Preparation and separation function of N‐isopropylacrylamide copolymer hydrogels

In this paper, N‐isopropylacrylamide (NIPA) was synthesized by acrylonitrile and isopropanol. Poly(N‐isopropylacrylamide) (PNIPA) was prepared by a chemical method. The dependence of its swelling behavior on temperature was studied. Results showed that PNIPA hydrogel was a temperature‐sensitive gel. Its LCST (lower critical solution temperature) was about 32 °C, and its swelling ratio (at 20 °C) was about 17–18. Sodium acrylate (SA) and sodium methylacrylate (SMA) were copolymerized with NIPA respectively. Equilibrium swelling ratios of the copolymer hydrogels at lower temperature were two to three times that of PNIPA. The LCST of the copolymer hydrogels could be controlled between 32 and 45 °C by adjusting the content of SA or SMA. Kinetics of P(NIPA‐co‐SA) hydrogels, whether swelling or shrinking processes, were in good agreement with apparent second order kinetic equations. Several experiments were designed to separate aqueous bovine serum albumin solution using the hydrogels prepared above. The separation efficiency was about 80%. Copyright © 2000 John Wiley & Sons, Ltd.     

Effect of the crosslinking level on the properties of temperature‐sensitive poly(N‐isopropylacrylamide) hydrogels

In this study, the effect of the level of crosslinking on the properties of poly(N‐isopropylacrylamide) (PNIPAAm) hydrogels was investigated in terms of their lower critical solution temperature (LCST), interior morphology, equilibrium swelling, and deswelling and swelling kinetics. The thermal analysis showed that PNIPAAm hydrogels, having a wide range of crosslinking levels, exhibited almost the same LCSTs, and this was different from what the conventional theory would have predicted. Scanning electron micrographs revealed that the interior network structure of the PNIPAAm matrix became more porous with an increase in the level of crosslinking. This more porous matrix provided numerous water channels for water diffusion in or out of the matrix and, therefore, an improved response rate to the external temperature changes during the deswelling process and the swelling process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 582–593, 2003     

Structure and properties of cellulose/poly(N‐isopropylacrylamide) hydrogels prepared by IPN strategy

Interpenetrating polymer network (IPN) strategy was developed to fabricate novel hydrogels composed of cellulose and poly(N‐isopropylacrylamide) (PNIPAAm) with high mechanical strength and adjustable thermosensitivity. Cellulose hydrogels were prepared by chemically cross‐linking cellulose in NaOH/urea aqueous solution, which were employed as the first network. The second network was subsequently obtained by in situ polymerization/cross‐linking of N‐isopropylacrylamide in the cellulose hydrogels. The results from FTIR and solid ¹³C NMR indicated that the two networks co‐existed in the IPN hydrogels, which exhibited uniform porous structure, as a result of good compatibility. The mechanical and swelling properties of IPN hydrogels were strongly dependent on the weight ratio of two networks. Their temperature‐sensitive behaviors and deswelling kinetics were also discussed. This work created double network hydrogels, which combined the advantages of natural polymer and synthesized PNIPAAm collectively in one system, leading to the controllable temperature response and improvement in the physical properties. Copyright © 2009 John Wiley & Sons, Ltd.     

Investigation of swelling,drug release and diffusion behaviors of poly(N‐isopropylacrylamide)/poly (N‐vinylpyrrolidone) full‐IPN hydrogels

The synthesis of sequential full interpenetrating polymer networks (IPNs) based on poly (N‐isopropylacrylamide) (PNIPAAm) and negatively charged poly(N‐vinyl‐2‐pyrrolidone) (PNVP) was described and their swelling, drug release, and diffusion studies were investigated. PNIPAAm was used as a host network. According to swelling experiments, IPNs gave relatively lower swelling ratios compared to PNIPAAm hydrogel due to the higher cross‐linking density. Lidocaine (LD) was used as a model drug for the investigation of drug release behavior of IPNs. LD uptake of the IPNs were found to increase from 24 to 166 (mg LD / g dry gel) with increasing amount of PNIPAAm and AMPS contents in the IPN structure. It was observed that the specific interaction between drug and AMPS co‐monomer influenced the drug release profile. In the diffusion transport mechanism study in water, the results indicated that the swelling exponents n for all IPNs are in the range from 0.50 to 0.72. This implies that the swelling transport mechanism was transferred from Fickian to non‐Fickian transport, with increasing AMPS content and NIPAAm character in the IPN structure. In addition, diffusion of LD within the IPNs showed similar trend. The incorporation of AMPS leads to an increase in electrostatic interaction between charge sites on carboxylate ions and cationic LD molecules. Therefore, the highest diffusion coefficient (D) of drug was found for IPN2 sample. Copyright © 2007 John Wiley & Sons, Ltd.     

