Surprising High Hydrophobicity of Polymer Networks from Hydrophilic Components Agnese Attanasio, †,‡ Ilker S. Bayer,* ,‡ Roberta Ruffilli, § Farouk Ayadi, † and Athanassia Athanassiou* ,‡ † Smart Materials Platform, Center for Bio-Molecular Nanotechnologies@Unile, Istituto Italiano di Tecnologia (IIT), Via Barsanti, 73010 Arnesano (Lecce), Italy ‡ Nanophysics Department, Istituto Italiano di Tecnologia (IIT), Via Morego, 16163 Genova, Italy § Nanochemistry Department, Istituto Italiano di Tecnologia (IIT), Via Morego, 16163 Genova, Italy * S Supporting Information ABSTRACT: We report a simple and inexpensive method of fabricating highly hydrophobic novel materials based on interpenetrating networks of polyamide and poly(ethyl cyanoacrylate) hydrophilic components. The process is a single-step solution casting from a common solvent, formic acid, of polyamide and ethyl cyanoacrylate monomers. After casting and subsequent solvent evaporation, the in situ polymerization of ethyl cyanoacrylate monomer forms polyamide-poly(ethyl cyanoacrylate) interpenetrating network films. The interpenetrating networks demonstrate remarkable waterproof properties allowing wettability control by modulating the concentration of the components. In contrast, pure polyamide and poly(ethyl cyanoacrylate) films obtained from formic acid solutions are highly hygroscopic and hydrophilic, respectively. The polymerization of ethyl cyanoacrylate in the presence of polyamide promotes molecular interactions between the components, which reduce the available hydrophilic moieties and render the final material hydrophobic. The wettability, morphology, and thermo-physical properties of the polymeric coatings were characterized. The materials developed in this work take advantage of the properties of both polymers in a single blend and above all, due to their hydrophobic nature and minimal water uptake, can extend the application range of the individual polymers where water repellency is required. KEYWORDS: polyamides, poly(ethyl-cyanoacrylates), interpenetrating polymer networks, wettability, hydrophobic surfaces ■ INTRODUCTION The general aim for creating polymeric blends is to combine the properties of the respective components within a near homogeneous material, while overcoming some of their weaknesses, although the latter goal is not always reached. 1 Among other properties, control of wetting characteristics of polymer blends is becoming highly important due to their increasing use in various industries such as coatings, membranes, and biotechnology to name a few. Wetting of polymeric blends is a complex phenomenon and is strongly related to a number of parameters such as hydrophobicity or hydrophilicity of the blends’ constituents, degree of phase separation, interfacial interactions, surface morphology, and chemical interactions. 2 Usually, blends of hydrophobic and hydrophilic polymers (such as copolymers) demonstrate intermediate wetting states depending on the relative constituent concentrations and degree of phase separation after forming. 3 Polyamides or nylons (PA) are among the most widely used thermoplastics having applications in different industrial fields (textile industry, membrane fabrication, food packaging). 4-8 Polyamides consist of polyethylene segments (CH 2 ) n separated by recurring NH-CO (amide) groups. The latter units provide hydrogen bonds between adjacent chains giving unique properties (high crystalline structure, high melting point, mechanical robustness, and chemical stability). 5,9-11 However, they tend to absorb water far more than other conventional polymer resins due to the hydrophilic character of the amide Received: March 28, 2013 Accepted: May 28, 2013 Published: May 28, 2013 Research Article www.acsami.org © 2013 American Chemical Society 5717 dx.doi.org/10.1021/am401131u | ACS Appl. Mater. Interfaces 2013, 5, 5717-5726