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1-Acrylamidopyrene (AAP) was synthesized for the first time in this study. A series of thermosensitive copolymeric hydrogels were prepared by copolymerization of AAP and N-isopropyl acrylamide (NIPAAm) by UV irradiation. The effect of AAP content in the copolymeric hydrogels on the swelling ratio, mechanical properties, and drug release behavior of the hydrogels was investigated. The swelling ratios decreased from 6.5 to 4.9 (g/g) when the AAP content in the copolymeric hydrogels increased from 0.1 to 0.9 mol% owing to their increasing hydrophobicity. In addition, the thermosensitive behavior obviously diminished with increasing AAP content in the copolymeric hydrogels, but the mechanical properties and cross-linking densities of the hydrogels swollen in ethanol solution were enhanced with increasing AAP content. The swelling ratios of the hydrogels in different solvents were varied with increasing AAP content. The result of caffeine release in the hydrogels showed that when the content of AAP in the hydrogel increased, the caffeine-loading amount decreased; however, their fractional release increased. The corresponding copolymers of the NIPAAm/AAP copolymeric hydrogels were synthesized. The UV absorbance and photoluminescent (PL) behavior of AAP, NIPAAm/AAP copolymeric hydrogels, and their corresponding copolymers in some solvents with different polarities were investigated.

Bis[4-(phenyl-isopropyl)phenyl]-4-nitrophenylamine (BiPNPA) (iii) was firstly synthesized via nucleophilic substitution of 4-fluoronitrobenzene (ii) and bis-[4-(phenyl-isopropyl)phenyl]amine (BiPA) (i) in this study, and then compound (iii) was reduced to bis[4-(phenyl-isopropyl)phenyl]-4-aminophenylamine (BiPAmPA) (iv). At last, acrylation of BiPAmPA with acryloyl chloride was performed to obtain a novel bis[4-(phenyl-isopropyl)phenyl]-4-acrylamidophenylamine (BiPAcPA) compound (v). Then, a series of thermosensitive hydrogels were prepared by copolymerization of BiPAcPA and N-isopropyl acrylamide (NIPAAm) by UV irradiation. The effect of BiPAcPA content in the copolymeric hydrogels on the swelling ratio, mechanical properties, and drug release behaviors of the hydrogels was investigated. Results showed that the swelling ratios of the copolymeric hydrogels decreased from 8.2 (g/g) to 5.01 (g/g) when the monomer BiPAcPA content in the copolymeric hydrogel increased from 0.1 mol% to 0.9 mol%. In addition, the thermosensitive behavior obviously decreased with increasing of BiPAcPA content in the hydrogels, but the mechanical properties and crosslinking density of the hydrogel increased with increasing of BiPAcPA content; the caffeine release ratio from 46 % decreased to 29 %. The result of caffeine release also showed that the caffeine-loading amounts decreased with increasing content of BiPAcPA in the hydrogel, but their fractional release increased. In addition, the corresponding copolymers of the copolymeric hydrogels were prepared. Furthermore, the UV absorbance and photoluminescent (PL) behavior of the BiPAcPA, NIPAAm/BiPAcPA copolymeric hydrogels, and their corresponding copolymers in some solvents with different polarities were investigated. The results showed the PL intensity increased with increasing BiPAcPA amounts, especially the wavelength had obvious blue shift phenomenon in THF solvent. The wavelength of UV absorbance and PL emission of BiPAcPA all appeared in visible region. No matter what BiPAcPA monomer, NIPAAm/BiPAcPA hydrogels or NIPAAm/BiPAcPA copolymers, the wavelengths of UV absorbance and PL emission in DMSO solvent are all the same.

A series of novel copolymeric hydrogels were prepared from 2-hydroxyethylmethacrylate (HEMA) and poly(ethyleneglycol) methacrylate (PEGMA), and silicon monomers such as trimethylsilylmethacrylate (TMSM) and 2-(trimethylsilyloxy) ethyl methacrylate (TMSOE). The effect of silicon monomer on the swelling and mechanical properties of the hydrogels was examined. The results showed that the addition of silicon monomers lowered the equilibrium water content of (PEGMA-co-HEMA) hydrogels due to their lower hydrophilicities than PEGMA and HEMA. From the swelling kinetics data, it was found that the hydrophobicity of TMSM is larger than TMSOE. The addition of TMSM effectively lowered Young's modulus and increased elongation of the synthesized hydrogels. The hydrogels containing TMSM showed pH-sensitivities, but those containing TMSOE showed a good stability in acid and base solutions.

Copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) methacrylate (PEGMA) and isopropanol as a diluent were prepared by photopolymerization. The swelling kinetics, mechanical properties, drug release behaviors, and the interaction between various drugs and the present copolymeric gels were investigated in this study. The results showed that the addition of PEGMA could effectively increase the equilibrium water content and the diffusion coefficient and penetration velocity of water though the gels. Although Young's modulus increased with the increase of PEGMA content, the resulting gels had smaller elongation and more brittle characteristics. The drug release behavior was strongly dependent on the interaction between the present copolymeric gels and drugs such as caffeine, crystal violet (CV), phenol red, and vitamin B12.

