Paper Number
PO55                         My Program 

Session
Poster Session

Title
Chemical and thermal sensitivity of parabolic focal conic defects in concentrated surfactant solutions

Presentation Date and Time
October 16, 2024 (Wednesday) 6:30

Track / Room
Poster Session / Waterloo 3 & 4

Authors (Click on name to view author profile)

  1. Kaboolian, Matthew (Purdue University, School of Materials Engineering)
  2. Kelkar, Parth U. (Purdue University, School of Materials Engineering)
  3. Lindberg, Seth (Procter & Gamble Co.)
  4. Erk, Kendra A. (Purdue University, School of Materials Engineering)

Author and Affiliation Lines (in printed abstract book)
Matthew Kaboolian1, Parth U. Kelkar1, Seth Lindberg2 and Kendra A. Erk1
1School of Materials Engineering, Purdue University, West Lafayette, IN 47906; 2Procter & Gamble Co., West Chester, OH 45069

Speaker / Presenter 
Kaboolian, Matthew

Keywords
experimental methods; surfactants

Text of Abstract
The appearance of parabolic focal conic defects, pFCDs, have often been a passing comment in surfactant phase literature. However, there is intricacy to the formation and growth mechanisms behind pFCDs, which have not been well studied in concentrated surfactant solutions; including sodium lauryl ether sulfates (SLEnS) one of the most common surfactants in cleaning and personal care product. The goal of this study was to understand how much the degree of ethoxylation (n) in SLEnS influences the temperature catalyzed formation of pFCDs in concentrated 70 wt.% SLEnS in water for n = 1, 2, 3. The formation of pFCDs was characterized using temperature controlled cross-polarized birefringence microscopy and small angle x-ray scattering (SAXS). These methods revealed that pFCD formation followed an inverse dependence with increasing n. SLE1S had an onset temperature of pFCD formation of 49.3 °C and a complete conversion by 70.5 °C. While SLE2S and SLE3S had lower onset and complete temperatures of 42.5 – 58.7 °C and 40.6 – 44.0 °C, respectively. These onset and completion temperature ranges were supported by SAXS measurements which showed inflections in the bilayer spacing, over similar intervals. The changes in pFCD formation temperatures and bilayer spacing suggests that bilayer flexibility is extremely sensitive to the number of ethoxy groups. The ability to detect and control the formation of pFCDs in surfactant bilayers may provide a simple way to measure bilayer mechanical properties and, in the future, may allow for the creation of tunable microlenses for photolithography.