Here we report the preparation and characterization of nanostructured thermo-responsive poly(acrylamide) (PAM)-based hydrogels. The addition of slightly crosslinked poly(N-isopropylacrylamide) (PNIPA) nanogels to AM reactive aqueous solution produces nanostructured hydrogels that exhibit a volume phase transition temperature (TVPT). Their swelling kinetics, TVPT's and mechanical properties at the equilibrium-swollen state (Heq) are investigated as a function of the concentration of PNIPA nanogels in the nanostructured hydrogels. Nanostructured hydrogels with PNIPA nanogels/AM mass ratios of 20/80 and above exhibit higher Heq and longer time to reach the equilibrium swelling than those of the conventional PAM hydrogels. However, the PNIPA nanogels possess thermo-responsive character missing in conventional PAM hydrogels. The TVPT of nanostructured hydrogels depends on PNIPA nanogel content but their elastic and Young moduli are larger than those of conventional hydrogels at similar swelling ratios. Swelling kinetics, TVPT, and mechanical properties are explained in terms of the controlled in-homogeneities introduced by the PNIPA nanogels during the polymerization. 相似文献
Thermo-sensitive poly (N-isopropylacrylamide) (PNIPA) hydrogel with fast response rate was prepared by polymerizing N-isopropylacrylamide (NIPA) in an aqueous hydroxyl-propyl-methyl cellulose solution. The volume phase transition temperature
of PNIPA hydrogels was characterized by differential scanning calorimetry (DSC), and the surface morphology was observed by
scanning electron microscopy (SEM). The swelling ratios of the hydrogels at different temperatures were measured. Furthermore,
the deswelling kinetics of the hydrogels was also studied by measuring their water retention capacity. In comparison with
a conventional PNIPA hydrogel prepared in water, the hydrogel synthesized in aqueous hydroxyl-propyl-methyl cellulose solution
has higher swelling ratios at temperatures below the lower critical solution temperature and exhibits a much faster response
rate to temperature changes. For example, the hydrogel made in aqueous hydroxyl-propyl-methyl cellulose solution lost 89%
water within 1 min and about 93% water in 4 min, whereas the conventional hydrogel lost only about 66% water in 15 min from
the deswelling measurement in similar conditions.
Translated from Chinese Journal of Applied Chemistry, 2006, 23(6): 581–585 (in Chinese) 相似文献
A new kind of pH- and temperature-responsive semi-interpenetrating polymer network hydrogel based on linear carboxymethylchitosan
(CMCS) and poly (N-isopropylacrylamide) (PNIPA) crosslinked by inorganic clay was prepared. The pH-and temperature-responsive behaviors, the
deswelling kinetics, and the mechanical properties of the hydrogel were investigated. The hydrogels exhibited a volume phase
transition temperature around 33 °C with no significant deviation from the conventional PNIPA hydrogels. The results of the
influence of pH value on the swelling behaviors showed that the minimum swelling ratios of the hydrogels appeared near the
isoelectric point (IEP) of CMCS, and when pH deviated from the IEP, the hydrogels behaved as polycations or polyanions. The
novel hydrogels had much higher response rate than the conventional CMCS/PNIPA hydrogels. Moreover, the semi-IPN hydrogels
crosslinked by clay could be elongated to more than 800% and the elongation could be recovered almost completely and instantaneously. 相似文献
A series of thermosensitive and fast-response poly(vinyl alcohol) (PVA)/poly(N-isopropylacrylamide) (PNIPA) hydrogels were prepared by incorporating PVA into cross-linked PNIPA to form a semi-interpenetrating polymeric network (semi-IPN). Compared to the conventional PNIPA hydrogel, the semi-IPN hydrogels thus prepared exhibit significantly faster response rates and undergo full deswelling in 1 min (lose about 95% water within 1 min) when the temperature is raised above their lower critical solution temperature, and have larger equilibrium swelling ratios at room temperature. These improved properties are attributed to the incorporation of PVA, which forms water-releasing channels and results in increased hydrophilicity, into the PNIPA hydrogel networks. 相似文献
A new kind of pH-/temperature-responsive semi-interpenetrating polymer network hydrogels based on linear sodium carboxymethylcellulose (CMC) and poly(N-isopropylacrylamide) (PNIPA) cross-linked by inorganic clay (CMC/PNIPA/Clay hydrogel) was prepared. The temperature- and pH-responsive behaviors, the mechanical properties of these hydrogels were investigated. The CMC/PNIPA/Clay hydrogels exhibited a volume phase transition temperature around 32 °C with no significant deviation from the conventional PNIPA hydrogels. The swelling ratio of the CMC/PNIPA/Clay hydrogels gradually decreased with increasing the contents of clay. The influence of pH value on swelling behaviors showed that there is a maximum swelling ratio at pH 5.9. Moreover, the CMC/PNIPA/Clay hydrogels exhibited excellent mechanical properties with high tensile stress and elongation at break in excess of 1200%. 相似文献
Macroporous temperature‐sensitive poly(N‐isopropylacrylamide) (PNIPA) hydrogels were prepared by a novel phase‐separation technique to improve the response properties. In comparison with a conventional PNIPA hydrogel prepared in water, these macroporous hydrogels, prepared by polymerization in aqueous sucrose solutions, have higher swelling ratios at temperatures below the lower critical solution temperature and exhibit much faster response rates to temperature changes.
Scanning electron microscopy image of the surface of a PNIPA hydrogel, prepared in 1.50 M aqueous sucrose solution. 相似文献
