Research Article Received: 21 January 2011 Revised: 9 February 2012 Accepted: 5 March 2012 Published online in Wiley Online Library: (wileyonlinelibrary.com) DOI 10.1002/pi.4278 Nanocomposites based on copolymers of fluorinated imide and polyhedral oligomeric silsesquioxane macromonomer: microstructure and morphology studies Dhorali Gnanasekaran, a Karunakaran Madhavan, a John Tsibouklis b and BoreddySR Reddy a∗ Abstract Towards the development of copolymeric nanocomposites, N-3(trifluoromethyl)phenyl-7-oxanorbornene-5,6-dicarboximide (TFI) monomer and a macromonomer of polyhedral oligomeric silsesquioxane (POSS) were synthesized. Ring-opening metathesis polymerization to copolymerization of specified proportions of the two co-monomers was carried out. All the monomers and polymers were characterized using Fourier transform IR analysis and 1 H and 29 Si NMR. Gel permeation chromatography shows that copolymeric nanocomposites have a lower average molar mass than a homopolymer of TFI (HTFI). TGA shows that the thermal stability of the copolymer is inversely proportional to the proportion of POSS units. DSC studies have demonstrated that the glass transition temperature (T g ) of a nanocomposite possessing 25 wt% POSS is at a higher temperature (180 ◦ C) than that of HTFI (175 ◦ C). Transmission electron microscopy and AFM images of copolymers are consistent with the self-assembled spherical aggregation of POSS units, while X-ray diffraction studies have confirmed the homogeneous dispersion of the same units within the nanocomposites. c  2012 Society of Chemical Industry Supporting information may be found in the online version of this article. Keywords: microstructure; fluorinated imide; nanocomposites INTRODUCTION Partial functionalization of polyhedral oligomeric silsesquioxane (POSS) with polymerizable moieties allows its incorporation into polymeric materials via covalent bonds, whilst complementary functionalization at the other R positions may result in polymer structures in which the inorganic core is solubilized within the polymer matrix. 1–4 Some of the functionalizations are known to increase the glass transition temperature of the parent polymer 5 and also to decrease thermal stability 6 and reduce flammability. 7 POSS molecules have been used for the modification of thermoplastics 8,9 including polystyrene, 10 polyimides, 11 siloxanes 12 and polyolefins. 13,14 Of particular interest is the use of POSS co-monomers in the preparation of norbornene- based nanocomposites by ring-opening metathesis polymeriza- tion (ROMP). 15–17 Here, we report a new type of POSS functionalized poly- mer synthesized through ring-opening metathesis polymeri- zation (ROMP)-facilitated of N-(POSS)-7-oxanorbornene-5,6- dicarboximide (PNDI) and N-3(trifluoromethyl)phenyl-7-oxanor- bornene-5,6-dicarboximide (TFI) copolymeric nanocomposites, and we evaluate the thermal properties, morphologies and mi- crostructure of these materials. EXPERIMENTAL Materials and measurements Cyclopentyl trichlorosilane, phenyl trichlorosilane, Grubbs (II) catalyst (tricyclohexylphosphine [1,3-bis(2,4,6-trimethylphenyl)-4, 5-dihydroimidazol-2-ylidene] [benzylidine] ruthenium(IV) dichlo- ride (1,3-dimesityl-4,5-dihydroimidazol-2-ylidene)) and 3-(tri- fluoromethyl)-aniline were all purchased from Aldrich (Bengaluru, India). Furan was purchased from Merck. Triethylamine, acetic anhydride, maleic anhydride, ammonium formate, acetic acid and sodium acetate trihydrate were purchased from Qualigens and used as received. Nitric acid, zinc (metal) powder, acetonitrile, tetrahydrofuran (THF), hexane and methanol were purchased from Rankem Chemicals and used as received. Fuming nitric acid was prepared by refluxing equal amounts of sulfuric acid and sodium ∗ Correspondence to: BoreddySR Reddy, Industrial Chemistry Laboratory, Central Leather Research Institute (Council of Scientific and Industrial Research), Chennai 600 020, India. E-mail: induchem2000@yahoo.com a Industrial Chemistry Laboratory, Central Leather Research Institute (Council of Scientific and Industrial Research), Chennai 600 020, India b Biomaterials and Drug Delivery Research Group, School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, Hampshire PO1 2DT, UK Polym Int (2012) www.soci.org c  2012 Society of Chemical Industry