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Urethane-urea copolymers with different main-chain structures have been synthesized, and their nonlinear optical (NLO) properties compared. The glass transition temperatures ( T g ) depended on their main-chain structures. The optimum poling temperature of each copolymer was 45° C higher than its T g , indicating the existence of forces preventing the disordering of poled NLO groups. The observed temporal behavior of d 33 at 100° C indicates that introducing urea groups into a polyurethane main chain can increase the temporal stability of the polyurethane without improving the stiffness of the main chain.
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Tsuchimori et al. (1997) studied this question.
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