Some Organic-Inorganic Composites, Illustrative Simulations on Elastomer Reinforcement, and an Overview of Symposium Contributions

Abstract

ABSTRACTThis review first describes organic-inorganic composites which have been prepared using techniques similar to those employed in the new sol-gel approach to ceramics. Organometallics such as silicates, titanates, and aluminates are hydrolyzed in the presence of polymer chains (for example polysiloxanes and polyamides) that typically contain hydroxyl groups. The functional groups are used to bond the polymer chains onto the silica, titania, or alumina being formed in the hydrolysis, thus forming novel organic-inorganic composites. When the polymer chains are present in excess, they constitute the continuous phase, with the ceramic-type material appearing as reinforcing particles. When present in smaller amounts, the polymer is dispersed in the continuous ceramic phase, to give a polymer-modified ceramic. Under some conditions,bicontinuous systems are obtained.The second part addresses one of the major unsolved problems in the area of rubberlike elasticity, specifically a molecular understanding of the mechanisms by which the mechanical properties of elastomers are improved by the incorporation of particulate fillers such as carbon black or silica. Theoretical work on the reinforcement thus obtained is illustrated by some Monte Carlo calculations on one aspect of the problem, namely excluded volume effects of the filler particles on the network chain configurations. The resulting end-to-end distributions are then used in standard molecular models to generate stress-strain isotherms, which document the nature of the reinforcement obtained.The final part provides an overview of the specific papers presented at this symposium, and attempts to place them into the broad general context of “Filled and Nanocomposite Polymer Materials”.