Preparation And Characterization Of PNIPA/LDHs And SA/PNIPA/LDHs Nanocomposite Hydrogels

Poly N-isopropyl Acrylamide(PNIPA)is a kind of smart hydrogel which is sensitive to temperature,with the characteristics of the excellent biocompatibility,elasticity,syringeability and low pollution.It is demonstrated that the PNIPA can be applied for synthesizing the support tissue because it is avirulent and effective to cells in the medical field.PNIPA can be widely used in the field of medicine carrier,enzyme stabilisation,artificial muscle and smart interrupteur based for its temperature sensibility.However the application of traditional chemical cross linking PNIPA is restricted with the bad properties of weak strength,low corresponding rate,crisp and fragile characteristics and difficulty to stretch.Therefore,improving the material properties is significant for many industries,especially in the engineering tissue field.The paper is composed of two following parts:On the one hand,we synthesized a kind of temperature sensibility hydrogel with hydrotalcite-like compounds(LDHs)and NIPA.The original composites of PNIPA/LDHs was synthesized by the radical polymerization which was initiated by potassium persulfate(KPS)and tetramethylethylenediamine(TEMED).We researched the effect of LDHs and the metal molar ratio(nMg: nAl)on the temperature sensibility of PNIPA/LDHs composites.It indicated that the LDHs played important role in effecting the composition of the composites.What's more,when the temperature up to 33 ?,the sol-gel reversible transformation can be easily observed.The TGA curves indicated that the thermal stability of composites can be enhanced greatly by adding the LDHs into system.The DSC curves showed that the endothermal peak is improved by increasing the content of LDHs and the ratio of nMg: nAl.The rheology results demonstrated that the composites structure can be effected by changing the content of LDHs 1 while can't be changed by the LDHs 2.It revealed that the composites of PNIPA/LDHs is non-Newtonian fluid with the characteristics of shear thinning.When increased the content of LDHs 1,the viscosity of hydrogel was reduced while the value of G' and G'' was reduced firstly and then increased.When increased the content of LDHs 2,the viscosity of hydrogel was increased and the value of G' and G'' was also increased gradually.The viscosity of the composites of PNIPA/LDHs 1 is larger than the PNIPA/LDHs 2 at the same mass fraction.All the raw materials used in the experiment have good biocompatibility and the composites will have bright future in the application of repairing injured cartilage tissue.On the other hand,to improve the mechanical strength of the composites,we used the LDHs,monomer,NIPA,initiator,KPS and TEMED to compose the composites by radical polymerization.At the same time,we also introduced the sodium alga acid(SA)into PNIPA structure with the technique of semi-interpenetrating polymer network to compose the composites of SA/PNIPA/LDHs.The results of light transmittance and DSC revealed that the addition amount of SA can't affect the LCST.While the gelatin time can be reduced by increasing the SA content.IR characterization demonstrated that the SA can be distributed well in the PNIPA network and existed stably.The rheology results indicated that the value of G' and G'' can be increased largely firstly and then reduced when increased the content of SA gradually.When the addition amount of SA up to 1.5mL,the compounds has the highest viscosity.And the composites is non-Newtonian fluid with the characteristics of shear thinning and thermal stability.Therefore,it is meet for the necessary of the injected temperature sensibility materials and can be applied in the field of repairing injured cartilage tissue hopefully.