Polymers block, diblock

Star-block copolymers are star polymers in which each arm is a block (diblock or triblock) copolymer. There are several methods used for the synthesis of star-block copolymers [142], and the most commonly used strategies are given in Scheme 67. 

In the following discussion, block copolymers will be simply designated by the acronym A-B for a diblock copolymer, A-B-A for a triblock copolymer with two identical outer blocks, A-B-C for an ABC triblock copolymer, etc. A complete list of abbreviations for the A, B, and C polymer blocks is given in the Abbreviations and Symbols section. 

Investigations on diblock copolypeptide amphiphiles by Deming and coworkers further elegantly proved the dependence of the aggregation behavior on the chain conformation of the polymer blocks.225 Well-defined block copolymers were synthesized containing... 

Another approach to block copolymers of the aromatic polyamide and coil polymer is the macroinitiator method the chain-growth condensation polymerization of 22a from a macroinitiator derived from coil polymer. A diblock... 

This name covers all polymer chains (diblocks and others) attached by one end (or end-block) at ( external ) solid/liquid, liquid/air or ( internal ) liquid/liq-uid interfaces [226-228]. Usually this is achieved by the modified chain end, which adsorbs to the surface or is chemically bound to it. Double brushes may be also formed, e.g., by the copolymers A-N, when the joints of two blocks are located at a liquid/liquid interface and each of the blocks is immersed in different liquid. A number of theoretical models have dealt specifically with the case of brush layers immersed in polymer melts (and in solutions of homopolymers). These models include scaling approaches [229, 230], simple Flory-type mean field models [230-233], theories solving self-consistent mean field (SCMF) equations analytically [234,235] or numerically [236-238]. Also first computer simulations have recently been reported for brushes immersed in a melt [239]. 

Another pyrrolidone-based phosphine has been incorporated into amphiphilic, water-soluble diblock co-polymers based on 2-oxazalone derivatives (Scheme 61). The synthesis involved the initial preparation of a diblock co-polymer precursor with ester functionalities in the side chain. This was achieved by sequential polymerization of 2-methyl-2-oxazoline to form the hydrophilic block that provides water solubility, and subsequently a mixture of ester-functionalized oxazoline 147 and 2-nonyl-2-oxazoline, the latter increasing the hydrophobicity of the second polymer block. Having made the backbone, the ester functionalities were converted into carboxylic acids giving polymer 148, which was then reacted with the phosphine ligand to give the desired supported material, 149. This was used in asymmetric hydrogenation reactions with success. 

Fig. 5.11 Schematics of thermodynamically stable diblock copolymer phases. The A-B diblock copolymer, such as the PS-b-PMMA molecule represented at the top, is depicted as a simple two-color chain for simplicity. The chains self-organize such that contact between the immiscible blocks is minimized, with the structure determined primarily by the relative lengths of the two polymer blocks ( ). Reproduced with permission from ref [95]...

Random copolymers have no pattern to the sequence of monomers. A random copolymer using repeat units A and B would be called poly(A-co-B). The term alternating copolymer is fairly self-explanatory with an alternating pattern of repeat units. Block copolymers consist of long-chain segments (blocks) of single-repeat units attached to each other. Block polymers most commonly employ two different repeat units and contain two or three blocks. Block copolymers are named poly(A-f B) or simply AB for polymers with two blocks (diblock polymer). A triblock copolymer would be named poly(A-b-B-b-A) or simply ABA. Grt0 copolymers consist of a backbone with side chains of a different repeat unit and are named poly(A-g-B). (See Fig. 11.6.)... 

To control the molecular weight (MW) and MWD, Sakurai and coworkers developed an anionic polymerization method with masked disilene, a highly strained precursor with biphenyl (Chart 13.4). Although the substituents are limited to alkyl and certain dialkylamino groups, this method made it possible to design well-defined Si Si sequences, leading to diblock polymers with organic polymer blocks such as poly(triphenylmethylmethacrylate) by means of chiral anionic catalysts. 

Block Polymers. A diblock polymer has the general structure... 

---