Study of cryostructuration of polymer systems. XVII. Poly(vinyl alcohol) cryogels: Dynamics of the cryotropic gel formation

Freeze‐thaw treatment of concentrated (>5 g/dL) aqueous solutions of poly(vinyl alcohol) (PVA) (MW 115,000; DD ≈100%) resulted in the formation of opaque gels. The extent of such a cryostructuration process was exhibited in the rheological properties of similar PVA cryogels. The gels' strength depended on the initial polymer concentration in the solution to be frozen and on the conditions of a cryogenic influence. The key factor was the defrostation dynamics: the slower the thawing rate, the stronger the cryogel sample formed, provided other parameters of the process were identical. The observation for the kinetics of the freeze‐thaw–induced gel formation revealed the extreme character of the temperature dependence of the efficacy of PVA cryotropic gelation, the maximum point being in the vicinity of −2°C. It was shown that the effect of the strengthening of PVA cryogels prepared by means of a single‐cycle cryogenic treatment could be reached either with use of as slow as possible thawing regimes, or by the prolonged frozen storage of the samples at “high” subzero temperatures. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2017–2023, 2000     

Study of cryostructuration of polymer systems. XVI. Freeze–thaw‐induced effects in the low concentration systems amylopectin–water

Studies of the freeze–thaw behavior of low‐concentrated (0.01–0.25 g/dL) water solutions and dilute pastes (0.5–1.0 g/dL) of maize starch amylopectin showed that cryogenic treatment of these systems resulted in the formation of precipitated matter, whose yield and thermal characteristics (melting temperature and enthalpy) depended on the initial polymer concentration and conditions of freezing, frozen storage, and thawing. Research of the kinetic features of these cryoprecipitation events revealed at least two stages for this process: (i) a rapid stage, when the precipitation of virtually all of the dissolved polysaccharide occurred while the system was freezing, and (ii) a slower stage, the rate of which was mainly dependent on the thawing regimes or duration of the sample storage frozen at subzero temperatures. Cryoprecipitation phenomena were observed to be most extensive at temperatures 1–2° below the melting point of the frozen system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1740–1748, 2000     

Synthesis and characterization of novel polyaspartimides derived from 2,2′‐dimethyl‐4,4′‐bis(4‐maleimidophenoxy)biphenyl and various diamines

A novel bismaleimide, 2,2′‐dimethyl‐4,4′‐bis(4‐maleimidophenoxy)biphenyl, containing noncoplanar 2,2′‐dimethylbiphenylene and flexible ether units in the polymer backbone was synthesized from 2,2′‐dimethyl‐4,4′‐bis(4‐aminophenoxy)biphenyl with maleic anhydride. The bismaleimide was reacted with 11 diamines using m‐cresol as a solvent and glacial acetic acid as a catalyst to produce novel polyaspartimides. Polymers were identified by elemental analysis and infrared spectroscopy, and characterized by solubility test, X‐ray diffraction, and thermal analysis (differential scanning calorimetry and thermogravimetric analysis). The inherent viscosities of the polymers varied from 0.22 to 0.48 dL g⁻¹ in concentration of 1.0 g dL⁻¹ of N,N‐dimethylformamide. All polymers are soluble in N‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, dimethylsulfoxide, pyridine, m‐cresol, and tetrahydrofuran. The polymers, except PASI‐4, had moderate glass transition temperature in the range of 188°–226°C and good thermo‐oxidative stability, losing 10% mass in the range of 375°–426°C in air and 357°–415°C in nitrogen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 279–286, 1999     

Pervaporation separation of water–ethanol mixtures using metal‐ion‐exchanged poly(vinyl alcohol) (PVA)/sulfosuccinic acid (SSA) membranes

