Hydrophilic surfaces contact angle

The low temperature ene reactions of 4-substituted-l,2,4-triazoline-3,5-diones (RTD) were used to modify polydiene surfaces. Hydrophilic surfaces (contact angles with water of 30-50°) were obtained on polybutadiene, poly-isoprene and styrene-butadiene copolymers by first treating the polymer at room temperature with RTD (R=Ph,... 

The use of lightly crosslinked polymers did result in hydrophilic surfaces (contact angle 50°, c-PI, 0.2 M PhTD). However, the surfaces displayed severe cracking after 5 days. Although qualitatively they appeared to remain hydrophilic, reliable contact angle measurements on these surfaces were impossible. Also, the use of a styrene-butadiene-styrene triblock copolymer thermoplastic elastomer did not show improved permanence of the hydrophilicity over other polydienes treated with PhTD. The block copolymer film was cast from toluene, and transmission electron microscopy showed that the continuous phase was the polybutadiene portion of the copolymer. Both polystyrene and polybutadiene domains are present at the surface. This would probably limit the maximum hydrophilicity obtainable since the RTD reagents are not expected to modify the polystyrene domains. 

Fused glass or quartz with a hydrophilic surface, contact angle 0, does not exceed a few... 

Figure 13.9 Illustrations of the cohesive coating mechanism and details of the coating flows, (a) Adhesive (Fj and cohesive (Fj force diagram between hydrophobic and hydrophilic surfaces. Contact angles depend on the relative forces between solvent molecules and surfaces. In the case of downward concavity, the cohesive force is higher than the adhesive force, whereas upward concavity means that the adhesive force is higher than the cohesive force, (b) The adhesive force dominant condition. Adhesive forces are enhanced by surface energy modifications, such as O2 plasma treatment. Therefore, the flow rate is reduced by adhesive forces, (c) Cohesive force dominant condition. Adhesive forces are relatively reduced by self-assembled monolayers (SAMs). Thus, the flow rate is increased. Reproduced from ref. 23 with the permission of Wiley-VCH Verlag GmbH Co. KGaA, 2014.

Hydrophilic/hydrophobic (HL/HB) patterning means creating adjacent areas of different contact angles. This is achieved by manipulating the surface chemistries or topographies, or both. At least one chemistry needs to be hydrophilic (water contact angle <90 ) and at least one chemistry needs to be hydrophobic (water contact angle >90°). 

Table 3 summarizes the plasma treatment conditions, CNT sample designation, and water surface contact angle data of untreated and plasma-treated CNTs [11], It can be seen that plasma treatment significantly reduced the water contact angle from 112° to as low as 8°. Such a significant improvement in surface hydrophilicity of CNTs would enhance their dispersion in the base fluid water. 

Characterization of Laser-Treated Surface. When the irradiation of ArF laser to a PTFE film was conducted at fluences of 27 mJ cm"2 pulse with 10 Hz in a hydrazine vapor atmosphere, the PTFE surface became hydrophilic. Water contact angle (CA) was measured as the easiest but sensitive method for characterization of our laser processing. Compared with CA of 130° on PTFE before the irradiation, CA was changed to 25° upon irradiation of 3000 pulses at 27 mJ cm 2 pulse" (Table I). 

Sketch showing the usual definition of the contact angle, for a very hydrophobic surface (high contact angle, left) and very hydrophilic (low contact angle right). 

The molecular structure and behavior of water near different substrates determines the hydro-phobicity and hydrophilicity of the surface. Contact angle (0) is an inverse measure of wettability. The relationship between contact angle and floatability of minerals is well established... 

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