REACTIVE BLENDING VIA METAL-OLEFIN COORDINATION IN DIENE POLYMERS - SOLID-STATE PROPERTIES THAT SUPPORT THE CONCEPT OF A NETWORK STRUCTURE

This study focuses on the properties of solid films formed from tetrah ydrofuran solutions containing diene polymers, polybutadiene or polyis oprene, and an inorganic salt, bis(acetonitrile)dichloropalladium(II). Upon mixing, effective cross-links are formed, because the acetonitri le ligands of the palladium salt are displaced by olefinic pendant gro ups of the polymers. Infrared data measured herein and previous studie s of the chemistry of palladium compounds suggest that a Heck-like mec hanism is operative to generate chemical cross-links via palladium-cat alyzed reactions. The swelling behavior of polybutadiene and polyisopr ene was studied in various solvents. In both cases, equilibrium swelli ng ratios decrease with an increase in salt content, indirectly suppor ting the concept of a network structure. Using the Flory-Rehner relati on, the number-average molecular weight between cross-link junction po ints (M(c)) was calculated from the swelling data. Relative to the und iluted polymers, the mechanical properties of polybutadiene and polyis oprene solid films show a dramatic increase of 3 orders of magnitude i n Young's modulus of elasticity when the palladium salt content is 4 m ol %. Thermogravimetric measurements show that an increase in the tran sition-metal salt (PdCl2) content, as well as annealing at 80 degrees C, enhances the thermal stability of solid films. The glass transition temperatures (T-g) of solid films determined by differential scanning calorimetry increase with PdCl2 content until the thermal plateau is achieved between 1 and 3 mol % palladium salt, where the increase in T -g (i.e., Delta T-g) is approximately 100 degrees C relative to the un diluted polymer.