Iridescent Features Correlating with Periodic Assemblies in Custom-Crystallized Arylate Polyesters.

Area of Science:

• Polymer Science
• Materials Science
• Crystallography

Background:

• Periodic hierarchical structures in polymers are formed through complex mechanisms.
• Aryl polyesters exhibit unique crystalline morphologies with potential for structural coloration.

Purpose of the Study:

• To investigate the formation of ring-banded spherulites in five aryl polyesters.
• To explore the relationship between micro/nanocrystal assemblies, internal grating structures, and iridescence.
• To understand the conditions leading to structural coloration in these polymers.

Main Methods:

• Crystallization of five aryl polyesters (PET, PTT, POT, PNT, PDT) within specific temperature ranges.
• Microscopic and nanoscopic analysis of spherulite morphology and internal structures.
• Laser diffraction analysis to confirm ringed spherulites and analyze diffraction patterns.
• Investigation of birefringence patterns and light interference for iridescence.

Main Results:

• All studied aryl polyesters, except poly(ethylene terephthalate) (PET), consistently form ring-banded spherulites.
• These spherulites exhibit periodic birefringence patterns and structural iridescence due to light interference.
• Laser diffraction confirmed the presence of ringed spherulites, producing arc diffraction patterns.
• Poly(ethylene terephthalate) (PET) did not regularly form ring-banded morphology, thus lacking iridescent color.

Conclusions:

• Ring-banded spherulites are a universal characteristic of crystallized aryl polyesters (PTT, POT, PNT, PDT) under suitable conditions.
• The internal lamellar assembly of these spherulites is responsible for birefringence and iridescence.
• Poly(ethylene terephthalate) (PET) is an exception, failing to produce regular ring-banded structures and iridescence.