Thermal characterizations of semi‐interpenetrating polymer networks composed of poly(ethylene oxide) and poly(N‐isopropylacrylamide)

Poly(N‐isopropylacrylamide) (PNIPAAm)/poly(ethylene oxide) (PEO) semi‐interpenetrating polymer networks (semi‐IPNs) synthesized by radical polymerization of N‐isopropylacrylamide (NIPAAm) in the presence of PEO. The thermal characterizations of the semi‐IPNs were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). The melting temperature (T_m) of semi‐IPNs appeared at around 60°C using DSC. DEA was employed to ascertain the glass transition temperature (T_g) and determine the activation energy (E_a) of semi‐IPNs. From the results of DEA, semi‐IPNs exhibited one T_g indicating the presence of phase separation in the semi‐IPN, and T_gs of semi‐IPNs were observed with increasing PNIPAAm content. The thermal decomposition of semi‐IPNa was investigated using TGA and appeared at around 370°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3922–3927, 2003     

Poly[(N‐isopropylacrylamide)‐co‐(itaconic acid)] hydrogels with poly(ethylene glycol)

The aim of the work reported here was to investigate temperature‐ and pH‐sensitive hydrogels of N‐isopropylacrylamide (NIPAM) and itaconic acid (IA) and their semi‐interpenetrating polymer networks (semi‐IPNs) with varying contents of poly(ethylene glycol) (PEG). The stimuli responsiveness, swelling behaviour and mechanical properties of the hydrogels and semi‐IPNs were studied in order to investigate the effect of various amounts of PEG. Pulsed‐gradient spin‐echo NMR experiments were carried out to investigate the diffusion process. The pH sensitivity increased with an increasing amount of PEG in the semi‐IPNs, while the overall rate of water uptake was diffusion‐controlled (n < 0.5). For certain PEG contents (5 and 10 wt%), the semi‐IPNs exhibited better mechanical properties than the poly(NIPAM‐co‐IA) copolymer. The calculated values of the self‐diffusion coefficients of water indicated facilitated diffusion of water through the system with increased amounts of PEG, while the self‐diffusion coefficients of a model compound, metoprolol tartrate, showed no significant dependence on the amount of PEG. According to the results obtained and compared to results reported in the literature, the investigated semi‐IPNs may have potential applications in the controlled release of macromolecular active agents such as proteins and peptides. Copyright © 2009 Society of Chemical Industry     

Synthesis and characterization of thermo‐ and pH‐sensitive block copolymers bearing a biotin group at the poly(ethylene oxide) chain end

A poly(ethylene oxide)‐block‐poly(dimethylamino ethyl methacrylate) block copolymer (PEO‐b‐PDMAEMA) bearing an amino moiety at the PEO chain end was synthesized by a one‐pot sequential oxyanionic polymerization of ethylene oxide (EO) and dimethylamino ethyl methacrylate (DMAEMA), followed by a coupling reaction between its PEO amino and a biotin derivative. The polymers were charac terized with ¹H NMR spectroscopy and gel permeation chromatography. Activated biotin, biotin‐NHS (N‐hydroxysuccinimide), was used to synthesize biotin‐PEO‐PDMAEMA. In aqueous media, the solubility of the copolymer was temperature‐ and pH‐sensitive. The particle size of the micelle formed from functionalized block copolymers was determined by dynamic light scattering. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3552–3558, 2006     

Synthesis and characterization of semi‐interpenetrating networks based on poly(dimethylsiloxane) and poly(vinyl alcohol)

