Evidence for helical structures in poly(1-olefin sulfones) by transmission electron microscopy

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Understanding polymer chain conformation in solution is crucial for predicting material properties.
• Previous dielectric measurements suggested differing solution conformations for polysulfones.

Purpose of the Study:

• To visualize the solution conformations of poly(1-tetradecene sulfone) and poly(cyclohexene sulfone) using transmission electron microscopy.
• To correlate microscopic observations with previous dielectric data.

Main Methods:

• Samples were prepared from dilute solutions (0.007% wt/vol) and rapidly freeze-dried.
• Vertical platinum-carbon (Pt-C) replication was employed for enhanced imaging.
• Transmission electron microscopy (TEM) was used to analyze the replicated polymer structures.

Main Results:

• Poly(1-tetradecene sulfone) displayed short helical regions with irregular turns and apparent helix diameters of 16-22 A.
• Side chains (n-C12H25) were occasionally visible on extended chain sections of poly(1-tetradecene sulfone).
• Poly(cyclohexene sulfone) appeared as individual, Pt-C-coated chains (10-12 A diameter) without discernible side-chain projections.

Conclusions:

• The observed helical structures in poly(1-tetradecene sulfone) and linear chains in poly(cyclohexene sulfone) directly reflect their inferred solution conformations.
• TEM imaging provides direct visual evidence supporting previous dielectric studies on polysulfone solution behavior.