A.K./Progres in Organic Coarings 55(2006)231-243 bonded zone free zone PUI-3 >PU-4 PUI-1 PUL6 PUI-2 PUI-1 188cm 160016501700 1750 1800 20 380 Wavenumber (cm) Wavenumber(cm) data(table not shown)as well as Fig.2a suggests that the peak v(C=O)band is highest for PUI-6 and lowest for PUI-3.This pvest for imide prepared from PPG. of(C=O)band among polyester based PU-urea-imide copoly- PUI-13,urea bond concentration is more since the used chain mers shows that the hydrogen bonded C=O contribution in the extender is a diamine [DDS],whereas in the case of PUI-16A.K. Mishra et al. / Progress in Organic Coatings 55 (2006) 231–243 237 Fig. 3. (a) Amide I region of FT-IR spectra of different PU-urea-imide copolymers; (b) N H zone of FT-IR spectra of different PU-urea-imide copolymers; (c) deconvoluted amide I region of PUI-16; and (d) FT-IR peak deconvolution of N H zone in PUI-16. data (table not shown) as well as Fig. 2a suggests that the peak contribution from the hydrogen bonded carbonyls from urea as well as urethane zone are highest for PUI-13 and lowest for PUI-16, when a comparison was made among the PU-urea￾imide copolymers prepared from PPG. Similarly, a comparison of ν(C O) band among polyester based PU-urea-imide copoly￾mers shows that the hydrogen bonded C O contribution in the ν(C O) band is highest for PUI-6 and lowest for PUI-3. This observation is attributed to the polar nature of DDS, which selectively enhances the hard segment cohesion and results in a better phase separation, whereas PD chain extended PU-urea￾imide copolymer shows more phase mixing characteristics. In PUI-13, urea bond concentration is more since the used chain extender is a diamine [DDS], whereas in the case of PUI-16