A series of polyurethane gels were synthesized by addition reaction of biomass polyols, sugar alcohols, tannic acid, castor oil (CO), and diisocyanate compounds, namely hexamethylene diisocyanate (HDI), and methylene diphenyl 4,4’-diisocyanate (MDI) in N,N’-dimethylformamide (DMF) as a solvent. The reactions with MDI yielded the gels faster than those with HDI due to the high reactivity of MDI with OH group. The Young’s modulus of the gels increased with increase in the monomer concentration and number of OH group in the polyol due to the increase in crosslinking density. The gels with MDI showed hard features derived from the rigid phenyl group in MDI. The gels with sugar alcohols in dimethyl sulfoxide or the gels with CO in terpenes were also prepared to study the effect of the solvent. These gels showed higher Young’s modulus than the corresponding gels prepared in DMF due to the high affinity between the network structure and the solvent used.
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