Preparation of alginate/poly(N‐isopropylacrylamide) semi‐interpenetrating and fully interpenetrating polymer network hydrogels with γ‐ray irradiation and their swelling behaviors

Semi‐interpenetrating polymer network (semi‐IPN) and fully interpenetrating polymer network (full‐IPN) hydrogels composed of alginate and poly(N‐isopropylacrylamide) were prepared with γ‐ray irradiation. The semi‐IPN hydrogels were prepared through the irradiation of a mixed solution composed of alginate and N‐isopropylacrylamide (NIPAAm) monomer to simultaneously achieve the polymerization and self‐crosslinking of NIPAAm. The full‐IPN hydrogels were formed through the immersion of the semi‐IPN film in a calcium‐ion solution. The results for the swelling and deswelling behaviors showed that the swelling ratio of semi‐IPN hydrogels was higher than that of full‐IPN hydrogels. A semi‐IPN hydrogel containing more alginate exhibited relatively rapid swelling and deswelling rates, whereas a full‐IPN hydrogel showed an adverse tendency. All the hydrogels with NIPAAm exhibited a change in the swelling ratio around 30–40°C, and full‐IPN hydrogels showed more sensitive and reversible behavior than semi‐IPN hydrogels under a stepwise stimulus. In addition, the swelling ratio of the hydrogels continuously increased with the pH values, and the swelling processes were proven to be repeatable with pH changes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4439–4446, 2006     

Preparation and Swelling Properties of Temperature‐Sensitive Semi‐Interpenetrating Polymer Networks Composed of Poly[(N‐tert‐butylacrylamide)‐co‐acrylamide] and Hydroxypropyl Cellulose

Summary: Temperature‐responsive hydrogels based on linear HPC and crosslinked P(NTBA‐co‐AAm) were prepared by the semi‐IPN technique. The structure of these semi‐IPN hydrogels was investigated by FT‐IR spectroscopy. An increase in normalized band ratios (A₂₉₈₀/A₁₆₆₅) was observed with increasing HPC content in the initial mixture. The swelling kinetics and water transport mechanism of these semi‐IPN hydrogels were examined and their temperature responsive behaviors were also investigated by measuring equilibrium swelling ratios and pulsatile swelling experiments. The results showed that these semi‐IPN hydrogels underwent a volume phase transition between 18 and 22 °C irrespective of the amounts of MBAAm and HPC. However, below the volume phase transition temperature, their equilibrium swelling ratios were affected by the amount of MBAAm and HPC. The pulsatile swelling experiments indicated that the lower the MBAAm and the higher HPC contents in semi‐IPN hydrogels the faster the response rate temperature change.

Equilibrium swelling ratios of the semi‐IPN P(NTBA‐co‐AAm)/HPC hydrogels in water shown as a function of temperature.     

Preparation and characterization of thermosensitive poly(N‐isopropylacrylamide)/poly(ethylene oxide) semi‐interpenetrating polymer networks

Temperature‐sensitive poly(N‐isopropylacrylamide) hydrogels were successfully synthesized by using poly(ethylene oxide) as the interpenetrating agent. The newly prepared semi‐interpenetrating polymer network (semi‐IPN) hydrogels exhibited much better properties as temperature‐sensitive polymers than they did in the past. Characterizations of the IPN hydrogels were investigated using a swelling experiment, FTIR spectroscopy, and differential scanning calorimetry (DSC). Semi‐IPN hydrogels exhibited a relatively high temperature dependent swelling ratio in the range of 23–28 at room temperature. DSC was used for the determination of the lower critical solution temperature of the semi‐IPN hydrogel. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3032–3036, 2003     

Synthesis and properties of the semi‐interpenetrating polymer network–like,thermosensitive poly(N‐isopropylacrylamide) hydrogel

A new strategy was used to prepare a semi‐interpenetrating polymer network (semi‐IPN)–like poly(N‐isopropylacrylamide) (PNIPAAm) polymeric hydrogel, consisting of either low (2300) or high (33,000) molecular weight linear PNIPAAm chains and the crosslinked PNIPAAm network. The properties of the resulting PNIPAAm hydrogels were characterized by DSC and SEM as well as their swelling ratios at various temperatures, the deswelling in hot water (48°C), and the oscillating shrinking–swelling properties within small temperature cycles. It was found that the deswelling rate of these semi‐IPN–like PNIPAAm hydrogels was improved if the molecular weight and/or composition of the linear PNIPAAm chains within the semi‐IPN–like PNIPAAm hydrogels were increased. This improved deswelling rate was attributed to the fast response nature of the linear PNIPAAm chains and the increased pore number in the matrix network, which provided numerous water channels for the water to diffuse out during the deswelling process at a temperature above the lower critical solution temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1935–1941, 2003     