A new thermo‐responsive block copolymer with tunable upper critical solution temperature and lower critical solution temperature in the alcohol/water mixture

The multi‐thermo‐responsive block copolymer of poly[2‐(2‐methoxyethoxy)ethyl methacrylate]‐block‐poly[N‐(4‐vinylbenzyl)‐N,N‐diethylamine] (PMEO₂MA‐b‐PVEA) displaying phase transition at both the lower critical solution temperature (LCST) and the upper critical solution temperature (UCST) in the alcohol/water mixture is synthesized by reversible addition‐fragmentation chain transfer polymerization. The poly[2‐(2‐methoxyethoxy)ethyl methacrylate] (PMEO₂MA) block exhibits the UCST phase transition in alcohol and the LCST phase transition in water, while the poly[N‐(4‐vinylbenzyl)‐N,N‐diethylamine] (PVEA) block shows the UCST phase transition in isopropanol and the LCST phase transition in the alcohol/water mixture. Both the polymer molecular weight and the co‐solvent/nonsolvent exert great influence on the LCST or UCST of the block copolymer. By adjusting the solvent character including the water content and the temperature, the block copolymer undergoes multiphase transition at LCST or UCST, and various block copolymer morphologies including inverted micelles, core‐corona micelles, and corona‐collapsed micelles are prepared. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4399–4412     

Attenuated total reflectance/fourier transform infrared studies on the phase‐separation process of aqueous solutions of poly(n‐isopropylacrylamide)

Temperature‐induced phase separation of poly(N‐isopropylacrylamide) in aqueous solutions was studied by attenuated total reflectance (ATR)/Fourier transform infrared spectroscopy. The main objectives of the study were to understand, on a molecular level, the role of hydrogen bonding and hydrophobic effects below and above the phase‐separation temperature and to derive the scenario leading to this process. Understanding the behavior of this particular system could be quite relevant to many biological phenomena, such as protein denaturation. The temperature‐induced phase transition was easily detected by the ATR method. A sharp increase in the peaks of both hydrophobic and hydrophilic groups of the polymer and a decrease in the water‐related signals could be explained in terms of the formation of a polymer‐enriched film near the ATR crystal. Deconvolution of the amide I and amide II peaks and the O? H stretch envelope of water revealed that the phase‐separation scenario could be divided, below the phase‐separation temperature, into two steps. The first step consisted of the breaking of intermolecular hydrogen bonds between the amide groups of the polymer and the solvent and the formation of free amide groups, and the second step consisted of an increase in intramolecular hydrogen bonding, which induced a coil–globule transition. No changes in the hydrophobic signals below the separation temperature could be observed, suggesting that hydrophobic interactions played a dominant role during the aggregation of the collapsed chains but not before. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1665–1677, 2001     

Preparation and properties of chitosan‐poly(N‐isopropylacrylamide) semi‐IPN hydrogels

Chitosan (CS), CS‐poly(N‐isopropylacrylamide)(PNIPAM) and their dyed (pyrene) hydrogels were prepared using glutaraldehyde (Glu) as a crosslinker. The gelation rate, swelling behaviors in ethanol/water mixtures, electricity‐induced contraction and thermoresponse of the gels were investigated using fluorescence probe technique. Results showed that CS/Glu, and PNIPAM‐containing CS/Glu gels exhibited similar properties in all aspects examined, except that the transparence of the CS‐PNIPAM/Glu gel is very dependent upon the temperature. The CS‐PNIPAM/Glu gel is transparent below 30°C, whereas opaque above 32°C. It is expected that this observation may be useful for the design and preparation of new kinds of hydrogel devices. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 474–481, 2000     

