Temperature-sensitive hydrogel is a kind of polymer material which has three dimensional networks and can response to slight temperature changes. From the perspective of molecular design in our studies, N-tert-butylacrylamide (NtBA) and acrylamide (AAm) were selected as the co-monomers and a series of temperature sensitive poly (N-tert-butylacrylamide-co-acrylamide) [P (NtBA-co-AAm)] linear and cross-linked copolymers were prepared. Furthermore, on the basis of this synthesis condition, different amounts of polyethylene glycol (PEG) and silica particles were used as pore-forming agents to synthesize macro-porous hydrogels. Synthesis reaction conditions on temperature sensitivity, equilibrium swelling property and swelling/deswelling kinetics were systematically studied, including the option to raise the system, the amount of monomer, crosslinking agent and pore-forming agent. The hydrogels were characterized by FTIR, SEM and DSC. Main results are listed as follows:1. Ammonium persulfate (APS) was used as the initiator, and N’N-methylene-bis-acrylamide (MBA) was selected as the crosslinking agent. The total concentration of monomer 1M, while the reaction temperature was 50℃. The prepared P (NtBA-co-AAm) linear and cross-linked copolymers were all showed excellent temperature-sensitive properties. Through the analysis of DSC, it was seen that linear copolymer was a random copolymer. The glass transition temperature (Tg) of linear copolymer was increased with increasing proportion of AAm.2. Linear copolymers and hydrogels with different NtBA/AAm molar ratio were synthesized (NtBA/AAm=30:70,40:60,50:50,60:40). The phase transition temperature increased with the decrease of NtBA/AAm ratio in feed. When the feed NtBA:AAm= 70:30, the gel phase transition temperature (VPTT) was 30 CC; when the feed NtBA:AAm=60:40, the VPTT was 18℃; when the feed NtBA:AAm= 50: 50, the VPTT was 42℃. The sensivity of hydrogel was not evident when NtBA: AAm=40:60.3. The amount of crosslinking agent MBA had great influences on the swelling properties. The equilibrium swelling rates were increased with the decrease of MBA for various kinds of hydrogels. SEM images showed that pore sizes of hydrogels with a low dose MBA were larger than others. However, the amounts of MBA did not change the VPTT of hydrogels.4. P (NtBA-co-AAm)/PEG composite hydrogels were prepared with different molecular weight of PEG (PEG400, PEG4000, PEG6000, and PEG8000) as pore-forming agents. The hydrogels were then washed with large amounts of deionized water. From FTIR spectra, it was found that there were no absorption peaks of PEG, indicating that PEG had been completely removed from inner structure of hydrogels. SEM images showed that the pore sizes of modified gel with pore-forming agents PEG were much larger than ordinary gel. Swelling results showed that PEG could greatly improve the swelling properties of hydrogels at low temperatures and deswelling properties at high temperatures. However, the change of the network structure of hydrogel did not affect the VPTT of hydrogel. The maximum equilibrium swelling ratio of modified hydrogel was up 160 (g H2O/g gel), much larger than normal hydrogel.5. P (NtBA-co-AAm)/silica composite hydrogels were prepared with different amounts of silica particles as pore-forming agents. From FTIR spectra, it was found that there was no absorption peak of Si-O, indicating that silica particles had been completely removed from hydrogel. In addition, no carboxyl stretching vibration band was found, indicating that amide group was not destroyed by HF. SEM images showed that with the addition of pore forming agents, the pore sizes of the modified hydrogels were significantly improved and larger than that of conventional hydrogels. Experimental results showed that swelling equilibrium properties of modified macro-porous hydrogels were also enhanced greatly.6. Different series of hydrogels were performed by data fitting processes. The fitting results showed that when the temperatures were below VPTT, the swelling processes were fitted for non-Fickian diffusion model. The diffusion coefficient D increased with the increase of swelling rates. The primary and secondary kinetic fitting equation for the swelling process showed a good correlation, the correlation coefficient R2≥0.995.7. Salicylic acid and aspirin were used as the model drugs to test the controlled drug release properties of hydrogels in preliminary study. The results showed that the releasing behavior of drugs can be well controlled by changing temperatures. The response rates of modified hydrogels were significantly better than traditional hydrogels. |