Study On Enhancement Mechanism Of Hydrogel Nanocomposites

Hydrogel is an important type of functional polymer. Its super absorbent, excellent water-holding capacity, low surface friction coefficient and superior biocompatibility, have caused a great interest on the field of hydrogel researches. But the traditional or natural hydrogel has some shortcomings, such as weak mechanical strength and poor reproducibility of its property, which limit its application. Compositing nano materials into the polymer network structure can improve the mechanical strength and other properties of hydrogel. However, different structural morphologies of nano materials show different effects on improving the properties of hydrogel, so, the influencing mechanism of various structural morphologies of nano materials remains to be discussed.In this paper, a common hydrogel material-polyacrylamide (PAM) was selected as researching object. We depend on molecular dynamics theory, and use the Materials Studio software to build the molecular models of the 1D and 2D nano fillers ——nanotubes and graphene, PAM hydrogels are based on acrylamide monomer and N,N-methylenebis(2-proprnamide) as its cross-linker, and the gel model has a 3D network structure, then the following contents are considered.1. Molecular dynamics simulation was performed to get a reasonable model, then calculation of mechanical properties was also performed to achieve the shear modulus, Young’s modulus, Poisson ratio, lame constant of the model.2. Due to the Amorphous Cell module which was used to construct the cell, the distribution of molecules in the cell are random, it may have an effect on the results of simulation, to minimize the deviation, we constructed several models, and ran simulations in the same parameters set to obtain the mechanical properties of different models.3. The unit cell of polyimide nano composites reinforced by nanotube was built, and the mechanical properties of it were obtained in the same way as the pure PAM gel. Then the shear modulus、Young’s modulus、Poisson ratio、lame constant of the model were achieved.4. The unit cell of polyimide nano composites reinforced by graphene was built, and the mechanical properties of it were obtained.5. At last, we made a comparison of the mechanical properties between polyimide nano composites and pure PAM gel to discuss the influences caused by nano fillers of different morphologies.