Arborescent Polystyrene-graft-poly(2-vinylpyridine) Copolymers:  Synthesis and Enhanced Polyelectrolyte Effect in Solution

Abstract

A technique is described for the preparation of arborescent copolymers containing poly(2vinylpyridine) (P2VP) segments. 2-Vinylpyridine is first polymerized with 1,1-diphenyl-2-methylpentyllithium in tetrahydrofuran in the presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA). The graft copolymers are obtained by titration of the P2VP anions with a solution of a chloromethylated polystyrene substrate. Copolymers incorporating either short (M w ≈ 5000) or long (Mw ≈ 30 000) P2VP side chains were prepared by grafting onto linear, comb-branched (G0), G1, and G2 chloromethylated arborescent polystyrenes. Branching functionalities ranging from 14 to 3880 and molecular weights ranging from 8.2 × 10 4 to 6.7 × 10 7 were obtained for the copolymers, while maintaining a low apparent polydispersity (Mw/Mn ≈ 1.06-1.15) after grafting. Characterization data for these materials from size exclusion chromatography and light scattering indicate that they have a highly compact structure. Dynamic light scattering results show that the arborescent poly(2-vinylpyridine) copolymers expand much more in solution than the linear homologous polymers when protonated with HCl. This is attributed to the higher charge density attained in the branched copolymers.

Small-angle neutron scattering of arborescent polystyrene-graft-poly(2-vinylpyridine) copolymers

“…However, the grafting process need not be restricted to one type of polymer. The process has been demonstrated for grafting other polymers including poly(ethylene oxide), poly (2-vinylpyridine), poly(tert-butyl methacrylate) onto polystyrene to make a highly branched copolymer [3,4]. These amphiphilic arborescent copolymers may form a unimolecular micelle-like structure in a solvent selective for only the grafted chains and not for the polystyrene core.…”

Phase-Segregated Dendrigraft Copolymer Architectures

“…The synthesis of arborescent polystyrene-graft-poly(2-vinylpyridine) copolymers was initially achieved by coupling poly(2-vinylpyridinyl)lithium with chloromethylated polystyrene substrates of generations up to G2 in tetrahydrofuran with N,N,N′,N′-tetramethylethylenediamine (TMEDA) [23]. This reaction is analogous to Scheme 2(a), where the 1,1-diphenylethylene-capped polystyryllithium species are replaced with the "living" poly(2-vinylpyridinyl)lithium chains without capping.…”

“…The ability to control the solution properties of arborescent polyelectrolytes by varying parameters such as the length and the number of P2VP segments in the molecules is interesting for the design of pH-sensitive reversible gels with tunable properties such as the sol-gel transition point and the gel modulus [23].…”

Arborescent polymers and other dendrigraft polymers: A journey into structural diversity

“…2(b)]. The synthesis of arborescent copolymers containing either short or long corona side chains was demonstrated initially for arborescent polystyrene substrates terminally grafted with poly(ethylene oxide) (PEO) segments, 13 and for copolymers obtained by grafting polyisoprene 14 and poly(2-vinylpyridine) 15 side chains randomly onto chloromethylated arborescent polystyrene substrates. Coupling reactions of reactive macroanions with chloromethylated polystyrene substrates are clean and proceed in high yield, but the chloromethylation procedure suffers from serious limitations.…”