A series of copolymers and their corresponding hydrogels were prepared essentially from N-isopropyl acrylamide (NIPAAm) and acrylamidoazobenzene (AAAB) at different molar ratios. The AAAB was synthesized in advance and verified by elemental analysis, 1H-, and 13C NMR techniques. The effect of AAAB contents on the thermal and ultraviolet response of the copolymer and their corresponding hydrogels was investigated. The results showed that a changed quantity of AAAB in the copolymers and hydrogels would only slightly affect their LCSTs and CGTTs. In addition, the copolymers and their hydrogels show good thermo- and photo-response due to NIPAAm structure and the cis-trans isomerization of azobenzene group upon UV irradiation. Furthermore, effects of AAAB contents on the physical properties and drug release behavior of the copolymeric hydrogels were also examined.

A series of xerogels based on different degrees of neutralizations (DN) of acrylic acid (AA) and N,N-methylene-bis-acrylamide (NMBA) were prepared by inverse suspension polymerization. The influence of the DN values of AA on water absorbency and swelling behavior for these highly absorbent polymers in deionized water and various saline solutions were investigated. Results indicate that the equilibrium-water absorbency (Qeq) increases with an increase in the DN of AA until the DN value reaches 95% and then decreases at 100% of the DN value. However, the initial absorption rate for these gels decreases with an increase in the DN value of AA in both deionized water and 0.9 wt% NaCl solution. The adsorption of copper ions by these gels was also investigated.

A series of copolymeric hydrogels were prepared from various molar ratios of N-isopropylacrylamide (NIPAAm), sodium-2-acrylamido-2-methylpropyl sulfonate (NaAMPS) and N,N′-dimethyl(acrylamido propyl) ammonium propane sulfonate (DMAAPS). The swelling behaviors of these copolymeric hydrogels were investigated in various saline solutions. The result showed that the phase transition temperatures of these gels changed insignificantly, and the thermosensitivity, in contrast, diminished. In addition, the copolymer gels exhibited polyelectrolytic behavior under lower salt concentration (10−5∼10−1 M), exhibited a nonionic gel (like NIPAAm) behavior at the salt concentration from 0.1 to 0.4 M, and showed an antipolyelectrolytic behavior (polyzwitterionic effect) at a salt concentration over 0.4 M. Finally, the presented coplymeric gels are investigated for use in drug release application.

A series of pH-thermoreversible hydrogels exhibiting volume phase transition were synthesized by three degrees of neutralization (DN) of acrylic acid (AA) and N-isopropylacrylamide (NIPAAm). The influence of environmental conditions, such as temperature and pH, on the swelling behavior of these copolymeric gels is investigated in this article. Results show that the negatively charged hydrogels exhibit different equilibrium swelling ratios at different pH values depending on the ionic composition. The pH-sensitivities of these gels also strongly depend on the DN of AA in the copolymeric gels. The results show that the higher the DN, the higher the gel pH-sensitivity. These hydrogels based on a temperature-sensitive hydrogel demonstrate a larger change of equilibrium swelling in aqueous media between a highly solvated, swollen gel state and a collapsed dehydrated network in response to a variation of temperature. On the other hand, a significant phenomenon that was found in the gel swelling kinetics was an overshooting under high temperature conditions. The presented hydrogels were used for release of model drugs that occur at the changes of surrounding conditions, such as temperature and pH, in this study. It was also found that the higher the DN of AA, the higher the gel transition temperature and the larger the release in a high temperature environment and, at the same time, the larger the swelling ratios.

A series of the 2-hydroxyethyl methacrylate/2-vinyl-l-pyridinium propane sulfonate (HEMA/VPPS) copolymeric gels have been prepared from HEMA and zwitterionic monomer VPPS of various molar ratios. The influence of the amount of VPPS in copolymeric gels on their swelling behavior in water and various saline solutions at different temperatures was investigated. Results indicate that the PHEMA hydrogels exhibit an overshooting phenomenon in their dynamic swelling behavior. The maximum overshooting value decreases with increasing temperature. The same results are also shown for the lower VPPS content HEMA/VPPS copolymeric gels. In the equilibrium swelling ratio, the PHEMA hydrogel exhibits a minimum swelling ratio at 55 °C. Then, the minimum swelling ratio disappears gradually with increasing VPPS content in HEMA/VPPS copolymeric gels. In the saline solution, the swelling ratios of HEMA/VPPS copolymeric gels increase rapidly with increasing salt concentration, for salts with a smaller ratio of charge/radius.

A series of N-isopropylacrylamide/diethyl methyl methacryloyloxyethyl ammonium iodide (NIPAAm/DEMMAI) copolymeric gels were prepared from blending NIPAAm, cationic monomer DEMMAI, and N,N′-methylene bisacrylamide (NMBA) in various molar ratios in this article. The effects of the amount of the cationic monomer in the copolymeric gels on the swelling behaviors in water and various saline solutions at various temperatures were investigated. Results showed that the swelling ratios of copolymeric gels were significantly larger than those of pure NIPAAm gel, and that the more the DEMMAI content, the higher the gel transition temperature. In the saline solution, results showed that the swelling ratio for pure NIPAAm gel had not changed significantly with an increase of the salt concentration until the salt concentration was larger than 0.1 M. The swelling ratios for the copolymeric gels NIPAAm/DEMMAI were decreased with increasing salt concentration. In various saline solutions, results showed that the anionic effects were greater than cationic effects in the presence of common anion with different cations and common cation with different anions for these hydrogels.