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     

Preparation of hydrogels composed of poly(vinyl alcohol) and polyethyleneimine and their electrical response

Semi‐ and full‐interpenetrating polymer network (IPN) hydrogels composed of poly(vinyl alcohol) and polyethyleneimine (PEI) were prepared to investigate the bending behavior under the electric response. To find out the characteristics of the hydrogel in the medium, swelling ratio, and rate and water state of the hydrogels were measured. The swelling ratio of the semi‐IPN hydrogels increased with PEI content in the matrix, whereas that of full‐IPN hydrogels dramatically decrease with increase of PEI contents in the hydrogels. In the water state of hydrogel, the bound water and free water of semi‐IPN hydrogels increased with PEI weight ratio. The full‐IPN hydrogels show the lower free water content in comparison with the semi‐IPN hydrogel. The IPN hydrogels exhibited bending angle change in response to external stimulus such as voltage, the bending angle increased with PEI concentration. In addition, the repeated bending behaviors according to the magnitude of the applied electric field revealed that the bending angle is reversible without collapse of formation of hydrogel in all samples. Thus, the hydrogels will be useful as novel modulation systems in the field of artificial organ and matrix for drug delivery. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Synthesis and properties of silver nanoparticles in chitosan‐based thermosensitive semi‐interpenetrating hydrogels

In this article, thermosensitive poly(N‐isopropyl acrylamide‐co‐vinyl pyrrolidone)/chitosan [P(NIPAM‐co‐NVP)/CS] semi‐interpenetrating (semi‐IPN) hydrogels were prepared by redox‐polymerization using N,N‐methylenebisacrylamide as crosslinker and ammonium persulfate/N,N,N′,N′‐tetramethylethylenediamine as initiator. Highly stable and uniformly distributed Ag nanoparticles were prepared by using the semihydrogel networks as templates via in situ reduction of silver nitrate in the presence of sodium borohydride as a reducing agent. Introduction of CS improves the hydrogels swelling ratio (SR) and stabilizes the formed Ag nanoparticles in networks. Scanning electron microscopy and transmission electron microscopy revealed that Ag nanoparticles were well dispersed with diameters of 10 nm. The semi‐IPN hydrogel/Ag composites had higher SR and thermal stability than its corresponding semi‐IPN hydrogels. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Swelling and diffusion characteristics of novel semi‐interpenetrating network hydrogels composed of poly[(acrylamide)‐ co‐(sodium acrylate)] and poly[(vinylsulfonic acid), sodium salt]

A series of novel semi‐interpenetrating polymer networks (IPNs) composed of poly[(acrylamide)‐co‐(sodium acrylate)] with varying amounts (5, 10, and 15 wt%) of poly[(vinylsulfonic acid), sodium salt] was synthesized. The semi‐IPN hydrogels were characterized by infrared spectroscopy. The swelling behavior of these IPNs was studied in distilled water/physiological solutions/buffer solutions/salt solutions. As the amount of poly[(vinylsulfonic acid), sodium salt] increased in the network, the swelling capacity of the semi‐IPNs increased considerably. The swelling and diffusion characteristics such as water penetration velocity (v), diffusion exponent (n), and diffusion coefficient (D) were calculated in distilled water, as well as in other physiological solutions. The highest swelling capacity was noted in urea and glucose solutions. The semi‐IPN hydrogels followed non‐Fickian diffusion behavior in water and physiological fluids, whereas Fickian behavior was observed in buffer solutions. The stimuli‐responsive characteristics towards physiological fluids, salt concentration, and temperature of these semi‐IPN hydrogels were also investigated. The swelling behavior of the semi‐IPNs decreased markedly with an increase of the concentration of the salt solutions. Copyright © 2006 Society of Chemical Industry     

