Aggregation Behavior Of Micelles Research Articles

Study on synthesis, properties, and aggregation behavior of sodium alkyl glycoside sulfate

In this work, sodium dodecyl and tetradecyl glycoside sulfate (APGS-Na) was synthesized by sulfating dodecyl and tetradecyl glycoside (APG1214) with chloro-sulfonic acid (CSA). The product was then characterized using FT-IR, 1H NMR, MS, and elemental analysis. Response surface methodology (RSM) was used to explore the sulfation modification conditions in order to achieve the maximum APG1214 conversion rate (84.79% with the molar ratio of CSA to APG1214: 2.17:1, reaction temperature: 16 °C, and reaction period: 2 h). Further studies were performed to establish the relationship between the pertinent structure and physicochemical characteristics, such as Krafft point, equilibrium surface tension, dynamic surface tension, aggregation behavior of micelles and lyotropic liquid crystals (LLCs), as well as application characteristics like foam property, emulsification, detergency, and irritability. The results demonstrated that the Krafft point of APGS-Na was below 0 °C, and the surface tension (γcmc ) was 39.4 mN·m−1 when the critical micellar concentration (CMC) was 2.40 g·L−1. At low concentration, the adsorption process was controlled by a diffusion step, different to a mixed kinetic-diffusion adsorption mechanism at high concentration, can form large size micelles and attractive LLCs in water. Moreover, the surfactant is nonirritant, with excellent foaming and decontamination capability. Accordingly, APGS-Na is expected to be widely used in diverse fields as a green anionic glycoside surfactant.

Synthesis and characterization of thermo-responsive supramolecular diblock copolymers

In this paper, we report the synthesis and characterization of a new thermo-responsive supramolecular amphiphiles diblock copolymer, methoxy poly (ethylene glycol)-block-Poly(N-isopropylacrylamide) (mPEG-b-PNIPAM). The mPEG with β-cyclodextrin (β-CD) group and the PNIPAM with adamantine (AD) group were synthesized, respectively, and mPEG-b-PNIPAM was then obtained by the host-guest inclusion between AD and β-CD. The structure and molecular weight of mPEG-b-PNIPAM was confirmed by 1H NMR and GPC measurements. At low temperature (T < 33 °C), the PNIPAM block is hydrophilic. With increasing temperature, the hydrophobicity the of PNIPAM block increases. This molecular feature leads to interesting aggregation behavior of micelles in aqueous solutions at different temperatures. The self-assembly was revealed by UV, DLS measurements, and TEM observations.

Self-consistent field theoretic simulations of amphiphilic triblock copolymer solutions: Polymer concentration and chain length effects

Using the self-consistent field lattice model, polymer concentration $\bar{\phi}_{{P}}$ and chain length $N$ (keeping the length ratio of hydrophobic to hydrophilic blocks constant) the effects on temperature-dependent behavior of micelles are studied, in amphiphilic symmetric ABA triblock copolymer solutions. When chain length is increased, at fixed $\bar{\phi}_{{P}}$, micelles occur at higher temperature. The variations of average volume fraction of stickers $\bar{\phi}_\textrm{co}^\textrm{s}$ and the lattice site numbers $N_\textrm{co}^\textrm{ls}$ at the micellar cores with temperature are dependent on $N$ and $\bar{\phi}_{{P}}$, which demonstrates that the aggregation of micelles depends on $N$ and $\bar{\phi}_{{P}}$. Moreover, when $\bar{\phi}_{{P}}$ is increased, firstly a peak appears on the curve of specific heat $C_V$ for unimer-micelle transition, and then in addition a primary peak, the secondary peak, which results from the remicellization, is observed on the curve of $C_V$. For a long chain, in intermediate and high concentration regimes, the shape of specific heat peak markedly changes, and the peak tends to be a more broad peak. Finally, the aggregation behavior of micelles is explained by the aggregation way of amphiphilic triblock copolymer. The obtained results are helpful in understanding the micellar aggregation process.