Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay Research paper Montmorillonite/poly(urethane-siloxane) nanocomposites: Morphological, thermal, mechanical and surface properties Ivan S. Stefanović a,⁎ , Milena Špírková b , Sanja Ostojić c , Plamen Stefanov d , Vladimir B. Pavlović e , Marija V. Pergal a a Institute of Chemistry, Technology and Metallurgy (ICTM), Center of Chemistry, University of Belgrade, Studentski trg 12-16, 11000 Belgrade, Serbia b Institute of Macromolecular Chemistry AS CR, v.v.i. (IMC), Heyrovsky Sq. 2, 16206, Prague 6, Czech Republic c Institute of General and Physical Chemistry, University of Belgrade, Studentski trg 12-16, 11000 Belgrade, Serbia d Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. Georgi Bonchev, 1113 Sofia, Bulgaria e Faculty of Agriculture, University of Belgrade, Nemanjina 6, 11000 Belgrade, Serbia ARTICLE INFO Keywords: Polyurethane nanocomposites Thermal properties Clay nano-fillers Surface properties Microphase separation ABSTRACT The aim of this work was to prepare and characterize the series of segmented polyurethane nanocomposites (PUNC) modified with poly(dimethylsiloxane) and based on montmorillonite (Mt) as a nano-filler. α,ω- Dihydroxy-poly(propylene oxide)-b-poly(dimethylsiloxane)-b-poly(propylene oxide) macrodiol was used as the soft segment component, while 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD) were selected as the hard segment components. PUNC were synthesized with different ratio of hard/soft segments. PUNC were morphologically, structurally, thermally, mechanically and surface characterized by XRD, TEM, FTIR, AFM, TGA, DMTA, tensile test, XPS, contact angle, surface free energy (SFE) and water absorption measurements. Added Mt (1 wt%) was completely delaminated and well dispersed in the form of mixed exfoliated/intercalated layers in the polymer matrix, and that PUNC have more pronounced microphase separated morphology, higher thermal stability, superior mechanical features, enhanced surface properties, as well as outstanding hydro- phobicity. Due to the improved features, developed polymers can be considered as candidates for materials with specific biomedical applications or as waterproof coatings. 1. Introduction Analyzing the dynamic progress that occurred in past few decades within polymeric materials, the outstanding accomplishments are re- lated to the preparation of new materials that combine different organic and inorganic materials. These new polymer materials should meet requirements for specific applications that were imposed by con- temporary disciplines such as biomedicine, electronics or aircraft in- dustry. Example of such materials includes also segmented copolymers, which combine polyurethane and polysiloxane block structures (Choi et al., 2009; Kozakiewicz, 1996; Yilgör et al., 1989). Segmented poly- urethanes (PU) are multiblock copolymers consisting of alternating soft segments (SS) and hard segments (HS) (Tang et al., 1994). The features of these PU copolymers can be controlled and adjusted by different nature of SS and HS. A large number of papers that include the pre- paration of PU based on poly(dimethylsiloxane) (PDMS) macrodiols as a part of SS and various comonomers as a part of HS (Hernandez et al., 2007; Sheth et al., 2004; Simmons et al., 2008; Yeh and Shu, 2010) has been published. Useful properties of PU copolymers mostly originate from their different composition and appropriate degree of microphase separation. Moreover, polyurethanes on one side have substantial strength, toughness and elasticity, while on the other side PDMS contributes to the excellent thermal and oxidative stability, outstanding hydro- phobicity, chemical inertness and good biostability and biocompat- ibility of the final PU (Adhikari et al., 2000; Hernandez et al., 2007; Roohpour et al., 2009). In spite the fact that PU combine these useful properties from their SS and HS, there has been a tendency among re- searchers toward incorporation of inorganic nano-fillers, such as clay minerals, inside these polymers in order to prepare different poly- urethane nanocomposites (PUNC) (Lee et al., 2013; Maji et al., 2009; Turri et al., 2008; Wang et al., 2009a,b). Addition of low quantities of clay nano-fillers usually leads to the significant improvement of thermal, mechanical, surface and barrier properties of PU. Due to the large specific surface area (750 g m -2 ), high aspect ratio (70–150) and high strength and stiffness of the clay mineral nanoparticles, it is an excellent choice for the use as nano-filler for polyurethanes (Ho et al., 2006). However, natural montmorillonite (Mt), which is the most http://dx.doi.org/10.1016/j.clay.2017.08.021 Received 27 January 2017; Received in revised form 21 August 2017; Accepted 22 August 2017 ⁎ Corresponding author. E-mail address: istefanovic@chem.bg.ac.rs (I.S. Stefanović). Applied Clay Science 149 (2017) 136–146 Available online 25 August 2017 0169-1317/ © 2017 Elsevier B.V. All rights reserved. MARK