Poly(vinyl alcohol)/sulfosuccinic acid (PVA/SSA) membranes in the hydrogen form were converted to monovalent metal ion forms Li⁺, Na⁺, and K⁺. The effect of exchange with metal ions was investigated by measuring the swelling of water–ethanol (10/90) mixtures at 30 °C and by the pervaporative dehydration performance test for aqueous ethanol solutions with various ethanol concentrations at 30, 40, and 50 °C. In addition, electron spectroscopy for chemical analysis (ESCA) analysis was carried out to study the quantity of metal ions in membranes. From the ESCA analysis, the lithium ion quantity in the resulting membranes is greater than that of any other metal ions in question because of the easy diffusion of a smaller metal ion into the membrane matrix. The swelling ratio was in the following order: PVA/SSA‐Li⁺ > PVA/SSA‐Na⁺ > PVA/SSA‐K⁺ membranes. For pervaporation, the PVA/SSA‐Na⁺ membrane showed the lowest flux and highest separation factor for all aqueous ethanol solutions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1867–1873, 2002     

Syntheses and properties of N‐vinylpyrrolidione‐g‐EPDM and its modified polymer

The graft copolymerizations of N‐vinylpyrrolidione(NVP) onto ethylene–propylene–diene terpolymer (EPDM) were carried out with benzoyl peroxide (BPO) as an initiator in toluene. The synthesized EPDM‐g‐NVP (ENVP) was characterized by infrared (IR) spectroscopy and gel permeation chromatography (GPC). The effects of initiator and monomer concentrations, reaction time, and temperature were investigated in the graft copolymerization. The highest graft efficiency was obtained at 0.04 mol of NVP, 2 g of EPDM, 2 wt % of BPO and 80°C for 72 h. Modified ENVP (MENVP) was obtained by the reaction of ENVP and KOH in MeOH. Properties of EPDM, ENVP, and MENVP were investigated by a thermogravimetric analyzer (TGA), an instron tensile tester, a Fade‐O‐Meter, and a UV spectrophotometer. Tensile strength and light resistance of ENVP were better than those of MENVP. The dyeability of polymers was increased in following order: MENVP > ENVP > EPDM. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1177–1184, 1999     

Study of cryostructuration of polymer systems. XXI. Cryotropic gel formation of the water–maltodextrin systems

The freeze–thaw behavior of water solutions containing dissolved maltodextrin (MD; enzymatically converted potato starch derivative with MW of 8000 Da) over a wide range of MD concentration (0.1–15 g/dL) and freezing temperatures from ?24 to ?6°C was studied. Cryogenic treatment of these systems resulted in the formation of precipitates or gels, whose yield and thermal characteristics (fusion temperature and enthalpy) depended on the initial polymer concentration and conditions of freezing, frozen storage, and thawing. There appeared to be at least two stages to this process: (i) a rapid stage, when partial insolubilization occurred while the system was freezing, and (ii) a slower stage, the rate of which was dependent mainly on the thawing regimes used or the duration of storage at subzero temperatures. In this respect, the cryostructuration of MD was very similar to the freeze–thaw behavior of amylopectin/amylose and locust bean gum water solutions studied earlier. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1658–1667, 2002     

Cryostructuring of polymer systems. XXVI. Heterophase organic–inorganic cryogels prepared via freezing–thawing of aqueous solutions of poly(vinyl alcohol) with added tetramethoxysilane

Composite heterophase organic–inorganic hybrid cryogels of poly(vinyl alcohol) (PVA) containing silica constituents were prepared and studied. Such constituents were formed in the course of hydrolytic polycondensation (sol‐gel process) of tetramethoxysilane (TMOS) introduced in to the aqueous polymer solution prior to its freeze–thaw treatment. It was shown that moderate (over the range of ?15 to ?30°C) freezing, then frozen storage, and subsequent thawing of the water/PVA/TMOS systems resulted in the formation of macroporous composite cryogels filled with dispersed silica particles (discrete phase). The continuous phase of such gel materials represents the supramolecular PVA network, which is supposed to be additionally cured with the silicon‐containing oligomeric cross agents formed from TMOS in the course of hydrolytic polycondensation. The incorporated silica components influenced the morphology of cryogels. The effects of significant increase in gel strength and heat resistance with increasing TMOS concentration in the initial feed and with thawing rate decreasing have also been observed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and characterization of new poly(amide‐imide)s based on 1,4‐bis(trimellitimido)‐2,5‐dichlorobenzene

