Synthesis and characterization of aqueous (polyurethane/aromatic polyamide sulfone) copolymer dispersions from castor oil

Aqueous dispersions of castor oil-based polyurethane (PUCO)/aromatic polyamide sulfone (APAS) block copolymers (PUCO-co-APAS) were successfully synthesized via a copolymerization reaction. PUCO was prepared by an emulsion polymerization process in four steps, namely isocyanate-terminated prepolymer preparation step (PUCONCO), neutralization step, chain extension step and dispersion step, using castor oil (CO), toluene diisocyanate (TDI), dimethylol propionic acid (DMPA) and ethylene diamine (EDA) as a chain extender. APAS was prepared by a polycondensation reaction between bis(4-aminophenyl)sulfone (in molar excess) and terephthaloyl chloride to produce amino-terminated APAS. Three PUCO-co-APAS were prepared via a copolymerization reaction between the amino-terminated APAS and isocyanate-terminated PUCONCO prepolymer. APAS, PUCO and PUCO-co-APAS copolymers were characterized using FTIR, H-1 NMR, particle size distribution (PSD), zeta potential (ZP), thermal analysis (DSC and TGA) and GPC. The effect of the copolymerization process on the thermal, chemical, physical and mechanical properties of PUCO films was studied. The obtained results revealed that the mean particle size of PUCO decreased from 80 rim to 46-49 rim after the copolymerization process. Additionally, narrower size distribution was obtained by the copolymerization process. However, the molecular weight increased with increasing the amount of APAS in the copolymer chains. The copolymerized samples showed better thermal stability than PUCO as a result of the stronger hydrogen bonds and the rigid aromatic groups introduced by APAS in the copolymeric chains. (C) 2014 Elsevier B.V. All rights reserved.