Synthesis triblock

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-... 

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. 

Controlled synthesis and detailed characterization of triblock copolymers of di-phenylsiloxane and dimethylsiloxane has been reported by Meier and co-workers147 148), who used lithium based initiators and the cyclic trimers of dimethyl and diphenyl-... 

Bifunctional initiators are sometimes needed e.g., for the synthesis of triblock copolymers, networks, or a,co-difunctional macromolecules. Whenever it is possible to carry out the polymerization in a polar solvent no major difficulty is involved, as bifunctional initiators covering a wide range of nucleophilicities are available (Table 2). 

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] ... 

Recently, Cohn and Salomon synthesized and characterized a series of PLCL thermoplastic bioelastomers by two-step synthesis procedure. First, ring-opening polymerization of L-lactide initiated by the hydroxyl terminal groups of the PCL chain. Second, chain extension polymerization of these PLA-PCL-PLA triblocks initiated by the hexamethylene diisocyanate (HDl). 

Based on the synthesis of polyphosphazenes and of diblock copolyphosp-hazenes by the living cationic polymerization of phosphoranimines [237,241], the triblock poly(phosphazene-ethylene oxide) copolymer XVIII was synthesized by Allcock [223]. 

The anionic method of polymerization is most useful for the synthesis of low molecular weight hydroxy-terminated oligomers and polymers that are to be further processed. For example, the treatment of hydroxy-terminated oligomers with isocyanates has been used to obtain polyester-urethanes (9,20), while triblock copolymers (PCL-PEG-PCL) are prepared by initiating the polymerization of e-caprolactone with the disodium alcoholate from polyethylene glycol (26). 

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.)... 

Song, C. X., and Feng, X. D., Synthesis of ABA triblock copolymers of e-caprolactone and DL-lactide, Macromolecules. 

Brzezinska KR, Deming TJ (2001) Synthesis of ABA triblock copolymers via acyclic diene metathesis polymerization and living polymerization of alpha-amino acid-N-carboxyanhy-drides. Macromolecules 34 4348 354... 

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. 

Making use of the higher reactivity of butadiene in anionic polymerisation y <1, 2 > 1) to get the triblock SBS copolymer in two steps. The first step is the synthesis of a PS sequence with a living end, then, upon addition of a mixture of styrene and butadiene, butadiene will add first, building a "pure" PB sequence, and styrene will finally build the third sequence (two steps). 

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... 

Symmetric triblock copolymers P4VP-fr-PBd-fo-P4VP were prepared using a difunctional initiator derived from the reaction of m-diisopropenylbenzene with f-butyllithium at - 20 °C (Scheme 9) [27]. The synthesis was conducted in a mixture of toluene and THF at temperatures higher than room temperature for the polymerization of Bd, followed by a lowering of the temperature at - 78 °C and finally addition of an extra quantity of THF and 4VP. The 4VP content was kept lower than 30% to avoid problems arising from the poor sol-... 

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,... 

The living character of the ROMP promoted by the initiator Ru(CHPh)(Cl)2 (PCy3)2 (Cy = cyclohexane) was tested with the synthesis of diblock, triblock, and tetrablock copolymers of norbornene derivatives carrying acetyl-protected glucose, [2,3,4,6-tetra-O-acetyl-glucos-l-O-yl 5-norbornene-2-carboxylate], A or maltose groups, [2,3,6,2/,3/,4/,6/-hepta-0-acetyl-maltos-1-O-yl 5-norbornene-2-carboxylate], B, shown in Scheme 41 [102]. The AB, ABA, and ABAB structures were prepared by sequential addition of monomers with narrow molecular weight distributions to quantitative conversions. 

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