# Thiol-Functionalized TiO2 as Reactive Nanoadsorbents for Residual Monomer Removal from Waterborne Polymer Dispersions

## TL;DR

This paper shows how thiol-functionalized titanium dioxide nanoparticles can remove harmful monomers from water-based polymer coatings and improve their mechanical strength.

## Contribution

The novel use of thiol-functionalized TiO2 nanoparticles as reactive nanoadsorbents for monomer removal and mechanical enhancement in polymer coatings is introduced.

## Key findings

- Thiol-functionalized TiO2 achieved up to 90% removal of MMA and nearly complete removal of BA monomers.
- Modified TiO2 nanoparticles chemically bonded up to 80–90% of adsorbed monomers irreversibly.
- Modified nanoparticles improved mechanical properties, increasing Young’s modulus by 75%.

## Abstract

This study explores the use of thiol-functionalized TiO2 nanoparticles to reduce residual methyl methacrylate (MMA)
and butyl
acrylate (BA) monomers in waterborne polymer dispersions (latexes).
TiO2 nanoparticles were modified with (3-mercaptopropyl)­triethoxysilane
(MPTES) to introduce −SH groups capable of thiol–ene
type reaction with CC bonds of monomers. The effects of functionalization
density, nanoparticle concentration, and mixing time on monomer removal
were systematically evaluated. Compared with unmodified TiO2, MPTES-modified nanoparticles achieved up to 90% removal of MMA
and nearly complete removal of BA, lowering total residual monomer
content from ∼1900 ppm to 120 ppm. About 80–90% of the
adsorbed monomers were chemically, thus, irreversibly bonded to the
TiO2 surface. DLS, TEM, and zeta potential analyses revealed
improved dispersion and reduced aggregation of modified nanoparticles
in the latex, leading to uniform distribution in films obtained by
water evaporation. TEM imaging further showed preferential localization
of modified TiO2 at the polymer particle surfaces, enabling
efficient monomer capture while maintaining good dispersion. The resulting
films displayed unchanged water sensitivity but significantly improved
mechanical properties, with Young’s modulus increasing by 75%.
Overall, thiol-functionalized TiO2 nanoparticles act as
reactive, multifunctional adsorbents that effectively reduce residual
monomer content and enhance the mechanical performance of MMA/BA polymer
latex coatings.