Semi‐interpenetrating networks (Semi‐IPNs) with different compositions were prepared from poly(dimethylsiloxane) (PDMS), tetraethylorthosilicate (TEOS), and poly(vinyl alcohol) (PVA) by the sol‐gel process in this study. The characterization of the PDMS/PVA semi‐IPN was carried out using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and swelling measurements. The presence of PVA domains dispersed in the PDMS network disrupted the network and allowed PDMS to crystallize, as observed by the crystallization and melting peaks in the DSC analyses. Because of the presence of hydrophilic (? OH) and hydrophobic (Si? (CH₃)₂) domains, there was an appropriate hydrophylic/hydrophobic balance in the semi‐IPNs prepared, which led to a maximum equilibrium water content of ～ 14 wt % without a loss in the ability to swell less polar solvents. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Curing and mechanical properties of dicyanate/poly(ether sulfone) semi‐interpenetrating polymer networks

Semi‐interpenetrating polymer networks (semi‐IPNs) composed of a dicyanate resin and a poly(ether sulfone) (PES) were prepared, and their curing behavior and mechanical properties were investigated. The curing behavior of the dicyanate/PES semi‐IPN systems catalyzed by an organic metal salt was analyzed. Differential scanning calorimetry was used to study the curing behavior of the semi‐IPN systems. The curing rate of the semi‐IPN systems decreased as the PES content increased. An autocatalytic reaction mechanism was used to analyze the curing reaction of the semi‐IPN systems. The glass‐transition temperature of the semi‐IPNs decreased with increasing PES content. The thermal decomposition behavior of the semi‐IPNs was investigated. The morphology of the semi‐IPNs was investigated with scanning electron microscopy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1079–1084, 2003     

Preparation of poly(butylene succinate)‐poly[2‐(dimethylamino)ethyl methacrylate] copolymers and their applications as carriers for drug delivery

Copolymers of poly[2‐(dimethylamino)ethyl methacrylate]–poly(butylene succinate)–poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA–PBS–PDMAEMA, PDBD) were synthesized through a chain‐extension reaction. The thermal properties characterized using differential scanning calorimetry showed that the introduction of PDMAEMA chains slightly decreased the melting temperature of PBS. The water contact angle of PDBD copolymer films with media of various pH decreased with a decrease of pH. This should be ascribed to the conformational transition of PDMAEMA blocks from a compact coil to an expanding shape in accordance with the variation of the pH of the surroundings. The results of dynamic light scattering and scanning electron microscopy revealed that PDBD copolymers could form spherical micelles with small particle size and narrow particle size distribution. Furthermore, drug loading (loading content, ca 10%; encapsulation efficiency, ca 60%) and release experiments were conducted using doxorubicin as a hydrophobic model drug. The results of release experiments of copolymer nanomicelles showed that these micelles had pH‐responsive properties. © 2018 Society of Chemical Industry     

Characterization of hydrogels based on chitosan and copolymer of poly(dimethylsiloxane) and poly(vinyl alcohol)

Copolymers composed of poly(vinyl alcohol) (PVA) and poly(dimethylsiloxane) (PDMS) were crosslinked with chitosan to prepare semi‐interpenetrating polymer network (IPN) hydrogels by an ultraviolet (UV) irradiation method for application as potential biomedical materials. PVA/PDMS copolymer and chitosan was cast to prepare hydrogel films, followed by a subsequent crosslinking with 2,2‐dimethoxy‐2‐phenylacetophenone as a nontoxic photoinitiator by UV irradiation. Various semi‐interpenetrating polymer networks (semi‐IPNs) were prepared from different weight ratios of chitosan and the copolymer of PVA/PDMS. Photocrosslinked hydrogels exhibited an equilibrium water content (EWC) in the range of 65–95%. Swelling behaviors of these hydrogels were studied by immersion of the gels in various buffer solutions. Particularly, the PCN13 as the highest chitosan weight ratio in semi‐IPN hydrogels showed the highest EWC in time‐dependent and pH‐dependent swelling. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2591–2596, 2002     

Semi‐interpenetrating polymer networks based on polyurethane and poly(vinyl pyrrolidone) obtained by photopolymerization: Structure‐property relationships and bacterial adhesion

