Pluronic-based lamellar phases: influence of polymer architecture on bilayer bending elasticity

ABSTRACT

In this study, we investigate the influence of the block copolymer architecture on the bending elasticity of polymer-rich lamellar phases. In detail, we study the polymer-rich system water/o-xylene/Pluronic triblock copolymer/C${}_8$TAB and change the polymer while keeping the mass ratios constant. We use neutron spin echo measurements (NSE) to determine κ. With the measurements we determine the relaxation rate ${\mathrm{\Gamma }}_{q_z,ZG}$ of the bilayer bending mode and subsequently calculate the bilayer bending modulus κ using the Zilman-Granek approach [Zilman et al., Phys. Rev. Lett. 77, 4788–4791 (1996)]. Moreover, we have investigated the lamellar phases via small-angle X-ray scattering (SAXS) and have analysed the data with the modified Caillé theory to obtain the Caillé parameter η. Based on κ the bulk compression modulus $\overline{B}$ can be calculated. Increasing values of κ are found with increasing EO and PO block size in the range of 3.8 to 13.4 $k_{\mathrm{B}}$T. The computed values of $\overline{B}$ are in the range of 10${}^3$ to 10${}^5$ Pa.

GRAPHICAL ABSTRACT

Keywords:

• Pluronics
• NSE
• SAXS
• lamellar phase
• bending elasticity

Acknowledgments

We gratefully acknowledge the BASF for providing the used Pluornics free of charge.

Data

The data which were collected during our beamtime at the ILL are available using the DOI: 10.5291/ILL-DATA.9-10-1541.

Disclosure statement

No potential conflict of interest was reported by the author(s).