Anionic amphiphilic copolymers

Well-Defined Amphiphilic Copolymers. Well-defined, controlled structure amphiphilic copol5miers may be prepared using a range of polymerization techniques that includes anionic, cationic, and controlled free radical approaches. The materials may be simple AB diblock copolymers or more structin-ally complex species such as ABA or ABC triblock copol5uners for example. 

Typical examples of well-defined amphiphilic anionic block copolymers are PS-PAA and PS-PMAA in the neutralized form (PS-PANa and PS-PMANa) which have been studied extensively over the last years by Tuzar [114,136] and by Eisenberg and co-workers [127, 178] who have also recently reviewed this topic of self-assembly of polyelectrolytes. These copolymers with a PAA or PMAA sequence have been examined in a very wide compositional and molar mass range. At high pH, the (meth)acryhc blocks are ionized resulting in stable micelles with extended shell regions, due to the electrostatic repulsion of the shellforming chains. 

Wu, Z. Meng, L. Li, C. Lu, X. Zhang, L. He, Y. Amphiphilic copolymer with pendant pyrenebutyryl hytRazide group synthesis, characterization, and recognition for carbonate anion. J. Appl. Polym. Sci. 2006,101, 2371-2376. 

Trialkylsilyl-protected oligo(ethylene glycol)methacrylates, 2- 2- (tert-butyldimethylsilyl)oxy]ethoxy ethyl methacrylate (1), and 2- 2-[2-[(ferf-butyldimethylsilyl)oxy] ethoxy] ethoxy ethyl methacrylate (2) (Scheme 7) were used for the synthesis of amphiphilic block copolymers by anionic poly-... 

Application of amphiphilic block copolymers for nanoparticle formation has been developed by several research groups. R. Schrock et al. prepared nanoparticles in segregated block copolymers in the sohd state [39] A. Eisenberg et al. used ionomer block copolymers and prepared semiconductor particles (PdS, CdS) [40] M. Moller et al. studied gold colloidals in thin films of block copolymers [41]. M. Antonietti et al. studied noble metal nanoparticle stabilized in block copolymer micelles for the purpose of catalysis [36]. Initial studies were focused on the use of poly(styrene)-folock-poly(4-vinylpyridine) (PS-b-P4VP) copolymers prepared by anionic polymerization and its application for noble metal colloid formation and stabilization in solvents such as toluene, THF or cyclohexane (Fig. 6.4) [42]. 

Tsitsilianis and coworkers [41] presented results on the micellization behavior of anionically synthesized amphiphilic miktoarm star copolymers with PS... 

CRP is a powerful tool for the synthesis of both polymers with narrow molecular weight distribution and of block copolymers. In aqueous systems, besides ATRP, the RAFT method in particular has been used successfully. A mrmber of uncharged, anionic, cationic, and zwitterionic monomers could be polymerized and several amphiphilic block copolymers were prepared from these monomers [150,153]. The success of a RAFT polymerization depends mainly on the chain transfer agent (CTA) involved. A key question is the hydrolytic stability of the terminal thiocarbonyl functionaHty of the growing polymers. Here, remarkable progress could be achieved by the synthesis of several new dithiobenzoates [150-152]. 

---