Triblock copolymer hydrogenation

The fusion of the triblock copolymer, hydrogenated poly(butadiene-isoprene-butadiene) 27 wt % hydrogenated poly(butadiene), crystallized under two different conditions, is one example of the role of the initial melt structure or crystallization... 

Weiss et al. [75] have synthesized Na and Zn salt of sulfonated styrene(ethylene-co-butylene)-styrene triblock ionomer. The starting material is a hydrogenated triblock copolymer of styrene and butadiene with a rubber mid-block and PS end-blocks. After hydrogenation, the mid-block is converted to a random copolymer of ethylene and butylene. Ethyl sulfonate is used to sulfonate the block copolymer in 1,2-dichloroethane solution at 50°C using the procedure developed by Makowski et al. [76]. The sulfonic acid form of the functionalized polymer is recovered by steam stripping. The neutralization reaction is carried out in toluene-methanol solution using the appropriate metal hydroxide or acetate. 

A polystyrene-poly(ethylene,l-butene)-polystyrene triblock copolymer is produced by the selective hydrogenation of the corresponding triblock copolymer in which the center block consists of random placements of 1,2-poly(1,3-butadiene) and 1,4-poly (1,3-butadiene) units. 

Since the anionic triblock copolymers are based on monomers susceptible to this mechanism, one recent approach to this synthesis has been to prepare butadiene-isoprene-butadiene triblock copolymers, which are then hydrogenated so that the high-1,4 polybutadiene end blocks become crystallizable, similar to high-pressure polyethylene (l -5 ). 

In this study, the effects of the variations in block sequence and composition (and thus relative block length) on the material properties of two series of triblock copolymers has been investigated. One of the blocks, the hydrogenated polybutadiene (HB), is semicrystalline, and the other block, the hydrogenated polyisoprene (HI) is rubbery at room temperature. Thus in one series, the HBIB block copolymers, the end blocks are semi-... 

The hydrogenated (H) block copolymers will be designated by giving the butadiene (B) or isoprene (i) block sequence followed by a number which represents the total weight percentage of butadiene in the polymer. For example HBIB-27 is a hydrogenated triblock copolymer of butadiene-isoprene-butadiene which contains 27% butadiene. Since the polymer is symmetric, the relative composition of each block is therefore 13.5% B -73% I -13.5% B. 

Table 19.3 Typical reaction conditions for the hydrogenation of polybutadiene (PB), styrene-butadiene diblock copolymer (SB), styrene-butadiene-styrene triblock copolymer (SBS) and nitrile butadiene rubber (NBR).

An example of the incorporation of an external component on the crystallization behavior of triblock copolymers was given by Schmalz et al. [126]. They obtained PS-fo-poly(ethylene-co-propylene)-fo-PE (PS-fo-PEP-fr-PE) triblock copolymers from the hydrogenation of PS-fr-PI-fo-PB. PS-fo-PEP-fr-PE triblock copolymers have the peculiarity that PEP and PE have an interaction parameter of 0.007 at 120 °C therefore, they form a homogeneous melt, which is segregated from the PS block and can be considered as an intermediate case between diblock and triblock copolymers. The crystallization of the PE block occurs at about 60 °C and the authors evaluated the influence of the incorporation of a solvent during the crystallization and segregation processes under... 

Fig. 18 Peak crystallization temperature as a function of self-nucleation temperature for hydrogenated and nonhydrogenated S27B15C58 triblock copolymers. (Reprinted with permission from [97]. Copyright 1998 American Chemical Society)...

Liu L, Jiang M. Synthesis of novel triblock copolymers containing hydrogen-bond interaction groups via chemical modification of hydrogenated poly(styrene-h/ock-butadiene-h/ock-styrene). Macromolecules 1995 28 8702-8704. 

Pharmaceutical research on polymeric micelles has mainly focused on two kinds of block copolymers, namely, AB block copolymers or diblock copolymers and ABA or BAB block copolymers known as triblock copolymers (Bader et al., 1984 Yokoyama et al., 1990,1991 Kwon and Okano, 1996, 1999 Kwon, 1998, 2003 Alakahov and Kabanov, 1998). The most common hydrophilic block (A) of the block copolymers is polyethylene oxide (PEO). This polymer is highly hydrated through hydrogen bonding and sterically stabilizes surfaces of the polymeric micelles in aqueous systems. 

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