The effect of acrylate functionality on frontal polymerization velocity and temperature

Abstract

Frontal polymerization is a method of converting monomer(s) to polymer via a localized reaction zone that propagates from the coupling of thermal diffusion with the Arrhenius kinetics of an exothermic reaction. Several factors affect front velocity and temperature with the role of monomer functionality being of particular interest in this study. Polymerizing a di and triacrylate of equal molecular weight per acrylate revealed that as the proportion of triacrylate was increased the velocity and temperature increased. This is attributed to increased crosslinking and autoacceleration. Comparing several different acrylate monomers, both neat and diluted with dimethyl sulfoxide (DMSO) so as to maintain constant acrylate group concentration, shows that velocity increases with increased functionality from mono to difunctional monomers. This trend breaks when applied to tri-and tetraacrylates, with fronts containing trifunctional monomer being the fastest. Acrylates containing hydroxyl functionality, as in the case of pentaerythritolbased triacrylates, are slower than acrylates without. This is attributed to a chain-transfer event and was tested using octanol and a hydroxyl-free acrylate. It has also been shown that small amounts of water cause a lowering of front velocity due to energy lost via vaporization, which lowers the front temperature.We are particularly interested in the effect of functionality on the front velocity, because the front velocity determines how Additional supporting information may be found in the online version of this article.

Analytical estimates of front velocity in the frontal polymerization of thermoset polymers and composites

“…Models that seek to add complexity by describing the multi-step chemical reaction mechanism happening during FP have been considered in other works. 21,32 For an arbitrary cure kinetic model, the front velocity can be obtained as…”

“…We note here that all of these models are phenomenological in nature with a single activation energy. Models that seek to add complexity by describing the multi‐step chemical reaction mechanism happening during FP have been considered in other works 21,32 …”

Recent Advances on Copper Complexes as Visible Light Photoinitiators and (Photo) Redox Initiators of Polymerization

“…As a result of this, thermal imaging can now be used to follow numerous chemical transformations. Indeed, the polymerization of acrylates and methacrylate is known to be exothermic [100,101] so that the polymerization process could be monitored by measuring the variation of temperature during the polymerization reaction. Examination of the ability of the three-component system to initiate a polymerization far from the irradiation point was realized by using a Pasteur pipette filled with the resin and by only irradiating the extremity of the Pasteur pipette.…”

“…As a result of this, thermal imaging can now be used to follow numerous chemical transformations. Indeed, the polymerization of acrylates and methacrylate is known to be exothermic [100,101] so that the polymerization process could be monitored by measuring the variation of temperature during the polymerization reaction. Considering the high reactivity of the three-component system Cu-4/Iod/Tin (II) (0.3%/0.85%/6% w/w/w), polymerization of filled samples was examined (See Figure 18).…”

Bismuthonium‐ and pyrylium‐based radical induced cationic frontal polymerization of epoxides

“…Due to the versatility of FP, a lot of research is performed towards creating FPs in various monomer systems with suitable initiators. For example, in thermally triggered (meth)acrylate‐based FP with commercial peroxides acting as initiators 7,8 . In addition, those (meth)acrylate FP can be triggered on demand via ultra violet (UV)‐light, using a commercial type I photoinitiator to start the reaction, whereas a difunctional peroxide represents the thermolabile initiator to ensure stable propagation 9 .…”