Nanostructured hyperbranched polyurethane elastomer hybrids that incorporate polyhedral oligosilsesquioxane Sibdas Singha Mahapatra 1 , Santosh Kumar Yadav, Jae Whan Cho ⇑ Department of Textile Engineering, Konkuk University, Seoul 143-701, South Korea article info Article history: Received 22 September 2011 Received in revised form 30 January 2012 Accepted 1 February 2012 Available online 9 February 2012 Keywords: Hyperbranched polymer Hybrids POSS Mechanical properties abstract Novel thermoplastic hyperbranched polyurethane (HBP) elastomer hybrids containing polyhedral oligo- meric silsesquioxane (POSS) have been synthesized using an A 2 +B 3 approach. Different compositions of these hybrid nanomaterials were obtained from reactions of POSS-diol, triethanolamine, poly(e-caprolac- tone)diol, and 4,4 0 -methylenebis(phenyl isocyanate) with a chain extender. The covalent attachment of POSS molecules to the backbone of the polyurethane chain was characterized with FT-IR and NMR spec- troscopies. The non-agglomerated homogeneous dispersion obtained through the covalent attachment of POSS molecules and the HBP matrix was observed by SEM imaging. The mechanical properties, including the tensile and yield strengths, Young’s modulus, and toughness, significantly increased after the intro- duction of POSS molecules into the hybrids; this increase can be ascribed to the nano-reinforcement effect of the POSS cages and the long-range branched structure of the polymer. Thermogravimetric anal- yses indicated that the thermal stability of the polymer matrix was improved by the introduction of a small amount of POSS. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The incorporation of inorganic or organometallic segments into organic polymers to improve their properties continues to be a driving force for the development of new hybrid materials [1–6]. Organic–inorganic hybrids have traditionally been prepared pri- marily via the sol–gel process and by intercalation and exfoliation of layered silicates by organic polymers [7–10]. Recently, the poly- hedral oligomeric silsesquioxane (POSS) macromer and POSS-con- taining polymers have emerged as potential nanomaterials for accessing organic–inorganic hybrids in various applications [11– 17]. POSS molecules possess nanosized, cage-like structures with the general formula [RSiO 3/2 ] n , where n is approximately 6–12, and R indicates various types of organic group. POSS molecules with reactive R groups can be introduced into a polymer matrix by formation of covalent bonds between the POSS cages and the polymer-chain backbone. In addition, the remaining unreacted R groups may impart desirable solubility properties to yield high- performance materials [10–17]. Therefore, the POSS-networked hybrids may be significantly different from conventional polymeric nanocomposites, including layered silicates or metal-oxide nano- particles because the POSS cage is chemically linked to the matrix polymer. In recent years, reactive POSS molecules have been grafted or copolymerized with a variety of polymeric materials, such as acrylics, epoxies, and polyimides [18–23]. Significant mate- rial property enhancements have been reported for the POSS–poly- mer hybrid systems, including enhanced mechanical strength, decreased flammability, ultraviolet stability, and oxidation resis- tance [24–27]. However, despite the growing scientific literature, few cases of the practical exploitation of POSS have been reported. One of the primary goals of nanotechnology is to find new methods for the controlled synthesis of nanostructured functional materials. Recently, dendrimers and hyperbranched polymers have attracted considerable attention from both industry and academia because of their remarkable and unique properties, including their reduced melt and solution viscosities, high solubilities, high func- tionalities due to large numbers of reactive end-groups within the molecules, their approximately spherical molecular shapes, and the absence of chain entanglements [28–33]. Dendrimers are prepared via step-wise reactions in which sev- eral purification steps are required to obtain well-controlled struc- tures. In contrast, hyperbranched polymers can be easily prepared in one-step reactions and typically have randomly distributed branches that make them attractive alternatives for numerous applications. Hence, the reasons why hyperbranched polymers have attracted such scientific interest over the past several decades are evident. Many studies that pertain to the construction of novel, tailor-made, and complex nanostructures have been reported using these highly versatile hyperbranched polymers [34–36]. 1381-5148/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.reactfunctpolym.2012.02.001 ⇑ Corresponding author. Tel.: +82 2 4503513; fax: +82 2 4585805. E-mail address: jwcho@konkuk.ac.kr (J.W. Cho). 1 Present address: Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. Reactive & Functional Polymers 72 (2012) 227–232 Contents lists available at SciVerse ScienceDirect Reactive & Functional Polymers journal homepage: www.elsevier.com/locate/react