To improve the water solubility of phosphoramidate siloxane and decrease the amount of flame-retardant additives used in the functional coating for cotton fabrics, a water-soluble phosphoramidate siloxane polymer (PDTSP) was synthesized by sol-gel technology and flame-retardant cotton fabrics were prepared with a multistep coating process. A vertical flammability test, limited oxygen index (LOI), thermogravimetric analysis, and cone calorimetry were performed to investigate the thermal behavior and flame retardancy of PDTSP-coated fabrics. The coated cotton fabrics and their char residues after combustion were studied by attenuated total reflection infrared spectroscopy (FTIR-ATR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). All results presented that PDTSP-coated cotton fabrics had good flame retardancy and char-forming properties. PDTSP coating was demonstrated to posess gas-phase flame-retardant mechanism as well as a condensed phase flame-retardant mechanism, which can be confirmed by thermogravimetric analysis-Fourier transform infrared spectroscopy (TG-IR) and cone calorimetry test. Also, the preparation process had little effect on the tensile strength of cotton fabrics, although the air permeability and whiteness had a slight decrease. After different washing cycles, the coated samples still maintained good char-forming properties.
Dually stimuli-responsive hyperbranched polyethylenimine derivatives (HPEI-star-PPOs) were successfully synthesized through Michael addition of commercial HPEI, poly(propylene oxide) dimethacrylate, and 2-mercaptoethanol. In aqueous solution, these HPEI-star-PPOs exhibited response to temperature and pH. The corresponding lower critical solution temperature (LCST) could be readily adjusted by changing the feed ratio of HPEI to PPO, which also presents the ratio of hydrophilicity to hydrophobicity, indicating that this LCST transition is based on hydrophilic-hydrophobic balance. Because of the tertiary amine as well as unreacted primary or secondary amine that can be protonated during pH decreases, HPEI-star-PPOs exhibited a pH-dependent thermoresponse. The 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay against COS-7 cells demonstrated that HPEIstar-PPO had relatively low cytotoxicity compared to HPEI. All these characteristic suggest that this stimuli-responsive polymer is a promising functional material for biomedical applications. ARTICLE Figure 7. Cell viability of COS-7 cells against HPEI and HPEI-star-PPO-1 after 24 h of incubation with different concentrations.ARTICLE 3254
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