Investigation of drug release from thermo‐ and pH‐sensitive poly(N‐isopropylacrylamide/itaconic acid) copolymeric hydrogels

N‐Isopropylacrylamide/itaconic acid copolymeric hydrogels were prepared by irradiation of the ternary mixtures of N‐isopropylacrylamide/itaconic acid/water by γ‐rays at ambient temperature. The dependence of swelling properties and phase transitions on the comonomer concentration and temperature were investigated. The hydrogels showed both temperature and pH responses. The effect of comonomer concentration on the uptake and release behavior of the hydrogels was studied. Methylene blue (MB) was used as a model drug for the investigation of drug uptake and release behavior of the hydrogels. The release studies showed that the basic parameters affecting the drug release behavior of the hydrogels were pH and temperature of the solution. Copyright © 2004 John Wiley & Sons, Ltd.     

Positron annihilation studies on radiation‐crosslinked poly(N‐isopropylacrylamide) hydrogels

The temperature‐sensitive poly(N‐isopropylacrylamide) hydrogels, prepared by γ and electron‐beam (EB) irradiation, were studied using positron annihilation lifetime spectroscopy (PALS). The effect of water content in the hydrogel on the ortho‐positronium (o‐Ps) lifetime and intensity was investigated. The observed positronium lifetime suggests microstructural differences between γ‐ and EB‐synthesized hydrogels. The distribution in positronium lifetime indicates nonhomogeneity in the distribution of free‐volume holes in EB‐synthesized hydrogels. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3462–3466, 2000     

Preparation and properties of poly(N‐isopropylacrylamide)/poly(N‐isopropylacrylamide) interpenetrating polymer networks for drug delivery

A novel poly(N‐isopropylacrylamide) (PNIPA)/PNIPA interpenetrating polymer network (IPN) was synthesized and characterized. In comparison with conventional PNIPA hydrogels, the shrinking rate of the IPN hydrogel increased when gels, swollen at 20 °C, were immersed in 50 °C water. The phase‐transition temperature of the IPN gel remained unchangeable because of the same chemical constituent in the PNIPA gel. The reswelling kinetics were slower than those of the PNIPA hydrogel because of the higher crosslinking density of the IPN hydrogel. The IPN hydrogel had better mechanical strength because of its higher crosslinking density and polymer volume fraction. The release behavior of 5‐fluorouracil (5‐Fu) from the IPN hydrogel showed that, at a lower temperature, the release of 5‐Fu was controlled by the diffusion of water molecules in the gel network. At a higher temperature, 5‐Fu inside the gel could not diffuse into the medium after a burst release caused by the release of the drug on the surface of the gel. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1249–1254, 2004     

Synthesis of transition‐metal‐ion‐selective poly(N‐isopropylacrylamide) hydrogels by the incorporation of an Aza crown ether

A functionalized cyclam was synthesized by the attachment of a polymerizable acryloyl group to one of the four nitrogens on the cyclam molecule. The polymerization of the functionalized cyclam was performed with N‐isopropylacrylamide and N,N′‐methylene bisacrylamide, and the gels obtained were studied in the presence of different transition‐metal‐ion solutions. There was a drastic difference in the phase‐transition temperature (T_c) of the poly(N‐isopropylacrylamide) (PNIPAAm)/cyclam gel in comparison with the pure PNIPAAm gel. For the described system, a T_c shift of 15 °C was obtained. The presence of functionalized cyclam increased the hydrophilicity and T_c of the aforementioned polymer gels in deionized water (at pH 6) because of the presence of protonated amino moieties. The PNIPAAm/cyclam gels showed a dependence of the swelling behavior on pH. T_c of the pure PNIPAAm gel was weakly influenced by the presence of any transition‐metal ions, such as Cu²⁺, Ni²⁺, Zn²⁺, and Mn²⁺. The addition of Cu²⁺ or Ni²⁺ to the PNIPAAm/cyclam gel reduced T_c of the polymer gel, and a shift of approximately 12 °C was observed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1594–1602, 2003     

