DYNAMIC WETTING AND CONTACT-ANGLE HYSTERESIS OF POLYMER SURFACES STUDIES WITH THE MODIFIED WILHELMY BALANCE METHOD
DYNAMIC WETTING AND CONTACT-ANGLE HYSTERESIS OF POLYMER SURFACES STUDIES WITH THE MODIFIED WILHELMY BALANCE METHOD
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DOI：
10.1021/la00017a047
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发表时间：
1994-05-01
期刊：
影响因子：
3.9
通讯作者：
IKADA, Y
中科院分区：
文献类型：
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作者：
TRETINNIKOV, ON;IKADA, Y
聚乙烯的动态润湿行为（PTFE）、聚乙烯（PE）、聚丙烯（PP）、聚（对苯二甲酸乙二醇酯）（PET），尼龙6，聚（醚尿烷）（PU），聚（乙烯醇）（PVA）、用Wilhelmy天平技术在1 ~ 50 mm/s的浸泡速度下研究了纤维素和纤维素的溶解情况。修改Wilhelmy方法，以便使用具有矩形孔的矩形平坦样品，在不将环外推到零浸没深度的情况下测定接触角。该方法的这种修改允许我们分别在靠近下（第一）和上（第二）样品孔边界的非常窄的样品区域上确定前进和后退接触角θ 1和θ 2。位于下边界的样品部分与润湿液体（水）的相互作用时间是上边界的两倍长。对于所有聚合物，在样品的下部和上部测量的前进接触角之间没有观察到差异（θ（ADV，1）= θ（ADV，2）），表明干燥的聚合物表面沿沿着样品长度的润湿性没有差异。然而，在PET、PU、尼龙6、PVA和纤维素的润湿测量期间，样品的下部变得比上部更亲水，导致后退接触角之间的差异（θ（REC，1）<θ（REC，2））。这种效果归因于亲水性和疏水性基团的时间依赖性表面重新取向，发生在聚合物样品浸入水中。一个密切的相关性之间的滞后的接触角和水下表面重建的聚合物：最强的滞后对应于最大的润湿性梯度所产生的时间依赖性的再取向过程。然而，即使当再取向的影响为零（PTFE、PE和PP）或非常低（纤维素）时，观察到的滞后仍然高达27度。极性基团的表面重新取向所观察到的滞后的贡献估计为0-25度，这取决于所研究的聚合物的化学结构。样品浸泡的速度对PTFE、PE和PP的润湿性没有可检测的影响。另一方面，随着浸渍速度的增加，PET、PU和尼龙6上的前进接触角增加，而后退接触角减小。这种行为可以通过参考三相边界处的大分子动力学模型来解释。
The dynamic wetting behavior of poly(tetrafluoroethylene) (PTFE), polyethylene (PE), polypropylene (PP), poly(ethylene terephthalate) (PET), nylon 6, poly(ether urethane) (PU), poly(vinyl alcohol) (PVA), and cellulose was studied by the Wilhelmy balance technique at speeds of immersion from 1 to 50 mm/min. The Wilhelmy method was modified so as to determine contact angles without extrapolation of the loop to the zero immersion depth, employing a rectangular flat sample having a rectangular hole. This modification of the method allowed us to determine the advancing and receding contact angles on the very narrow sample area close to the lower (first) and the upper (second) sample-hole boundaries, theta1 and theta2, respectively. The interaction time of the sample part located at the lower boundary with the wetting liquid (water) was twice as long as that of the upper boundary. No difference was observed between the advancing contact angles measured at the lower and the upper parts of the sample (theta(ADV,1) = theta(ADV,2)) for all the Polymers, displaying that the dried polymer surfaces had no difference in wettability along the sample length. However, the lower part of the sample became more hydrophilic than the upper part during the wetting measurement for PET, PU, nylon 6, PVA, and cellulose, resulting in the difference between the receding contact angles (theta(REC,1) < theta(REC,2)). The effect was attributed to the time-dependent surface reorientation of hydrophilic and hydrophobic groups, occurring upon immersion of the polymer sample in water. A close correlation was observed between the hysteresis of the contact angle and the underwater surface reconstruction of polymers: the strongest hysteresis corresponds to the greatest wettability gradient generated by the time-dependent reorientation process. However, even when the effect of reorientation was zero (PTFE, PE, and PP) or very low (cellulose), the observed hysteresis was still as high as 27-degrees. The contribution of the surface reorientation of polar groups to the observed hysteresis was estimated to amount to 0-25-degrees, depending on the chemical structure of the polymer investigated. The speed of the sample immersion had no detectable effect on the wettability of PTFE, PE, and PP. On the other hand, the advancing contact angle on PET, PU, and nylon 6 increased while the receding contact angle decreased, as the immersion speed became higher. This behavior may be accounted for by referring to a model of macromolecular dynamics at the three-phase boundary.