Core and Corona Structure of Mixed Polymeric Micelles

Abstract

Mixed polymeric micelles have been prepared from aqueous solutions of poly(2-(dimethylamino)ethyl methacrylate)-block-poly(glyceryl methacrylate), PDMAEMA45-b-PGMA90, and poly(acrylic acid)-block-poly(acrylamide), PAA42-b-PAAm417, through complex coacervation of the oppositely charged blocks. Rather monodisperse, spherical aggregates are formed with a R h = 15.2 ± 0.4 nm. The extent of chain mixing between poly(acrylic acid) and poly(2-(dimethylamino)ethyl methacrylate) in the micellar core and poly(acrylamide) and poly(glyceryl methacrylate) in the micellar corona has been investigated by 2D 1H NMR NOESY experiments. The presence of cross-peaks for protons in different core and corona blocks indicates that the two blocks are in close proximity (<0.5 nm) and micelles are formed in which both core and corona are mixed.

Electrostatic hierarchical co-assembly in aqueous solutions of two oppositely charged double hydrophilic diblock copolymers

“…A more detailed introduction on the technique can be found in a previous publication [11]. 1 H NMR spectra of the micellar solutions were recorded at 298 K on a Bruker AMX-500 spectrometer, operating at 500 MHz, located at the Wageningen NMR Centre.…”

“…In sharp contrast to traditional polymeric micelles consisting of amphiphilic polymers, C3Ms may be in thermodynamic equilibrium [1,11]. To test whether this also applies to the system under investigation, we have compared micellar sizes for C3Ms of P2MVP 38 -b-PEO 211 and PAA 305 -b-PVOH 184 at the preferred micellar composition prepared in a one-step fashion by simply mixing the polymer solutions and those obtained in the corresponding LS-T experiment, using the same stock solutions (Table 1).…”

“…Naturally, the tendency to phase separate is tuneable with parameters influencing the electrostatic interaction between the two (macro)molecules, such as ionic strength, mixing fraction, and pH in case of weak acids and/or bases. Moreover, the associative phase separation can be restricted to the colloidal domain by attaching a solvophilic group to one or both of the molecules, resulting in mixed aggregates, such as vesicles [2,3] or micelles [2][3][4][5][6][7][8][9][10][11][12][13]. As complex coacervation is the governing principle in the formation of this type of colloids, we employ the term complex coacervate core micelles (C3Ms) [9][10][11][12].…”

“…Moreover, the associative phase separation can be restricted to the colloidal domain by attaching a solvophilic group to one or both of the molecules, resulting in mixed aggregates, such as vesicles [2,3] or micelles [2][3][4][5][6][7][8][9][10][11][12][13]. As complex coacervation is the governing principle in the formation of this type of colloids, we employ the term complex coacervate core micelles (C3Ms) [9][10][11][12]. Other equivalent terms in use are polyion complex micelles [2][3][4][5], block ionomer complexes [6,7], or interpolyelectrolyte complexes (IPEC) [8].…”

“…Clearly, the force balance is delicate: strongly segregating neutral blocks cannot be employed, as they might lead to dissociation of the micelles, while on the other hand too compatible hydrophilic blocks will result in a mixed corona. This concept has been explored in a series of recent papers [11,12,[24][25][26] where we observed that a pair of relatively miscible hydrophilic blocks yielded spherical C3Ms with a mixed shell and a pair of relatively immiscible hydrophilic blocks yielded ellipsoidal micelles with a laterally segregated corona (Janus-micelles). A combination of poly(2-(N,N-dimethylamino)ethyl methacrylate)-blockpoly(glyceryl methacrylate), PDMAEMA 45 -b-PGMA 90 and poly(acrylic acid)-block-poly(acrylamide), PAA 42 -bPAAm 417 resulted in spherical micelles with a mixed corona [11], while the Janus-type segregation was achieved in aqueous mixtures of poly(N-methyl-2-vinyl pyridinium iodide)-block-poly(ethylene oxide), P2MVP 42 -b-PEO 446 and poly(acrylic acid)-block-poly(acrylamide), PAA 42 -bPAAm 417 [12,24,25].…”