Inorganic-Organic Hybrid Copolymers derived from Silsesquioxanes or Carborane Building Blocks
- PDF / 182,209 Bytes
- 7 Pages / 432 x 648 pts Page_size
- 0 Downloads / 155 Views
Inorganic-Organic Hybrid Copolymers derived from Silsesquioxanes or Carborane Building Blocks Gunjan Gadodia,1 Gregoire Cardoen,1 Yoan Simon,1 Hiroshi Abe,2 E. Bryan Coughlin1 1 Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst MA 01002 U.S.A. . 2 Sekisui Integrated Research Inc. 2-2, Kamichoshi-cho, Kamitoba Minami-ku, Kyoto 601-8105 JAPAN . ABSTRACT To explore competitive or cooperative effects novel organic-inorganic hybrid copolymers are being prepared and studied. The use of polyhedral oligomeric silsesquioxanes (POSS), a molecularly precise isotropic comonomer, is being utilized to take advantage of the inherent size scale of these particles, average diameters of 1-2 nm. The organic component selected for study in these hybrid systems are either semi-crystalline or amorphous polymers. The architectures of the hybrid copolymers range from random, to precise block copolymers, as well as telechelic and hemi-telechelic end-functionalized model compounds. The degree of POSS aggregation that occurs is found to be a function of thermal history, and processing conditions. Templating, or arresting, aggregation can be achieved using either crystalline organic polymer scaffolds in the bulk. The second inorganic comonomers for study has been constructed from icosahedral carboranes. Dicarbo-closo-decaboranes have been widely investigated for their thermal stability, chemical resistance, unique geometry, and the high cross-section for the capture of thermal neutrons. While carboranes have been widely incorporated into small molecules, metal complexes, and on a limited basis in polymer systems relatively little work exists relating their unique properties to systems with extended π-conjugation. Details of the syntheses, characterization and performance properties of both sets of hybrid systems will be discussed. INTRODUCTION POSS molecules with short peripheral groups act as spheres and pack in a hexagonal arrangement.1 However, when POSS is attached to the backbone, the connecting linkage restricts the mobility of the cage and imposes considerable spatial constraints on the crystal shape.2 Crystalline polymers have properties much different than amorphous polymers and the crystalline content must be considered for a given polymer application. In semi-crystalline block copolymers, one block can crystallize while the other block remains amorphous. The crystalline copolymer can effect the mechanical properties,3 morphology4-7 domain spacing,8 and the kinetics of microphase separation.9-11 When POSS is incorporated into the backbone of the polymer there is a competition of microphase separation between minimizing the interfacial energy or the thermodynamic driving force of crystallization.12 As a result interesting morphologies can be obtained with the current system. A bottom-up approach was used to combine the newly emerging class of Polyhedral Oligomeric Silsesquioxanes (POSS) with conventional polymers to produce semi-crystalline conformationally asymmetric hybrid
423
materials w
Data Loading...
