SURFACE MODIFICATION OF POLY(ETHYLENE-TEREPHTHALATE) TO PREPARE SURFACES WITH SILICA-LIKE REACTIVITY

Reactions of semicrystalline poly(ethylene terephthalate) (PET) film w ith 3-aminopropyltrialkoxysilanes at the film-solution interface and s ubsequent hydrolysis render silanol (Si-OH) functionality that is atta ched to the PET surface by amide linkages (PET-CONH(CH2)(3)Si(OH)(3)). Toluene was found to be the preferred solvent for the initial amidati on reaction, rendering a higher surface concentration of silanol group s than that for other solvents. Polycondensation of tetraethyl orthosi licate on the surface of PET-CONH(CH2)(3)Si(OH)(3) produces thin silic a films, the thickness of which can be controlled with reaction time. The surface of this composite film (PET-(SiO2)(x)-OH) also contains re active silanol groups. These two reactive surfaces were further modifi ed using other reactive silanes to introduce alkyl, perfluoroalkyl, br omoalkyl, and aminoalkyl functionality to the PET film surface. The su rface density of attached groups was assessed by X-ray photoelectron s pectroscopy, and wettability of the surfaces was determined using cont act angle analysis. The reactivity of these surfaces was compared to t hat of oxidized silicon wafers, and we conclude that these PET modific ation procedures (amidation with 3-aminopropyltrialkoxysilanes and pol ycondensation of tetraethyl orthosilicate) produce surfaces that react with the versatility of oxidized silicon wafers.