“…Within pH-responsive systems, poly(N-isopropylacrylamide) (PNIPAm) is perhaps the most studied polymer [18][19][20][21][22] . These are network-like systems that contain pH-dependent ionizable groups.…”
SbstractA pH-sensitive blend of polyurethane (PU) and poly(2-(diethyl amino)ethyl methacrylate (PDEA) with good film-forming capacity was prepared from the corresponding aqueous dispersions. The polymer matrix was first characterized by using FTIR, DSC, water vapor transmission and water swelling capacity at different pHs. The drug release profile of films was evaluated using a vertical Franz Cell and theophylline as model drug. The water swelling degree increases from 54 to 180% when the pH of the medium is changed from 6 to 2, demonstrating the pH-responsive behavior of the film. The in-vitro release studies indicate that an anomalous transport mechanism governs the theophylline release.
“…Within pH-responsive systems, poly(N-isopropylacrylamide) (PNIPAm) is perhaps the most studied polymer [18][19][20][21][22] . These are network-like systems that contain pH-dependent ionizable groups.…”
SbstractA pH-sensitive blend of polyurethane (PU) and poly(2-(diethyl amino)ethyl methacrylate (PDEA) with good film-forming capacity was prepared from the corresponding aqueous dispersions. The polymer matrix was first characterized by using FTIR, DSC, water vapor transmission and water swelling capacity at different pHs. The drug release profile of films was evaluated using a vertical Franz Cell and theophylline as model drug. The water swelling degree increases from 54 to 180% when the pH of the medium is changed from 6 to 2, demonstrating the pH-responsive behavior of the film. The in-vitro release studies indicate that an anomalous transport mechanism governs the theophylline release.
“…cally. [1][2][3][4][5] On the other hand, the studies on the Hirasa et al 8,12,13 synthesized porous poly(viapplicable use of these gels to extraction, 6 adsorpnyl methyl ether) (PVME) or poly-N-isopropylation, 7 actuator, 8 drug-delivery systems (DDS), 9 crylamide (PNIPAm) gels by g-ray irradiation to and so on have been also done actively. PVME or PNIPAm, which are thermosensitive In these applications, one of the important facpolymers.…”
ABSTRACT:The simplified method for the synthesis of thermosensitive porous hydrogels by a radical polymerization was presented and their swelling properties were examined experimentally. N,N-Diethylacrylamide (DEAAm) or N-isopropylacrylamide (NIPAm) as primary monomers and N,N-methylenebisacrylamide (BIS) as a crosslinker were used. They were polymerized in water at various temperatures above the lower critical solution temperature (LCST) of poly-DEAAm (ca. 32ЊC) or poly-NIPAm (ca. 31ЊC) by using N,N,N ,N-,tetramethylethylenediamine (TEMED) and ammonium peroxsodisulfate (APS) as the polymerization accelerator and initiator, respectively. From the observation by a scanning electron microscope, it was found that these gels consisted of aggregated microgel particles, namely, a porous structure. The gels swelled below their LCSTs, and the swelling degree increased with lowering temperature. Furthermore, the gels swelled or shrank very fast in response to the change in temperature, and the shrinking rate was larger than the swelling rate. Such swelling properties and mechanical properties depended on the porous structure of the gels such as the size of the microgels and the pore volume, which largely changed with the synthesis temperature and the component of the primary monomer.
“…16 In fact, the gels showing the volume phase transition in response to inÐnitesimal changes in their surrounding environment contain more or less charges on their network chains,17 except N-substituted acrylamide gels. 6,7 Meanwhile, all of the reported transitions occur in aqueous solutions except for a specially designed charge-transfer gel system swollen in benzene. 18 These experimental results indicate that the electrostatic interaction is the most important factor among the above four to initiate the volume phase transition in polymer gels.…”
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