Mixed micelles of oppositely charged poly(N‐isopropylacrylamide) diblock copolymers

Mixed micelle formation between two oppositely charged diblock copolymers that have a common thermosensitive nonionic block of poly(N‐isopropylacrylamide) (PNIPAAM) has been studied. The block copolymer mixed solutions were investigated under equimolar charge conditions as a function of both temperature and total polymer concentrations by turbidimetry, differential scanning calorimetry, two‐dimensional proton nuclear magnetic nuclear Overhauser effect spectroscopy (2D ¹H NMR NOESY), dynamic light scattering, and small angle X‐ray scattering measurements. Well‐defined and electroneutral cylindrical micelles were formed with a radius and a length of about 3 nm and 35 nm, respectively. In the micelles, the charged blocks built up a core, which was surrounded by a corona of PNIPAAM chains. The 2D ¹H NMR NOESY experiments showed that a minor block mixing occurred between the core blocks and the PNIPAAM blocks. By approaching the lower critical solution temperature of PNIPAAM, the PNIPAAM chains collapsed, which induced aggregation of the micelles. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1457–1469     

Hydration‐mediated effects of saccharide stereochemistry on poly(N‐isopropylacrylamide) gel swelling

To shed new light on the mechanisms of saccharide stereochemistry effect on macromolecules in aqueous solutions, we studied the effect of three monosaccharide stereoisomers, glucose, galactose, and mannose, on the swelling of Poly(N‐isopropylacrylamide) (PNIPA) hydrogels. We equilibrated PNIPA hydrogels in sugar solutions of different concentrations at 25 °C, and determined gel volume and mass swelling ratios, and sugar concentration imbalance. The volume‐phase‐transition occurred at molal concentrations of 0.587 ± 0.004 (galactose), 0.724 ± 0.003 (glucose), and 0.846 ± 0.004 (mannose). The same order of sugars emerged for the gel‐swelling and the magnitude of the sugar concentration‐imbalance, which correlated with sugar isentropic molar compressibility and hydration number. The more hydrated the sugar, the worse a cosolvent it is for the polymer, hence the larger the deswelling and the more negative the sugar concentration imbalance. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Poly(N‐isopropylacrylamide)‐based comb‐type grafted hydrogel with rapid response to blood glucose concentration change at physiological temperature

A new type of glucose‐responsive hydrogel with rapid response to blood glucose concentration change at physiological temperature has been successfully developed. The polymeric hydrogel contains phenylboronic acid (PBA) groups as glucose sensors and thermo‐responsive poly (N‐isopropylacrylamide) (PNIPAM) groups as actuators. The response rate of the hydrogel to environmental glucose concentration change was significantly enhanced by introducing grafted poly(N‐isopropylacrylamide‐co‐3‐acrylamidophenylboronic acid) [poly(NIPAM‐co‐AAPBA)] side chains onto crosslinked poly(NIPAM‐co‐AAPBA) networks for the first time. The synthesized comb‐type grafted poly(NIPAM‐co‐AAPBA) hydrogels showed satisfactory equilibrium glucose‐responsive properties, and exhibited much faster response rate to glucose concentration change than normal type crosslinked poly(NIPAM‐co‐AAPBA) hydrogels at physiological temperature. Such glucose‐responsive hydrogels with rapid response rate are highly attractive in the fields of developing glucose‐responsive sensors and self‐regulated drug delivery systems. Copyright © 2008 John Wiley & Sons, Ltd.     