Mechanical Strengths of Hydrogels of Poly(N,N‐Dimethylacrylamide)/Alginate with IPN and of Poly(N,N‐Dimethylacrylamide)/Chitosan with Semi‐IPN Microstructures

Tough hydrogels receive continuous attention because of their promising applications in many fields. Herein, tough hydrogels of poly (N,N‐dimethylacrylamide) (PDMAA)/alginate (SA) are prepared, with interpenetrating network (IPN) and of PDMAA/chitosan (CS) with semi‐IPN microstructure, respectively. The toughening of the hydrogel by incorporating natural polymers is studied by compressing tests and dynamic mechanical analyses. Moreover, cyclic load–unload compressing of the two types of hydrogels are performed at low strains and under relatively high strains, in order to compare their strength and anti‐fatigue properties. The results indicate that the mechanical strength can be markedly improved upon addition of the natural polymers, and the IPN hydrogel of PDMAA/SA reveals much higher mechanical performances but is less stable. However, the semi‐IPN hydrogel of PDMAA/CS displays excellent anti‐fatigue stability, but with relatively low strength. Swelling tests, scanning electron microscopy, and Fourier transform infrared spectroscopy are carried out to study the microstructures of the hydrogels, which are carefully analyzed to understand the difference in mechanical performances of those hydrogels. The results suggest that the presence of sacrificial unit and higher chain density in the IPN are helpful for toughening hydrogels, while the semi‐IPN network is beneficial to improve the energy dissipation efficiency.     

Swelling behavior of semi‐interpenetrating polymer network hydrogels composed of poly(vinyl alcohol) and poly(acrylamide‐co‐sodium methacrylate)

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) (PVA) and poly(acrylamide‐co‐sodium methacrylate) poly(AAm‐co‐SMA) were prepared by the semi IPN method. These IPN hydrogels were prepared by polymerizing aqueous solution of acrylamide and sodium methacrylate, using ammonium persulphate/N,N,N¹,N¹‐tetramethylethylenediamine (APS/TMEDA) initiating system and N,N¹‐methylene‐bisacrylamide (MBA) as a crosslinker in the presence of a host polymer, poly(vinyl alcohol). The influence of reaction conditions, such as the concentration of PVA, sodium methacrylate, crosslinker, initiator, and reaction temperature, on the swelling behavior of these IPNs was investigated in detail. The results showed that the IPN hydrogels exhibited different swelling behavior as the reaction conditions varied. To verify the structural difference in the IPN hydrogels, scanning electron microscopy (SEM) was used to identify the morphological changes in the IPN as the concentration of crosslinker varied. In addition to MBA, two other crosslinkers were also employed in the preparation of IPNs to illustrate the difference in their swelling phenomena. The swelling kinetics, equilibrium water content, and water transport mechanism of all the IPN hydrogels were investigated. IPN hydrogels being ionic in nature, the swelling behavior was significantly affected by environmental conditions, such as temperature, ionic strength, and pH of the swelling medium. Further, their swelling behavior was also examined in different physiological bio‐fluids. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 302–314, 2005     

Physical–chemical properties of xylan/PAAc magnetic semi‐interpenetrating network hydrogel

A novel magnetic semi‐IPN hydrogel based on xylan and poly(acrylic acid) was prepared, and the prepared hydrogels had excellent thermal stability, magnetic‐, and pH‐ sensitive properties. The physical‐chemical properties of the prepared hydrogels depended on the contents of xylan and Fe₃O₄ nanoparticles. The thermal stability of the hydrogels enhanced as the contents of xylan and Fe₃O₄ nanoparticles increased; however, the equilibrium swelling ratio decreased with increasing the contents of Fe₃O₄ nanoparticles and xylan. The interconnected pore channels were formed in the hydrogels and the amount of the channels increased with an increase in xylan content. The prepared hydrogels had a super‐paramagnetic property, and the magnetization increased with an increase in the content of Fe₃O₄ nanoparticles. The superior characteristics of the xylan/PAAc magnetic semi‐IPN hydrogel would expand its applications in drug delivery and magnetic separation aspects. POLYM. COMPOS., 36:2317–2325, 2015. © 2014 Society of Plastics Engineers     

Swelling characterizations of chitosan and polyacrylonitrile semi‐interpenetrating polymer network hydrogels

