Multilayered polymer microspheres by thermal imprinting during microsphere growth

Area of Science:

• Polymer Chemistry
• Materials Science
• Nanotechnology

Background:

• Precipitation polymerization is a versatile technique for synthesizing polymer microspheres.
• Controlling microsphere morphology and internal structure is crucial for advanced applications.
• Temperature plays a significant role in polymerization kinetics and polymer properties.

Purpose of the Study:

• To investigate the effect of modulated polymerization temperature on microsphere formation.
• To develop a method for creating polymer microspheres with nested, onion-type structures.
• To explore the potential for 'thermal imprinting' of temperature profiles within microspheres.

Main Methods:

• Utilized precipitation polymerization of chloromethylstyrene and divinylbenzene-55 in acetonitrile.
• Employed a temperature ramping strategy between 65 and 75 degrees C during copolymerization.
• Analyzed the resulting microspheres for size, monodispersity, cross-linking, and radial density profiles.

Main Results:

• Successfully synthesized monodisperse, cross-linked polymer microspheres with approximately 10 mum diameter.
• Observed that the radial density profiles of the microspheres closely mirrored the applied temperature ramping profiles.
• Attributed this 'thermal imprinting' phenomenon to the copolymer being near its theta point during polymerization.

Conclusions:

• Modulating polymerization temperature is an effective strategy for creating complex polymer microsphere architectures.
• The observed thermal imprinting allows for the recording of reaction temperature history within the microsphere structure.
• This technique offers a novel approach for designing functional polymer materials with embedded thermal information.