Structure and molecular properties of saponified starch–graft‐polyacrylonitrile

Rodehed, Cenita; Rånby, Bengt

doi:10.1002/app.1986.070320134

Cited by 29 publications

(18 citation statements)

References 15 publications

(4 reference statements)

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“…In the case of H-SPAN, a maximum conversion of 70% of nitrile to carboxyl groups has been reported, and the remaining 30% are amide groups. 18 In the case of H-chitoPAN, we are trying to determine the amide/acid ratio. However, we realized that precise control of the ratio is practically impossible.…”

Section: Synthesis and Spectral Characterizationmentioning

confidence: 99%

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Modified chitosan. II. H‐chitoPAN, a novel pH‐responsive superabsorbent hydrogel

Pourjavadi

Mahdavinia

Zohuriaan‐Mehr

2003

J of Applied Polymer Sci

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ABSTRACT:Chitosan was modified with polyacrylonitrile (PAN) through ceric-initiated graft copolymerization. The chitosan-g-PAN product was saponified using sodium hydroxide aqueous solution to prepare a novel superabsorbent hydrogel, H-chitoPAN. Duration of completing the saponification reaction as well as the water absorbency capacity of the hydrogel was decreased with increasing the alkaline concentration. Either chitosan-g-PAN or H-chito-PAN was characterized by FTIR spectroscopy and DSC, TGA, and DTG thermal methods. According to FTIR, all the nitrile groups were converted to carboxylate and carboxamide groups. Both modified chitosans exhibited enhanced thermal stability over chitosan. The H-chitoPAN superabsorbent hydrogel was recognized to be highly responsive to pH. Study of net effect of H ϩ /OH Ϫ concentration (in absent of buffer solution) showed several sharp and large volume changes vs small pH variation in the range of 2-13. This abrupt swelling behavior was explained based on variety of pH-dependent interactions of functional groups incorporated in the gel network by an external pH modulation.

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Section: Synthesis and Spectral Characterizationmentioning

confidence: 99%

“…For instance, the incomplete hydrolysis is interpreted as being related to steric and polar factors, for example, hydrogen bonding of neighboring amide and carboxyl groups. 18 Weaver et al 19 suggested that condensation may also occur between carboxyl and amide groups to form imide structures.…”

Section: Synthesis and Spectral Characterizationmentioning

confidence: 99%

Modified chitosan. II. H‐chitoPAN, a novel pH‐responsive superabsorbent hydrogel

Pourjavadi

Mahdavinia

Zohuriaan‐Mehr

2003

J of Applied Polymer Sci

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“…It has been reported, in the case of hydrolyzed starch-g-PAN (H-SPAN), a maximum conversion of 70% of nitrile to carboxyl groups and the remaining 30% are amide groups. 25 In fact, details of the chemical processes and mechanism involved in H-SPAN synthesis are not yet well understood. For instance, the incomplete hydrolysis is interpreted as being related to steric and polar factors.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Properties of Partially Hydrolyzed Acrylonitrile-co-Acrylamide Superabsorbent Hydrogel

Pourjavadi¹,

Hosseinzadeh²

2010

Bulletin of the Korean Chemical Society

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In this work, a novel method to synthesis of an acrylic superabsorbent hydrogel was reported. In the two stage hydrogel synthesis, first copolymerization reaction of acrylonitrile (AN) and acrylamide (AM) monomers using ammonium persulfate (APS) as a free radical initiator was performed. In the second stage, the resulted copolymer was hydrolyzed to produce carboxamide and carboxylate groups followed by in situ crosslinking of the polyacrylonitrile chains. The results from FTIR spectroscopy and the dark red-yellow color change show that the copolymerization, alkaline hydrolysis and crosslinking reactions have been do take place. Scanning electron microscopy (SEM) verifies that the synthesized hydrogels have a porous structure. The results of Brunauer-Emmett-Teller (BET) analysis showed that the average pore diameter of the synthesized hydrogel was 13.9 nm. The synthetic parameters affecting on swelling capacity of the hydrogel, such as AM/AN weight ratio and hydrolysis time and temperature, were systematically optimized to achieve maximum swelling capacity (330 g/g). The swollen gel strength of the synthesized hydrogels was evaluated via viscoelastic measurements. The results indicated that superabsorbent polymers with high water absorbency were accompanied by low gel strength. The swelling of superabsorbent hydrogels was also measured in various solutions with pH values ranging from 1 to 13. Also, the pH reversibility and on-off switching behavior makes the hydrogel as a good candidate for controlled delivery of bioactive agents. Finally, the swelling of synthesized hydrogels with various particle sizes obey second order kinetics.

