Copolymerization triblock copolymers

The next step concerned the synthesis of the polyester-polyimide copolymers. Triblock copolymers have been prepared by a step-growth copolymerization of stoichiometric amounts of an aromatic diamine and dianhydride (e.g., PMDA and 3FDA, as depicted in Scheme 41a) added with the single oo-amino polyesters as chain end-cappers. Graft copolymers can be prepared as well. In this case, the diamine end-functionalized oligomeric macromonomers are copolymerized with the polyimide condensation comonomers (Scheme 41b). 

Xing and Mattice (1998) applied Monte Carlo simulation techniques to study the models of BAB triblock copolymeric micelles with solubilizates in a selected solvent. They focused on a microscopic picture regarding the locus of solubilizates in BAB triblock copolymer micelles when the... 

Due to the lack of vinyl monomers giving rise to crystalline segment by cationic polymerization, amorphous/crystalline block copolymers have not been prepared by living cationic sequential block copolymerization. Although site-transformation has been utilized extensively for the synthesis of block copolymers, only a few PIB/crystalline block copolymers such as poly(L-lactide-fc-IB-fc-L-lactide) [92], poly(IB-fr- -caprolactone( -CL)) [93] diblock and poly( -CL-fr-IB-fr- -CL) [94] triblock copolymers with relatively short PIB block segment (Mn< 10,000 g/mol) were reported. This is most likely due to difficulties in quantitative end-functionalization of high molecular weight PIB. 

Random copolymerization of MMA with other polar monomers proceeds in a living fashion with relative monomer reactivity ratios in the order BuA > MMA = EtMA > /-PrMA when mediated by 4(Sm Me)/THF [60, 89]. Block polymerization of MMA with other polar monomers as lactone yields ideal living copolymers (PDI = 1.11-1.34) under these conditions. Similarly, ABA triblock copolymers were obtained by sequential addition of MMA, BuA, and MMA [89]. AB block copolymers could be obtained by sequential addition of (L,L)-lactide and (D,D)-lactide (PDI = 1.38) as well as -caprolactone and (l,l)- lactide monomers (PDI = 1.36) in the presence of Y(OCH2CH2NMe2) [82]. 

The authors also reported on the supramolecular self-assembly from rod—coil—rod triblock copolymers prepared by copolymerization of 5-acetyl-2-aminob-ezophenone with diacetyl functionalized polystyrene with low polydispersity (Scheme 12).110 In contrast to the rod—coil diblock copolymers which exhibit multiple morphologies, the triblock copolymers were found to spontaneously form only microcapsules or spherical vesicles in solution as evidenced by optical polarized, fluorescence optical, and scanning electron microscopies (Figure 33). 

A series of ABA- and BAB-type triblock copolymers (B-22 to B-24) were obtained by two-step block copolymerization with bifunctional initiators202 or by three-step block copolymerization with monofunctional initiators.202 366 368 ABC-type block copolymers B-25203 and B-26202 consisting of styrene, MA, and tBA can be obtained by the latter method the tBA segment may be hydrolyzed to give amphiphilic triblock copolymers. 

Barbier-Baudry [147,148,185-188] studied in detail the ani a-samarocene allyl and chloride complexes 91-93 (Fig. 14) as the single-component catalysts for the copolymerization of a series of a-oleflns with conjugated dienes. The resultant copolymers contained about 6% linear a-oleflns. Each olefin unit randomly inserted between two tran5-l,4-isoprenes. It was worth noting that the afforded copolymers with different precatalysts were characterized with almost the same properties, denoting the same catalytic active species formed during polymerization [147,186]. In addition, these catalysts were able to copolymerize isoprene with e-caprolactone to form diblock copolymers [186,187] and triblock copolymer poly[isoprene-ct -... 

ABA type triblock copolymerization of MMA/BuA/MMA should give rubberlike elastic polymers. The resulting copolymers should have two vitreous outer blocks, where the poly(MMA) moiety (hard segment) associates with the nodules, and the central soft poly(BuA) elastomeric block provides rubber elasticity. The first step polymerization of MM A gave Mn of 15,000 with Mw/Mn=1.04 and then a mixture of MMA and BuA was added to this growing end to result in the formation of desired ABA triblock copolymer (BuA polymerized more rapidly than MMA) (Fig. 8). Table 4 shows the typical mechanical properties of the ABA... 

Liu, J.S. et al., Tuning the electrical conductivity and self-assembly of regioregular polythiophene by block copolymerization Nanowire morphologies in new di- and triblock copolymers, Angew. Chem. Int. Ed. 41, 329, 2001. 

Hydrophobic regions can be one or two small, well-defined blocks of pendant hydrophobic moieties in an otherwise water-soluble polymer (2-4). An example is a water-soluble sulfonated BAB triblock copolymer where B is hydrophobic f-butylstyrene and A is vinyltoluene (2). However, hydro-phobic regions can also be less well-defined as well as more numerous in a polymer molecule than is the case for a triblock copolymer (5-22). For example, pendant alkyl esters appear to have been randomly incorporated in styrene-maleic anhydride (5) and vinyl benzyl ether-styrene-maleic anhydride (6-ii) copolymers. Also, alkyl polyoxyethylene acrylate monomers can be copolymerized with acrylamide to yield copolymers with pendant hydrophobic chains (12-15). More recently it was found (16-22) that small amounts of water-insoluble monomers that are solubilized by surfactants into aqueous solutions of a hydrophilic monomer produce copolymers with pendant hydrophobic chains, but the size, number, and nature of the hydro-phobic regions has not been determined. 

Furthermore, LCEs have been prepared by block copolymerization and hydrogen bonds (Cui et al., 2004 Li et al., 2004). Li et al. (2004) proposed a musclelike material with a lamellar structure based on a nematic triblock copolymer (Components 8a-c, Fig. 3.10). The material consists of a repeated series of nematic (N) polymer blocks and conventional rubber (R) blocks. The synthesis of block copolymers with well-defined structures and narrow molecular-weight distributions is a crucial step in the production of artificial muscle based on triblock elastomers. Talroze and coworkers studied the structure and the alignment behavior of LC networks stabilized by hydrogen bonds under mechanical stress (Shandryuk et al., 2003). They synthesized poly[4-(6-acryloyloxyhexyloxy)benzoic acid], which... 

B.J. Kim, J.L. White, Anionic copolymerization of lauryl lactam and polycaprolactone for the production of a poly(ester amide) triblock copolymer, J. Appl. Polym. Sd. 90 (2003) 3797-3805. 

The preparation of novel glassy(A)-b-rubbery(B)-l)-crystalline(C) linear triblock copolymers have been reported where A block is PaMeSt, B block is rubbery PIB, and C block is crystalline PPVL. The synthesis was accomplished by living cationic sequential block copolymerization to yield living poly(aMeSt-l)-IB) followed by site transformation to polymerize PVL [243]. In the first synthetic step, the GPC traces of poly(aMeSt-b-IB) copolymers with (w-methoxycarbonyl functional group exhibited bimodal distribution in both refractive index and UV traces, and the small hump at higher elution volume was attributed to PaMeSt homopolymer. This product was fractionated repeatedly using hexanes/ethyl acetate to remove homo PaMeSt and the pure poly(aMeSt-b-IB) macroinitiator was then utilized to initiate AROP of PVL to give rise to poly(aMeSt-b-IB-b-PVL) copolymer. 

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