N‐Isopropylacrylamide/monoalkyl itaconate copolymers and N‐isopropylacrylamide/itaconic acid/dimethyl itaconate terpolymers

Temperature‐ and pH‐sensitive copolymers and terpolymers of N‐isopropylacrylamide (NIPAAm) with itaconic acid (IA), monomethyl itaconate (MMeI), monobutyl itaconate (MBuI), monooctyl itaconate (MOcI), monocetyl itaconate (MCeI), and dimethyl itaconate (DMI) were prepared by free radical solution polymerization method. The dependence of coil‐to‐globule transition on pH and composition, molecular structures, and reactivities of monoalkyl itaconates, molecular weight distributions, and glass transition temperatures of copolymers and terpolymers were investigated using FT‐IR and UV–visible spectroscopic techniques, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and acid–base titration methods. The temperature‐/pH‐dependent coil‐to‐globule transition measurements showed that, upon increasing the content and length of alkyl chains, the lower critical solution temperatures (LCSTs) were shifted to higher temperatures. This meant that with increase in the length of hydrophobic alkyl chain in the monoitaconates intramolecular intreactions between the carboxyl groups were suppressed and LCSTs increased. The aqueous solution behaviors of NIPAAm/IA/DMI terpolymers also revealed that, even if the terpolymer hydrophobicity is increased by adding DMI units, the presence of IA units overcame the decrease in hydrophilicity of the terpolymers. The presence of DMI units in the terpolymers balanced the hydrophilic character of IA. DSC results supported the ones obtained from the pH‐dependent coil‐to‐globule transition measurements. An increase in both the chain length of alkyl groups attached to the monoitaconates and the contents of the mono‐ and dialkyl itaconates in the copolymers and terpolymers decreased the T_gs. In the case of NIPAAm/IA and NIPAAm/MMeI copolymers, the presence of the carboxyl groups forming hydrogen bonds increased the T_g, while the monoalkyl and dialkyl itaconates such as MBuI, MOcI, MCeI and DMI lead to a decrease in T_g of copolymers and terpolymers because of the suppression of intramolecular interactions (resulting from the ? COOH and ? COO^? groups) through the longer alkyl spacers. The dependence of the thermosensitivity of these NIPAAm copolymers and terpolymers on different conditions of pH, and the nature and content of comonomers suggests that they can be useful in biotechnology and drug delivery applications which involve small changes in pH and temperature. Copyright © 2009 John Wiley & Sons, Ltd.     

Novel temperature‐ and pH‐responsive graft copolymers composed of poly(L‐glutamic acid) and poly(N‐isopropylacrylamide)

A series of novel temperature‐ and pH‐responsive graft copolymers, poly(L ‐glutamic acid)‐g‐poly(N‐isopropylacrylamide), were synthesized by coupling amino‐semitelechelic poly(N‐isopropylacrylamide) with N‐hydroxysuccinimide‐activated poly(L ‐glutamic acid). The graft copolymers and their precursors were characterized, by ESI‐FTICR Mass Spectrum, intrinsic viscosity measurements and proton nuclear magnetic resonance (¹H NMR). The phase‐transition and aggregation behaviors of the graft copolymers in aqueous solutions were investigated by the turbidity measurements and dynamic laser scattering. The solution behavior of the copolymers showed dependence on both temperature and pH. The cloud point (CP) of the copolymer solution at pH 5.0–7.4 was slightly higher than that of the solution of the PNIPAM homopolymer because of the hydrophilic nature of the poly(glutamic acid) (PGA) backbone. The CP markedly decreased when the pH was lowered from 5 to 4.2, caused by the decrease in hydrophilicity of the PGA backbone. At a temperature above the lower critical solution temperature of the PNIPAM chain, the copolymers formed amphiphilic core‐shell aggregates at pH 4.5–7.4 and the particle size was reduced with decreasing pH. In contrast, larger hydrophobic aggregates were formed at pH 4.2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4140–4150, 2008     

Living anionic polymerization of N‐methoxymethyl‐N‐isopropylacrylamide: Synthesis of well‐defined poly(N‐isopropylacrylamide) having various stereoregularity

