Practical two-step chain extension method to prepare sulfonated waterborne polyurethanes based on aliphatic diamine sulphonate

We reported a novel synthesis route to fabricate sulfonated aliphatic waterborne polyurethane dispersions (SWPU) only based on 2-[(2-aminoethyl) amino] ethane sulphonate sodium (AAS-Na) by two-step chain extension method with the assistance of acetone and water cosolvent. When AAS-Na was added, only less than 50% of AAS-Na was incorporated into polyurethane chain in the first-step chain extension and the residual AAS-Na formed molecular aggregates which were insoluble in acetone due to the high polarity of AAS-Na. Subsequently, the mixture of acetone and water was added, the residual AAS-Na aggregates dissolved, undertaking the further second-step chain extension reaction, and the ultimate reaction conversion of AAS-Na rose to more than 90%. The mechanism for acetone and water cosolvent to affect the preparation of SWPU dispersions was studied, as well as the water resistance, mechanical properties and hydrolysis resistance of as-prepared SWPU dispersions. With the decrease of AAS-Na content from 2.0% to 1.2%, the peak area of the melting peaks for SWPU films increased, as well as the water resistance. And the as-prepared polyester SWPU exhibited good hydrolytic stability.