Isoprene styrene

Butadiene is also known to form mbbery polymers caused by polymerization initiators like free radicals or oxygen. Addition of antioxidants like TBC and the use of lower storage temperatures can substantially reduce fouling caused by these polymers. Butadiene and other olefins, such as isoprene, styrene, and chloroprene, also form so-called popcorn polymers (250). These popcorn polymers are hard, opaque, and porous. They have been reported to... 

Somewhat less well known are the styrene-isoprene-styrene (SIS) triblocks. The commercial grade (Cariflex TR-1107) is stated to have a styrene-isoprene... 

Figure 12.4 Cliromatograms of a styrene-isoprene-styrene tiiblock copolymer sample (a) microcolumn SEC trace (b) capillary GC ti ace of the inti oduced section x . Peak identification is as follows 1, ionol 2, not identified 3, Iiganox 565. Reprinted with pennission from Ref. (12).

Linear triblock copolymers of the type styrene-butadiene-styrene (SBS) and styrene-isoprene-styrene (SIS) are produced commercially by anionic polymerization through sequential addition of monomers in the reaction chamber [10] as shown below ... 

Short fiber reinforcement of TPEs has recently opened up a new era in the field of polymer technology. Vajrasthira et al. [22] studied the fiber-matrix interactions in short aramid fiber-reinforced thermoplastic polyurethane (TPU) composites. Campbell and Goettler [23] reported the reinforcement of TPE matrix by Santoweb fibers, whereas Akhtar et al. [24] reported the reinforcement of a TPE matrix by short silk fiber. The reinforcement of thermoplastic co-polyester and TPU by short aramid fiber was reported by Watson and Prances [25]. Roy and coworkers [26-28] studied the rheological, hysteresis, mechanical, and dynamic mechanical behavior of short carbon fiber-filled styrene-isoprene-styrene (SIS) block copolymers and TPEs derived from NR and high-density polyethylene (HOPE) blends. 

Sequential addition of different monomer charges to a living anionic polymerization system is useful for producing well-defined block copolymers. Thermoplastic elastomers of the triblock type are the most important commercial application. For example, a styrene-isoprene-styrene triblock copolymer is synthesized by the sequence... 

Abbreviation for styrene-isoprene-styrene block copolymer, a thermoplastic elastomer. 

Styrenic SBS/SIS (styrene-isoprene-styrene block copolymers) CariflexTR, Kraton... 

The synthetic importance of non-nucleophilic strong bases such as lithium diisopro-pylamide (LDA) is well known but its synthesis involves the use of a transient butyl lithium species. In order to shorten the preparation and make it economically valuable for larger scale experiments an alternate method of synthesis has been developed which also involves a reaction cascade (Scheme 3.14) [92]. The direct reaction of lithium with diisopropylamine does not occur, even with sonication. An electron transfer agent is necessary, and one of the best in this case is isoprene. Styrene is used in the commercial preparation of LDA, but it is inconvenient in that it is transformed to ethylbenzene which is not easily removed. It can also lead to undesired reactions in the presence of some substrates. The advantages of isoprene are essentially that it is a lighter compound (R.M.M. = 68 instead of 104 for styrene) and it is transformed to the less reactive 2-methylbutene, an easily eliminated volatile compound. In the absence of ultrasound, attempts to use this electron carrier proved to be unsatisfactory. In this preparation lithium containing 2 % sodium is necessary, as pure lithium reacts much more slowly. 

Kraton 1107 brand elastomer was from Shell Chemical Co., and it is synthesized by coupling the isoprenyl anion ends of a styrene/isoprene (SI) block copolymer to give styrene/isoprene/styrene (SI IS). Proton NMR analysis indicated 84% (wt.) isoprene and 16% (wt.) styrene. 

The mechanical properties at low strain rates, dynamic mechanical properties, creep-recovery behaviour, thermal expansion and thermal conductivity of foams manufactured from blends of LDPE with an EVA and with an isoprene-styrene block copolymer were studied as a function of the LDPE content in the blends. The experimental results demonstrated important aspects related to the modification of the foam properties by blending. 16 refs. 

Discuss the use of homogeneous versus heterogeneous reaction conditions for the coordination and traditional Ziegler-Natta polymerizations of propene, isoprene, styrene, methyl methacrylate, and n-butyl vinyl ether. 

A second route is termed sequential anionic polymerization. More recently, also controlled radical techniques can be applied successfully for the sequential preparation of block copolymers but still with a less narrow molar mass distribution of the segments and the final product. In both cases, one starts with the polymerization of monomer A. After it is finished, monomer B is added and after this monomer is polymerized completely again monomer A is fed into the reaction mixture. This procedure is applied for the production of styrene/buta-diene/styrene and styrene/isoprene/styrene triblock copolymers on industrial scale. It can also be used for the preparation of multiblock copolymers. 

Chlorosulfonated styrene resins and carboxyaminoacid polymers were also found to possess thromboresistant properties by Josefonwicz and coworkers [483]. Studies included investigation of the effect of spacer length between amine and carboxylic groups as well as modification of styrene/isoprene/styrene blocks with chlorosulfonyl isocyanate giving sulfamate and carboxylic functionality [484],... 

Figure 9. of a styrene-isoprene styrene triblock copolymer... 

The most obvious reaction is simply to add more styrene and convert the isoprene anion to a styryl anion and grow it to a desired size and form the styrene-isoprene-styrene triblock of which we are more familiar in all the theoretical work that has been reported (ji, 7). The last example employs a bifunctional monomer, divinylbenzene, to form miniblocks of divinylbenzene as it reacts with a number of diblocks into what is called a star-block configuration (8). The active anionic sites are now on the divinylbenzene. These materials are then terminated by protonating agents to obtain the final product. The number of arms or diblocks that united into a starblock of this type is controlled by the relative amounts of the diblock to the divinylbenzene. 

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