The interaction between a double-hydrophilic comb copolymer with the polyanionic backbone poly[methacrylic acid-statpoly(ethylene glycol) methyl ether methacrylate] (PMAA−PEGMA) and the cationic surfactant N-dodecylpyridinium chloride (DPCl) was studied in alkaline aqueous solutions by using a combination of light and X-ray scattering techniques, covering 5 orders of magnitude in space (the q vector range from 10 −5 to 5 nm −1 ) and time (from milliseconds to several hours). The results showed that the polyelectrolyte−surfactant (PE−S) complex of PMAA−PEGMA and DPCl forms micrometer-sized coacervate particles containing collapsed PMAA−PEGMA chains with attached and densely packed DPCl micelles. Time-resolved SAXS measurements coupled with a stopped-flow apparatus revealed that the phase separation of the PE−S complex into a coacervate phase occurred in <25 ms after mixing the polyelectrolyte and the surfactant. Thus, microphase separation was faster than the self-assembly of DPCl into densely packed micelles. The terminal stages of polyelectrolyte−surfactant coacervation were dictated by the Ostwald ripening of the droplets in the time range of hours.

Comicellization of poly(N-isopropylacrylamide) with dodecyl and carboxyl terminal groups (mPNIPAm) with cationic surfactant N-dodecylpyridinium chloride was studied by scattering techniques (light scattering, SAXS), isothermal titration calorimetry, fluorescence spectroscopy, and coarse-grained simulations using dissipative particle dynamics (DPD) as a function of charge ratio of N-dodecylpyridinium (DP + ) ions to mPNIPAm terminal carboxylate groups, Z = [DP + ]/[COO − ]. While both experimental results and DPD data indicate that up to Z = 2 tails of the surfactant enter and swell the dodecyl core of mPNIPAm micelles, the further increase in the size of the core for Z > 2 caused by the dehydration and collapse of inner parts of PNIPAm chains observed by SAXS is not reproduced by DPD simulations. Nevertheless, the study demonstrates that the simplified coarse-grained model can account for hydrogen bonding and elucidate the mechanism of comicellization. The study shows that the electrostatic interactions modify appreciably the behavior of mPNIPAm, but the assembly with cationic surfactant is governed by hydrophobic interactions.

We report here the influence of hydrophobic terminal groups from RAFT chain transfer agent 4-cyano-4-[(dodecylsulfanylthiocarbonyl) sulfanyl]pentanoic acid on the coassembly behavior of two oppositely charged double-hydrophilic block polyelectrolytes (DHBPs), poly{[2-(methacryloyloxy)ethyl]trimethyl ammonium iodide}-b-poly(N-isopropyl acrylamide) (QPDMAEMA-PNIPAm), with the dodecyl group at the end of the PNIPAm block, and poly(acrylic acid)-b-poly(N-isopropyl acrylamide) (PAA-PNIPAm). The co-assembly process was investigated using dynamic light scattering (DLS), differential scanning calorimetry (DSC), time-resolved small-angle X-ray scattering (SAXS), and cryo-transmission electron microscopy (TEM). The terminal dodecyl group of QPDMAEMA-PNIPAm induced hydrophobic association of PNIPAm coronas of QPDMAEMA-PNIPAm/PAA-PNIPAm core−corona particles into micrometer-sized aggregates. In ca. 2 s after mixing the DHBPs, the aggregates formed an ordered structure with constant distances (∼30 nm) between interpolyelectrolyte complex cores of the core−corona particles. This paper thus shows that a modification of double-hydrophilic block polyelectrolytes by low-molecular-weight hydrophobic terminal groups is a simple route for preparation of nanostructured networks of physically cross-linked nanoparticles with potential application as containers for encapsulation and delivery of multivalent ions.

Here we report on the synthesis of dumbbell-like linear-dendritic copolymers based on polyethylene glycols bearing aspartic dendrons with terminal amino and carboxylic groups. The ionic complexes of such oppositely charged...

Structure and dynamics of an anionic comb polyelectrolyte poly[methacrylic acid-stat-poly(ethylene glycol) methyl ether methacrylate] (PMAA−PEGMA) and a cationic surfactant N-dodecylpyridinium chloride (DPCl) in coacervate emulsion formed by electrostatic complexation of PMAA−PEGMA and DPCl were followed by a combination of diffusion-ordered and nuclear Overhauser effect NMR spectroscopies (DOSY and NOESY NMR), small-angle neutron scattering (SANS), and neutron spin echo (NSE) spectroscopy. The measurements were conducted for various charge ratios Z of the number of DPCl positive charges to the number of PMAA−PEGMA negative charges. NMR spectra showed splitting of signals caused by partitioning of both PMAA−PEGMA and DPCl between the bulk aqueous phase and coacervate particles formed at Z > 0.7, with much slower diffusion of both the polymer and surfactant in the coacervate phase. SANS measurements revealed the formation of two types of DPCl micellar structures in the system: (i) Small elongated micellar aggregates forming the PE−S complex with PMAA−PEGMA chains. These structures exhibited fast diffusion and weak NOESY contacts of DPCl heads with PEGMA side chains. (ii) Large aggregates of densely packed micelles forming the PE−S complex with PMAA−PEGMA chains. These structures exhibited slow diffusion and strong NOESY contacts of DPCl heads with PEGMA side chains. The difference in dynamics between the two types of DPCl aggregates was confirmed by NSE, showing that apparent diffusion coefficients, D app (q), in the high q region, 1.1−2.0 nm −1 , dominated by scattering from densely packed DPCl micelles were much lower (hydrodynamic radius, R H > 10 2 nm) than those in the low q region, 0.2−1.1 nm −1 , dominated by scattering from small elongated aggregates of DPCl micelles (R H of ca. 4 nm). NSE measurements thus confirmed that densely packed DPCl micelles were present in large aggregates, while the scattering contribution in 0.2−1.1 nm −1 originated from small elongated micellar aggregates in the bulk solution.