Understanding the swelling behavior of P(DMAA-co-MABP) copolymer in paper-based actuators

TL;DR

This study explores how a specific copolymer coating enhances paper's swelling and humidity responsiveness, enabling its use in environmentally friendly, humidity-sensitive actuators with rapid response times.

Contribution

It introduces a detailed analysis of P(DMAA-co-MABP) copolymer's swelling behavior on paper and proposes models for its actuation mechanisms in response to humidity changes.

Findings

Polymer coating significantly increases paper's hygroscopicity.

AFM shows rapid height and stiffness changes with humidity.

Modified paper actuates between 10% and 90% RH.

Abstract

As interest in sustainable materials grows, paper is being reimagined as a multifunctional substrate with significant potential for future technologies for innovative, environmentally friendly solutions. This study investigates the swelling behavior and environmental responsiveness of a copolymer, poly(N,N-dimethylacrylamide-co-4-methacryloyloxybenzophenone) (P(DMAA-co-MABP)), when applied to cellulosic paper for use in humidity-sensitive actuators. The copolymer's swelling behavior was characterized using dynamic vapor sorption (DVS) and in-situ atomic force microscopy (AFM). DVS measurements demonstrated that the polymer coating significantly enhances the hygroscopic properties of the paper, while AFM revealed the polymer's fast response to relative humidity (RH) changes, shown by immediate height adjustments, increased adhesion, and decreased stiffness at higher RH levels.Studies on polymer-modified paper-based bilayer actuators demonstrate that incorporating the hydrophilic P(DMAA-co-MABP) results in actuation in response to relative humidity variations between 10% and 90% RH. From these findings, two models were proposed to assess key mechanisms in the swelling behavior: the correlation between the heterogeneity in crosslinking and the polymer swelling behavior, and the correlation between polymer-paper interactions and the hygro-responsive bending behavior. Additionally, thermal analysis was performed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), providing a comprehensive profile of the copolymer's behavior.