Isocyanate terminated prepolymers were synthesised using poly(tetramethylene oxide) glycol of molecular weight 1 000 (PTMG1000) and poly(propylene oxide) glycol of molecular weight 1 000 (PPG1000) with tolylene‐2,4‐diisocyanate (TDI). The prepolymers were chain extended with N,N‐bis(2‐hydroxyethyl)isonicotinamide to form polyurethanes containing pyridine moieties. These polyurethanes were converted to cationomers by crosslinking with (a) 1,4‐dibromobutane to form short‐chain crosslinked polymers (SCCPs) and (b) bromine‐terminated prepolymers to form long‐chain crosslinked polymers (LCCPs). The cationomers were characterised by Fourier transform infrared spectroscopy, thermal and mechanical analysis. FTIR spectral results of SCCPs and LCCPs confirmed the quaternisation of heterocyclic nitrogen leading to crosslinking. Dynamic mechanical analysis showed better damping properties for LCCPs than SCCPs. The stress‐strain measurements showed higher elongation and lower tensile strength for LCCPs.
ABSTRACT:Vinyl-terminated polyurethane (VTPU) was prepared by end-functionalizing isocyanate-terminated prepolymers with 2-bromoethanol and subsequently quartenizing with 4-vinylpyridine. The vinyl functionality was then effectively utilized for preparing AB crosslinked polymers (ABCPs) with methyl methacrylate (MMA). ABCPs prepared with variable weight ratios on PTMG 1000 -based VTPU/MMA (8/2, 6/4, 5/5, 4/6, 2/8) and those prepared at a 5/5 weight ratio with different polyols (PTMG 1000 , PPG 1000 , and PCL 1250 ) in VTPU were characterized by Fourier transform infrared spectroscopy (FTIR) and further analyzed for thermal and mechanical properties. FTIR spectral results confirm quartenization of heterocyclic nitrogen, leading to crosslinking. Thermogravimetric analyses show enhanced thermal stability of the crosslinked systems. The stress-strain measurements reveal increasing tensile strength with increasing amounts of MMA. Comparison of dynamic mechanical spectra of ABCPs based on PTMG 1000 shows that the 5/5 composition exhibits good damping over a broad temperature range.
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