Star-shaped polymers amphiphilic

Recent advances in controlled synthesis of macromolecules, in particular in coti-troUed radical polymerization, have allowed the cmistraction of polymers with various topologies and compositions. Successful design of star-shaped polymers, molecular polymer brashes, and amphiphilic block copolymers and terpolymers has... 

An important feature of this methodology is that by applying opposite pol)mierization sequences for AcOVE and IBVE, two types of amphiphilic star-shaped pol)miers may be prepared (5a and 5b Scheme 1) namely, polymer 5a carries hydrophilic polyalcohol segments in its outer layer, whereas 5b does in its inner layer. Therefore, 5a and 5b are expected to be different in their properties (such as solubility), even though they are the same in segment composition and degree of polymerization. Amphiphilic star-shaped polymers 5... 

B. Heteroarmed Amphiphilic Star-Shaped Polymers of Vinyl Ethers... 

The core functionalization in 21 may lead to the higher accumulation of polar hydroxyl groups in a core region that should be smaller in size than the arm moiety of the star-shaped polymers with functionalized arms. Another important feature of 21 is that an outer hydrophilic shell of 21 can effectively surround the hydrophilic microgel core with many hydroxyl groups. Therefore, the core-functionalized star polymers are amphiphilic but are expected to possess properties that differ from those of the star block and the heteroarm star amphiphiles. 

Such amphiphilic graft polymers may have almost uniform number of branches, provided that living polymerization of 23 is available. In addition, unlike the various types of star-shaped polymers previously reported [7,12,13], graft polymer 24 has no hydrophobic microgel core that may possess some dimensions. Therefore, the amphiphilic graft polymers are expected to possess properties and functions differing from those of the corresponding star block amphiphiles. 

Finally, Lecomte and coworkers reported the synthesis of mikto-arm star-shaped aliphatic polyesters by implementing a strategy based on click chemistry (Fig. 36) [162]. Firstly, the polymerization of sCL was initiated by a diol bearing an alkyne function. The chain-ends were protected from any further undesired reaction by the esterification reaction with acetyl chloride. The alkyne was then reacted with 3-azidopropan-l-ol. The hydroxyl function located at the middle of the chain was then used to initiate the ROP of sCL and y-bromo-s-caprolactone. Finally, pendant bromides were reacted successfully with sodium azide and then with N, N-dimethylprop-2-yn-l-amine to obtain pendant amines. Under acidic conditions, pendant amines were protonated and the polymer turned out to exhibit amphiphilic properties. 

An important group of surface-active nonionic synthetic polymers (nonionic emulsifiers) are ethylene oxide (block) (co)polymers. They have been widely researched and some interesting results on their behavior in water have been obtained [33]. Amphiphilic PEO copolymers are currently of interest in such applications as polymer emulsifiers, rheology modifiers, drug carriers, polymer blend compatibilizers, and phase transfer catalysts. Examples are block copolymers of EO and styrene, graft or block copolymers with PEO branches anchored to a hydrophilic backbone, and star-shaped macromolecules with PEO arms attached to a hydrophobic core. One of the most interesting findings is that some block micelle systems in fact exists in two populations, i.e., a bimodal size distribution. 

Polymers e-g may also be called collectively as polymers with controlled spatial shapes amphiphilic polymers (h) may include block, star-shaped, and graft polymers covered in classes b, e, and f. Comparison of Figs. 1 and 2 also tells us that, unlike the anionic and coordination (Zieglar-Natta) counterparts, cationic polymerization still fails to provide general methods to control the steric structures of polymers, although the first indication... 

B. S. Lele and J. C. Leroux, Synthesis of novel amphiphilic star-shaped poly(e-caprolactone)-Wocfc-poly(N-(2-hydrox)rpropyl) methacrylamide) by combination of ring-opening and chain transfer polymerization. Polymer, 43,5595-5606 (2002). 

Xu, J. and Zubarev, E.R. (2004) Synthesis of heteroarm star-shaped amphiphiles with 12 alternating arms ofpolybntadieneandpoly(ethylene oxide). ACSPo/yw. Prepr. (Div. Polym. Chem.), 45(1), 762-763. 

Figure 4.2 Macromolecular topologies of amphiphilic polymers capable of forming self-assembled networks (a) linear block copolymers, (b) star-shaped copolymers, (c) graft copolymers.

Narumi A, Satoh T, Kaga H, Kakuchi T (2002) Glycoconjugated polymer. 3. Synthesis and amphiphilic property of core-glycoconjugated star-shaped polystyrene. Macromolecules 35(3) 699-705... 

Wang et repotted the synthesis of a series of initiators characterized by the presence of one, two, three, or four thioa-cetates, which, when deprotected with sodium methanolate, produce the corresponding number of thiolates. These initiating systems were rrsed to produce linear monofunctional or difiincdonal growing polymers and three-arm or four-arm star-shaped thiol-terminated PMTs. In the same paper, the synthesis (and some properties) of star-shaped amphiphilic block copolymers based on PMT and PEG are described. In a subsequent paper by the same group, the role of disulfides in MT polymerization and the methods to minimize their presence and their effect on the final polymer stmctures are described. ... 

So far, there have been only few reports about the synthesis of amphipolar polymer brushes, i.e. with amphiphilic block copolymer side chains. Gna-nou et al. [115] first reported the ROMP of norbornenoyl-endfunctionalized polystyrene-f -poly(ethylene oxide) macromonomers. Due to the low degree of polymerization, the polymacromonomer adopted a star-like rather than a cylindrical shape. Schmidt et al. [123] synthesized amphipolar cylindrical brushes with poly(2-vinylpyridine)-block-polystyrene side chains via radical polymerization of the corresponding block macromonomer. A similar polymer brush with poly(a-methylstyrene)-Wocfc-poly(2-vinylpyridine) side chains was also synthesized by Ishizu et al. via radical polymerization [124]. Using the grafting from approach, Muller et al. [121, 125] synthesized... 

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