Chemical analysis and aqueous solution properties of charged amphiphilic block copolymers PBA-b-PAA synthesized by MADIX.
We have linked the structural and dynamic properties in aqueous solution of amphiphilic charged diblock copolymers poly(butyl acrylate)-b-poly(acrylic acid), PBA-b-PAA, synthesized by controlled radical polymerization, with the physico-chemical characteristics of the samples. Despite product imperfections, the samples self-assemble in melt and aqueous solutions as predicted by monodisperse microphase separation theory. However, the PBA core are abnormally large; the swelling of PBA cores is not due to AA (the Flory parameter chi(PBA/PAA), determined at 0.25, means strong segregation), but to h-PBA homopolymers (content determined by liquid chromatography at the point of exclusion and adsorption transition, LC-PEAT). Beside the dominant population of micelles detected by scattering experiments, capillary electrophoresis CE analysis permitted detection of two other populations, one of h-PAA, and the other of free PBA-b-PAA chains, that have very short PBA blocks and never self-assemble. Despite the presence of these free unimers, the self-assembly in solution was found out of equilibrium: the aggregation state is history dependant and no unimer exchange between micelles occurs over months (time-evolution SANS). The high PBA/water interfacial tension, measured at 20 mN/m, prohibits unimer exchange between micelles. PBA-b-PAA solution systems are neither at thermal equilibrium nor completely frozen systems: internal fractionation of individual aggregates can occur.
Jacquin
M
M
Complex Fluids Laboratory, CNRS UMR 166, 350 George Patterson Blvd, Bristol, PA 19007, USA.
Muller
P
P
Talingting-Pabalan
R
R
Cottet
H
H
Berret
J F
JF
Futterer
T
T
Théodoly
O
O
D000179:Acrylates / Q000138:chemical synthesis* / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D008823:Micelles; D010316:Particle Size; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry; D012996:Solutions / Q000737:chemistry; D014867:Water / Q000737:chemistry
D000179:Acrylates; D008823:Micelles; D011108:Polymers; D012996:Solutions; C525619:poly(butyl acrylate)-b-poly(acrylic acid); D014867:Water; C032490:n-butyl acrylate; C036658:acrylic acid