Novel block-comb/graft copolymers with the macromonomer strategy and anionic polymerization

The following block-comb/graft copolymers of styrene (S), isoprene (I), and butadiene (B)-PS-b-(PB-g-PB), PS-b-(PB-g-PB)-b-PS, (PB-g-PB)-b-P2VP, (PS-g-PB)-b-(PI-g-PS), (PS-g-PB)-b-(PI-g-PS)-b-(PB-g-PI), (PS-g-PB)-b-(PI-g-PS)- b-(PB-g-PI)-b-(PI-g-PS)-b-(PS-g-PB), and (PS) 2(PB-g-PB) [where PS is polystyrene, PB is polybutadiene, P2VP is poly(2-vinylpyridine) (2VP), and PI is polyisoprene] - were synthesized with the macromonomer strategy and anionic polymerization high-vacuum techniques. The synthetic approach involves the synthesis and block copolymerization of styrenic macromonomers in situ without isolation. The prepared samples were characterized by size exclusion chromatography with a differential refractometer detector, size exclusion chromatography with a two-angle laser light scattering detector, and NMR spectroscopy. © 2005 Wiley Periodicals, Inc

Micelles of poly(isoprene-b-2-vinylpyridine-b-ethylene oxide) terpolymers in aqueous media and their interaction with surfactants

Well-defined poly(isoprene-b-2-vinylpyridine-b-ethylene oxide) (PI-P2VP-PEO) triblock terpolymers were synthesized by anionic polymerization high-vacuum techniques. The terpolymers formed spherical three-layer (onion-type) micelles in neutral and acidic pH aqueous media as evidenced by static and dynamic light scattering. In pure water, kinetically frozen micelles with a core composed of a soft PI inner part and a hard P2VP outer shell and protected by a neutral PEO corona were formed. In acidic media the core was formed by the soft PI hydrophobic segment, whereas the corona consisted of an inner cationic polyelectrolyte P2VPH+ part and an outer PEO shell. The aggregation numbers were found to be high in all cases, due to the high hydrophobicity of the core-forming blocks. In the latter case an increase in size was observed due to the electrostatic repulsions between the P2VPH + chains in the inner part of the corona, which is also responsible for the lower aggregation numbers observed in the acidic solutions. The interaction of these onion-type micelles with cationic (DTMAB) and anionic (SDS) surfactants led to the formation of mixed polymer/surfactant aggregates. Their structural characteristics could be varied by combining changes in surfactant type and concentration, solution pH and type of electrostatic interaction, leading to interesting, block-copolymer-based, environmentally responsive colloidal systems

Origin of glass transition of poly(2-vinylpyridine). A temperature- and pressure-dependent dielectric spectroscopy study

The dynamics of poly(2-vmylpyridine) (P2VP) have been studied as a function of temperature (in the range from 123 to 453 K), pressure (0.1-270 MPa), and molecular weight (1.1 × 108-3.0 × 10 4 g/mol), using dielectric spectroscopy (DS) within the frequency range from 10-2 to 106 Hz. Structural methods (wide-angle X-ray scattering) have been employed in parallel with tnermodynamic methods (pressure-volume-temperature). Three relaxation processes were found: two above the glass temperature (Tg) associated with the segmental (α-) process and a slower process with an apparent activation volume comparable to the monomer volume and another well below Tg, with an Arrhenius T dependence (β-process). The results from the dynamic study combined with the thermodynamic results revealed that both decreasing thermal energy and insufficient volume lead to glass formation at lower temperatures, with the former having the stronger effect at temperatures near Tg (i.e., values of the ratio of apparent activation energies at constant volume and constant pressure in the range QV/QP ∼ 0.6-0.85 for the different temperatures and pressures investigated)