Australian Mineral Science Research Institute, Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia.
J Colloid Interface Sci. 2010 Feb 15;342(2):586-92. doi: 10.1016/j.jcis.2009.10.049. Epub 2009 Oct 24.
Poly (N-isopropylacrylamide) (PNIPAM) is a temperature responsive polymer. At temperature below its lower critical solution temperature (LCST 32 degrees C) PNIPAM is soluble in water and hydrophilic. At temperature above the LCST, the polymer becomes hydrophobic and insoluble in water. At temperatures above the LCST, PNIPAM has been shown to induce flotation of previously hydrophilic minerals. The mechanism is believed to be an increase in particle hydrophobicity when PNIPAM adsorbs to the particle surfaces at high temperature. This paper investigates the interaction forces between bare silica surfaces in PNIPAM solutions. The influence of three phase contact angles on these interactions, in the presence of polymers of different molecular weights, is also examined. It was found that the presence of PNIPAM on silica surfaces significantly increases their hydrophobicity at a temperature above the LCST. The AFM measurements of surface forces at high temperature also showed that strong adhesion is present between the PNIPAM coated surfaces, which is absent in the absence of polymer. These findings lead to the conclusion that the detected attractive force and subsequent adhesion result from hydrophobic attraction induced by PNIPAM at temperature above the LCST.
聚（N-异丙基丙烯酰胺）（PNIPAM）是一种温度响应性聚合物。在低于其低临界溶液温度（LCST32°C）的温度下，PNIPAM可溶于水且亲水。在 LCST 以上的温度下，聚合物变得疏水且不溶于水。在 LCST 以上的温度下，PNIPAM 已被证明可以诱导先前亲水矿物的浮选。据信，其机制是当 PNIPAM 在高温下吸附到颗粒表面时，颗粒的疏水性增加。本文研究了 bare silica 表面在 PNIPAM 溶液中的相互作用力。还研究了在存在不同分子量的聚合物的情况下，三相接触角对这些相互作用的影响。结果发现，在 LCST 以上的温度下，PNIPAM 的存在会显著增加硅表面的疏水性。高温下的 AFM 表面力测量还表明，在聚合物存在的情况下，PNIPAM 涂覆的表面之间存在强烈的粘附力，而在没有聚合物的情况下则不存在。这些发现得出的结论是，在 LCST 以上的温度下，PNIPAM 诱导的疏水力导致检测到的吸引力和随后的粘附。
