Wilhelmy Dynamic Contact Angles and Wettability

Similar to static contact angles from the sessile droplet method, Wilhelmy dynamic contact angles are an excellent indication of the change in surface characteristics due to surface modification techniques such as plasma polymerization coating. The cosine of dynamic advancing contact angles from the first immersion, cos 0D,a,i of untreated, TMS-treated, and (TMS-I-02)-treated conventional 

Eight of 10 TMS-treated polymers exhibited contact angles within an average cos 0D a,i =—0-381 (0D,a,i = 112 3.6), and all of them showed the negative cos 0. This indicates that the surface of plasma polymer of TMS-deposited films is clearly hydrophobic and independent of the substrate material for these polymers. TMS-treated PTFE and UHMWPE were slightly more hydrophobic with average cos 0D,a,i = -0.785 (0D,a,i = 141 4.2). 

The (TMS 02) plasma-modified polymers were made considerably more hydrophilic with average cos 0D,a,i= 0.654 (Op,a,i =49.2 11.7) but remain in the domain of amphoteric surface, under the conditions of plasma polymerization used. (TMS + O2) plasma-deposited films were slightly more dependent on the nature of the conventional polymer substrates. This is probably due to the fact that substrate polymers have different oxygen plasma susceptibilities. 

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