The synthesis of traditional polyurea (PUR) involves toxic, hazardous, and harmful isocyanates. Sustainable biobased feedstocks are significant for future industrial development. A range of nonisocyanate poly(amide-urea) (NIPURs) are obtained by melt polycondensation from biobased dicarboxylic acids, urea, and diamines without catalysts and high pressure. Excessive hydrogen bonding in NIPURs leads to high crystallinity, which renders it difficult to obtain a polymer material with both high strength and satisfactory toughness. The hydrogen bonding content and distribution can be regulated by changing the molar ratio of dicarboxylic acids/urea and the structure of the dicarboxylic acids. It is remarkable that NIPURs exhibit excellent mechanical and thermal properties. Its yield strength is up to 61 MPa, tensile strength is as high as 7069 MPa, and it maintains an elongation at break of 241%; its melting point ranges from 166 to 200 °C and it maintains initial decomposition temperature (T5%) higher than 345 °C. The adjustable mechanical and thermal properties of NIPURs offer significant potential for various applications. This work could provide new insights into designing PUR with enhanced mechanical properties.
A novel poly(amide-urethane@imide) reverse osmosis (RO) composite membrane with chlorine-tolerant property was prepared on a polysulfone supporting film through two-step interfacial polymerization. The crosslinking agent – 5-choroformyloxyisophaloyl chloride (CFIC) was first reacted with 4-methyl-phenylenediamine (MMPD) via interfacial polymerization to get the nascent poly(amide-urethane) base membrane (CFIC–MMPD) without curing treatment. Then the resultant base membrane contacted again with the second aqueous solution containing functional secondary amine – N,N′-dimethyl- m -phenylenediamine (DMMPD) to obtain the poly(amide-urethane@imide) TFC RO membrane (MMPD–CFIC@CFIC–DMMPD). X-ray photoelectronic spectroscopy (XPS) was combined with attenuated total reflectance infrared (ATR-IR) to verify that the ultrathin polyimide film (CFIC–DMMPD) has been successfully grafted on the surface of the MMPD–CFIC base membrane. The images of scanning electronic microscopy (SEM) and atomic force microscope (AFM) showed that the poly(amide-urethane@imide) membrane has much smoother, more hydrophilic surface than the poly(amide/imide-urethane) membrane (MMPD/DMMPD–CFIC) prepared by conventional one-step interfacial polymerization of CFIC and composite MMPD/DMMPD. However, the permeation experiment revealed that the poly(amide-urethane@imide) membrane has a slight loss in both salt rejection and water flux than the poly(amide/imide-urethane) membrane and conventional commercialized polyamide membrane (MPD–TMC), but exhibits better chlorine-tolerant property due to the introduction of ultrathin polyimide film (CFIC–DMMPD) on the outmost surface of the TFC RO membrane, and the combination of IR and XPS analyses shows a good agreement with the chlorine exposure results of membranes.
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