Synthesis And Properties Of Double Network Nanocomposite Hydrogel

Hydrogels are a class of functional polymers which could be used in many fields. However, the low fracture toughness of typical chemically crosslinked hydrogels restricts their application in biomedicine, organ engineering and other fields. It is a challenging problem in modern gel science to fill the gap between man-made and biological gels. Many efforts have been made to increase the mechanical strength of hydrogels.At first, we present a novel double network nanocomposite hydrogel by using Poly[(dimethylimino)(2-hydroxy-1,3-propanedily)chloride] (PDMIHPC) and Laponite to fabricate the first network. The subsequently network is made of PAA chemically crosslinked by N, N'-methylenebisacrylamide (MBAM). The mechanical strength was examined by varying the reaction temperature, PDMIHPC/Clay composite dose, MBAM dose and water content. The results indicated that when the reaction temperature was 35oC, PDMIHPC/Clay composite/AA is 1: 10 and MBAM dose was 0.050 wt% (based on the weight of AA), the novel hydrogel achieved high compressive strength of 100.05 KPa in water content of 98.8%.To enhance the mechanical strength of the hydrogels, ethylenediamine was introduced for the fabrication of first network instead of dimethyl amine. A novel double network nanocomposite hydrogel consisting of the first network of poly[(1,2-ethylenediamino) (2-hydroxy-1,3-propanedily) chloride] (PEIECH)/laponite and the second network of crosslinked PAA was synthesized by two-step solution polymerization. The resulting PEIECH/Laponite/PAA nanocomposite double network hydrogels achieved a high compressive stress of 148.0 KPa even in higher water content of 98.7% when the PEIECH/Laponite nanocomposite dose is 0.05 ml, the dose of AA was 3.6 ml, N, N'-methylenebisacrylamide (MBAM) dose was 0.04 wt% (based on the weight of AA) and reaction temperature was 0oC, There is a small decline in the maximum stress of the hydrogels at the fixed strain of 45% even after three cyclic compressions.In order to simplify the fabrication of the novel double network nanocomposite hydrogel, PEG/Laponite/PAA hydrogels were synthesized using PEG/Laponite as the first network while crosslinked PAA as the second network. The mechanical strength was examined by varying the PEG/Laponite composite and the molecular weight (MW) of the PEG. The results showed the hydrogel had a high compressive stress of 40.2 KPa in high water content of 99.5% when the MW of the PEG was 10000, the PEG10000/Laponite composite dose of 1 ml, the dose of AA was 3.6 ml, N, N'-methylenebisacrylamide (MBAM) dose was 0.05 wt% (based on the weight of AA) and reaction temperature was 42oC. Based on the dynamic mechanical analysis (DMA), it was found that the dynamic storage (E') moduli increased as the dose of the PEG/Laponite and MW of PEG increased. Besides, in the range of the frequency (0.1~10 Hz), dynamic storage (E') moduli of the hydrogels increased as the frequency increased.