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“…Assuming that the water melting at 274 K has the same heat of fusion as distilled water, the heat of fusion of the water melting at 268 K can be calculatkd from eq. (lh12 (1) where A HF = heat of fusion at TF (268 K), AHo = heat of fusion at To (274 K), and ACp = difference in the molar heat capacities of liquid water and ice.…”

Section: Each Individual Sample Gives Reproducible Results On Which Tmentioning

confidence: 99%

Characterization of sorbed water in saponified start–g‐polyacrylonitrile with differential scanning calorimetry

Rodehed

Rånby

1986

J of Applied Polymer Sci

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SynopsisA saponified starch-polyacrylonitrile graft copolymer containing water was studied using differential scanning calorimetry. The samples had a moisture content in the range of 0-1.05 g water per gram of dry polymer. Molar heat capacity measurements at temperatures higher than 273 K gave partial molar values between those of ice and bulk liquid water. No crystallizable water was detected in samples with water contents lower than 0.44 g/g dry polymer.In samples containing larger amounts of water, both the amount of "bound" uncrystallizable water and the amount of "free" crystallizable water increased linearly. Two melting endotherms were detected, suggesting that the free water could be divided into two components with different melting points (268 K and 274 K, respectively). INTRODUCTIONThe recent developments of a highly water-absorbing polymer at this laboratory1.2 gave reason to study the water structure in hydrophilic polymers. Many investigators have tried to interpret the structure of water in aqueous solutions of polymers as well as adsorbed water or water in swollen polymeric substance^.^-^ Most of the work regarding water structure has been carried out using broad-line nuclear magnetic resonance spectroscopy (NMR)3 and differential scanning calorimetry (DSC)P-9 Broad-line proton-NMR experiments investigate the mobility of protons in various energy states. Using DSC measurements, the heat capacity, the heat of fusion, the melting temperature, and the amount of water that can crystallize can be estimated.Although there are many different hypotheses on the structure of water in polymers, it is generally accepted that water molecules in a polymer matrix behave differently from those in bulk water because of interaction between water and polymer. Schematically there are two opinions; first, that water in hydrophilic polymers can be divided into bound water and free liquid ~a t e r ,~-~ and second, all sorbed water is liq~idlike.'-~ Yasuda et al.3 studied the hydrogel of a polymer of glycerol monomethacrylate (poly-GMA) with NMR and DSC. They suggested that a constant amount of water is strongly associated with the macromolecules and does not crystallize when the temperature is lowered well below the freezing presented DSC data for mucopolysaccharides and cellulose acetate membranes, respectively, which contained multiple endothermic peaks. They suggested different states of water in the vicinity of the polymer segments.On the other hand, on the basis of heat capacity measurements on waterswollen poly[2-(2-hydroxyethoxyl)ethyl methacrylate)] (PHEOEMA), Pouchly et al.' claimed that the structure of water sorbed by the polymer is similar to liquid water and rather labile. After investigations of heat capacities of the water-collagen system, Hoeve8s9 suggested a liquidlike, onephase model consisting of chains of hydrogen-bonded water molecules that diffuse through the interstices preserving their mutual hydrogen bonding to each other.This work has been carried out using DSC on watercontaining hydrolyzed sta...

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Structure and molecular properties of saponified starch–graft‐polyacrylonitrile

Cited by 29 publications

References 15 publications

Modified chitosan. II. H‐chitoPAN, a novel pH‐responsive superabsorbent hydrogel

Modified chitosan. II. H‐chitoPAN, a novel pH‐responsive superabsorbent hydrogel

Synthesis and Properties of Partially Hydrolyzed Acrylonitrile-co-Acrylamide Superabsorbent Hydrogel

Characterization of sorbed water in saponified start–g‐polyacrylonitrile with differential scanning calorimetry

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