# Curvature Dynamics of PEGDA Asymmetric Networks via Frontal Photopolymerization: Effect of Chain Length and Optical Attenuation

## TL;DR

This study explores how the chain length and optical properties of PEGDA affect the polymerization process and resulting material curvature during frontal photopolymerization.

## Contribution

The novel contribution is the demonstration of how PEGDA chain length and optical attenuation influence curvature dynamics through a minimal evaporation–diffusion model.

## Key findings

- Longer PEGDA precursors lower the solidification threshold but do not change front velocity.
- Photoinitiator concentration has a nonmonotonic effect on polymerization kinetics.
- Curvature fluctuations depend on PEGDA chain length and are modeled via evaporation–diffusion.

## Abstract

We investigate how the oligomer molecular mass, chain
length, and
optical attenuation affect both polymerization kinetics and the spatiotemporal
response of materials patterned via frontal photopolymerization (FPP).
We employ model poly­(ethylene glycol) diacrylate (PEGDA) oligomers
of different chain lengths and investigate their FPP kinetics and
response following solvent development, focusing on the emergence
and evolution of the material curvature. We find that longer precursors
yield a lower dose (or time) threshold for solidification, effectively
benefiting from an “early start,” while the front velocity
remains unchanged with chain length; by contrast, photoinitiator concentration
leads to a nonmonotonic impact on kinetics due to the combined effects
on rate and optical attenuation, which we collapse on a master curve.
FPP networks can exhibit nonmonotonic, spontaneous curvature fluctuations,
from flat or convex, to concave, and back to convex, that we show
to depend on PEGDA chain length and describe by a minimal evaporation–diffusion
model. These findings demonstrate how the interplay between molecular
structure, soft mechanics, and solvent transport can be harnessed
to program the response of asymmetric polymer networks.