Recently

some attention has been paid to hydrophobically modified gels (HM-gels) with a small number of hydrocarbon side groups in their chain backbones．However

few papers can be retrieved for fluorocarbon-modified gels although fluorocarbon groups show the strong ability of hydrophobic association than hydrocarbon ones．In HM-gels

the association of hydrophobic side groups affects directly the state and amount of water．Therefore it is necessary to investigate the states of water in fluorocarbon-modified gels in order to understand the relationship between their hydrophobic microstructure and macroscopic properties．In this paper

a series of hydrophobically modified poly(acrylic acid) (HM-PAA) gels were prepared by radical copolymerization of acrylic acid (AA) and a small amount of hydrophobical comonomers

2-(N-ethylperfluorooctanesulfoamido)ethyl methacrylate (FMA) in tert-butanol．The effects of hydrophobic modification on water states of gels were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)．For HM-PAA gel with FMA content of 1％

no melting peaks were observed with water content(Wc) lower than 0.698 mol％ and two melting peaks appeared with Wc higher than 0.698 mol％ in DSC heating curves

which proved the existence of three states of water molecules

that is

free water

non-freezing water and freezing bound water in FMA-modified gels．A method for calculating the melting enthalpy of different states of water in gels the numbers of non-freezing and freezing bound water molecules associated with a polymer unit

n0 and n1 was brought forward．The numbers of non-freezing and freezing bound water molecules associated with a polymer unit

n0 and n1

increased after hydrophobic modification．For the gel sample PAA-FMA1％

the melting enthalpies of freezing bound water and free water were measured to be 7589.03 and 6864.06 J／mol

respectively.