Novel multifunctional hybrid diallyl ether monomer via azide alkyne click reaction as crosslinking agent in protective coatings

Kinetics of Polycycloaddition of Flexible α-Azide-ω-Alkynes Having Different Spacer Length

Two flexible α-azide-ω-alkynes differing in the length of the hydrocarbon spacers (C₈ vs. C₁₂) between functional groups are synthesized. Their bulk polymerization kinetics is studied by differential scanning calorimetry (DSC) and parameterized with the aid of isoconversional methodology. The monomer with a shorter hydrocarbon spacer has somewhat greater reactivity. The effect is traced to a moderate increase in the effective value of the preexponential factor that arises from the fact that the respective monomer has a higher initial molar concentration in itself. The techniques of GPC and NMR provide additional kinetic and mechanistic insights into the studied reaction.

New Bio-Based Furanic Materials Effectively Absorb Metals from Water and Exert Antimicrobial Activity

Development of sustainable bio-based materials for removal of toxic contaminants from water is a high priority goal. Novel bio-based binary and ternary copolymers with enhanced ion-exchange, adsorption and antibacterial properties were obtained by using plant biomass-derived diallyl esters of furandicarboxylic acid (FDCA) as crosslinking agents and easily available vinyl monomers. The synthesized copolymer materials showed higher sorption capacities for Ni^II , Co^II and Cu^II compared to the commercial ion-exchange resins, and they maintained their high metal adsorption capacities for over 10 cycles of regeneration. The synthesized copolymer gels containing 1-5 wt % of the crosslinker showed excellent water absorption capacities. The synthesized copolymers with 1 % crosslinker content showed swelling ratios high enough to also act as moisture absorbents. Synthesized copolymers with crosslinker content of 10 wt % performed as contact-active antibacterials by inhibiting the growth of Gram-positive (S. aureus) and Gram-negative bacteria (E. coli, K. pneumonia) in suspension tests.

Intumescent Phosphorus and Triazole-Based Flame-Retardant Polyurethane Foams from Castor Oil

Synthesis of a novel phosphorus and triazole-functionalized flame-retardant (FR) monomer (PTFM) using azide-alkyne "click" reaction between triprop-2-ynyl phosphate and 2-azidoethanol that can impart intumescent FR property to polyurethane foams (PUFs) has been reported. Polyurethane triazole foams (PUTFs) were prepared using the as-synthesized PTFM and a hydroxylated castor polyol with a hydroxyl value of ∼310 mg KOH/g for application as reactive FR rigid foams. PTFM and the castor polyol were characterized for structural elucidation using Fourier transform infrared and ¹H, ¹³C, and ³¹P NMR. PUTFs with a varying loading content of PTFM were subjected to the lab-scale flame test, cone calorimetry test, Underwriters Laboratory 94 Vertical burning test (UL 94V), and limiting oxygen index (LOI) test. A significant increase in the char yields, reduction in heat release rates, V-1 rating, and 27% of LOI were observed for PUTFs compared to PUFs and proportional to the percentage loading of PTFM. The cumulative effect of nitrogen and phosphorus in PUTFs on their intumescent behavior was evident from the thermogravimetric analysis and scanning electron microscopy micrographs, which were further supplemented by X-ray photoelectron spectroscopy studies, indicating expulsion of N₂ and overall improvement in compression strength as well. Such environment-friendly reactive FRs can be good replacements to the halogenated ones.

Protective Coatings for Aluminum Alloy Based on Hyperbranched 1,4-Polytriazoles

Organic polymers are widely used as coatings and adhesives to metal surfaces, but aluminum is among the most difficult substrates because of rapid oxidative passivation of its surface. Poly(1,4-disubstituted 1,2,3-triazoles) made by copper-catalyzed azide-alkyne cycloaddition form strongly bonded interfaces with several metal substrates. In this work, a variety of alkyne and azide monomers were explored as precursors to anticorrosion coatings for a standard high-strength aluminum-copper alloy. Monomers of comparatively low valency (diazide and trialkyne) were found to act as superior barriers for electrolyte transfer to the aluminum surface. These materials showed excellent resistance to corrosive pitting due to the combination of three complementary properties: good formation of highly cross-linked films, as observed by Fourier transform infrared spectroscopy and differential scanning calorimetry; good adhesion to the aluminum alloy substrate, as shown by pull-off testing; and excellent impermeability, as demonstrated by electrochemical impedance spectroscopy.