behavior in different solvents of IPNs based on poly(butyl acrylate) and modified polystyrene containing strong proton-donor hydroxyl groups is studied. The experimental data of the volume fractions of the networks in the swollen state V_expt at equilibrium are compared with those expected from the Thiele-Cohen equation (V_TC), which assumes that the two networks are independent and no additional crosslinks form during the formation of the IPNs. For the IPNs without inter-component hydrogen bonding, V_expt in toluene are in good agreement with V_TC. As the hydroxyl content increases, the deviation of V_expt from V_TC increases indicating more crosslinks form in the process of IPN formation. This deviation in the solvents of proton-acceptor type becomes smaller but still apparent. This result implies that hydrogen bonding between the components is destroyed by the solvents but the physical entanglements formed during the formation of the IPNs remain.     

Interpenetrating polymer networks

Interpenetrating polymer networks (IPNs) composed of two or more chemically distinct networks are not only intrinsically interesting as examples of macromolecular chemical topological isomerism but are in practice useful means of controlling mutual miscibility and phase morphology in crosslinked polymers. We will first review briefly the synthesis and properties of such IPN systems. This will be followed by an outline of a phenomenological theory of the phase stability and linearised theory of spinodal decomposition of binary, chemically quenched, low crosslink density IPNs recently developed by K. Binder and the author. Finally, we will discuss some aspects of the synthesis of ternary IPNs and the thermochromic properties of IPNs containing a crosslinked polydiacetylene.     

Composition-dependent dynamics in miscible polymer blends: influence of intermolecular hydrogen bonding

Dynamics of the miscible blend of poly(vinyl methyl ether) and poly(4-vinylphenol) [PVME/PVPh] have been studied using broadband dielectric relaxation spectroscopy (DRS). The results are compared with those reported for PVME/polystyrene [PS] and PVME/poly(2-chlorostyrene) [P2CS] blends to examine the effect of intermolecular hydrogen bonding. These blends have similar chemical structures, with the exception that strong intermolecular hydrogen bonds are formed between PVME and PVPh. Whereas PVME and P2CS (or PS) relax individually in their blends due to intrinsic mobility differences and the absence of strong intermolecular interactions, the segmental relaxations of PVPh and PVME are coupled in the blends controlled by intermolecular hydrogen bonding. Dynamic heterogeneity was observed in PVPh/PVME blends with PVPh concentration higher than 50%. This is due to the decoupling arising from the strong intramolecular hydrogen bonding between PVPh segments. Finally, in the blend, the secondary relaxation processes of both components occur at approximately the same temperature-frequency location as those in corresponding neat polymers, but with much lower intensity, suggesting suppression by the intermolecular hydrogen bonding. Our results suggest that the composition-dependent dynamics in PVPh/PVME are even more complicated than that observed in blends without strong intermolecular interactions.     

The influence of intermolecular hydrogen bonding on the flow behavior of polymer melts

The influence of hydrogen bonding on the flow behavior of polymer melts at high shear rate has been investigated using a capillary extrusion rheometer. The systems studied were copolymers of ethylene and acrylic or methacrylic acid. Hydrogen bonding was found to substantially enhance both flow activation energy and viscosity level, as well as the degree of dependence of viscosity on rate of shear. It was also found that hydrogen bonding does not influence the critical shear stress for onset of “melt fracture.” The data support the view that hydrogen bonds act effectively as temporary (quasi-) crosslinks during the short time scales of deformation involved in flow at high shear rates.     

Infrared spectroscopy method reveals hydrogen bonding and intermolecular interaction between components in polymer blends

An infrared spectroscopy method was devised to uncover evidence of hydrogen bonding and intermolecular interaction between components in solid poly(lactic acid) (PLA) and poly(hydroxyester ether) (PHEE) blends. The method compares Gaussian/Lorentzian deconvoluted infrared spectra of the polymer blends with deconvoluted spectra of weight ratio‐equivalent mixtures of the physically separated polymers. Infrared spectra of polymer blends, where hydrogen bonding exists, differ from spectra of physical mixtures of the polymers. Deconvoluting spectra of the blends into their underlying peaks revealed theoretically expected differences between hydrogen‐bonded and nonhydrogen bonded components. The findings are supported by differential scanning calorimetry, scanning electron microscopy, and mechanical rheometry studies. The new method, differential spectral deconvolution, afforded a quantitative estimate of the extent of hydrogen bonding between PLA and PHEE and could therefore be used to measure the degree of interaction between components in thermoplastic blends. This technique is superior to conventional spectral subtraction and it should be applicable to intimate mixtures or solid solutions in general. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 813–821, 2005     

