The effect of degree of polymerization on intra- and interchain micellization of a tail-type cationic polysoap

Abstract

We have used Reversible Addition Fragmentation chain Transfer (RAFT) to polymerize the T-type surfactant monomer a,u-methacryloylundecyltrimethylammonium bromide (MUTAB) to various degrees of polymerization, and thereby investigate how its self-assembly is affected. Small-angle neutron scattering (SANS) shows that the interchain aggregation into micelles with an approximately constant number of MUTAB monomer equivalents occurs at low degrees of polymerization, but that micelle elongation occurs when the degree of polymerization exceeds a critical value. In this regime interchain aggregation gives way to intrachain assembly into unimolecular or "unimer" micelles. As with conventional cationic surfactant solutions, addition of salicylate produces long, worm-like micelles containing many amphiphilic polymer chains at all degrees of polymerization. Oscillatory rheology reveals a transition from scission-to reptation-dominated relaxation as increasing polymer chain length also increases the distance between potential scission points. The measured relaxation times lie in the range of hundredths to a few secondsthus demonstrating the rapidly equilibrating nature of these micellar systems even at the highest degrees of polymerization achieved.

Aqueous Polymeric Hollow Particles as an Opacifier by Emulsion Polymerization Using Macro-RAFT Amphiphiles

“…The micelle morphology can also change during polymerization of small-molecule surfactants into polysoaps. 54,55 In the present case, the packing parameter changes during emulsion polymerization as the Sty chain grows. At the beginning of the reaction, the hydrophobic polymer chain consists of only ∼49 Sty monomers compared to 117/58 BA/ deprotonated AA in the hydrophilic block of the macro-RAFT copolymers.…”

“…These depend on the ratio of the area covered by the hydrophilic heads to the length/volume occupied by the hydrophobic tails, which in turn depend on the degrees of polymerization of the two blocks and solvent quality, at least for the polar block. The micelle morphology can also change during polymerization of small-molecule surfactants into polysoaps. , …”

Cationic Hydrolytically Degradable Flocculants with Enhanced Water Recovery for Oil Sands Tailings Remediation

“…PCL n ChMA macromonomers can be classified as tail‐type polymerizable surfactants (surfmers) because they are amphiphiles that possess a cationic head and contain a vinyl group within the hydrophobic tail . In general, the micellar structure undergoes extensive reorganization during surfmer polymerization, and the resulting polyelectrolytes can reach high MW due to compartmentalization of the polymerizeable group . As depicted by Scheme , PCL n ChMA surfmers form micelles in aqueous solution (CMC determined via Figure S5, Supporting Information); the rapid consumption of 10 wt% PCL 3 ChMA during a batch radical homopolymerization at 50 °C in D 2 O was demonstrated in situ using 1 H‐NMR, with 90% conversion reached almost twice as fast as AM under identical conditions (see Figure S6, Supporting Information).…”

Pulsed laser studies of cationic reactive surfactant radical propagation kinetics

“…The particle size distributions for 10 wt% macromonomer aqueous solutions at 25 and 70 °C, shown by Figure S7 provide evidence for PCL2ChMA compartmentalization, where the bimodal intensity scattering could indicate that PCL2ChMA micelles may have non-spherical geometries, 49 as was observed for polymer produced by PCLnChMA homopolymerization 47 and as has been documented for micelles of the chemically similar MUTAB surfmer. [18][19][20] In addition, the dispersion parameters summarized by Table S2 highlight the dynamic nature of the system; in particular, the decreasing as well as a measured decrease in the EA for kp of partially and fully ionized MAA aqueous homopropagation systems. 37 As a further indication that PCL2ChMA aqueous propagation is prominent at 85 °C, the secondary (non-PLP) peaks of the MMDs of Figure 3 shift with increasing NaCl concentrations from logM = 7.0 towards logM = 5.7 and then to logM = 4.5.…”

“…while at intermediate conversions rod-like mixed polymer/monomer micelles (with length and cross-section radius ranging roughly from 200-3000 Å and 10-30 Å, respectively) coexist in dynamic equilibrium with unpolymerized micelles. [18][19][20] The structures of poly(MUTAB) systems are also sensitive to environmental factors, responding dynamically and reversibly to temperature, counterion, and salt addition. 21 Furthermore, as suggested by Hamid and Sherrington, 22 cationic tail-type surfmers, such as MUTAB, can adopt a "looped" or "hairpin" conformation where both cationic head and polar methacrylate tail reside at the micelle/water interface.…”