Triblock copolymers. See

Table 4. Tensile properties of the poly(CL-[7-DXO-[7-CL) ABA triblock copolymers (see Scheme 39) ...

A comparative study of MAH and diethyl maleate grafting—initiated by DCP—to styrene-(ethylene-butylene)-styrene triblock copolymer (SEES) and PS blended with a random ethylene-1-butene copolymer has been described elsewhere (66). The weight ratio of PS to PO components in the block copolymer was the same as in the blend (20% PO and 80 wt% PS). The analysis of the functionalized PS/PO blend—after PS had been extracted in a solvent—showed that the monomer was grafted only to the PO component. Considering that the PS/ PO blend and SEES have quite similar phase and molecular structures, it was concluded that in styrene-containing block copolymers only aliphatic blocks become functionalized. 

Styrene/butadiene triblock copolymer. See Styrene/butadiene/styrene block copolymer Styrene, p,a-dimethyl-. See p-a-Dimethylstyrene... 

An alternative approach is to incorporate reactive functional groups Into the elastomer, producing an in-situ graft copolymer. This reduces interfacial tension, improving dispersion in processing, and improves the adhesion of the rubber to the thermoplastic In the solid state. A maleated polystyrene/poly(ethylene-co-butylene)/polystyrene triblock copolymer (SEES) has been used successfully to toughen polyamides and polyesters. 

The phosphoranimine terminated poly(propyleneglycol) (59), that was used as an intermediate in the synthesis of amphiphilic polyphosphazene polyethyleneglycol-polyphosphazene triblock copolymers (see Section 3), was prepared using commercially available poly(propyleneglycol) (M ca. 4000) with NH2 terminal groups. ... 

LLDPE/PP Poly(S-block (E-co-B-l)-block S) triblock copolymers SEES... 

Moreover, the viscosity ratio rjpirjpgj- should be less than 1 to favor the encapsulation of PET with P nonreactive polymer [75]. The poly(styrene- -ethylene-butylene-fe-styrene) triblock copolymer (SEES) shows these two characteristics in PET matrix hosting PE-dispersed phase. [76] If polyethylene is the matrix, only the former condition is respected. When the polymer P is reactive, the encapsulation of the dispersed phase was observed in different compositions of PA6/PP blends [72,73] and of PET/PP blends.[74]... 

Figure 5.23 Examples of two nonlamellar morphologies - (a) core-shell cylinders and (b) core-shell gyroid - generated by blending a nearly symmetric B-M diblock copolymer with a symmetric S-B-M triblock copolymer (see Figure 5.22). The blend compositions are 52/48 B-M/S-B-M in (a) and 21/79 B-M/S-B-M in (b). A simulated projection of the gyroid morphology is included for comparison in (c). (Adapted from Goldacker, T. and Abetz, V. Macromolecules 32, 5165, 1999, and reprinted with permission. Copyright (1999) American Chemical Society.)...

Butadiene copolymers are mainly prepared to yield mbbers (see Styrene-butadiene rubber). Many commercially significant latex paints are based on styrene—butadiene copolymers (see Coatings Paint). In latex paint the weight ratio S B is usually 60 40 with high conversion. Most of the block copolymers prepared by anionic catalysts, eg, butyUithium, are also elastomers. However, some of these block copolymers are thermoplastic mbbers, which behave like cross-linked mbbers at room temperature but show regular thermoplastic flow at elevated temperatures (45,46). Diblock (styrene—butadiene (SB)) and triblock (styrene—butadiene—styrene (SBS)) copolymers are commercially available. Typically, they are blended with PS to achieve a desirable property, eg, improved clarity/flexibiHty (see Polymerblends) (46). These block copolymers represent a class of new and interesting polymeric materials (47,48). Of particular interest are their morphologies (49—52), solution properties (53,54), and mechanical behavior (55,56). 

Thermoplastic Elastomers. These represent a whole class of synthetic elastomers, developed siace the 1960s, that ate permanently and reversibly thermoplastic, but behave as cross-linked networks at ambient temperature. One of the first was the triblock copolymer of the polystyrene—polybutadiene—polystyrene type (SheU s Kraton) prepared by anionic polymerization with organoHthium initiator. The stmcture and morphology is shown schematically in Figure 3. The incompatibiHty of the polystyrene and polybutadiene blocks leads to a dispersion of the spherical polystyrene domains (ca 20—30 nm) in the mbbery matrix of polybutadiene. Since each polybutadiene chain is anchored at both ends to a polystyrene domain, a network results. However, at elevated temperatures where the polystyrene softens, the elastomer can be molded like any thermoplastic, yet behaves much like a vulcanized mbber on cooling (see Elastomers, synthetic-thermoplastic elastomers). 

