Ethylene—Styrene Copolymerization

Abstract

Abstract Ethylene—styrene copolymers are new materials developed within the last decade using the new homogeneous olefin polymerization catalysts (generally referred to as “metallocene catalysts”). By proper selection of the catalytic system and the reaction conditions, a variety of copolymers with different compositions, structures, and properties can be obtained. Thus, copolymers containing a very low amount of styrene (or p-methylstyrene) on a substantially polyethylenic backbone are crystalline thermoplastics, which could be used to produce functionalized PEs. Increasing the styrene content leads to a rapid decrease in the crystallinity, affording materials which show good thermoelastomeric properties. Copolymers containing around 20 mol % styrene are effective compatibilizers for polyethylene—polystyrene blends. The molecular structure of these copolymers has been defined being “pseudorandom,” since EEE, EES, ESE, and SES sequences are observed, and no SS sequences are present, thus the styrene content cannot exceed 50 mol %. Very recently, however, a random copolymer containing SS sequences in a stereoregular arrangement has been reported. Also, truly alternating E-S copolymers have been obtained with suitable catalysts. These poly(ethylene-alt-styrenes) can be either atactic (and thus amorphous) or stereoregular, depending on the particular catalyst used. Interestingly, isotactic poly(ethylene-alt-styrene) is a new crystalline material with a melting point of 145 °C, whose crystal structure has recently been determined. In conclusion, further research on ethylene—styrene copolymerization promises to afford a variety of new interesting materials starting from two widespread, easily available and inexpensive monomers.