Interpenetrating polymer networks of photocrosslinkable cellulose derivatives

A series of interpenetrating polymer networks has been prepared from two cellulose derivatives, one of which contains cinnamate groups and the other containing randomly substituted cinnamate and allyl groups. The latter derivative forms a crosslinked network in less than 5 min on exposure to ultraviolet radiation and can be used to make amorphous interpenetrating polymer networks containing 50% by weight loading level of crosslinked vinyl polymers. The syntheses of both derivatives and the thermal properties and film morphologies of their interpenetrating polymer networks are discussed. © 1996 John Wiley & Sons, Inc.     

Interpenetrating polymer networks of bismaleimide and polyurethane-crosslinked epoxy

This study prepared an interpenetrating polymer network of bismaleimide and polybutylene adipate-based polyurethane-crosslinked epoxy (BMI/PU-EP IPN) using the simultaneous bulk polymerization technique. Infrared spectra analysis was also performed to identify the polyurethane-crosslinked epoxy (PU-EP). Also investigated herein were the mechanical properties including tensile strength, fracture energy, and Izod impact strength of various bismaleimide content in PU-EP matrix. In addition, differential scanning calorimetry and thermogravimetric analyses of the BMI/PU-EP IPN were conducted as well. Analyses results demonstrate that the bismaleimide was dissolved primarily in the polyurethane domains of the epoxy matrix to form a compatible system, thereby increasing the mechanical strength of the BMI/PU-EP IPNs. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 529–536, 1998     

Interpenetrating polymer networks of polyurethane and polystyrene ionomers

Interpenetrating polymer networks (IPNs) and linear blends of polyurethane (PUN) and poly(styrene–acrylic acid) (PSAA), which contain mutually opposite charge groups, i.e., tertiary amine and carboxyl groups, respectively, were synthesized through simultaneous bulk polymerization. Physical and mechanical properties of these IPNs and linear blends are discussed in the present paper. The tensile strength of both PUN/PSAA IPNs and linear blends has shown to increase with an increase of acrylic acid (AA) content in PSAA in any PUN/PSAA composition. A maximum value emerged in both polymer systems with 30 mol % AA in PSAA and the PUN/PSAA ratio of 25/75. A minimum swelling ratio as well as a maximum density was also observed in the IPNs and linear blends, respectively, related to this PUN/PSAA ratio. From dynamic mechanical analysis, two distinct relaxation transitions for the IPN or linear blend without AA in the system have merged into a single broad transition as the AA was introduced into PSAA. Two-Phase morphology was observed from scanning electron microscopy studies for the polymer systems in the absence of charge groups; however, one-phase morphology was observed when the charge groups were introduced.     

Interpenetrating polymer networks derived from epoxide-amine adducts in either polymer network

A new type of interpenetrating polymer network was synthesized via photoinitiated free-radical polymerization of α,ω-methacryloyl terminated macromonomers prepared from epoxide-amine-adducts, followed by thermal addition polymerization of bisphenol-A diglycidyl ether and 4,4′-diaminodiphenylsulfone or 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.0.^2,6]decane. The interpenetrating polymer networks are optically transparent and show only one glass transition temperature ranging from -10 to 130°C, as a function of the macromonomer/addition polymer mixing ratio. The presence of a single phase was confirmed by scanning electron microscopy (SEM).     

