Ethylene-styrene pseudo-random

Ethylene-styrene pseudo-random copolymers (known as ethylene-styrene interpolymers) [14] have also been used to improve the compatibility between sPS and polyolefins, mainly polyethylene (entry 12). 

Instead of block copolymers, the use of pseudo-random linear copolymers of an aliphatic a-olefin and a vinyl aromatic monomer has been reported [20], where the styrene content of the polymer must be higher than 40 wt%. Preferred are styrene and ethylene copolymers. These blends may contain, amongst other things, an elastomeric olefinic impact modifier such as homopolymers and copolymers of a-olefins. Presumably the styrene-ethylene copolymer acts as a polymer emulsifier for the olefinic impact modifier. Using 5 wt% of an ethylene-styrene (30 70) copolymer and 20% of an ethylene-octene impact modifier in sPS, a tensile elongation (ASTM D638) of 25 % was obtained. 

As a result of the catalyst and process conditions used in their manufacture, the particular copolymers of current major interest are atactic, and contain typically up to about 50 mol% ( 80 wt%) styrene. These materials have been described as pseudo-random , since successive head-to-tail styrene chain insertions have been shown to be absent, even at high levels of styrene incorporation [1,2]. The term ethylene-styrene interpolymer (ESI) is used here to describe the specific ethylene-styrene copolymers produced via INSITE Technology. For convenience, all subsequent comonomer contents are expressed in weight percentages, unless otherwise stated. For example, the code ES70 refers to an interpolymer having 70 wt.% comonomer styrene incorporation. 

Other complexes that have been used in ethylene-styrene co-polymerizations are 42, which is inactive in styrene homopolymerization but has been claimed to produce ethylene/styrene co-polymers with styrene content in the range 35-87 mol%.6 2 Living ethylene/styrene co-polymerization can be achieved using the MAO-activated complex 43. Although a relatively low amount of styrene was incorporated (about 10 mol%), NMR analysis indicated that trace amounts of pseudo-random tail-to-tail S-S or S-E-S sequences were observed.6 Marks and co-workers showed that bimetallic catalysts based on 44 can effectively yield ethylene/styrene co-polymers and, in contrast to the monometallic CGCs, styrene incorporation can be higher than 50%.664... 

Effective ethylene-styrene co-polymerization with the post-metallocene catalysts has been achieved with the pentacoordinated complexes 195 and 196.159,1245 Pseudo-random ethylene-styrene co-polymers (i.e., co-polymers with no regioregularly arranged styrene-styrene units)642 were synthesized. The synthesis of an alternating crystalline co-polymer with isotactic styrene units and a Tm of 116 °C was also claimed. In these first studies, the importance of the S atom was noted, since the CH2-bridged complex 197 showed no co-polymerization activity. However, further studies demonstrated that the S atom is not fundamental, since complex 198 also promotes ethylene-styrene co-polymerization. Moreover, it was shown that complexes 195 and 196 incorporate a rather minor amount of styrene units (about 6-10 mol%) in the co-polymer relative to complex 198 (about 35 mol%), but they are roughly 1-2 order of magnitude more active than 198. 

Since the early 1990 s the constrained geometry metallocene catalysts have been used by Dow to produce either alternating or pseudo-random ethylene-co-styrene interpolymers (ESI) [Stevens et al., 1991]. ESI with up to 50 wt% styrene is semicrystalline, it is known to compatibilize PE/PS... 

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