Polymers star-block

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. ... 

Kennedy J.P. and Shim J.S., Star-block polymers having multiple polyisobutylene containing diblock copolymers arm radiating from a siloxane core and a method of synthesis thereof. Disclosure 318, US Patent, Notice of Allowance, 2001. 

By the use of the polymer-linking method with 20a, a variety of starshaped poly(vinyl ethers) have been synthesized (Scheme 12) [208-212]. A focus of these syntheses is to introduce polar functional groups, such as hydroxyl and carboxyl, into the multiarmed architectures. These functionalized star polymers include star block (23a,23b) [209,210], heteroarm (24) [211], and core-functionalized (25) [212] star polymers. Scheme 12 also shows the route for the amphiphilic star block polymers (23b) where each arm consists of an AB-block copolymer of 1BVE and HOVE [209] or a vinyl ether with a pendant carboxyl group [210], Thus, this is an expanded version of triarmed and tetraarmed amphiphilic block copolymers obtained by the multifunctional initiation (Section VI.B.2) and the multifunctional termination (Section VI.B.3). Note that, as in the previously discussed cases, the hydrophilic arm segments may be placed either the inner or the outer layers of the arms. 

The ABA-type block copolymers B-86 to B-88 were synthesized via termination of telechelic living poly-(THF) with sodium 2-bromoisopropionate followed by the copper-catalyzed radical polymerizations.387 A similar method has also been utilized for the synthesis of 4-arm star block polymers (arm B-82), where the transformation is done with /3-bromoacyl chloride and the hydroxyl terminal of poly(THF).388 The BAB-type block copolymers where polystyrene is the midsegment were prepared by copper-catalyzed radical polymerization of styrene from bifunctional initiators, followed by the transformation of the halogen terminal into a cationic species with silver perchlorate the resulting cation was for living cationic polymerization of THF.389 A similar transformation with Ph2I+PF6- was carried out for halogen-capped polystyrene and poly(/>methoxystyrene), and the resultant cationic species subsequently initiated cationic polymerization of cyclohexene oxide to produce... 

It is also possible to carry out living cationic polymerization of isobutylene, initiated by a difiinctional initiator." This results in a formation of bifunctional living segments of polyis-obutylene that are soft and rubbery. Upon completion of the polymerization, another monomer, one that yields stiff segments and has a high Tg value, like indene, is introduced into the living charge. Polymerization of the second monomer is initiated from both ends of the formed polyisobutylene. When the reaction is complete, the polymerization is quenched. Preparations of a variety of such triblock and star block polymers have been described." ... 

Substituted farans have been shown to be effective end-quenchers in both the TiCU- and BCls-initiated polymerization of PIBs resulting in quantitative functionalization as determined by NMR. In addition, the allylic cation formed upon functionalization was found to be an effective initiating species for the polymerization of methyl vinyl ether to form the corresponding PIB-I7-PVE by sequential monomer addition, and the concept was extended to the preparation of three-armed star block polymers. Other bis-furanyl derivatives have also been used as coupling agents for the preparation of telechelic PIBs. °... 

Soga, M. Tatekawa, M. Matsno, H. Ink for ink-jet recording containing an amphiphilic star block polymer, and ink cartridge and recording apparatus including the same. U.S. Pat. Appl. Publ. US 2004087679, 2004 Chem. Abstr. 2004,140, 376700. 

Block Polymers. This section discusses structure-based and source-based nomenclature for ordered, segmented, and unordered block pol5oners, and polymers with nonpolymeric spacer imits or junction imits. Star-block polymers are discussed imder star polymers. 

The terms star poljuner and star-shaped polymer are used somewhat imprecisely. The same term is used to describe at least two physically different pol5mieric clusters. A star polymer may be a polymer comprising a precise center of known structure from which radiate a known number of arms. The arms, which may contain one or more SRUs or polymerized monomers, may be random, statistical, or blocky poljuners containing the latter are usually called star-block polymers. 

Comprehensive reviews of nomenclatiu-e for structure-based and source-based representations for dendritic, hyperbranched, and hyper-cross-linked polymers (21,35-38), and for star and star-block polymers (21), have been published. 

Over a period of about 50 years, representation of polymer structures, both on paper and in databases, has developed from a virtually random system to a highly organized and sophisticated one. Polyoners are represented sometimes by structure-based methods, sometimes by source-based methods, and sometimes by both. Both methods survive because each offers advantages and disadvantages. Both methods involve structural representation of polymers by a precisely defined set of rules developed over several decades by CAS, lUPAC, and the Committee on Nomenclature of the Division of Polymer Chemistry of the ACS. Areas still in need of improved representation are copolymers of imterminated SRU types aftertreated (post-treated) polymers, and dendritic (52), hyperbranched, hyper-cross-linked, star, and star-block polymers. Also needed are hierarchical relationships between intellectually related polymers (53). 

Dendritic, Hyperbranched, Hypercrosslinked, Star, and Star-block Polymers... 

Fig. 5.13. Topology of lyotropic star-block polymer liquid crystals.

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