Abstract
Chitin was chemically extracted from crab shells and then dissolved in N,N-dimethylacetamide (DMAc) solvent with lithium chloride (LiCl) at 3, 5, 7, and 10%. The concentrated chitin-DMAc/LiCl solutions were used for the preparation of chitin hydrogels by water vapor-induced phase inversion at 20°C. The coagulation process was investigated while altering the concentration of LiCl in the DMAc solution. The shear viscosity of the chitin solution increased with higher LiCl amounts and decreased when the concentration of LiCl was reduced by adding water to the chitin solution, implying high LiCl concentration delayed the coagulation of chitin solution in the presence of water. The viscoelasticity of the chitin solutions indicated the gel formation intensification was dependent on the dose of LiCl and chitin in the DMAc solution. After the chitin solution was coagulated, the resultant hydrogels had water contents of 387–461% and the tensile strength varied from 285 to 400 kPa when the concentration of LiCl in the hydrogel was adjusted to 3% and 7%, respectively. As for viscoelasticity, the complex modulus of the chitin hydrogels indicated that the increment of the LiCl concentration up to 7% formed the tight hydrogels. Atomic force microscopic (AFM) image revealed the formation of the entanglement network and larger domains of the aggregated chitin segments. However, the hydrogel prepared at 10% LiCl in DMAc solution exhibited weak mechanical properties due to the loose hydrogel networking caused by the strong aggregation of the chitin segments.
Highlights
Hydrogels are defined as the hydrophilic structure being able to hold an excess amount of water inside their threedimensional polymeric network [1,2,3,4], which can be classified based on different criteria, such as source, polymeric composition, configuration, and type of crosslinking [5]. e most common way to classify hydrogel is based on the material source
As seen from these studies, the reason for choosing the concentration of the added LiCl in DMAc solution has not been clear. erefore, in the present study, the LiCl concentration in DMAc solution is investigated in the range of 3, 5, 7, and 10% to study the effect of LiCl on the formation of the hydrogels and on the properties of the obtained chitin hydrogels by using the phase inversion method under water vapor. erefore, the resultant chitin solutions and hydrogels prepared from different LiCl concentrations were systematically investigated
Meaningful and original conclusions of the chitin hydrogel resulted in the phase inversion process. e properties of the chitin solutions were characterized in terms of viscosity with the addition of the coagulation water and viscoelasticity to observe the difference in the network formation between chitin segment and DMAc/LiCl solvent
Summary
Hydrogels are defined as the hydrophilic structure being able to hold an excess amount of water inside their threedimensional polymeric network [1,2,3,4], which can be classified based on different criteria, such as source, polymeric composition, configuration, and type of crosslinking [5]. e most common way to classify hydrogel is based on the material source. The phase inversion method was successfully used to obtain biomass hydrogel contracting without cross-linker chemicals at room temperature [11, 14] In this process, the biomass polymer is transformed in a controlled way from a solution state to a solid state by the solvent exchange in polymer solution to Journal of Chemistry nonsolvent, leading the polymer coagulation. Erefore, in the present study, the LiCl concentration in DMAc solution is investigated in the range of 3, 5, 7, and 10% to study the effect of LiCl on the formation of the hydrogels and on the properties of the obtained chitin hydrogels by using the phase inversion method under water vapor. The effect of LiCl concentration on the characteristics was measured in water content, mechanical strength, and topography with the surface roughness values to carry out the influence of the LiCl contents on the formation of the obtained hydrogels as the first report
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