Self-Association in Water of Copolymers of Acrylic Acid and N-Dodecylmethacrylamide As Studied by Fluorescence, Dynamic Light Scattering, and Rheological Techniques

Abstract

The self-association of random copolymers of acrylic acid (AA) and N-dodecylmethacrylamide (DodMAm) with 5.1-28.4 mol % DodMAm contents (fDod) in water was investigated by fluorescence, quasielastic light scattering (QELS), and rheological methods as a function of fDod and pH. The copolymers exhibited a strong tendency for interpolymer association, forming micelle-like multipolymer aggregates. This is a striking contrast to the previous finding that random copolymers of 2-(acrylamido)-2-methylpropanesulfonate (AMPS) and DodMAm exhibited a strong tendency for intrapolymer association, forming unimolecular micelles. At pH 10, the AA/DodMAm copolymers with a smaller fDod formed multipolymer aggregates with a larger size, the size decreasing with increasing fDod. At pH 4, this trend was opposite; the size of the multipolymer aggregate increased with increasing fDod. Independent of fDod and pH, the size of the multipolymer aggregates increased with increasing polymer concentration (Cp). The association behavior and the nature of multipolymer aggregates of the AA/DodMAm copolymers with small fDod values (e9.1 mol %) were markedly different from those with larger fDod (g12.8 mol %). As the pH was decreased, the size of the multipolymer aggregate decreased when fDod e 9.1 mol % whereas it increased when fDod g 12.8 mol %. Independent of fDod, the mean aggregation number (Nagg) of dodecyl groups in one hydrophobic microdomain decreased with decreasing pH. Multipolymer aggregates formed from the AA/DodMAm copolymer of a small fDod (9.1 mol %) at high Cp were more dynamic in nature than those from the copolymer of larger fDod (22.4 mol %), the former showing shear rate dependent viscosity behavior while the latter did not. On the basis of the characterization data, multipolymer association models for the AA/DodMAm copolymers were proposed.

Amphiphilic Polymer Nanoparticles: Characterization and Assessment as New Drug Carriers

“…Essentially, the energy provided by heating was enough to weaken the hydrophobic interaction and cause dissociation of the polymer chains. Since the larger aggregate at high concentration corresponds to secondary association of individual micelles (associated unicore micelles),19 they are more compact and stable and do not undergo any change in their association properties in the range of the heating cycle.…”

“…Unlike block copolymers, they do not display any specific CAC values, but rather form micelles through hydrophobic interaction within a single polymer chain (intra‐molecular association) or between different polymer chains (inter‐molecular association) 15–17. Depending on the chemical structures these are known to form different types of micellar aggregates, such as unimer micelles, unicore multipolymer micelles, and polycore multipolymer micelles 18, 19. Since hydrophobic chains in such types of micelles are more tightly packed and less mobile in contrast to low‐molecular‐weight surfactants, these are very stable to dilution.…”

Hyperbranched (Meth)acrylates in Solution, Melt, and Grafted From Surfaces

“…Potentiometric titration curves (Fig. 9) suggest that the apparent pK a values (taken as the pH at 50% ionization) of the branched PAAs with a comonomer ratio g=10 and 100 are comparable to the corresponding value for linear PAA homopolymer of pK a,app @5.8 [98]. The branched PAA at g=2.5 become insoluble at pH≤4.7.…”

Hydrophobically Modified Sulfonated Polyacrylamides for IOR: Correlations between Associative Behavior and Injectivity in the Diluted Regime

“…Various techniques have been implemented among which viscosimetry [4][5][6][7][8][9][10][11][12], fluorescence [13][14][15][16], transmission, scanning and environmental scanning electron microscopy (TEM, SEM and ESEM) [16][17][18], 19 F NMR spectroscopy [19,20], neutron scattering [21][22][23][24] and Static and Dynamic Light Scattering (SLS and DLS) [14][15][16][25][26][27][28][29][30][31][32][33][34][35][36][37]. Theoretical approaches have also been proposed to describe HMWSP static [38,39] and dynamic [40] properties.…”

“…These results are consistent with DLS studies performed by other authors, in which two decay modes in diluted HMWSP solutions have also been reported and also associated to the presence of both single chain objects, with or without intramolecular hydrophobic bonds and multichain aggregates. This is in particular the case for Dai et al [25][26][27] working on Hydrophobically modified Alkali Soluble Emulsions (HASE) made of random copolymers of methacrylic acid and ethyl acrylate with 1 mol% of various ethoxylated alkyl hydrophobic monomers, Sato et al [15] working on random copolymers of acrylic acid and N-dodecylmethacrylamide at rather high molar fractions (5 to 30 mol%), Vidal et al [35] working on carboxymethylcellulose modified with 1 to 6 mol% randomly distributed N,N-dihexylamine side-groups and Alami et al [36], working on polyethylene oxyde endcapped with C12 chains. However, to our knowledge, DLS evidence of aggregates in diluted solutions of random HMWSP with SPAM backbones is reported here for the first time.…”