Block copolymer synthesis triblock copolymers

Z. Fodor and R. Faust, Polyisobutylene-based thermoplastic elastomers. IV. Synthesis of poly (styrene-block-isobutylene-block-styr-ene) triblock copolymers using n-butyl chloride as solvent, J. Macromol. Sci.-Chem., 33(3) 305-324, March 1996. 

The architecture of copolymers can be controlled by the synthesis procedure, and it is possible to prepare diblock, triblock, multiblock, starblock and graft copolymers. These are illustrated in Fig. 1.1. Examples of other exotic architectures that have recently been synthesized are shown in Fig. 2.33. The possibilities for molecular design seem to be almost limitless, only being limited by the chemist s imagination. This book is concerned with block copolymers, and graft copolymers... 

Janus micelles are non-centrosymmetric, surface-compartmentalized nanoparticles, in which a cross-linked core is surrounded by two different corona hemispheres. Their intrinsic amphiphilicity leads to the collapse of one hemisphere in a selective solvent, followed by self-assembly into higher ordered superstructures. Recently, the synthesis of such structures was achieved by crosslinking of the center block of ABC triblock copolymers in the bulk state, using a morphology where the B block forms spheres between lamellae of the A and C blocks [95, 96]. In solution, Janus micelles with polystyrene (PS) and poly(methyl methacrylate) (PMMA) half-coronas around a crosslinked polybutadiene (PB) core aggregate to larger entities with a sharp size distribution, which can be considered as supermicelles (Fig. 20). They coexist with single Janus micelles (unimers) both in THF solution and on silicon and water surfaces [95, 97]. 

Block Copolymer Synthesis by Three-Step Sequential Monomer Addition The preparation of block copolymers by sequential addition of monomers using living anionic polymerization and a monofunctional initiator is the most direct method for preparing well-defined block copolymers. Detailed laboratory procedures for anionic synthesis of block copolymers are available [37, 230], Several important aspects of these syntheses can be illustrated by considering the preparation of an important class of block copolymers (Scheme 7.22), the polystyrene-fe-polydiene-( -polystyrene triblock copolymers. 

Hosono N, Pitet LM, Palmans ARA, Meijer EW (2014) The effect of pendant benzene-1,3,5-tricarboxamides in the middle block of ABA triblock copolymers synthesis and mechanical properties. Polym Chem 5(4) 1463-1470... 

While not related exclusively to block copolymer synthesis, the formation of many of the more complex architectures available through RAFT polymerization - including those based on a single monomer - shares the characteristics and caveats of linear block copolymer formation. One technique to obtain such structures (aldn to the triblock synthesis mentioned above) is the use of higher-level, multifunctional RAFT agents. A synthetic approach with a multifunctional core or a RAFT agent-functionalized polymer backbone allows... 

Wu Q, Sun SQ, Yu PHF, Chen AXZ, Chen GQ (2000) Environmental dependence of microbial synthesis of polyhydroxyalkanoates. Acta Polym Sin 6 751-756 Wu LP, Cheng ST, Chen GQ, Xu KT (2008) Synthesis, characterization and biocompatibihty of novel biodegradable poly[((R)-3-hydroxybutyrate)-block-(D,L-lactide)-block-(epsilon-caprolactone)] triblock copolymers. Polym Int 57 939-949... 

A remarkable example reported by Huang indicates versatility of the transformation approaches in block copolymer synthesis. In his recent work, an ABC triblock terpolymer (PSt-Z -PEO-l7-PtBA) was prepared by a combination of three... 

The sequential copolymerization of cyclosiloxanes is particularly suitable for the synthesis of well-defined diblock and triblock all-siloxane functionalized copolymers. Using a monofunctional initiator leads to diblock copolymers, while triblock copolymers are formed with bifunctional initiators. Some typical examples of AB block copolymers are shown in Table 3.7. It is recommended that the less-reactive monomer be polymerized in the first step, and this is the case of the examples in which D3 and V4 are polymerized first. The comonomer should be introduced not later than at 90-95% of conversion of the first monomer, in order to avoid the processes that lead to chain randomization. Those monomers which have func-... 

