Quantification Characterization of Hierarchical Structure of Polyurethane by Advanced AFM and X-ray Techniques

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Polyurethane (PU) exhibits microphase separation, crucial for tunable properties.
• Quantifying this microphase separation in PU remains a challenge.
• Understanding structure-property relationships in PU is vital for advanced applications.

Purpose of the Study:

• To develop and apply a systematic method for quantifying microphase separation in polyurethane.
• To investigate the influence of chain extender and cross-linking agent ratios on PU's microphase separation.
• To elucidate the hierarchical structure of polyurethane and its relation to mechanical properties.

Main Methods:

• Atomic Force Microscopy (AFM) nanomechanical mapping with Gaussian fitting for quantitative analysis.
• Variation of chain extender to cross-linking agent ratios.
• X-ray analysis, Transmission Electron Microscopy (TEM), and AFM-based Infrared Spectroscopy (AFM-IR) for hierarchical structure investigation.

Main Results:

• A quantitative framework for analyzing PU microphase separation was established.
• Decreasing the chain extender to cross-linking agent ratio weakened hydrogen bonding and reduced hard segment (HS) domain quantity.
• Microphase separation degree decreased, altering mechanical properties and viscoelasticity.
• A spherulite pattern with lamellae and increasing cross-linking density was observed within HS domains.

Conclusions:

• The study provides a quantitative method to analyze PU microphase separation.
• Component ratios significantly influence hydrogen bonding, HS domain characteristics, and overall microphase separation.
• The findings offer insights into PU's hierarchical structure and its impact on material properties.