Temperature‐ and pH‐responsive semi‐interpenetrating polymer network (semi‐IPN) hydrogels constructed with chitosan and polyacrylonitrile (PAN) were studied. The characterizations of semi‐IPN hydrogels were investigated using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). IPN hydrogels exhibited a relatively high swelling ratio, 23.31%–145.20% at room temperature. The swelling ratio of hydrogels depends on pH and temperature. DSC was used to determine the amount of free water in IPN hydrogels. The amount of free water increased with increasing chitosan content in the semi‐IPN hydrogels. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2011–2015, 2003     

Poly(N‐isopropylacrylamide‐co‐sodium acrylate) hydrogels: Interactions with surfactants

Poly(N‐isopropylacrylamide‐co‐sodium acrylate) [poly(NIPAM‐co‐SA)] hydrogels were modified with three different kind of surfactants (cationic, anionic, and nonionic) to study the effect on the swelling properties. The structural variation of the surfactant‐modified hydrogels was investigated in detail. The interaction between the surfactants and the hydrogel varies and strictly depends on the surfactant type. The variation in thermal stability of the modified surfactant hydrogels was investigated and compared with unmodified hydrogel. Further, the hydrogel swelling/diffusion kinetic parameters were investigated and diffusion of water into hydrogel was found to be of the non‐Fickian transport mechanism. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3423–3430, 2007     

Synthesis and characteristics of an amphoteric semi‐IPN hydrogel composed of acrylic acid and poly(diallydimethylammonium chloride)

Semi‐interpenetrating polymer network (IPN) hydrogels, with acrylic acid (AA) and poly(diallydimethylammonium chloride) (PDMDAAC), were constructed by a sequential IPN method. The characterizations of the IPN hydrogels were investigated by FTIR, DTA, and swelling tests under various conditions. The prepared semi‐IPN hydrogels exhibited relatively high swelling capacity, in the range of 477–630 g/g at 25°C. The results show that the swelling capacity of AA/PDMDAAC semi‐IPN hydrogels was pH and temperature dependent. Swelling behaviors were also studied in the different salt solutions. Swelling kinetic parameters are given. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 345–350, 2007     

Swelling dynamics of IPN hydrogels including acrylamide‐acrylic acid‐chitosan and evaluation of their potential for controlled release of piperacillin‐tazobactam

For to be used in controlled releasing of piperacillin‐tazobactam, a series of semi and full IPN type hydrogels composed of acrylic acid (AA), acrylamide (AAm) and Chitosan (CS) were prepared via free‐radical polymerization. Ethylene glycol dimethacrylate (EGDMA) was used for crosslinking of PAAm and PAA chains to form semi‐IPN hydrogels. However, the full‐IPN type hydrogels were prepared by using glutaraldehyde (GA) and EGDMA as cocrosslinkers. Characteristics of the hydrogels were investigated by swelling experiments and SEM and FTIR analysis. Generally, full‐IPN type hydrogels swell much more than the semi‐IPN types. By comparing the full‐IPN type hydrogels in between, it is found that the increasing amount of GA causes the decreasing in S% values from 4860 to 4300%. Releasing of piperacillin‐tazobactam from selected three hydrogels were investigated in phosphate buffer solution at pH = 7.4, 37°C. The kinetic release parameters, n and k were calculated and non‐Fickian type diffusion was established for these hydrogels. The behaviors of the piperacillin‐tazobactam loaded hydrogels in Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) culture suspensions were also studied and the statistically significant differences for the microorganism growth values were determined. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A novel pH‐sensitive gelatin–DNA semi‐interpenetrating polymer network hydrogel

Gelatin and DNA were mixed together in various ratios followed by the addition of glutaraldehyde as a cross‐linker. FT‐IR spectroscopy confirmed the formation of a semi‐interpenetrating polymer network (semi‐IPN) between the gelatin and DNA. The gelatin–DNA semi‐IPN hydrogel underwent, reversibly, remarkable changes in swelling degree in response to the variation of pH. In the low‐pH range, the hydrogel showed a lower swelling degree; with an increment in pH, the hydrogel was highly swollen, which is considered to originate from the complexation and de‐complexation between gelatin and DNA, as was verified by turbidity measurements. Higher contents of DNA result in an increase in the swelling degree, which is presumably due to the easy outward expansion of free DNA moieties. The permeability coefficient, P, for a model molecule, cimetidine, through the semi‐IPN hydrogel membranes was determined in pH 1.0 and pH 12.0 buffer solutions. The results show that the permeation of cimetidine is responsive to pH change, and an evident variation in the P values occurs in response to the pH of the media. Copyright © 2004 Society of Chemical Industry     

