Gel Pore Size Regulation Based On Brij Template And Its Induced Crystallization Behavior Of Calcium Carbonate

The structural characteristic of surfactants made themselves have solubilizing, emulsifying and foaming ability, and they have been applied in textiles, agriculture, cosmetic and food industries. In recent years, the using of surfactants as template to preparate materials show some excellent performance, people explore a new direction on surfactant. On the other hand, temperature-sensitive poly(N-isopropylacrylamide) (NIPAM) gels have attracted much attention due to broad applications in drug controlled release, biological substances, bio-separation and tissue culture. However, the traditional PNIPA gels always display some disadvantages in the swelling properties and controlling the porous, and the unstable crystaltion shape in the process of biomineralization. Therefore, the improvement of above mentioned performance has become an important issue that needs to be resolved urgently.First of all, in order to improve the template is not easy to remove, the high cost and solvent pollution, the NIPAM/Brij-58/MBA templatinghydrogel (CLH) and bionic calcification of hydrogels were synthesized with Brij-58 as a template. The chemical composition, crystal structure and temperature-sensitivity of PNIPAM hydrogels before and after template were compared and confirmed by FTIR, XRD and DSC. The optical performance, pore shape and (de)swelling behavior of prepared CLH hydrogels were investigated by UV/vis, SEM and gravimetric method. The disappearance of characteristic absorption peak at 1062-1146 cm-1 and coincidental absorption peak at 195 nm, and recovery of diffraction peak at 2θ= 7.8° and 20= 20.75° all confirmed that Brij-58 plays a template action and could be removed after 48 h. With increasing mass ratios of Brij-58/NIPAM from 0 to 2, the critical time of optical transmittance of CLH hydrogels dropping to 0 from 100 decreases to 7.5 min from 22 min, while maximum equilibrium swelling ratios increase from 6.3 to 10.31 g/g. SEM graphs show that, with increasing mass ratios of Brij-58/NIPAM from 0 to 2, CLH hydrogels firstly form homogeneous and smaller pore, and then pore sizes increase from 4-1 0μm to 50-100μm together with interconnected pore structure. With increasing mass ratios of Brij-58/NIPAM, thermo-responsibility of CLH hydrogels containing Brij-58 template disappeared gradually and then recovered after removing template. The deswelling rates of CLH hydrogels depend on the mass ratios of Brij-58/NIPAM, as r=Brij-58/NIPAM<l/10, the hydrogels lose over 70% water within 60 min, while the hydrogel loses over 70% water within 10 min as r=Brij-58/NIPAM=2. This kind of templated hydrogel with adjustable porous structure has much potential in the fields of drug delivery system, tissue engineering and chemical separation.Furthermore, on the basis of the characteristics of liquid crystal surfactant Brij-58, this experiment discussed the induced effect of Brij-58 to crystallization of calcium carbonate and systematically studied effect to crystal type, size and morphology of the calcium carbonate under the different reaction conditions (such as temperature, stirring speed, reaction time, pH, etc.). According to the experimental results, the mechanism of calcium carbonate crystallization has been put forward. Results show that under the condition of different pH at 30℃, the prepared calcium carbonate is rhombohedral crystals without Brij-58, but when the mass concentration of Brij-58 in the aqueous solution is 0.01 g/L, the calcite crystals present cubic block. Until the the mass concentration of Brij-58 increase to the 0.75 g/L and 2.5 g/L, rhombic hexahedron and ellipsoid are obtained. On the other hand, under 60℃ and 80℃, calcium carbonate crystal type present the cube and rod type of mixed crystal structure. To sum up, compared with other mass concentration of Brij-58, when the mass concentration of Brij-58 is 0.01 g/L, the micelle easier to induce the directional growth of calcium carbonate crystal.Finally, on the basic of the preparation of porous hydrogels by templating, we selected hydrogel as substrate to induce crystallization of calcium carbonate to preparat the bionic calcification hydrogel (CLH-Ca), due to it is the most similar with organisms. Using the Brij-58 induced crystallization, calcium carbonate present different crystal forms, its stability depend on pH, temperature and the content of the template. Results show that the crystal crystal morphology presented the neat cube crystal model in the early stage, with increasing the time to 24 h,72 h and 120 h, the amount of calcium carbonate crystal showed a trend of first increase and after sharply reduced the in the CLH-CaO, CLH-Ca75 and CLH-Ca250 hydrogels, and there are two kinds of crystal type, including irregular acicular crystal whisker, while the amount of calcium carbonate in CLH-Ca001 hydrogel did not significantly change. In addition, also found that With the mass ratios of Brij-58/NIPAM increased 1/150,1/2 and 5/3, the crystal size were 1 μm、5 μm and 2 μm, respectively, and the nucleation number has been increased. Based on the above, we concluded that CLH-Ca001 hydrogel environment was the most conducive to the growth of calcium carbonate.