A series of new aromatic poly(amide‐imide)s were synthesized by the triphenyl phosphite‐activated polycondensation of the diimide‐diacid, 1,4‐bis(trimellitimido)‐2,5‐dichlorobenzene (I), with various aromatic diamines in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP), pyridine, and calcium chloride. The poly(amide‐imide)s had inherent viscosities of 0.88–1.27 dL g⁻¹. The diimide‐diacid monomer (I) was prepared from 2,5‐dichloro‐p‐phenylenediamine with trimellitic anhydride. All the resulting polymers were amorphous and were readily soluble in a variety of organic solvents, including NMP and N,N‐dimethylacetamide. Transparent, flexible, and tough films of these polymers could be cast from N,N‐dimethylacetamide or NMP solutions. Cast films had tensile strengths ranging from 92 to 127 MPa, elongations at break from 4 to 24%, and initial moduli from 2.59 to 3.65 GPa. The glass transition temperatures of these polymers were in the range of 256°–317°C, and the 10% weight loss temperatures were above 430°C in nitrogen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 271–278, 1999     

Study of cryostructuration of polymer systems. XX. Foamed poly(vinyl alcohol) cryogels

Foamed poly(vinyl alcohol) (PVA) cryogels, which are formed as a result of freeze–thaw treatment of whipped PVA water solutions (polymer with MW of 69,000 Da and DD ～99 mol % was used), were obtained and their properties were studied. The rheological characteristics and macrostructure of these gel materials were controlled by the same factors as for the ordinary nonfoamed PVA cryogels (initial polymer concentration and freezing–thawing regimes) and also by the conditions of generation of fluid PVA foams. The study of the kinetics of the freeze–thaw‐induced gel formation of these foams revealed that the temperature dependence of the efficiency of cryotropic gelation showed a maximum at about ?1.5°C. The presence of low molecular weight admixtures in the initial polymer solution appears to be a rather important factor because the admixtures were capable of decreasing the stability of fluid PVA foams and weakening both foamed and nonfoamed cryogel samples. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1609–1619, 2001     

Epoxy–imide resins from N‐(4‐ and 3‐carboxyphenyl)trimellitimides. I. Adhesive and thermal properties

Epoxy–imide resins were obtained by curing Araldite GY 250 (diglycidyl ether of bisphenol‐A and epichlorohydrin; difunctional) and Araldite EPN 1138 (Novolac–epoxy resin; polyfunctional) with N‐(4‐ and 3‐carboxyphenyl)trimellitimides derived from 4‐ and 3‐aminobenzoic acids and trimellitic anhydride. The adhesive lap shear strength of epoxy–imide systems at room temperature and at 100, 125, and 150°C was determined on stainless‐steel substrates. Araldite GY 250‐based systems give a room‐temperature adhesive lap shear strength of about 23 MPa and 49–56% of the room‐temperature adhesive strength is retained at 150°C. Araldite EPN 1138‐based systems give a room‐temperature adhesive lap shear strength of 16–19 MPa and 100% retention of room‐temperature adhesive strength is observed at 150°C. Glass transition temperatures of the Araldite GY 250‐based systems are in the range of 132–139°C and those of the Araldite EPN 1138‐based systems are in the range of 158–170°C. All these systems are thermally stable up to 360°C. The char residues of Araldite GY 250‐ and Araldite EPN 1138‐based systems are in the range of 22–26% and 41–42% at 900°C, respectively. Araldite EPN 1138‐based systems show a higher retention of adhesive strength at 150°C and have higher thermal stability and T_g when compared to Araldite GY 250‐based systems. This has been attributed to the high crosslinking possible with Araldite EPN 1138‐based systems arising due to the polyfunctional nature of Araldite EPN 1138. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1729–1736, 2000     

Preparation and properties of organo‐soluble polyimides based on 4,4′‐diamino‐3,3‐dimethyldiphenylmethane and conventional dianhydrides

