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LIU MingZhu;CHENG Rongshi(Department of Chemistry, Nanjing University,, Nanjing 210093)QIAN Renyuan(Institute of Chemistcy, Academia Sinica, Beijing 10080)  
n the basis of previous investigation of concentration dependence of cryogenic gelation for aqueous solution of poly (vinyl alcohol) (PVA), the physical hydrogels with high water content were prepared by freezing and thawing to the PVA aqueous solution. The properties of the hydrogels in distilled water have been investigated. A swelling kinetic equation was proposed:Qt= Qe-(Qe- Qo) /eldThis equation fits the experimental results. A quantitative relationship between equilibrium swelling ratio and the solution concentration was also obtained: Qe=60.3 -4.45×102C. It was found that eqinlibrium swelling ratio Qe, dissolution amount W of the hydrogels and the times N of freezing-thawing cycles followed the power laws:Qe; W, as N≤5. By comparing the results of this work with that of previous paper, we found that Qe, reflected the intermolecular hydrogen bonding cohesional entanglement of concentrated soloution of PVA and [η], described the intramolecular hydrogen bonding cohesional entanglement in dilute solution of PVA are equal in value.
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