A range of semi‐interpenetrating polymer networks (semi‐IPNs) based on polyurethane (PU) and poly(vinyl pyrrolidone) (PVP) have been synthesized and characterized with respect to their thermodynamic characteristics, morphology, mechanical properties, surface properties, water sorption and bacterial adhesion. The free energies of mixing of PU and PVP in semi‐IPNs have been determined by the vapor sorption method and were shown to be positive for all compositions. The surface properties of semi‐IPNs were investigated using the dynamic contact angle analysis. It was shown that the advancing contact angle changes from 83.1° to 65.3° with increasing PVP from 7.05% to 57.38%. Scanning electron microscopy demonstrated that the semi‐IPNs are two‐phase systems with incomplete phase separation. The mechanical properties reflect the changes in structure of semi‐IPNs with increasing of amounts of PVP in the system. Incorporation of PVP into the semi‐IPN with PU restricts the ability of PVP to sorb water. As infection is likely to be caused by bacterial adherence to biomedical implants, the bacterial adhesion data suggests that the semi‐IPNs with PVP content below 22.52% may be useful for biomedical material applications. Polym. Eng. Sci. 44:940–947, 2004. © 2004 Society of Plastics Engineers.     

pH/temperature‐responsive semi‐IPN hydrogels composed of alginate and poly(N‐isopropylacrylamide)

Amino semitelechelic poly(N‐isopropylacrylamide) (PNIPAAm) was prepared by radical polymerization with aminoethanethiol hydrochloride as a chain‐transfer agent. Semi‐interpenetrating polymer network (semi‐IPN) hydrogels, composed of alginate and amine‐terminated PNIPAAm, were prepared by crosslinking with calcium chloride. From the swelling behaviors of semi‐IPNs at various pH's and Fourier transform infrared spectra at high temperatures, the formation of a polyelectrolyte complex was confirmed from the reaction between carboxyl groups in alginate and amino groups in modified PNIPAAm. Semi‐IPN hydrogels reached an equilibrium swelling state within 24 h. The water state in hydrogels, investigated by differential scanning calorimetry, showed that sample CAN55 [alginate/PNIPAAm (w/w) = 50/50] exhibited the lowest equilibrium water content and free water content among the hydrogels tested, which was attributed to its more compact structure compared to other samples and the high content of interchain bonding within the hydrogels. Alginate/PNIPAAm semi‐IPN hydrogels exhibited a reasonable sensitivity to the temperature, pH, and ionic strength of swelling medium. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1128–1139, 2002     

Thermal and pH dual‐responsive hydrogels based on semi‐interpenetrating network of poly(N‐isopropylacrylamide) and collagen nanofibrils

Hydrogels with environment‐sensitive properties have great potential applications in the controlled drug release field. In this paper, hybrid hydrogels with semi‐interpenetrating polymer networks (semi‐IPNs), composed of poly(N‐isopropylacrylamide) (PNIPAM) as the thermo‐sensitive component by in situ polymerization and self‐assembled collagen nanofibrils as the pH‐sensitive framework, were prepared for controlled release of methyl violet as a model drug. From Fourier transform infrared spectroscopy and scanning electron microscopy, it was indicated that the crosslinking of PNIPAM in the presence of collagen nanofibrils led to the formation of semi‐IPNs with homogeneous porous structure, and the semi‐IPNs showed improved thermal stability and elastic properties compared with the native collagen as determined using differential scanning calorimetry and rheologic measurements. Furthermore, the semi‐IPNs possessed swelling behaviors quite different from those of neat collagen or PNIPAM hydrogel under various pH values and temperatures. Correspondingly, as expected, the drug release behavior in vitro for semi‐IPNs performed variously compared with that for single‐component semi‐IPNs, which revealed the tunable performance of semi‐IPNs for release ability. Finally the thermo‐ and pH‐responsive mechanism of the semi‐IPNs was illuminated to provide guidance for the application of the thermo‐ and pH‐sensitive collagen‐based hybrid hydrogels in controlled drug delivery systems. © 2019 Society of Chemical Industry     

