Catalytically Active Vegetable-Oil-Based Thermoplastic Hyperbranched Polyurethane/ Silver Nanocomposites Niranjan Karak,* Rocktotpal Konwarh, Brigitte Voit* Introduction In the past few years, the accord of polymer science with nanodimension material design has unveiled a wide panorama of utilities. As an example, the modulation of chemical and physical properties of structurally incompa- tible hard and soft segments distributed within the backbone of thermoplastic polyurethanes (TPU) leads to many useful and interesting properties. [1,2] The incorpora- tion of a hyperbranched moiety in a polyurethane structure is a way for the introduction of additional functionality and tuning of rheological parameters. However, the low possibility for chain entanglements often makes the pure hyperbranched polymers brittle. [3] The incorporation of long chain branching [4] has been successfully utilized for the enhancement of the mechanical properties in case of hyperbranched polyurethane/carbon nanotube nanocom- posites. [5] In our system, we incorporate a hyperbranched polyether moiety in polycaprolactone containing long segmented TPU without any gel formation by employing a pre-polymerization technique. Furthermore, the thermo- stable s-triazine units in the hyperbranched polyethers are expected to contribute to a better thermostability and mechanical properties of the resulting polymer. Recently, ‘‘going green’’ has become the steering guide- line for research across the globe. In this context, biodegradability, versatility in structure and properties, adequate availability, and overall cost effectiveness are the luring facets of vegetable oil as a feedstock for various polymerization protocols. [6,7] Thus, in the present investi- gation a monoglyceride of a vegetable oil, namely sun- flower oil, has been used as a part of the chain extender to prepare this class of industrially important polymer. Hyperbranched polymers, with branched architecture and various functionalities, allow the fine-tuning of interactions for high dispersion of inorganic nanoparticles Full Paper N. Karak, R. Konwarh Advanced Polymer and Nanomaterial Laboratory, Department of Chemical Sciences, Tezpur University, Tezpur 784028, Assam, India Fax: þ91 37 1226 7006; E-mail: karakniranjan@yahoo.com B. Voit Leibniz-Institute of Polymer Research Dresden e.V., Hohe Strasse 6, D-01069 Dresden, Germany E-mail: voit@ipfdd.de Sunflower oil-based HBTPU/Ag and LTPU/Ag nanocomposites have been prepared by in situ catalytic reduction of a silver salt. The virgin polymer and their nanocomposites are soluble in various polar organic solvents and amenable for both solution-casting and hot pressing. XRD, TEM, and UV spectroscopic analyses ascertained well- dispersed, narrow-sized Ag nanoparticles. Tensile test- ing, dynamic mechanical, thermogravimetric, and DSC analyses showed desirable mechanical and thermal features with improvement upon incorporation of Ag nanoparticles and the presence of a hyperbranched component in the nanocomposites. RSM has been used to evaluate the catalytic efficacy of the nanocompo- sites. Macromol. Mater. Eng. 2010, 295, 159–169 ß 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/mame.200900211 159