The temperature sensitivity of poly(N-isopropyl acrylamide)(PNIPAAm)-grafted films was investigated through water absorbency and water contact angle measurements．Though it contributed little to the water absorbency of grafted films

the introduction of MBAAm retarded water evaporation from the grafted layers and also enhanced their hydrophilicity. It was found that below a certain critical temperature

the surface contact angle of the grafted films decreased during the measurement

which was related with the interaction process between the probing water drops and the film surfaces．A Temperature-dependent Real Time Contact Angle Measurement method (TRTCA)

which is especially suitable for the LCST determination of temperature-sensitive grafted films

was developed based on a newly proposed contact angle modification algorithm to eliminate the influence of water evaporation．Finally

a two-stage model was proposed to describe the interaction process between the grafted films and water．Corresponding to this model

the critical grafting yield for grafted films crosslinked with MBAAm showing significant change of surface behavior was found to be around 0.6 mg／cm2．