Stability of a photoreactive polymer LB film

Dynamic contact angles and their hysteresis for LB films of p-phenylenediac rylic acid mono-decylester (p-PDAmC10) and poly(vinyl alcohol) bearing p-PD AmC10 as the side chain (PVPI-p-PDAmC10) were investigated by the Wilhelmy plate method. The hysteresis loops of the contact angle showed that: (1) PV A-p-PDAmC10 forms a more stable LB film than that of p-PDAmC10 which is eas ily detached when contacted with water; (2) PVA-p-PDAmC10 LB film transferr ed at high surface pressure (greater than or equal to 20 mN/m) with more th an 3 layers can provide a uniform surface and same wettability; (3) PVA-p-P DAmC10 LB film has a very large contact angle hysteresis (>80 degrees), whi ch means that reorientation of the surface configuration takes place dramat ically; and (4) the hysteresis can be greatly reduced (<30 degrees) by UV-i rradiation due to the photocycloaddition in the side chains of PVA-p-PDAmC1 0.