Arborescent polymers copolymers

Well-characterized systems. This depends on the appropriate chemistry and subsequent characterization (typical issues here are the polydispersity, control of grafting density, reproducibility of procedure to obtain identical particles). One frequent problem here is that the price one pays for such systems is tlie availability of small amounts (sometimes only fractions of 1 g) of material. For example, multiarm star polymers are in many ways unique, clean, soft colloids [ 19,23], but their nontrivial synthesis makes them not readily available. On the other hand, recent developments witli block copolymer micelles from anionically synthesized polymers [54-58] and arborescent graft copolymer synthesis [40] appear to have adequately addressed this issue for making available different alternative star-like systems. 

Another embodiment of this technique was used for the synthesis of high molecular weight, low B arborescent polymers by Yuan and Gauthier in a one-pot synthesis of arborescent PSs [114]. In this case, the anionic copolymerization of styrene (Sty) and 1,3-diisopropenylbenzene (DIB) initiated by iec-butyllithium was carried out in a semibatch process. Following complete monomer conversion, the chains were terminated and the isopropenyl moieties of the DIB units were activated with xec-butyllithium to produce a polyfunctional anionic macroinitiator without additional workup. Further styrene-DIB monomer mixture additions yielded a comb-branched (GO) copolymer, and... 

Highly branched, so called hyperbranched macromolecules have recently attracted interest, because of their interesting properties, which closely resemble those of dendrimers. Vinyl monomers with pendant initiating moieties, for example, 3-(l-chloroethyl)-ethenylbenzene, have been reported to give rise to hyperbranched polymers in a process termed self-condensing vinyl polymerization [253]. Hyperbranched PIBs have been synthesized by cationic copolymerization of 4-(2-methoxyisopropyl)styrene and IB [254]. Using a similar approach the preparation of arborescent block copolymers of IB and St (arb-PIB-h-PSt) has also been reported (see above) [226]. 

Viville, R, Leclere, P., Deffieux, A. et al. (2004) Atomic force microscopy study of comb-like vs. arborescent graft copolymers in thin films. Polymer, 45,1833 1843. 

This chapter focuses on the latest efforts in our laboratory aimed at the synthesis and the physical characterization of arborescent polymers. The synthesis of arborescent styrene and isoprene homopolymers is discussed, together with copolymers incorporating a polystyrene substrate grafted with side chains of different compositions such as poly(2-vinylpyridine). 

Puskas, J.E. Biomacromolecular engineering Design, S3mthesis and characterization. One-pot synthesis of block copolymers of arborescent polyisobutylene and polystyrene, Polym. Adv. TechnoL, 7, 1, 2006. 

Kwon, Y., Antony, P., Paulo, C., and Puskas, J.E. Arborescent polyisobutylene-polystyrene block copolymers—a new class of thermoplastic elastomers, Polym. Prepr., 43, 266-267, 2002. 

Puskas, J.E. Dendritic (arborescent) pol3tisobutylene-polystyrene block copolymers DMTA analysis and swelling studies, Polym. Mater. Sci. Eng., 91, 875-876, 2004. 

Figure 1 Macromolecular architectures linear macromolecular chains (homopolymer, block-copolymer and statistical copolymer [14]), brushed-polymer (= linear chains attached to a polymer-chain brush-polymer, brush-copolymers [14]), star polymer [4], mikto-star-polymer [16], arborescent graft polymer (=repeated grafting of linear chains on a macromolecule [17,18]), dendrimer (= maximally branched, regular polymer [15])...

Figure 30.10 Percent mass fraction of lidocaine released from an arborescent PS- -P2VP G1 ( ) copolymer, and of indomethacin released from G1 (0), G2 ( ), and G3 (A) copolymers. Source Reproduced with permission from Njikang GN, Gauthier M, Li J. Polymer 2008 49 5474 [120], Copyright 2008 Elsevier.

The effects of side chain architectures on the properties and proton conductivities of graft copolymer membranes for DMFCs were studied by Su et al. [126]. Poly(vinylidene fluoride)-g-poly(styrene sulfonic acid) (PVDF-g-PSSA) copolymers with either linear graft (LG) or arborescent graft (AG) PSSA side chains were prepared. Scheme 6.29 shows the structures of LG and AG polymers. 

Figure 6.3 Release profiles for (a) indomethacin and (b) lidocaine in 0.05M HCl in the free state ( ) and from GlPS- ra/ -P2VP copolymer ( ). Mt is the cumulative mass released at time t, and Mgq is the mass released at equilibrium. (Reprinted from Polymer, 49, G.N. Njikang, M. Gauthier and J. Li, Sustained release properties of arborescent polystyrene-grq/it-poly (2-vinylpyridine) copolymers, 5474-5481, 2008, with permission from Elsevier.)...

Yun, S., Briber, R.M., Kee, R.A., and Gauthier, M. (2003) SmaU-angle neutron scattering of arborescent polystyrene-grayt-poly(2-vinylpyridine) copolymers. Polymer, 44,6579-6787. 

Njikang, G., Gauthier, M., and Li, J. (2008c) Arborescent polystyrene-grq -poly(2-vinylpyridine) copolymers as unimolecular micelles. Solubilization studies. Polymer, 49,1276-1284. 

Kwon Y, Antony P, Paulo C and Puskas J E (2002) Arborescent polyisobutylene-polystyrene block copolymers - A new class of thermoplastic elastomers, Polym Prepr ACS 43 266-267. 

Antony P, Kwon Y, Puskas J E, Kovar M and Norton P R (2004) Atomic force microscopic studies of novel arborescent block and linear triblock polystyrene-polyisobutylene copolymers, Eur Polym J 40 149-157. 

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