Swelling mechanism of porous P(VP‐co‐MAA)/PNIPAM semi‐IPN hydrogels with various pore sizes prepared by a freeze treatment

Abstract

BACKGROUND: The objective of the work reported was to investigate the effect of gel microstructure on the swelling mechanism. A series of porous gels with various pore sizes were prepared by freeze-treating a conventional hydrogel that contained various amounts of water at −20 • C. Scanning electron microscopy and differential scanning calorimetry were used to characterize the microstructure of the porous gels. RESULTS:The experimental results showed that the water content during freezing was the key factor controlling the microstructure. Measurement of swelling kinetics showed that a greater amount of water during the freezing process would lead to a rapid swelling rate. The apparent diffusion coefficients (D p ) at all times during the swelling process were obtained by fitting the experimental data to the diffusion equation. The values of D p suggested that the swelling mechanism of the gels depends on the pore size. The diffusion exponent (n) obtained by fitting the fractional mass change (M t /M ∞ ) to equation of Fick's law further confirmed that the swelling mechanism of the gels is determined by the pore size. CONCLUSION: The swelling mechanism of the gels is determined by the microstructure related to the pore size and the thickness of struts. The microstructure can be controlled by adjusting the water content of the hydrogels by changing the pH of the swelling medium prior to freezing.

Thermally Tunable Dynamic and Static Elastic Properties of Hydrogel Due to Volumetric Phase Transition

“…Moreover, from 22.4 to 39 °C, the net volumetric swelling change for N-isopropylacrylamide/chlorophyllin copolymer gel [ 36 ], sensitive to temperature and light, is approximate 34% of original volume, which is two times smaller than PVA-PNIPAm hydrogel. This higher deswelling phenomenon makes PVA-PNIPAm hydrogel especially useful in biomedical applications, such as tissue engineering [ 14 ], mini-invasive surgery [ 25 ], 4D bio-printing [ 37 ], swelling-controlled drug delivery [ 38 ], and biomedical soft robots [ 39 ]. Other potential applications for PVA-PNIPAm hydrogel includes Microfluidic actuator [ 40 ], self-folding devices [ 41 ], and tunable micro-lenses [ 42 ].…”

Dual pH‐ and temperature‐responsive hydrogels with extraordinary swelling/deswelling behavior and enhanced mechanical performances

“…Moreover, the outstanding thermal conduction of GO is beneficial to our temperature responsive hydrogel as faster heat conduction may facilitate faster response from the hydrogel. For example, an IR‐light‐responsive glycidyl methacrylate functionalized graphene‐oxide (GO–GMA) incorporated hydrogel nanocomposite that undergoes significant volumetric change when irradiated by IR light has been reported by Lo . In that report, it was fully illustrated that the superior thermal conductivity of GO can facilitate faster response from the hydrogel.…”

Investigation of Swelling, Adsorption and Mechanical Properties of Sodium Acrylate Based Hydrogel and Cryogels

“…Jellerin şişme davranışları "difüzyon kontrollü" veya "relaksasyon (gevşeme) kontrollü" olabilmektedir. Genel olarak, suyun jele difüzyonu aşağıdaki eşitlik ile ifade edilmektedir [20]. …”

“…Bu eşitlik kullanılarak, ln F ve ln t değerleri arasında çizilen grafikten elde edilen doğrunun eğimi (n) ve kesim noktasından (ln k) kinetik parametreler bulunur [19], [20].…”