Segments, block copolymers

Thermoplastic copolyester elastomers are generally block copolymers produced from short-chain aUphatic diols, aromatic diacids, and polyalkjlene ether-diols. They are often called polyesterether or polyester elastomers. The most significant commercial product is the copolymer from butane-l,4-diol, dimethyl terephthalate, and polytetramethylene ether glycol [25190-06-1J, which produces a segmented block copolyesterether with the following stmcture. 

Step-Growth Gopolymerization. A sample of a block copolymer prepared by condensation polymerisation is shown in equation 30 (37). In this process, a prepolymer diol (HO—Z—OH) is capped with isocyanate end groups and chain extended with a low molecular-weight diol (HO—E—OH) to give a so-called segmented block copolymer, containing polyurethane hard blocks and O—Z—O soft blocks. 

At present there are five types of thermoplastic rubber (TPR). Three of these, the polyurethane, the styrenic and the polyester are termed segmented block copolymers in that they consist of thermoplastic molecules grafted to the rubbery molecules. At room temperature it is the thermoplastic molecules which clump together to anchor the rubbery molecules. When heat is applied the thermoplastic molecules are capable of movement so that the material may be shaped using conventional thermoplastic moulding equipment. 

Block copolymer—These copolymers are built of chemically dissimilar terminally connected segments. Block copolymers are generally prepared by sequential anionic addition or ring opening or step growth polymerization. 

Hedrick et al. reported imide aryl ether ketone segmented block copolymers.228 The block copolymers were prepared via a two-step process. Both a bisphenol-A-based amorphous block and a semicrystalline block were prepared from a soluble and amorphous ketimine precursor. The blocks of poly(arylene ether ether ketone) oligomers with Mn range of 6000-12,000 g/mol were coreacted with 4,4,-oxydianiline (ODA) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in NMP in the presence of A - me thy 1 morphi 1 i nc. Clear films with high moduli by solution casting and followed by curing were obtained. Multiphase morphologies were observed in both cases. 

Imide aryl ether ketone segmented block copolymers, 360 Imide chemistry, 292-295 Imide cyclization, 301 Imide exchange, polyimide syntheses by, 268... 

Walch E. and Caymans R.J., Synthesis and properties of poly(butylenes terephthalate)-b-polyisobutylene segmented block copolymers, Polymer, 35, 636, 1994. 

Deschamps AA, Grijpma DW, and Feijen J. Poly(ethylene oxide)/poly(butylenes terephthalate) segmented block copolymers The effect of copolymer composition on physical properties and degradation behavior. Polymer, 2001, 42, 9335-9345. 

In one of their notable examples, the hydroboration polymerization of low molecular weight allyl-telechelic polyisobutylene with tripylborane (trip = 2,4,6-triisopropylphenyl) was found to yield air-stable organoboron segmented block copolymers. These boron main-chain polymers (8) (Fig. 8), unlike the general ones, were stable to air. The stability was due to the steric hindrance of the bulky tripyl groups preventing oxygen attack of the borons.28... 

Figure 8 The air-stable 77-conjugated organoboron segmented block copolymer (8) obtained by the hydroboration polymerization of allyl-telechelic polyisobutylene, 1,9-decadiene, and tripylborane. (Adapted from ref. 28.)...

The preparation of a functional segmented block copolymer was also investigated (scheme ll).15 First hydroboration polymerization of the oligomer using thexylborane was carried out. Then the obtained organoboron polymer was subjected to a chain-transformation reaction (DCME rearrangement). DCME and lithium alkoxide of 3-ethyl-3-pentanol in hexane was added to a THF solution of the polymer at 0°C. 

For example, a PE-fe-poly(ethylene-co-propylene) diblock composed of crystalline PE and amorphous ethylene/propylene copolymer segments was synthesized from ethylene and ethylene/propylene. The addition of MAO and Ti-FI catalyst 40 (Fig. 25) to an ethylene-saturated toluene at 25 °C resulted in the rapid formation of a living PE (Mn 115,000, MJMn 1.10). The addition of ethylene/propylene (1 3 volume ratio) to this living PE formed a PE-/>poly(ethylcnc-co-propylcnc) block copolymer (Mn 211,000, MJMn 1.16, propylene content 6.4 mol%) [30], As expected, the polymer exhibits a high Tm of 123 °C, indicating that this block copolymer shows good elastic properties at much higher temperatures than the conventional random copolymers of similar densities. 

These structures are well defined by conducting the polymerization in the presence of appropriate mono- and difunctional reagents. They are of considerable interest for the preparation of segmented block copolymers.24,25 For instance, the fluorinated macrodiols 21 have already been used to prepare an interesting new series of partially fluorinated segmented polyurethanes,26 and we are investigating other novel polymers that can be prepared from these intermediates. 

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