Thermoreversible hydrogel. XVII. Investigation of the drug release behavior for [N‐isopropylacrylamide‐co‐trimethyl acrylamidopropyl ammonium iodide‐co‐3‐dimethyl (methacryloyloxyethyl) ammonium propane sulfonate] copolymeric hydrogels

A series of copolymeric hydrogels were prepared from various molar ratios of N‐isopropylacrylamide (NIPAAm), trimethyl acrylamidopropyl ammonium iodide (TMAAI), and 3‐dimethyl (methacryloyloxyethyl) ammonium propane sulfonate (DMAPS). Results showed that the swelling ratios of these copolymeric hydrogels increased with an increase of TMAAI content. The drug release behavior of the ionic thermosensitive hydrogels related to their ionicity and drug types. Results indicated that the release ratio of caffeine in the hydrogels was not affected by the ionicity of hydrogels, but increased with increasing of the swelling ratio. The anionic solute (phenol red) strongly interacted with cationic hydrogel (very large K_d), so the phenol red release ratio in cationic gels was very low. On the other hand, CV was adsorbed only on the skin layer of the cationic hydrogel because of the charge repulsion, and released rapidly. Therefore the release ratio was highest for cationic hydrogel to cationic drug. In addition, the partition coefficients (K_d) and the drug delivery behavior of the present gels were also investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1592–1598, 2002     

Preparation and antidehydration of interpenetrating polymer network hydrogels based on 2‐hydroxyethyl methacrylate and N‐vinyl‐2‐pyrrolidone

This work reports the preparation of 2‐hydroxyethyl methacrylate (HEMA)/N‐vinyl‐2‐pyrrolidone (NVP) interpenetrating polymer network (IPN) hydrogels by UV‐initiated polymerization in the presence of free radical photoinitiator Darocur 1173 and cationic photoinitiator 4,4′‐dimethyl diphenyl iodonium hexafluorophosphate. The polymerization mechanism was investigated by the formation of gel network. The structure and morphology of the HEMA/NVP IPN hydrogels were characterized by fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The results showed that the IPN gels exhibited homogeneous morphology. The dehydration rates of HEMA/NVP IPN hydrogels were examined by the gravimetric method. The results revealed that the hydrogels had a significant improvement of antidehydration ability in comparison with poly(2‐hydroxyethyl methacrylate)(PHEMA) hydrogel embedded physically with poly(N‐vinyl‐2‐pyrrolidone)(PVP). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and swelling properties of semi‐IPN hydrogels based on chitosan‐g‐poly(acrylic acid) and phosphorylated polyvinyl alcohol

The phosphorylated poly(vinyl alcohol) (P‐PVA) samples with various substitution degrees were prepared through the esterification reaction of PVA and phosphoric acid. By using chitosan (CTS), acrylic acid (AA) and P‐PVA as raw materials, ammonium persulphate (APS) as an initiator and N,N‐methylenebisacrylamide as a crosslinker, the CTS‐g‐PAA/P‐PVA semi‐interpenetrated polymer network (IPN) ssuperabsorbent hydrogel was prepared in aqueous solution by the graft copolymerization of CTS and AA and followed by an interpenetrating and crosslinking of P‐PVA chains. The hydrogel was characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) techniques, and the influence of reaction variables, such as the substitution degree and content of P‐PVA on water absorbency were also investigated. FTIR and DSC results confirmed that PAA had been grafted onto CTS backbone and revealed the existence of phase separation and the formation of semi‐IPN network structure. SEM observations indicate that the incorporation of P‐PVA induced highly porous structure, and P‐PVA was uniformly dispersed in the polymeric network. Swelling results showed that CTS‐g‐PAA/P‐PVA semi‐IPN superabsorbent hydrogel exhibited improved swelling capability (421 g·g^?1 in distilled water and 55 g·g^?1 in 0.9 wt % NaCl solution) and swelling rate compared with CTS‐g‐PAA/PVA hydrogel (301 g·g^?1 in distilled water and 47 g·g^?1 in 0.9 wt % NaCl solution) due to the phosphorylation of PVA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009