4,4′‐Diamino‐3,3′‐dimethyldiphenylmethane was used to prepare polyimides in an attempt to achieve good organo‐solubility and light color. Polyimides based on this diamine and three conventional aromatic dianhydrides were prepared by solution polycondensation followed by chemical imidization. They possess good solubility in aprotonic polar organic solvents such as N‐methyl 2‐pyrrolidone, N,N‐dimethyl acetamide, and m‐cresol. Polyimide from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane and diphenylether‐3,3′,4,4′‐tetracarboxylic acid dianhydride is even soluble in common solvents such as tetrahydrofuran and chloroform. Polyimides exhibit high transmittance at wavelengths above 400 nm. The glass transition temperature of polyimide from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane and pyromellitic dianhydride is 370°C, while that from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane and diphenylether‐3,3′,4,4′‐tetracarboxylic acid dianhydride is about 260°C. The initial thermal decomposition temperatures of these polyimides are 520–540°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1299–1304, 1999     

Synthesis and properties of new poly(amide‐imide)s based on 2,5‐bis(trimellitimido)chlorobenzene

A series of new aromatic poly(amide‐imide)s were synthesized by the triphenyl phosphite‐activated polycondensation of the diimide‐diacid, 2,5‐bis(trimellitimido)chlorobenzene (I) with various aromatic diamines in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP), pyridine, and calcium chloride. The poly(amide‐imide)s had inherent viscosities of 0.76–1.42 dL g⁻¹. The diimide‐diacid monomer (I) was prepared from 2‐chloro‐p‐phenylenediamine with trimellitic anhydride. Most of the resulting polymers showed an amorphous nature and were readily soluble in a variety of organic solvents, including NMP and N,N‐dimethylacetamide. Transparent, flexible, and tough films of these polymers could be cast from N,N‐dimethylacetamide or NMP solutions. Their cast films had tensile strengths ranging from 74 to 95 MPa, elongations at break from 7 to 11%, and initial moduli from 1.38 to 3.25 GPa. The glass transition temperatures of these polymers were in the range of 233°–260°C, and the 10% weight loss temperatures were above 450°C in nitrogen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1691–1701, 1999     

Application of syndiotacticity‐rich PVA hydrogels prepared at a low temperature to thermo‐ and pH‐responsive release devices

Three kinds of physically cross‐linked syndiotacticity‐rich poly(vinyl alcohol) (s‐PVA) hydrogels were prepared at 0°C with use of the buffer solutions (BS) of pHs 4.0, 7.4, and 9.0. Three gels swelled at first and then began to shrink after 12 h when they were dipped in the same BS for preparation at higher temperature than 0°C. The release of Brilliant Blue (3 mg/1 mL) from the cylindrical gels prepared using BS of pH 7.4 was studied at 27, 37, and 47°C. Brilliant Blue has been released spending 4–12 h almost completely. The rate of release from the gel at temperatures of 27, 37, and 47°C became large with increasing temperature. The main factor on release of Brilliant Blue is not the contraction of gel, but swelling, because the degree of swelling (DS) became large with increasing temperatures for 27, 37, and 47°C. The rate of release from the gel (pH 4.0) was larger than that (pH 7.4) due to the increased DS of the hydrogel in early step at pH of 4.0. The apparent diffusion exponents of these releases at pH 7.4 evaluated from first 60% of the fractional release were lower than 0.45 due to the swelling during release. The exponent at pH 4.0 was 0.45 due to immediate swelling. The on‐off of shrinking behavior of atactic PVA (a‐PVA) hydrogel was observed under several temperature changes. The rate of release of Brilliant Blue at 5°C was lower than that at 27°C and no change was observed at 5°C after one on‐off cycle. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 41–46, 2000     

Study of cryostructuration of polymer systems. XIV. Poly(vinyl alcohol) cryogels: Apparent yield of the freeze–thaw‐induced gelation of concentrated aqueous solutions of the polymer