Feasibility of conducting semi‐interpenetrating networks based on a poly(ethylene oxide) network and poly(3,4‐ethylenedioxythiophene) in actuator design

A new type of synthetic pathway—the use of interpenetrating polymer networks (IPNs)—is proposed to design conducting polymer‐based actuators. Two types of materials with interesting conducting properties were prepared: (1) a semi‐IPN between poly(3,4‐ethylenedioxythiophene) (PEDOT) and branched poly(ethylene oxide) (PEO) network; (2) a tricomponent IPN between PEDOT and a PEO/polycarbonate (PC)–based network as the ionic conducting partner. In the first case, the influence of the amount of branching in the PEO network on the EDOT uptake and electrochemical properties was studied. A maximum conductivity (15 S cm^?1) was obtained for 60 wt % branched PEO in the material. Moreover, the dispersion profile of PEDOT in the material was shown by elemental analysis and energy dispersion spectroscopy to follow a gradient through the thickness of the film leading to a built‐in three‐layered device. With respect to PEO/PC materials, the best results were obtained for about 80 wt % PEO in the matrix where the material remains sufficiently elastomeric. In this case, the conductivity reaches about 1 S cm^?1 for a 10 to 30 wt % polycarbonate content. These materials are capable of reversible 45° angular deflections under a 0.5V potential difference. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3569–3577, 2003     

Temperature‐, pH‐, and ion‐stimulus‐responsive swelling behaviors of poly(dimethylaminoethyl methacrylate) gel containing cholic acid

Poly(dimethylaminoethyl methacrylate) hydrogels containing cholic acid (PDMAEMA–CA) were synthesized by radiation crosslinking. The introduction of 10 and 20 mol% cholic acid (CA) into the poly(dimethylaminoethyl methacrylate) (PDMAEMA) hydrogel decreased the maximum swelling ratio (SR) of the gel from 40 to 6 and 5, respectively. The incorporation of CA with dimethylaminoethyl methacrylate led to a decrease in the lower critical swelling temperature of the gel from 44 to 42°C but did not exert big influence on the ion‐stimulus‐responsive properties of the gel. However, the pH sensitivity of the PDMAEMA–CA gel was quite different from that of PDMAEMA gel. The SR of PDMAEMA gel decreased at pH 2.5, whereas the SRs of the PDMAEMA–CA gels showed a convex‐upward function of pH; that is, SR of the PDMAEMA–10% CA gel first increased (pH 1.2–3.2) and then decreased (pH 3.2–11.9) with increasing pH. The pH‐stimulus‐responsive swelling behavior of the PDMAEMA–20% CA gel was similar to that of the PDMAEMA–10% CA gel except for the unique swelling behavior exhibited in the lower pH region. The unique decrease in SR in strong acidic solutions was attributed to aggregations driven by the hydrophobic interactions between CA molecules. Phase separation of the gel in strongly acidic solutions was observed; that is, the margin of the swollen gel was transparent and elastic (cellular structure), whereas the core of it was opaque (aggregated structure) as recorded by scanning electron microscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39998.     

Miscibility and thermal and dynamic mechanical behaviour of semi‐interpenetrating polymer networks based on polyurethane and poly(hydroxyethyl methacrylate)

