Study of Moisture-Curable Hybrid NIPUs Based on Glycerol with Various Diamines: Emergent Advantages of PDMS Diamines

Abstract

A sol/gel curing method is used in this work to synthesize hybrid partially bio-based polyhydroxyurethanes (PHUs) from dicarbonates derived from glycerol and various diamines. The method consists of end-capping the PHU prepolymers with moisture-sensitive groups, so sealants and adhesives can be produced from partially sustainable hybrid PHUs (HPHUs), similar to their preparation from end-capped conventional polyurethanes. Diglycerol dicarbonate (DGC) is synthesized and polymerized with different diamines of various chain lengths, and the resulting structural and thermal properties of the PHUs are qualitatively and quantitively characterized. This characterization led to two potential candidates: PHU 4, made of DGC and a poly­(propylene glycol) diamine, and PHU 10, prepared from DGC and a poly­(dimethylsiloxane) diamine. These polymers, with respective relative number-average molecular weights of 3200 and 7400 g/mol, are end-capped and left to cure under ambient lab conditions (22 °C and 40–50% humidity), and the curing processes are monitored rheologically. Notably, moisture curing does not require any catalyst. The chemical stability of the resulting hybrid PHUs (HPHUs) 4 and 10 in pure water is investigated to check the viability of applying them under outdoor conditions. Only HPHU 10 is found to be resistant to water and shows hydrophobicity with a contact angle of 109°. Tensile tests are conducted on HPHU 10 samples cured under lab conditions for a week and others cured for another week while being immersed in water. The mechanical properties, tensile strength and elongation at break, improve with the samples cured in water, indicating the high-water repellency of HPHU 10.

Moisture Curable Hybrid Polyhydroxyurethanes from Sugar‐Derived Dicarbonates

“…This particular diamine was studied as it is similar to the PPG‐based diols often used as the soft segment in the formulation of conventional polyurethane sealants and adhesives. [ 40 ] SBC‐PHU 1 and MBC‐PHU 1 oligomers consist of a few hydroxyurethane units and these oligomers are liquid‐like at room temperature, making them good candidates to be considered for end‐capping in bulk. Besides, the same formulation of SBC/MBC and Jeffamine D‐2000 led to PHUs with similar M n , and this is most likely caused by the low reactivity of the diamine.…”

“…Similar trends in the reactivities of similar diamines were observed in our previous DGC study. [ 40 ]…”

“…Recently, HPHUs have gained much attention, [ 32,33 ] especially the ones employing sol/gel crosslinking. [ 34–40 ] The studies by Kathelawar et al. [ 34 ] and Decostanzi et al.…”

“…[ 40 ] Different diamines were coupled with DGC to prepare the PHUs; however, Jeffamine D‐2000 (or poly(propylene glycol) bis(2‐aminopropyl ether)), based on poly(propylene glycol) (PPG) with M n = 2000 g mol −1 , and PDMS‐5k‐(NH 2 ) 2 (or aminopropyl terminated poly(dimethylsiloxane)), based on poly(dimethylsiloxane) (PDMS) with M n = 5000 g mol −1 , proved to give resins suitable for sealants and adhesives applications. [ 40 ] The PDMS diamine added the needed hydrophobicity and mechanical properties for these applications, which was noted by Panchireddy et al. who added PDMS into their PHU thermoset structures to prevent the water swelling of the films and delamination of the coatings from the aluminum surface.…”

“…Depending on the oligomer end groups, either amine or carbonate, the requisite moisture curing agent was added, [3‐(2,3‐epoxypropoxy)‐propyl]‐trimethoxysilane (known as GLYMO) or N ‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilane (known as DAMO), respectively, whose chemical structures are given in Scheme . The guidelines, summarized in Figure 13 of our previous work on moisture curable DGC‐based HPHUs, [ 40 ] were followed herein to synthesize new partially sustainable hybrid materials.…”