Poly(vinyl alcohol) (PVA) cryogels, which are formed as a result of freeze–thaw treatment of concentrated solutions of the polymer, were studied in respect to the amount of gel and sol fractions in these heterogeneous macroporous gel materials depending on the conditions of the thawing step of similar cryotropic gelation. It was shown that the yield of gel fraction (the efficiency of the gelation process) was not quantitative; this was controlled by the initial PVA concentration in the solution to be frozen, and to a higher extent, by the thawing rate, when the yield increased with slowing of the defrostation process. The sol fraction could be extracted from the PVA cryogels by their rinsing with water at room temperature; the extraction of the sol was accompanied with the variations of the swelling parameters of the gels (initial slight upswelling and subsequent gradual deswelling), as well as with analogous, in their character, variations of the gel strength. It was also demonstrated that at the evaluation of the fusion enthalpies of PVA cryogels with the aid of the Eldridge–Ferry equation a consideration of the values of gel‐fraction yield gave rise to the significantly higher ΔH values than in traditional cases commonly used for the thermoreversible gels, where such an yield was not taken into account. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1822–1831, 2000     

Carbon dioxide sorption and diffusion in poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐CO‐3‐hydroxyvalerate)

CO₂ sorption and diffusion in poly(3‐hydroxybutyrate) and three poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) copolymers were investigated gravimetrically at temperatures from 25° to 50°C and pressures up to 1 atm. The sorption behavior proved to be linear for all the copolymers studied. An additional set of measurements performed in a pressure decay apparatus at 35°C showed that the linearity could be extrapolated to pressures up to 25 atm. The sorption results obtained from both techniques were in good agreement. The poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) sorption kinetics were increasingly non‐Fickian at the higher temperatures, thus preventing the calculation of diffusion coefficients above 35°C. Interestingly, this was not the case for poly(3‐hydroxybutyrate), and diffusion coefficients and permeabilities could be calculated at all of the investigated temperatures. The 35°C permeabilities were fairly low, which is attributed to the high degree of crystallinity of this polyester family. Finally, the poly(3‐hydroxybutyrate) barrier properties against CO₂ are successfully compared with those of some selected common thermoplastics. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2391–2399, 1999     

Study of cryostructuration of polymer systems. XVIII. Freeze–thaw influence on water‐solubilized artificial mixtures of amylopectin and amylose

The effects caused by cryogenic treatment (freezing–frozen storage–thawing) of 0.5–2.0 g/dL solutions of individual starch polysaccharides, namely, amylopectin (solvents: water or 0.35M NaCl aqueous solution) and amylose (solvent: 0.35M NaCl aqueous solution), and also of 0.5 g/dL solutions of their artificial mixtures with various amylopectin/amylose ratios were studied. Freezing of these systems at temperatures from −6 to −24°C for 18 h and subsequent thawing resulted in the formation of cryogelled or cryoprecipitated matter whose morphology and yield depended on the type of polysaccharide, initial polymer concentration, portion of each macromolecular component in the mixed systems, and conditions of cryogenic treatment. Comparison of the process efficiency in the mixed systems during the formation of precipitates (from storage at room temperature) and cryoprecipitates (as a result of cryogenic treatment) revealed the promoting effects of the freezing–thawing influence on polymer–polymer association and showed the presence of some synergism in the mutual interaction of these polysaccharides. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 371–381, 2000     

New poly(amide‐imide) syntheses. 24. Synthesis and properties of fluorinated poly(amide‐imide)s based on 2,2‐bis[4‐(trimellitimidophenoxy)phenyl]hexafluoropropane and various aromatic diamines

An imide ring‐performed dicarboxylic acid bearing one hexafluoroisopropylidene and two ether linkages between aromatic rings, 2,2‐bis[4‐(4‐trimellitimidophenoxy)phenyl]hexafluoropropane (II), was prepared from the condensation of 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane and trimellitic anhydride. A novel series of poly(amide‐imide)s having inherent viscosities of 0.72 ∼ 1.86 dL g⁻¹ was prepared by the triphenyl phosphite‐activated polycondensation from the diimide‐diacid (II) with various aromatic diamines in a medium consisting of N‐methyl‐2‐pyrolidone, pyridine, and calcium chloride. Several of the resulting polymers were soluble in polar amide solvents, and their solutions could be cast into transparent, thin, flexible films having good tensile properties and high thermal stability. The 10% weight loss temperatures were all above 495°C in air or nitrogen atmosphere, and the glass transition temperatures were in the range of 237°–276°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 823–831, 1999     