Anionic polymerization of N‐methoxymethyl‐N‐isopropylacrylamide ( 1 ) was carried out with 1,1‐diphenyl‐3‐methylpentyllithium and diphenylmethyllithium, ‐potassium, and ‐cesium in THF at ?78 °C for 2 h in the presence of Et₂Zn. The poly( 1 )s were quantitatively obtained and possessed the predicted molecular weights based on the feed molar ratios between monomer to initiators and narrow molecular weight distributions (M_w/M_n = 1.1). The living character of propagating carbanion of poly( 1 ) either at 0 or ?78 °C was confirmed by the quantitative efficiency of the sequential block copolymerization using N,N‐diethylacrylamide as a second monomer. The methoxymethyl group of the resulting poly( 1 ) was completely removed to give a well‐defined poly(N‐isopropylacrylamide), poly(NIPAM), via the acidic hydrolysis. The racemo diad contents in the poly(NIPAM)s could be widely changed from 15 to 83% by choosing the initiator systems for 1 . The poly(NIPAM)s obtained with Li⁺/Et₂Zn initiator system possessed syndiotactic‐rich configurations (r = 75–83%), while either atactic (r = 50%) or isotactic poly(NIPAM) (r = 15–22%) was generated with K⁺/Et₂Zn or Li⁺/LiCl initiator system, respectively. Atactic and syndiotactic poly(NIPAM)s (42 < r < 83%) were water‐soluble, whereas isotactic‐rich one (r < 31%) was insoluble in water. The cloud points of the aqueous solution of poly(NIPAM)s increased from 32 to 37 °C with the r‐contents. These indicated the significant effect of stereoregularity of the poly(NIPAM) on the water‐solubility and the cloud point in water © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4832–4845, 2006     

From poly(N‐isopropylacrylamide)‐block‐poly(ethylene oxide)‐block‐poly(N‐isopropylacrylamide) triblock copolymer to poly(N‐isopropylacrylamide)‐block‐poly(ethylene oxide) hydrogels: Synthesis and rapid deswelling and reswelling behavior of hydrogels

Poly(N‐isopropylacrylamide)‐block‐poly(ethylene oxide)‐block‐poly(N‐isopropylacrylamide) (PNIPAAm‐b‐PEO‐b‐PNIPAAm) triblock copolymer was synthesized via the reversible addition‐fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process with xanthate‐terminated poly(ethylene oxide) (PEO) as the macromolecular chain transfer agent. The successful synthesis of the ABA triblock copolymer inspired the preparation of poly(N‐isopropylacrylamide)‐block‐poly(ethylene oxide) (PNIPAAm‐b‐PEO) copolymer networks with N,N′‐methylenebisacrylamide as the crosslinking agent with the similar approach. With the RAFT/MADIX process, PEO chains were successfully blocked into poly(N‐isopropylacrylamide) (PNIPAAm) networks. The unique architecture of PNIPAAm‐b‐PEO networks allows investigating the effect of the blocked PEO chains on the deswelling and reswelling behavior of PNIPAAm hydrogels. It was found that with the inclusion of PEO chains into the PNIPAAm networks as midblocks, the swelling ratios of the hydrogels were significantly enhanced. Furthermore, the PNIPAAm‐b‐PEO hydrogels displayed faster response to the external temperature changes than the control PNIPAAm hydrogel. The accelerated deswelling and reswelling behaviors have been interpreted based on the formation of PEO microdomains in the PNIPAAm networks, which could act as the hydrophilic tunnels to facilitate the diffusion of water molecules in the PNIPAAm networks. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Preparation and characterization of macroporous poly(N‐isopropylacrylamide) hydrogels for the controlled release of proteins

Macroporous, temperature‐sensitive poly(N‐isopropylacrylamide) (PNIPAAm) hydrogels were synthesized with poly(ethylene glycol)s (PEGs; molecular weight = 2000–6000) as the pore‐forming agents. The influence of the molecular weight and PEG content on the responsive kinetics of these macroporous hydrogels was investigated. The PEG‐modified PNIPAAm hydrogels were characterized by the swelling ratio, deswelling–reswelling kinetics, Fourier transform infrared, and differential scanning calorimetry. The morphology of these hydrogels was analyzed with scanning electron microscopy. The prepared macroporous hydrogels exhibited some unique properties in comparison with the gels with low molecular weight PEGs (molecular weight < 2000) as the pore‐forming agents. In addition, a preliminary study on the controlled release of bovine serum albumin from these macroporous hydrogels was carried out. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 152–159, 2003