Starting with a functionaUzation of a,(o-dihydroxy-terminated poly(ethylene oxide) or poly(propylene oxide) by HDl 18, followed by a reaction with a,(0-diamino-terminated copolymer of butadiene and acrylonitrile, a triblock macroactivator was synthesized the anionic polymerization of CL at 140 °C in the presence of this copolymer gave an A-B-C-B-A copolymer [61]. A similar macroactivator for block copolymer synthesis was prepared by a stepwise anionic polymerization of isoprene (with dilithium a-methylstyrene tetramer) and oxirane [62]. 

The gel permeation chromatogram shown in Fig. 6 illustrates the purity of a block copolymer obtained by ion coupling. It is seen that about 5% of uncoupled block copolymer contaminates a triblock copolymer of narrow molecular weight distribution. The synthesis of star block polymers owes its recent development to the use of new coupling agents412. ... 

Somewhat limited work has been reported over the last decade. There are several reports on the synthesis and physical and structural characterization of styrene-dimethylsiloxane 141 144) and methylmethacrylate-dimethylsiloxane145> diblock, triblock and multiblock copolymers. Several reports are also available on the thermal223), solution 224,2251 and surface196 2261 characterization of various styrene-dimethyl-siloxane block copolymers synthesized by anionic techniques. 

Triblock copolymers of ABA type, where B is the central elastomeric block and A is the rigid end-block, are well-known commercially available polymers [7,8]. The chemical structures of some common TPEs based on styrenic block copolymers are given in Eigure 5.1. Synthesis of such ABA-type polymers can be achieved by three routes [9] ... 

FIGURE 5 Stepwise synthesis of a triblock copolymer (PCL-PLA-PCL) of PCL and polylactic acid using aluminum coordination catalysts to minimize randomization of the block structure by transesterification. (From Ref. 43.)... 

Synthesis of vinyl block copolymers is accomplished by living polymerisation, mostly by anionic polymerisation. Several strategies can be used, illustrated here by the example of the Styrene-Butadiene-Styrene (or SBS) triblock copolymer. 

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 ). 

Abstract This review highlights recent (2000-2004) advances and developments regarding the synthesis of block copolymers with both linear [AB diblocks, ABA and ABC triblocks, ABCD tetrablocks, (AB)n multiblocks etc.] and non-linear structures (star-block, graft, miktoarm star, H-shaped, dendrimer-like and cyclic copolymers). Attention is given only to those synthetic methodologies which lead to well-defined and well-characterized macromolecules. 

Further work related to the synthesis of copolymers with either P2VP or P4VP blocks has been reported in the literature. Triblock terpolymers PS-fc-P2VP-fo-PEO were synthesized in THF at - 78 °C by sequential polymerization of styrene and 2VP, initiated by s-BuLi in the presence of IiCl [25]. The living polymer was terminated with EO. The end-hydroxyl group was... 

Monofunctional and difunctional xanthates, shown in Scheme 30, were employed as chain transfer agents in the synthesis of block and triblock copolymers of acrylic acid, AA and acrylamide, AAm PAA-fr-PAAm, PAAm-fr-PAA-fo-PAAm and P(AA-sfaf-AAm)-fr-PAAm [81]. The polymerizations were conducted in aqueous solutions at 70 °C with 4,4 -azobis(4-cyanopentanoic acid) as the initiator. The yields were almost quantitative,... 

A combination of ATRP and ROP was employed for the synthesis of PLLA-fr-PS block copolymers and PLLA-fr-PS-fo-PMMA triblock terpoly-mers [120]. Styrene was initially polymerized using the functional initiator /3-hydroxyethyl a-bromobutyrate, HEBB, and the catalytic system CuBr/bpy. 

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