The light scattering peak (LS peak) near the surfactant critical micelle concentration (cmc) demonstrates that low hydrophobic dopant levels can cause supramolecular assembly of surfactants into metastable structures much more massive than dopant-free micelles. These supramicellar assemblies (SA) exist over the entire LS peak region, which extends from above the cmc down to well below the cmc. Dodecanol (D) was the dopant, and sodium dodecyl sulfate (SDS) and dodecyl trimethyl ammonium bromide (DTABr) were the surfactants in this work. Well above the cmc dopant is solubilized by micelles. The SA appear above the cmc, dependent on dopant level and solution ionic strength, as seen by an abrupt increase in LS. Hence, the micelles do not simply release their hydrophobic payload at the cmc; rather, the dopant causes a morphological change from normal micelles above the LS peak concentration regime into SA as the LS regime is entered from above the cmc. Below the cmc the LS peak has a cutoff concentration corresponding to the solubility limit of dodecanol in water, which can be termed a "critical supramicellar assembly concentration" (csac). A three-component model is proposed that self-consistently yields maximum micellar dopant loading, SA mass, and dopant solubility in solution. The constancy of SA molar mass under widely different ionic strength and dopant levels conditions is surprising and not currently understood.

Abstract:A new Automatic Continuous Online Monitoring of Polymerization reactions (ACOMP) system has been developed with multiple light scattering and viscosity detection stages in serial flow, where solution conditions are different at each stage. Solution conditions can include ionic strength (IS), pH, surfactants, concentration, and other factors. This allows behavior of a polymer under simultaneous, varying solution conditions to be monitored at each instant of its synthesis. The system can potentially be used for realtime formulation, where a solution formulation is built up additively in successive stages. It can also monitor the effect of solution conditions on stimuli responsive polymers, as their responsiveness changes during synthesis. In this first work, the new ACOMP system monitored light scattering and reduced viscosity properties of copolymeric polyelectrolytes under various IS during synthesis. Aqueous copolymerization of acrylamide (Am) and styrene sulfonate (SS) was used. Polyelectrolytes in solution expand as IS decreases, leading to increased intrinsic viscosity (η) and suppression of light scattering intensity due to electrostatically enhanced second and third virial coefficients, A 2 and A 3 . At a fixed IS, the same effects occur if polyelectrolyte linear charge density (ξ) increases. This work presents polyelectrolyte response to a series of IS and changing ξ during chemical synthesis.Keywords: ACOMP; online monitoring; copolymeric polyelectrolytes; light scattering; viscosity Background and MotivationThis work introduces a new version of the Automatic Continuous Online Monitoring of Polymerization reactions (ACOMP) system ("second generation ACOMP") whose aim is to monitor the onset and evolution of stimuli responsive behavior, under multiple simultaneous solution conditions, during the synthesis of stimuli responsive polymers (SRP). SRP is a vast area of modern polymer science and engineering, aimed at producing polymers that can respond to such stimuli as temperature, radiation, and solution conditions such as pH, ionic strength, polymer concentration, presence of such agents as surfactants, nanoparticles, hydrophobic species, etc. The types of responses that can occur in response to these stimuli include coil/globule phase transitions, polymer coil expansion or shrinkage, micellization, aggregation, and other forms of spontaneous self-assembly.These next-generation materials are expected to have applications in medicine, sensors, self-healing materials, and environmental remediation [1][2][3][4][5]. Hydrogels ofpoly(N-isopropylacrylamide), for example, have a lower critical solution temperature (LCST), near body temperature, which makes it a candidate for drug delivery applications in which the NIPAM-based polymer releases its medical

Certain hydrophobic dopants in surfactant solutions cause massive "supramicellar assemblies" (SAs) to form near the critical micelle concentration (CMC), characterized by a light-scattering peak (LSP). The SAs are large, dynamic, metastable nanostructures composed of surfactant/ dopant. Here, a water-soluble polymer, poly(vinylpyrollidone) (PVP) suppresses SA formation in sodium dodecyl sulfate (SDS) solutions doped with dodecanol, but increases solution instability. Binding of SDS to PVP is stronger than micellization in the LSP regime, refl ected in a decreased SA population and a dramatic reduction and inversion of Rayleigh scattering I R as [PVP] increases, since SAs are much more massive than PVP/SDS association structures. Above the LSP regime, SAs no longer exist and thus I R must re-establish its order, increasing with increasing [PVP]. This causes a cross-over in I R vs [SDS] with an "iso-scattering point," where I R converges at a specifi c [SDS]. Weak LSP suppression is found using dodecyl tri ethyl ammonium bromide (DTAB). Poly(ethylene oxide) (PEO)'s effect is small compared with PVP. electrically charged when SDS binds to it and shows polyelectrolyte-like behavior.To the authors' knowledge, few reports have considered the effect of polymers on the interaction between surfactants and dopants. [18][19][20] Our recent report [ 21 ] shows that certain hydrophobic dopants and surfactants in solution lead to formation of large metastable "supramicellar assemblies" (SAs) in a concentration regime from near the critical micelle concentration (CMC) down to the dopant's solubility limit; i.e., the surfactant micelles do not merely release their hydrophobic payload the CMC, but remain associated with it. This property may help understanding of dispersant, e.g., those used in oil spills, where it is often thought that the surfactant will release the oil below the CMC and re-coalesce, diminishing the effectiveness of the dispersant. The SA shows that is not necessarily the case. Here, it was found that adding PVP to solutions containing SAs can completely suppress the formation of SAs from near the CMC down to the CAC. Many industrial and medical applications involve the use of self-assembly of surfactants, which makes the study of the polymeric