Triblock copolymers can be prepared from diblock copolymers by a third monomer addition. They can also be prepared using a bis-funetional NMP or ATRP initiator or a bis-RAFT agent (for examples, see Table 9.13). Symmetrical trithiocarbonates (Table 9.15) should also be considered as bis-RAFT agents in... 

AABB polyimides, synthesis of, 300-302 AA-BB-type polymers, 135 AA-BB-type sulfonylation, 330 AA monomers, 11-12 A-B-A triblock copolymers, 7 A-B copolymers, 7 AxBy monomers, 8 AB polyamides, 173-180 AB polyimides, 304-307 syntheses of, 306 Abrasion resistance test, 243-244 ABS. See Acrylonitrile-... 

Transformation of active end-groups 95 Transient catalysts 19 Transition state (see Activated complex) Triblock copolymers 151,166... 

FIGURE 20.10 (a,b) Phase images of cryo-ultramicrotomed surfaces of triblock copolymer styrene and ethylene-butylene (SEES) samples of neat material and loaded with oil (40 wt%), respectively. (c,d) Phase images of film of triblock copolymer poly(methyl methacrylate-polyisobutylene-poly(methyl methacrylate) (PMMA-PIB-PMMA) immediately after spin-casting and after 3 h annealing at 100°C, respectively. Inserts in the top left and right comers of the images show power spectra with the value stmctural parameter of microphase separation. 

FIGURE 17.16 2DLC separation of a PEO-PPO-PEO triblock copolymer, first dimension LCCC, second dimension SEC. (See color plate.)... 

Only a few publications deal with ABC triblock copolymers where two of the blocks are able to crystallize. The systems that have been investigated include PS-b-PE-b-PCL [94,98], PE-b-PS-6-PCL [94], PS-fc-PEO-fo-PCL [30,134-136] and PE-fo-poly(ethylene-propylene)-fr-PEO [101,119] (see also Table 1). 

Fig. 6.14 NSE spectra from the junction-labelled PEP-PEE triblock copolymer (sample VII) at different Q-values (filled circles Q=0.2 A open circles Q=0.08 A" squares Q=0.05 A" ). The solid lines indicate the initial slope fits. The dashed lines are the expectations for Rouse relaxation in the system (see text). (Reprinted with permission from [284]. Copyright 2002 EDP Sciences)...

Considerable effort has been carried out by different groups in the preparation of amphiphihc block copolymers based on polyfethylene oxide) PEO and an ahphatic polyester. A common approach relies upon the use of preformed co- hydroxy PEO as macroinitiator precursors [51, 70]. Actually, the anionic ROP of ethylene oxide is readily initiated by alcohol molecules activated by potassium hydroxide in catalytic amounts. The equimolar reaction of the PEO hydroxy end group (s) with triethyl aluminum yields a macroinitiator that, according to the coordination-insertion mechanism previously discussed (see Sect. 2.1), is highly active in the eCL and LA polymerization. This strategy allows one to prepare di- or triblock copolymers depending on the functionality of the PEO macroinitiator (Scheme 13a,b). Diblock copolymers have also been successfully prepared by sequential addition of the cyclic ether (EO) and lactone monomers using tetraphenylporphynato aluminum alkoxides or chloride as the initiator [69]. 

A variation of the sequential anionic polymerization is the use of dianions as initiator, like sodium naphthalene. One starts with the polymerization of monomer A. Then monomer B is fed to the reaction mixture which adds immediately to the living anions at each end of block A and thus leads to a triblock copolymer with an A-middle block and two B-outer blocks. This triblock copolymer is still alive and repetition of the above procedure results in a multiblock copolymer (see Example 3-49). 

The parent triblock copolymer t-BMA-b-S-b-t-BMA and the hydrolyzed triblock copolymer acrylic acid-b-styrene-b-acrylic acid should be analyzed by IR spectroscopy.The ester and acid carbonyl peaks indicate the saponification (see Sect.2.3.2.2.)... 

Self-consistent field theory (SCFT, see Sections 2.3.3 and 3.4,2) has recently been applied to the phase behaviour of ordered micellar solutions. Noolandi et al. (1996) compared continuum SCFT to the lattice version of this theory for triblock copolymers such as the Pluronics in aqueous solution. From a different viewpoint, this work represents an extension of the SCFT employed by Hong and Noolandi (1981, 1983) and Matsen and Schick (1994) for the phase behaviour of block copolymer melts to block copolymers in solution. The approximations introduced by the adoption of a lattice model are found to lead to some significant differences in the solution phase behaviour compared with the continuum theory, as illustrated by Fig. 4.44. For example, the continuum theory predicts ordered phases for Pluronic L64 (PE013PP03oPEO 3), whereas the lattice theory (neglecting polydispersity) predicts none. 

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