Achieving miscible ternary polymer blends with hydrogen bonding

Poly(vinyl phenol) (PVPh) has previously been found to be successful in making immiscible poly(methyl methacrylate) (PMMA)/poly(vinyl acetate) (PVAc) miscible. Poly(ethyl methacrylate) (PEMA) with one more methyl group than PMMA is also immiscible with PVAc. PEMA and PVAc are miscible with PVPh according to the literature. To determine whether PVPh can also cosolubilize PEMA/PVAc, PVPh samples of two different molecular weights have been mixed in this study with PEMA and PVAc to produce a ternary blend. On the basis of the calorimetry data, the ternary PEMA/PVAc/PVPh blend, regardless of the molecular weight of PVPh, has been determined to be miscible. The reason for the observed miscibility is probably that the interactions between PVAc and PVPh are similar in magnitude to those between PEMA and PVPh. A modified Kwei equation based on the binary interaction parameters proposed previously is used to describe the experimental glass‐transition temperature of the miscible ternary blend almost quantitatively well. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 643–652, 2006     

Interpenetrating polymer networks based on polyurethane and organic-inorganic copolymer

The investigation of the features of the formation of interpenetrating polymer networks (IPNs) based on cross-linked polyurethane and organic-inorganic copolymer (OIC) based on hydroxyethyl methacrylate (HEMA) and titanium isopropoxide (Ti(OPrⁱ)₄) was carried out using the IR spectroscopy method. It has been demonstrated that during the synthesis of organic-inorganic IPNs (OI IPNs), three-dimensional cross-linked structures with the inclusion of (-TiO₂-) fragments in the polymer chain of poly(hydroxyethyl methacrylate) are formed. The examinations of the viscoelastic properties and thermal stability of organic-inorganic IPNs by dynamic mechanical (DMA) and thermogravimetric analysis (TGA) showed that the value of M _c decreases with an increase in the content of (-TiO₂-) fragments in OI IPN; in addition, the thermal stability of the obtained hybrid OI IPNs increases significantly compared to the parent systems.     

Interpenetrating polymer networks from castor oil and dibasic acids

Prepolyesters were obtained from castor oil and dibasic acids, viz oxalic, malonic, succinic, glutaric, adipic, suberic and sebacic acid. These prepolyesters (PPE) were subsequently interpenetrated with methyl methacrylate containing 1% ethylene glycol dimethacrylate as crosslinker by radical polymerization initiated with benzoyl peroxide. The novel PPE poly(methyl methacrylate) PPE/PMMA interpenetrating polymer networks (IPNs) were obtained as powder. They were characterized by solubility behaviour, IR spectral study and thermal behaviour.     

Phase behavior of ternary polymer blends with hydrogen bonding

Atactic poly (methyl methacrylate) (aPMMA) was found to be almost completely immiscible with poly(vinyl acetate) (PVAc). Both aPMMA and PVAc are known to be miscible with poly(vinyl phenol) (PVPh) according to literature. Adding of PVPh into immiscible aPMMA/PVAc mixtures is likely to improve their miscibility. Therefore, PVPh can be used as cosolvent to cosolubilize aPMMA and PVAc. A ternary blend consisting of aPMMA, PVAc, and PVPh was prepared and determined calorimetrically in this article. According to the calorimetry data, the ternary blend was determined to be miscible. The reason for the observed miscibility is because the interactions between PVAc and PVPh are similar to those between aPMMA and PVPh. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2797–2802, 2004     

Interpenetrating polymer networks: A review on synthesis and properties

A review containing 83 references on the chemistry aspects (mechanism and structure–property relationships) for IPN synthesis is presented.     

Interpenetrating polymer networks. I. Photopolymerization of multiacrylate systems

The light-induced polymerization of a triacrylate monomer (TMPTA) has been carried out in a polymer matrix to generate a semi-interpenetrating polymer network (IPN). The reaction kinetics was followed by IR spectroscopy for the various polymer binders studied: poly(vinyl chloride) (PVC), poly(methyl methacrylate), polystyrene, and crosslinked polyurethane. Under intense illumination, crosslinking occurred extensively within a fraction of a second, with formation of a hard and highly resistant polymer material. These semi-IPNs were found to be essentially insoluble in the organic solvents, thus indicating that the acrylate network is grafted onto the polymer matrix, probably because of an efficient chain transfer process. The monomer and photoinitiator concentration, as well as the light intensity were shown to have a great influence on both the rate of polymerization and the final degree of conversion. By using an acylphosphine oxide photoinitiator, PVC–;TMPTA blends have been cured within a few minutes in an accelerated QUV-A weatherometer, which emits low-intensity UV radiation similar to sunlight. © 1994 John Wiley & Sons, Inc.     

