Synthesis And Properties Of N-maleyl Gelatin-co-p(n-isopropylacrylamide) Hydrogel With Thermoresponsive And Ultrahigh Mechanical

Intelligent hydrogel not only have high water retention properties of traditional hydrogels,but also react specifically to minor changes in the environment?temperature,ionic strength,pH,etc.?.Poly?N-isopropylacrylamide??PNIPAAm?hydrogel or PNIPAAm-based composite hydrogels which are thermo-responsive often exhibits abrupt phase transition from the swollen state to the collapsed state,called volume phase transition temperature?VPTT?,which is close to organism temperature.So the PNIPAAm hydrogel have been widely applied in biomedicine,agriculture,industry and so on.By introducing maleylgelatin?MAGEL?into the conventional PNIPAAm hydrogel,a series of composite P?NIPAAm-co-MAGEL?hydrogels with combined features were fabricated.Thermo-responsive behaviors,equilibrium swelling ratio?ESR?,compression strength,tensile strength?TS?and elongation at-break?E?,cyclic compression tests,and thermal stability properties of hydrogels with different amount of MAGEL were investigated.The different valent metal ions(Na⁺,Mg²⁺,Al³⁺)was introduced to P?NIPAAm-co-MAGEL?hydrogel to form M-P?NIPAAm-co-MAGEL?hydrogel(M=Na⁺,Mg²⁺,Al³⁺).The effects of different valent metal ions(Na⁺,Mg²⁺,Al³⁺)on the transparency with varying temperature,swelling ratios and mechanical strength are studied.In particular,the addition of Al³⁺allows the hydrogel to form a double network?DN?structure with more compact and high mechanical strength,and systematically inspects the appearance structure,thermal stability and reversibility of Al³⁺-P?NIPAAm-co-MAGEL?hydrogel.1.When the MAGEL content was blow 30%,the P?NIPAAm-co-MAGEL?hydrogel had kept a good thermo-responsive behavior.However,when the MAGEL content was more than 30%,the thermo-sensitivity of the hydrogel samples became unapparent.2.With the increase of the MAGEL content in the hydrogel samples,the equilibrium swelling ratios demonstrated gradually increased tendency.Therefore,changing the ratio of MAGEL/NIPAAm was an effective method to adjust the ESR.3.The P?NIPAAm-co-MAGEL?hydrogel with weight ratio 30:70 also exhibit extraordinary mechanical properties,favorable anti-fatigue and extraordinary toughness,and the P?NIPAAm-co-MAGEL?hydrogel can be tied to a knot and even it could withstand stretching up to 100%of its original length without fracture.Upon removal of the deformation force,the gel can quickly recover to its initial length.4.The tensile strength?TS?and elongation at-break?E?of hydrogels increased with the increase of the MAGEL content from 0 to 30%in the hydrogel samples and increased from 0.55 MPa,134.5%to 3.38 MPa,241.5%and by 614.55%,179.55%.5.P?NIPAAm-co-MAGEL?hydrogel was similar to PNIPAAm hydrogel in having splendid thermal stability.And,the suitable addition of MAGEL had no discernible effect on the thermal stability of the novel hydrogels.6.The LCST of M-P?NIPAAm-co-MAGEL?hydrogel shifts to a lower temperature with increasing concentrations of ions.There is a good linear relationship between LCST and the salt concentration.The linear graph of C_NaCl,MgCl2-LCST and C_AlCl3-LCST were defined by the equation of Y₁=-12.75X₁+33.08,R₁²=0.98491 and Y₂=-17.94X₂+33.34,R₂²=0.98365.7.At low temperature,different types of hydrogel ESR were sorted:Al³⁺-P?NIPAAm-co-MAGEL?>Mg²⁺-P(NIPAAm-co-MAGEL?P?NIPAAm-co-MAGEL?>Na⁺-P?NIPAAm-co-MAGEL?.8.The Al³⁺-P?NIPAAm-co-MAGEL?hydrogel exhibited higher mechanical properties than Na⁺-P?NIPAAm-co-MAGEL?and Mg²⁺-P?NIPAAm-co-MAGEL?.Because the carboxyl groups of MAGEL formed close-knit network structures and a three-dimensional valent bonding structure by the Al³⁺-ligand coordination interactions.9.The results of thermal stability indicated that P?NIPAAm-co-MAGEL?hydrogel and Al³⁺-P?NIPAAm-co-MAGEL?hydrogel exhibited splendid thermal stability.10.The swelling/deswelling rate of 0.5Al³⁺-P?NIPAAm-co-MAGEL?hydrogel much more rapidly than P?NIPAAm-co-MAGEL?hydrogel.Before and after the volume phase transition,the transmittance of P?NIPAAm-co-MAGEL?and 0.5Al³⁺-P?NIPAAm-co-MAGEL?were completely reversible.