The thermodynamic miscibility and thermal and dynamic mechanical behaviour of semi‐interpenetrating polymer networks (semi‐IPNs) of crosslinked polyurethane (PU) and linear poly(hydroxyethyl methacrylate) (PHEMA) have been investigated. The free energies of mixing of the semi‐IPN components have been determined by the vapour sorption method and it was established that the parameters are positive and depend on the amount of PHEMA in the semi‐IPN samples. Thermal analyses glass transition temperatures evidenced two in the semi‐IPNs in accordance with the investigation of the thermodynamic miscibility of these systems. Dynamic mechanical analysis revealed a pronounced change in the viscoelastic properties of the PU‐based semi‐IPNs with different amounts of PHEMA in the samples. The semi‐IPNs have two distinct tan δ maxima related to the relaxations of the two polymers in their glass temperature domains. The temperature position of PU relaxation maximum tan δ is invariable but its amplitude decreases in the semi‐IPNs with increasing amount of PHEMA in the systems. The tan δ maximum of PHEMA is shifted to a lower temperature and its amplitude decreases with increasing amount of PU in the semi‐IPNs. The segregation degree of components α was calculated using the viscoelastic properties of semi‐IPNs. It was concluded that the studied semi‐IPNs are two‐phase systems with incomplete phase separation. The different levels of immiscibility lead to the different degree of phase separation in the semi‐IPNs with compositions. Copyright © 2004 Society of Chemical Industry     

Preparation,characterization, and drug‐release properties of pH/temperature‐responsive poly(N‐isopropylacrylamide)/chitosan semi‐IPN hydrogel particles

Novel poly(N‐isopropylacrylamide) (PNIPAAm)/chitosan (CS) semi‐interpenetrating polymer network hydrogel particles were prepared by inverse suspension polymerization. The prepared particles were sensitive to both temperature and pH, and they had good reversibility in solution at different temperatures and pH values. The swelling ratios of PNIPAAm/CS hydrogel particles decreased slightly with the addition of CS, which did not shift the lower critical solution temperature. The drug‐release behavior of the particles was investigated using cyclic adenosine 3′,5′‐monophosphate (cAMP) as a model drug. The release of cAMP from the hydrogel particles was affected by temperature, pH, and the CS content in the particles. These results showed that semi‐IPN hydrogel particles appeared to be of great promise in pH‐ and temperature‐sensitive oral drug release. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal characteristics of interpenetrating polymer networks composed of poly(vinyl alcohol) and poly(N‐isopropylacrylamide)

Interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(N‐isopropylacrylamide) (PNIPAAm) were prepared by the sequential‐IPN method. The thermal characterization of the IPNs was investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). Depression of the melting temperature (T_m) of the PVA segment in IPNs was observed with increasing PNIPAAm content using DSC. DEA was employed to ascertain the glass‐transition temperature (T_g) of IPNs. From the result of DEA, IPNs exhibited two T_g values, indicating the presence of phase separation in the IPNs. The thermal decomposition of IPNs was investigated using TGA and appeared at near 200°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 881–885, 2003     

Insolubilization of sodium chondroitin sulfate by forming a semi‐interpenetrating polymer network with acrylic acid: A potential carrier for colon‐specific drug delivery

To reduce the highly hydrophilic property of chondroitin sulfate (ChS), a semi‐interpenetrating polymer network (semi‐IPN) of chondroitin sulfate/polyacrylic acid (PAA) was prepared as a drug carrier by crosslinking acrylic acid with diethyleneglycol diacrylate. The swelling properties of the semi‐IPNs with different concentrations of crosslinking agent were correlated. The moisture sorption profiles were evaluated using differential thermal analysis. Ketoprofen was used as a drug probe to evaluate the performance of the drug released from the semi‐IPN matrices. The prepared semi‐IPNs demonstrated significant swelling reduction properties with both gastric and intestinal fluids compared with those of both the pure ChS and the ChSAA blend without the crosslinking agent. The amount of accumulated drug released from the semi‐IPNs was less than 30 wt % at pH 1.2 and up to 80 wt % at pH 7.4. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 114–122, 2002     

Blood protein adsorption onto macroporous semi‐interpenetrating polymer networks (IPNs) of poly(ethylene glycol) (PEG) and poly(2‐hydroxyethyl methacrylate) (PHEMA) and assessment of in vitro blood compatibility

