Styrene incorporation

An interesting class of styrene-based polymers is ethylene/styrene co-polymers, which have many promising applications as films or foams, as compatibilizers, and as modifiers for bitumens and asphalts. The preparation of these co-polymers by a variety of catalysts has been reported, including both heterogeneous and homogeneous catalysts, but the co-polymers thus obtained typically contained low levels (<4mol%) of styrene incorporation or were heterogeneous in nature. ... 

Figure 11. Styrene incorporation from butadiene-styrene (75/25) in cyclohexane solutions at 30-121°C (59).

Figure 14. Effect of amount of diethyl ether styrene incorporation at 50°C (16).

At this stage, we do not know whether the styrene incorporated in polymer chain is a block styrene or not. However, it is speculated that the block styrene will be resulted based on the lithium morpholinide system. More work along this line is in need in order to qualify this statement. 

Alkyl vinylethers and methacrylate are monomers with substituents of different ionic nature. They require opposites of ionicities for their isotactic initiator systems. Styrene incorporates both ionicities into one monomer. 

The addition of small amounts of a polar solvent can markedly alter the copolymerization behavior of, for example, the diene-styrene pair. The solvation of the active centers manifests itself in two ways the incorporation of styrene is enhanced and the modes of diene addition other than 1,4 are increased 264,273). Even a relatively weak Lewis base such as diphenyl ether will bring about these dual changes in anionic copolymerizations, as the work of Aggarwal and co-workers has shown 260>. Alterations in polyisoprene microstructure and the extent of styrene incorporation were found for ether concentrations as low as 6 vol. % (diphenyl ether has been shown52) to cause partial dissociation of the poly(styryl)lithium dimers. The findings of Aggarwal and co-workers 260) are a clear demonstration that even at relatively low concentrations diphenyl ether does interact with these anionic centers and further serve to invalidate the repetitive claim 78,158-i60,i6i) tjjat diphenyl ether — at an ether/active center ratio of 150 — does not interact with carbon-lithium active centers. 

Table 28 Increase of styrene incorporation by the addition of cyclopentadienyl (C) derivatives (catalyst system NdV/MAO) [498,499]...

For the copolymerization of BD and St Zhang et al. use various Nd precursors in combination with TIBA and DIBAC [502]. These authors obtain copolymers with a content of incorporated styrene of ca. 10-20 mol %. At this level of incorporated styrene the BD moieties exhibit cis- 1,4-contents between 90 to 97%. The amount of incorporated St increases with increasing polymerization temperature and with increasing St content in the monomer feed. It is demonstrated that the cis- 1,4-content of the incorporated BD moieties decreases with increasing content of incorporated St. In this study styrene incorporation depends on the composition of the catalyst system. The highest amount of styrene is incorporated at the molar ratios of TiBA/ Nd = 20 and Cl/ Nd = 3. 

Entry Ratio Styrene/ butadiene Ratio Barium/ Butadiene Tg ( C) Styrene Incorporation (%) Cis (%) Trans (%) Vinyl (%)... 

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. 

Figure 26.2 Dynamic mechanical spectroscopy (DMS) plot of tan<5 versus temperature, measured at 10rad/s, for a series of ESI with styrene incorporation ranging from 24 (ES24) to 77wt% (ES77)...

The successful co-polymerization of ethylene with styrene is another polymeric material conquest of homogeneous catalysis. At low styrene incorporation, the co-polymer is substantially a functionalized crystalline polyethylene. Increasing the styrene content results in a decrease of crystallinity while elastomeric properties arise, 3 up to about 80 mol% styrene for higher styrene contents, the co-polymer becomes a glassy amorphous material. A comprehensive review on the properties of ethylene/styrene co-polymers is available.624... 

Even at high styrene incorporation, the co-polymers are formed by ethylene blocks and isolated styrene units.627 Half-sandwich titanium complexes such as 35-39 have also been reported to be active in the ethylene/styrene co-polymerization. The performance of the MAO-activated complex 35 is highly dependent on the Al/Ti ratio. At a ratio of 100, a co-polymer composed of polyethylene blocks with essentially isolated styrene units could be fractionated from the homopolymers. By contrast, at Al/Ti ratios of 1000, a co-polymerization at the same feed ratio resulted in the production of only homopolymers, or co-polymers composed of long PE and sPS blocks at most.628 Subsequent 13C NMR analysis of the co-polymers obtained at 20°C indicated that up to 36 mol% of styrene was incorporated.629 However, under very similar conditions, only formation of the homopolymers was reported.630,631 This may be reasonable since catalytic systems 35/MAO and 36/MAO give rise to several active species with different catalytic properties. Thus, remarkably different results can be obtained with small differences in the experimental procedure. 

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... 

The counterion also has a dramatic effect on copolymerization behavior for styrene and dienes [61]. It is particularly noteworthy that the monomer reactivity ratios for styrene (r = 0.42) and butadiene (rg = 0.30) are almost equal for copolymerization in toluene at 20 °C using a hydrocarbon-soluble organosodium initiator 2-ethylhexylsodium [210,211]. Thus, an alternating-type copolymer structure (r rg = 0.126) would be formed for this system however, butadiene is incorporated predominantly as vinyl units (60% 1,2). In contrast, initial preferential styrene incorporation (r = 3.3 rg = 0.12) is observed for an analogous organopotassium initiator, the DPE adduct of 2-ethylhexylpotassium [61]. 

Filled conductive polymers used for packaging include polycarbonate, polyolefin, and styrenics incorporating fillers such as carbon, aluminum, and steel flakes and fibers. A polycarbonate/ABS blend (Bayblend ME) introduced by Bayer is 4% aluminum filled and suited to many screening functions. 

In many cases, the polarities of the monomers or the macroions are very different for example, in the anionic copolymerization of styrene (1) and methyl methacrylate (2). A styryl anion can add methyl methacrylate therefore /ci2 7 0 but styrene will not add on to the methyl methacrylate anion (/c2i = 0). All the styrene incorporated into the polymer must therefore come from the starting step and the propagation step immediately following it. Thus, for the unipolymerization. 

Based on the high styrene incorporation for all monomer feed compositions, styrene is seen to be more reactive than vinylborazine in the polymerization. This qualitative observation was quantitatively confirmed by the determination of the monomer reactivity ratios, r, (styrene) = 4.02, and rj (vinylborazine) = 0.078. The resulting... 

EFFECT OF STYRENE CONTENT AND MOLE RATIO OF TMEDA/BllLi ON THE AMOUNT OF STYRENE INCORPORATED AS LONG SEQUENCES IN SBR... 

It is useful to compare the detailed monomer sequence distribution in SBRs obtained with emulsion free-radical and n-BuLi systems with the SBRs prepared with Ba/Mg/Al. We will begin by discussing how styrene incorporation varies with extent of conversion, then examine reactivity ratios and sequence distribution information obtained by proton NMR. 

Variation of Composition with Conversion The amount of styrene incorporated into an experimental h -trans SBR at any given conversion is compared (Fig. 16) with that for a polymer prepared by free-radical emulsion polymerization and one... 

However, copolymer density does not continue to decrease with higher levels of styrene incorporated into the copolymer. This effect is clearly demonstrated with copolymers containing 50-75 wt% styrene as the copolymer... 

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