Small Angle Neutron Scattering Study of Polyelectrolyte Conformation Incorporated into Hybrid Threadlike Micelles under Strong Shear Flows

Abstract

A small angle neutron scattering study revealed that polyelectrolytes, sodium salts of partially sulfonated polystyrenes with narrow distributed molar masses of Mn = 27 x 10(3) and 340 x 10(3), which were incorporated into hybrid threadlike micelles formed with cetyltrimethylammonium bromide in aqueous (deuterium oxide) solutions at a quiescent state, behaved as rigid rods with lengths of 16 and 200 nm and the same radius of 2.3 approximately 2.4 nm, respectively. Under strong shear flows at shear rates much higher than the reciprocal of the mechanical relaxation time for the solution, the formed hybrid threadlike micelles were highly orientated to the shear flow axis owing to the generation of a shear induced liquid crystalline phase. The polyelectrolytes incorporated into the highly orientated micelle also maintained essentially the same conformation as those in the randomly orientated micelles in a quiescent state even at high shear rates.

Formation and Physicochemical Features of Hybrid Threadlike Micelles in Aqueous Solution

“…These L and r values are given in Table 1. The r value obtained coincides with that calculated from the slope of a crosssection plot of lnA C H T U N G T R E N N U N G {I coh (x D )q} versus q 2 , [32,33] and that evaluated from the TEM image. [30] These suggest that the PA C H T U N G T R E N N U N G (St/NaSS) molecules are incorporated into the hybrid threadlike micelles with the same radius of r, irrespective of M n .…”

“…Figure 1 shows typical examples of combinations of surfactants and polymers that form long hybrid threadlike micelles. [30][31][32][33] An aqueous system of the cationic surfactant CTAB and poly(styrene-ran-sodium styrenesulfonate) (PA C H T U N G T R E N N U N G (St/NaSS)) and that of the anionic surfactant sodium tetradecylsulfate (NaC 14 S) and poly(N,N-diallyl-N-methylamine-ran-N,N-diallyl-N-ethyl-Nmethylammmonium bromide) (P(DAM/DAEMBr)) form the hybrid threadlike micellar systems, CTAB: ly. [34] In these systems, the electrostatic interaction between the surfactants and polymers was carefully controlled by altering the degree of sulfonation (x S ), of PA C H T U N G T R E N N U N G (St/NaSS) in CTAB:PA C H T U N G T R E N N U N G (St/ NaSS)/W or the degree of quarternization (x q ), of P(DAM/ DAEMBr) in NaC 14 S:P(DAM/DAEMBr)/W.…”

“…[46] Small-angle neutron scattering (SANS) measurements on the hybrid threadlike micellar system including both normal and deuterated polymers provides conformational information about the polymers incorporated in hybrid threadlike micelles. [32,33] We prepared hybrid threadlike micelles consisting of normal and deuterated polyelectrolytes, PA C H T U N G T R E N N U N G (St/NaSS) and P-A C H T U N G T R E N N U N G (St/NadSS), bearing the same M n and x S values, and CTAB in , and x D2 , as given by Equation (1) [32,33,47,48] with the parameters: Avogadro's number (N A ), the number density of the examined polymer (N d ), the degree of polymerization (Z), the average partial monomer molar volume " Figure 3 shows the q dependence of P 1 (q) for the CTAB:PA C H T U N G T R E N N U N G (St/ NaSS):PA C H T U N G T R E N N U N G (St/NadSS)/D 2 O system with the two M n at 25 8C. The solid lines in Figure 3 represent the theoretical prediction for the particle scattering factors for rigid rods [49] with a length of L = 200 nm and a radius of r = 2.3 nm for the CTAB:PA C H T U N G T R E N N U N G (St/ NaSS):PA C H T U N G T R E N N U N G (St/NadSS)/D 2 O system with M n = 3.…”

Effect of the salt-induced micellar microstructure on the nonlinear shear flow behavior of ionic cetylpyridinium chloride surfactant solutions

“…This finding is in line with many examples of complex systems, where such additional stress relaxation mechanisms cannot be detected through simple rheology. Examples include blends of architecturally different polymers with strongly disperse times [50][51][52][53]. In these systems, depending on the concentration of the various structures, the hierarchical relaxation mechanism of the different characters could be hidden in a rheological measurement, while showing up clearly in scattering experiments.…”

Scattering from polymer-like micelles

“…Recent reports continue to demonstrate the solution conditions of these aggregates [37,38] and how robust the aggregates are to concentration [39] and adsorption at an interface [40,41]. A similar system has been reported with a different polyelectrolyte (partially sulfonated polystyrene rather than fully carboxylated polystyrene) prepared from premade polyelectrolyte rather than counterion polymerization [42,43]. Solubilization of a conjugated polyelectrolyte was carefully characterized in a recent report with interesting results on the ability of a wormlike micelle, in this case formed from nonionic surfactant, to isolate polymer chains [44].…”