Polymerization-induced self-assembly (PISA) is conducted based on “non-living” radical dispersion polymerization in the form of addition–fragmentation chain transfer (AFCT) polymerization.
Polymerization-induced self-assembly of 2-hydroxypropyl methacrylate is conducted in water and water/MeOH using a CO -responsive macroRAFT agent in the form of a statistical copolymer comprising N,N-diethylaminoethyl methacrylate (DEAEMA) and poly(ethylene glycol) methyl ether methacrylate (M = 475 g mol ). Pressurization with CO leads to protonation of DEAEMA units within the stabilizer block, thereby offering a means of adjusting the charge density of the coronal layer. It is demonstrated that a wide range of tunable particle morphologies are accessible by simply varying the CO pressure during polymerization in the range of 10-45 bar.
Polymerization-induced self-assembly (PISA) based on ATRP has been successfully conducted in scCO2 resulting in polymer particles of high order morphology.
The current methods used to impart flameretardant or fire-resistant properties to flexible polyurethane foams (PUFs) to meet fire safety requirements entail the use of halogenated phosphorus-based compounds. Whereas these are highly effective as flame retardants, the associated toxicity derived from halogens in the burning fumes are deadly. To address this problem, we herein present a facile and efficient method of fabricating highly fire-resistant flexible PUF using halogen-free nature-inspired coatings. All of the active ingredients used to fabricate the coatings originated from natural or widely available sources: chitosan from crustacean shells, acetic acid that is found in vinegar, and expandable graphite mined from mineral rocks, thus making this strategy environmentally friendly and sustainable. These coatings offer excellent flame-retardant properties; with a limiting oxygen index (LOI) value as high as 31%, the coated foam could potentially pass the highest levels within the British Standard 5852, which is a commonly accepted global industry standard for meeting the fire safety requirement of flexible PUF. Furthermore, cone calorimeter testing revealed the superior fire safety performance of the coated foam, including very low heat and smoke release upon burning. The flame retardancy of the coated PUFs is tunable depending on the amount of graphite employed in the coating solutions. It is anticipated that the coating strategy described here is applicable to other substrates.
A series of water-dispersible blocked polyisocyanates were synthesized from toluene 2,4-diisocyanate (TDI), isophorone diisocyanate (IPDI), dimethylol propionic acid, methyl ethyl ketoxime (MEKO), ethyl cellosolve (EC), and e-caprolactam (CL). The physical properties, such as the viscosity, pH, and storage stability, of the blocked-polyisocyanate adducts were measured. All aqueous dispersions of the blocked polyisocyanates showed good storage stability. The prepared blocked polyisocyanates were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, and thermogravimetric analysis techniques. The FTIR confirmed that the ANCO groups of the original TDI and IPDI molecules were completely blocked by the blocking agents. The thermal analysis measurements revealed that both the blocked TDI-and IPDI-based polyisocyanates started to deblock at about 55-85 C. Compared to the CL-blocked polyisocyanates, the MEKOand EC-blocked polyisocyanates had lower thermal dissociation temperatures and faster deblocking rates. We also found that the initial deblocking temperatures of the TDI-based adducts were lower than those of the IPDI-based adducts. The water resistance and tensile properties of the composite films from the blocked-polyisocyanate crosslinkers and hydroxyl-polyurethane emulsion (HPUE) matrix were studied. The tensile strength increased and the elongation at break were lower in the composites compared to the pure HPUE film.
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