Effects of the coagulation temperature on the properties of wet‐spun poly(vinyl alcohol)–graphene oxide fibers

Graphene oxide (GO) as a positive reinforcement filler was dispersed into a poly(vinyl alcohol) (PVA) dope and wet‐spun into composite fibers. The effects of two EtOH coagulation baths maintained at ?5 and 25 °C, respectively, on the morphology, structure, and mechanical properties of the composite fibers were investigated. The results show that gel spinning at ?5 °C led to a relatively large shrinkage ratio, thin diameter, and low porosity of the as‐spun fibers. Simultaneously, the low coagulation temperature also greatly contributed to the formation and preservation of the liquid‐crystalline phase of the GO sheets and interrupted the crystalline zone of PVA less. As a result, either the tenacity or the elongation at break of the fibers spun at ?5 °C was higher than those of the fibers spun through a coagulation bath at 25 °C. In particular, 1 wt % GO showed the highest reinforcement effects among all of the wet‐spun composite fibers. Hence, controlling the gelling–demixing process at a low temperature will provide more instructive insights for tailoring functional industrial textiles with excellent mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45463.     

Synthesis and characterization of new rigid‐rod and organosoluble poly(amide–imide)s based on 1,4‐bis(trimellitimido)‐2,3,5,6‐tetramethylbenzene

A series of new aromatic poly(amide–imide)s (PAIs) was synthesized by triphenyl phosphite‐activated polycondensation of the diimide–diacid, 1,4‐bis(trimellitimido)‐2,3,5,6‐tetramethylbenzene (I), with various aromatic diamines in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP), pyridine, and calcium chloride. The PAIs had inherent viscosities of 0.82–2.43 dL/g. The diimide–diacid monomer (I) was prepared from 2,3,5,6‐tetramethyl‐p‐phenylenediamine with trimellitic anhydride (TMA). Most of the resulting polymers showed an amorphous nature and were readily soluble in a variety of organic solvents including NMP, N,N‐dimethylacetamide (DMAc), and N,N‐dimethylformamide (DMF). Transparent, flexible, and tough films of these polymers could be cast from DMAc solutions. Their cast films had tensile strengths ranging from 80 to 95 MPa, elongation at break from 10 to 45%, and initial modulus from 2.01 to 2.50 GPa. The 10% weight loss temperatures of these polymers were above 510°C in nitrogen. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1162–1170, 2000     

Preparation and characterization of biocompatible spongy cryogels of poly(vinyl alcohol)–gelatin and study of water sorption behaviour

Porous biocompatible spongy hydrogels of poly(vinyl alcohol) (PVA)–gelatin were prepared by the freezing–thawing method and characterized by infrared and differential scanning calorimetry. The prepared so‐called ‘cryogels’ were evaluated for their water‐uptake potential and the influence of various factors, such as the chemical architecture of the spongy hydrogels, pH and the temperature of the swelling bath, on the degree of water sorption by the cryogels was investigated. It was found that the water sorption capacity constantly decreased with increasing concentration of PVA while initially an increase and thereafter a decrease in swelling was obtained with increasing amounts of gelatin in the cryogel. The water sorption capacity decreased with an increase in the number of freeze–thaw cycles. The hydrogels were also swollen in salt solutions and various simulated biological fluids and a fall in swelling ratio was noticed. The effect of the drying temperature of the cryogel on its water sorption capacity was also investigated, and a decrease in swelling was obtained with increasing temperature of drying. The biocompatibility of the prepared materials was assessed by in vitro methods of blood‐clot formation, platelet adhesion, and per cent haemolysis. It was noticed that with increasing concentration of PVA and gelatin the biocompatibility increased, while a reduced biocompatibility was noted with an increasing number of freeze–thaw cycles. Copyright © 2005 Society of Chemical Industry