Optical and Thermomechanical Properties of Doped Polyfunctional Acrylate Copolymers.

Thomas Hanemann,Kirsten Honnef

doi:10.3390/polym10030337

Thomas Hanemann, Kirsten Honnef

Open Access

https://doi.org/10.3390/polym10030337

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Abstract

Three different polyfunctional acrylate monomers—trimethylolpropantriacrylate (TMPTA), pentaerythritol triacrylate (PETA) and di(trimethylolpropane) tetraacrylate (DTTA)—have been used as comonomers in combination with a reactive resin consisting of poly(methylmethacrylate), dissolved in its monomer methylmethacrylate. Phenanthrene has been added to form a guest–host system. The level of phenanthrene present may be adjusted to tailor the refractive index in the system. Prior to curing, the shear rate and temperature-dependent viscosity as a function of the composition were measured. It could be demonstrated that, with respect to different shaping methods, a tailor-made flow behaviour can be adjusted. After thermally-induced polymerization, the resulting optical (refractive index, optical transmittance) and thermomechanical (glass transition behavior, Vickers hardness) properties were characterized. A significant refractive index increase—up to a value close to 1.56 (@589 nm)—under the retention of good optical transmittance was able to be obtained. In addition, the photopolymerization behaviour was investigated to overcome the undesirable oxygen inhibition effect during the light-induced radical polymerization of acrylates. The level of acrylate units in the copolymer can compensate for the plasticizing effect of the dopant phenanthrene, enabling higher concentrations of the dopant in the guest–host system and therefore larger refractive index values suitable for polymer waveguide fabrication.

Highlights

Due to the rapid increase in data traffic both in the private as well as in the business sector, which is being accelerated by the expanding internet, classical copper-cable-based wideband lines are reaching their limits
The further development of customized wearables containing sensors for, e.g., health monitoring, requires the use of flexible polymer waveguides with tailored characteristics [1,2,3,4,5,6,7]
The three different polyfunctional acrylate monomers investigated—trimethylolpropantriacrylate (TMPTA), pentaerythritol triacrylate (PETA) and di(trimethylolpropane) tetraacrylate (DTTA)—were copolymerized at different monomer ratios with a commercial MMA/PMMA-based reactive resin

Summary

Introduction

Due to the rapid increase in data traffic both in the private as well as in the business sector, which is being accelerated by the expanding internet, classical copper-cable-based wideband lines are reaching their limits. Optical data transmission is increasingly important due to higher data transmission rate, lower damping and improved security. Beyond the application of the established fused silica cables in the fiber-optic network, polymer optical fibers are gaining more and more importance for short distance data transmission, e.g., in the automotive sector, due to their low weight and higher bending flexibility. Only very few polymers with acceptable optical properties are available commercially. The most important of these for technical applications are poly(methylmethacrylate) (PMMA), poly(methylmethacrylimide) (PMMI), poly(carbonate) (PC)

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