Interpenetrating polymer networks from castor oil based polyurethanes,XI

Under different experimental conditions, various liquid polyurethanes (PU) were synthesized from castor oil and isophorone diisocyanate varying NCO/OH ratio. These polyurethanes were then subsequently interpenetrated with n-butyl acrylate (nBA) monomer and ethylene glycol di-methacrylate as crosslinker by radical polymerization using benzoyl peroxide as an initiator. This leads to the formation of novel PU/PnBA interpenetrating polymer networks (IPNs) by transfer molding. These IPNs were characterized by their resistance to chemical reagents, thermal behavior (TGA), mechanical properties, namely; tensile strength, Young's modulus, elongation at break (%) and hardness (Shore A). The morphology of the IPNs was studied by Scanning Electron Microscopy. The dielectric behavior was computed in terms of electrical conductivities, dielectric constant (ε′), loss tangent (tan δ) and dielectric loss (ε″).     

Interpenetrating polymer networks based on nitrile rubber and metal methacrylates

Interpenetrating polymer networks (IPNs) based on nitrile rubber (NBR) as first component and zinc dimethacrylate (ZnDMA), aluminum trimethacrylate (AlTMA), or zirconium tetramethacrylates (ZrTeMA) as second component were synthesized. Sequential IPNs (SeqIPN) were formed by two routes such as compression molding (CM) and swelling/curing (SC). The IPNs were found to have superior properties compared to metal oxide/hydroxide‐filled NBR. Tensile strength has increased to a large extent while maintaining appreciable elongation. Total crosslink density (covalent and ionic) was found to increase in the order NBR/metal oxide or hydroxide < SeqIPN(CM route) < SeqIPN (SC route). IPNs are found to retain high storage modulus even in the rubbery region. It is observed that change of technique for IPN formation has drastically changed the modulus of the present system. Decrease in tan δ value and inward shifting of peaks were observed because of IPN formation. Morphology of SeqIPN by SC process was found to be more uniform compared to others. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2542–2548, 2006     

Interpenetrating polymer networks derived from silylated soybean oil and polydimethylsiloxane

A series of interpenetrating polymer networks (IPNs) was prepared using various concentrations of silylated soybean oil and polydimethylsiloxane (PDMS) that were cross linked with inorganic silicates. This series of IPNs was prepared from emulsions of silylated soybean oil and PDMS together with colloidal silica and dioctyltin dilaurate catalyst at pH 10. Under these conditions, water soluble silicates reacted with silanols in the oil phase and formed intraparticle siloxane cross links. Upon casting films and evaporation of the water, additional interparticle cross linking were obtained between the coagulating particles to produce entangled networks of soybean oil and PDMS that were further reinforced by fine silica particles. The morphology revealed intimate mixing of the two immiscible components. The mechanical properties depended on the ratio of the soft, flexible PDMS phase and the rigid, brittle cross linked silylated soybean oil phase. These IPNs can be used as high release liners, low friction materials, or as a general protective coating. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2479–2486, 2013     

Interpenetrating polymer networks from castor oil-based polyurethanes and polystyrene,XXV

Interpenetrating polymer networks (IPNs) of castor oil-based polyurethanes and polystyrene were prepared by simultaneous polymerization. The liquid prepolyurethanes were formed by reacting the hydroxyl functionality of castor oil with isophorone diisocyanate using different stoichiometric NCO/OH ratios. These prepolyurethanes were mixed with styrene monomer and subsequently polymerized by free radical polymerization initiated by benzoyl peroxide in the presence of the crosslinker 1,4-divinyl benzene. The interpenetrating polymer networks. PU/PS IPNs, were obtained as tough and transparent films by the transfer moulding technique. These IPNs were characterized by the static mechanical properties (tensile strength, Young's modulus and % elongation), thermal properties and morphology. The dielectric relaxation properties (σ, E′, E″ and tanδ) of the IPNs at different temperatures were studied.     

Interpenetrating polymer networks from polyurethanes and poly(methyl acrylate)

Simultaneous two-component interpenetrating polymer networks (IPNs) of polyurethane (PU)–poly(methyl acrylate) (PMA) were prepared, as well as the corresponding pseudo-IPNs. A comparison was made between the full IPNs, pseudo-IPNs, and the respective homopolymers. Their ultimate mechanical properties were obtained and the dynamic glass transition temperatures (T_g's) were found using a thermomechanical analyzer. At all compositions, a single T_g(except 50–50 wt %) was found.