This work reports a study of the adsorption of fibrinogen (Fgn) onto the surface of semi‐interpenetrating polymer networks (IPNs) of poly(ethylene glycol) (PEG) and poly(2‐hydroxyethyl methacrylate) (PHEMA). The semi‐IPNs were prepared by polymerizing 2‐hydroxyethyl methacrylate with a redox system and in the presence of PEG and crosslinker ethyleneglycol dimethacrylate. The proposed spongy IPNs were characterized by Fourier transform infrared and environmental scanning electron microscopy methods, and network structural parameters, such as molecular weight between crosslinks and crosslink density, were calculated using swelling measurements. The adsorption of Fgn was carried out onto the spongy IPNs and kinetic constants of the adsorption process as well as isotherm constants were evaluated. The adsorption process was also studied under varying pH, ionic strengths, and chemical architecture of the IPNs. The anti‐thrombogenic behaviour of the polymer matrices was judged using in vitro tests. Copyright © 2006 Society of Chemical Industry     

Synthesis and swelling properties of pH‐sensitive hydrogels based on chitosan and poly(methacrylic acid) semi‐interpenetrating polymer network

A novel semi‐interpenetrating polymer network (semi‐IPN) hydrogel composed of chitosan and poly(methacrylic acid) was synthesized using formaldehyde as a crosslinker. The amount of crosslinker was searched and optimized. The structure of the hydogel was investigated by Fourier transform infrared (FTIR) spectroscopy. The spectrum shows that a structure of polyelectrolyte complex exists in the hydrogel. The effects of pH, ionic strength, and inorganic salt on the swelling behaviors of the hydrogel were studied. The results indicate the hydrogel has excellent pH sensitivity in the range of pH 1.40 to 4.50, pH reversible response between pH 1.80 and 6.80, and ionic strength reversible response between ionic strength 0.2 and 2.0M. The results also show that the hydrogel has a bit higher swelling capacity in a mix solution of calcium chloride (CaCl₂) and hydrochloric acid (HCl) solution than in a mix solution of sodium chloride (NaCl) and HCl. These results were further confirmed through morphological change measured by scanning electron microscope (SEM). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1720–1726, 2005     

Biodegradable block copolymers with poly(ethylene oxide) and poly(glycolic acid‐valine) blocks

Biodegradable ABA triblock copolymers with poly(ethylene oxide) and poly(glycolic acid‐valine) blocks were synthesized via ring‐opening polymerization of cyclo(glycolic acid‐valine) using Ca‐alcoholates of hydroxytelechelic PEO as the initiator. The L‐valine residue racemized during copolymerization of cyclo(glycolic acid‐valine). The crystallization of the block copolymers decreases with decreasing PEO content in the triblock copolymers and with increasing length of the poly(glycolic acid‐valine) block. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2916–2919, 2002     

Preparation and characterization of pH‐ and temperature‐responsive semi–interpenetrating polymer network hydrogels based on linear sodium alginate and crosslinked poly(N‐isopropylacrylamide)

In this study, pH‐ and temperature‐responsive hydrogels based on linear sodium alginate (SA) and crosslinked poly(N‐isopropylacrylamide) (PNIPAAm) were prepared by semi‐interpenetrating network (semi‐IPN) technique. The dually responsive hydrogels were characterized by FTIR, DSC, and SEM, and their temperature‐ and pH‐responsive behaviors were investigated by measuring equilibrium swelling ratios and pulsatile swelling experiments. The results showed that these hydrogels underwent volume phase transition at around 33°C irrespective of the pH value of the medium, but their pH sensitivity was evident only below their volume phase transition temperature. Under basic conditions, the swelling ratios of SA/PNIPAAm semi‐IPN hydrogels were greater than that of pure PNIPAAm hydrogel and increased with increasing SA content incorporated into the hydrogels, but the case was inverse under acidic conditions. The pulsatile swelling experiments indicated that the higher the SA content in SA/PNIPAAm semi‐IPN hydrogels, the faster the response rate to both pH and temperature change. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1931–1940, 2005