Synthesis and characterization of novel room temperature vulcanized (RTV) silicone rubbers using Vinyl-POSS derivatives as cross linking agents Dongzhi Chen a, b , Shengping Yi a, b , Weibing Wu a , Yalan Zhong a , Jun Liao b, * , Chi Huang a, b, ** , Wenjuan Shi a a College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, PR China b Engineering Research Center of Organosilicon Compound and Material, Ministry of Education of China, Wuhan, 430072, PR China article info Article history: Received 8 February 2010 Received in revised form 9 June 2010 Accepted 15 June 2010 Available online 25 June 2010 Keywords: Polyhedral oligomeric silsesquioxanes (POSS) RTV silicone rubbers Cross-linkers abstract Two kinds of novel POSS cross-linkers were firstly prepared via hydrosilylation of Vinyl-POSS and tri- methoxysilane. And two types of novel polydimethylsiloxane (PDMS) polymer composites as RTV sili- cone rubbers were prepared using Vinyl-POSS derivatives as cross-linkers in the presence of organotin catalyst. To completely exhibit superiorities of two kinds of novel cross-linkers, RTV silicone rubbers prepared with two proportions of different cross-linkers were assessed. The chemical inclusion of novel POSS into PDMS networks by hydrolytic condensation reaction was verified by attenuated total reflection (ATR) infrared spectroscopy. Morphologies, thermal properties, mechanical properties and hardness of these novel RTV silicone rubbers were studied. The results exhibited significantly enhanced effects of POSS on thermal stabilities, mechanical properties and hardness as compared to the PDMS polymers prepared with the traditional tetra-functional TMOS and TEOS cross-linkers. The striking improvements in thermal properties, mechanical properties and hardness could be attributed to the synergistic effect of the increase of dimensionality of cross-linked networks in novel RTV silicone rubbers resulting from special three-dimensional structure of novel POSS cross-linkers, plasticization of self-cross-linked POSS cross-linkers and uniform distribution of POSS cross-linkers. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Polyhedral oligomeric silsesquioxanes (POSS) with their combined inorganiceorganic chemistry properties have attracted considerable attention in the field of organic/inorganic hybrid nano-materials over the past decades. POSS molecules with a generic empirical formula (RSiO 1.5 ) n (where n is an even number, n > 4) are a type of building blocks, and their sizes range from 1 to 3 nm, which can be thought of as the smallest spherical silica. The substituent groups (R) connected with the Si atoms in the cage can be divided into hydrogen, reactive organic groups and inert organic groups. POSS with n ¼ 8 nano-structured cage has been explored extensively, and several reviews [1e3] have been published recently. Due to the modifiable substituent groups (R), POSS derivatives can be easily incorporated into common polymer systems via chemical bonds or physical blending as enhancement nano-filler [4]. The incorporation of POSS derivatives into polymeric materials can obviously enhance polymer properties, such as used tempera- tures, decomposition temperatures, oxidation resistance, surface hardening, mechanical properties, flammability resistance, heat evolution and so on [1]. These improvements have been shown to apply to a wide range of polymeric systems. Some specific examples were enumerated as the following, such as polystyrene [5e10], polyimide [11e 14], polyurethane [15e17], poly(methyl methyl- acrylate) [18,19], poly(e-caprolactone) [20], polyvinylchloride [21], poly(ethylene oxide) [22] and polybenzoxazine [23e26]. However, due to insurmountable disadvantages of incompatibility and aggregation of POSS monomers, like the above enhanced polymer composite materials are difficult to be prepared by simply physical blending. The incorporation of POSS into polymeric materials by chemical bonding may be the best alternative for material scientists when they encounter these insurmountable problems, so synthesis of the novel POSS derivatives with reactive functionalities for polymerization or grafting into polymer is a new research focus for scientists. * Corresponding author. ** Corresponding author. College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, PR China. Tel.: þ86 027 68752701; fax: þ86 027 68754067. E-mail addresses: junliao@whu.edu.cn (J. Liao), chihuang@whu.edu.cn (C. Huang). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2010.06.028 Polymer 51 (2010) 3867e3878