# Self-Assembled Microplastic-Free Microcapsules Using Aromatic Bis-Ureas with Improved Strength and Tunable Barrier Properties for Encapsulating Cinmethylin

## TL;DR

Researchers developed microcapsules without microplastics to safely store and release a herbicide, offering a sustainable alternative to traditional methods.

## Contribution

A one-pot self-assembly method for creating microplastic-free microcapsules with tunable release properties.

## Key findings

- Microcapsules showed >99% encapsulation efficiency and reduced herbicide evaporation by 90%.
- Bis-urea microcapsules were mechanically stronger than conventional polyurea microcapsules.
- Release rates increased with payload, showing tunable barrier properties.

## Abstract

Microencapsulation technology can be used for safe handling
and
controlled release of agrochemicals. Commercial microencapsulated
formulations typically use cross-linked polymeric microcapsules, which
encapsulate agrochemicals for improved efficiency and precise application.
However, these polymeric microcapsules are nonbiodegradable and add
to the growing microplastic pollution challenge at the end of their
life cycle. Herein, we demonstrate a simple one-pot process for the
interfacial self-assembly of aromatic bis-urea molecules to synthesize
microplastic-free microcapsules encapsulating cinmethylin, an effective
cineolic pre-emergence herbicide commonly used against grass weeds
in annual crops. The urea linkages act as hydrogen-bonding motifs
forming a self-assembled supramolecular shell at the oil–water
interface. The shell material’s chemical composition was analyzed
using infrared spectroscopy, 1H-NMR, and mass spectrometry.
Four batches of well-dispersed microcapsules (diameter, 1–10
μm) with encapsulation efficiency >99% and varying payload
were
synthesized. Accelerated thermal release tests proved that encapsulation
reduced the cinmethylin evaporation by up to 90%, over nonencapsulated
cinmethylin, and crucially, the release profiles of the bis-urea microcapsules
were comparable to conventional polyurea microcapsules prepared industrially.
The release rate of cinmethylin increased with payload, indicating
that barrier properties of bis-urea microcapsules are tunable, making
them adaptable for encapsulating a variety active ingredients. Additionally,
all the four batches of bis-urea microcapsules were mechanically stronger
than the polyurea microcapsules. Synthesized using a straightforward
process requiring no modifications to existing industrial equipment,
these bis-urea microcapsules have great potential to replace commercial
nonbiodegradable microplastic microcapsules.