The association of octadecyl-end-capped poly-(sodium 2-acrylamido-2-methylpropanesulfonates) in water and salt solutions: A study by fluorescence spectroscopy and isothermal titration calorimetry

Abstract

Steady-state fluorescence spectroscopy and isothermal titration calorimetry (ITC) have been used to study the aggregation in aqueous solutions of poly-(2-acrylamido)-2-methylpropanesulfonic acids, sodium salt mono-endcapped with either N,N-di-n-octadecyl or N-4-[(1-pyrenyl)butyl]-N-n-octadecyl which were prepared by free radical polymerization of 2-(acrylamido)-2-methylpropane sulfonic acid (AMPS) initiated with the azo compounds, 4,4'-azobis{cyano-N,N-di-n-octadecyl}pentanamide and 4,4'-azobis{cyano-N,N-[4-(1-pyrenyl)butyl]-n-octadecyl}pentanamide, respectively. Both techniques indicate the occurrence of multimolecular aggregates in solutions of the polymers in water and in 0.2 M NaCl. The concentration range for aggregation is about 1-14 mmol AMPS l −1 (0.5-2.7 g l −1 ) in 0.2 M NaCl and the enthalpy of micellization, estimated from ITC data, is ∼100 J [mol AMPS] −1 . The accessibility of the chromophores to neutral molecules and to cationic species was assessed by quenching of fluorescence with nitromethane and thallium nitrate, respectively. The association of the mono-endcapped polymers is compared to that of PAMPS derivatives carrying hydrophobic groups randomly attached along the chain.

Synthesis of a Cylindrical Micelle from Hydrophilic Polymers Connected with a Single Supramolecular Structure-Directing Unit

“…To examine the validity of the hypothesis on greater stability of the cylindrical micelle over spherical aggregates, we examined their concentration-dependent disassembly by isothermal calorimetry (ITC) studies. ,, A freshly prepared solution of P1 in 10% THF/H 2 O ( c = 2.5 mg/mL) was injected in the ITC cell (Figure a). The concentration was adjusted in such a way so that for initial few injections, the concentration of the polymer in the cell reached below its critical aggregation concentration (CAC) and thus the heat change could be attributed to the heat of dissociation.…”

A Look at the Thermodynamics of the Association of Amphiphilic Polyelectrolytes in Aqueous Solutions: Strengths and Limitations of Isothermal Titration Calorimetry

“…Critical Aggregation Concentration (cac) and Enthalpy of Demicellization ( Δ H demic ). Discussed first are the results obtained for the end-modified sample (C 18 ) 2 -PAMPS, a polymer forming multipolymeric micelles . In a typical experiment, aliquots of a concentrated aqueous polymer solution (20 g L -1 ) are titrated at constant temperature into an aqueous NaCl solution of same electrolyte concentration.…”

Structurally controlled “polysoaps” via RAFT copolymerization of AMPS and n-dodecyl acrylamide for environmental remediation

“…Of special note were the early owerlike micelle model [21][22][23] and second and third order unimeric micelle models subsequently developed by Morishima and coworkers. [24][25][26][27][28] Hydrophilic units could be non-ionic, 29 cationic, [30][31][32] anionic 26,28,[33][34][35][36] or zwitterionic, [37][38][39][40][41] while hydrophobic units could be varied from hydrocarbons with different chain lengths 23,26,28,36,42 to aromatic, vinyl ether, and even stimuli-responsive ones. 43 Numerous photophysical probes and labels such as pyrenyl, 20,27,[44][45][46] naphthyl, 26,28,34,47,48 dansyl groups, 35 and others 49 have been used to investigate the behavior of domain forming (co)polymers.…”