Photoinduced Polymerization of Eugenol-Derived Methacrylates

Abstract

Biobased monomers have been used to replace their petroleum counterparts in the synthesis of polymers that are aimed at different applications. However, environmentally friendly polymerization processes are also essential to guarantee greener materials. Thus, photoinduced polymerization, which is low-energy consuming and solvent-free, rises as a suitable option. In this work, eugenol-, isoeugenol-, and dihydroeugenol-derived methacrylates are employed in radical photopolymerization to produce biobased polymers. The polymerization is monitored in the absence and presence of a photoinitiator and under air or protected from air, using Real-Time Fourier Transform Infrared Spectroscopy. The polymerization rate of the methacrylate double bonds was affected by the presence and reactivity of the allyl and propenyl groups in the eugenol- and isoeugenol-derived methacrylates, respectively. These groups are involved in radical addition, degradative chain transfer, and termination reactions, yielding crosslinked polymers. The materials, in the form of films, are characterized by differential scanning calorimetry, thermogravimetric, and contact angle analyses.

Biobased Composites by Photoinduced Polymerization of Cardanol Methacrylate with Microfibrillated Cellulose

“…The peroxyl radicals, particularly when ether groups are present on the growing chain, may then form hydroperoxides, abstracting hydrogen atoms from the polymer backbone and thus originating a carbon-centered polymer radical that can react with the (meth)acrylate monomers, causing the re-initiation of the polymerization reaction [ 41 ]; this gives rise to a typical sigmoidal curve for the conversion as a function of time. Confirming this type of mechanism, a band centered around 3400 cm −1 , characteristic of hydroperoxides, appeared [ 30 , 42 ], as shown in the area shaded in gray in Figure 3 . At the same time, the peak centered at 3008 cm −1 decreased, indicating that the unsaturations of the alkyl side chain were consumed; almost 70% of the side chain double bonds were consumed after 5 min of irradiation, and 85% by the end of the irradiation time (9 min).…”

“…The slow initial rate of reaction was attributed to oxygen inhibition, typical for (meth)acrylate resins [ 39 , 40 ]. Indeed, oxygen can scavenge the initiating free radicals and the growing polymer radicals, forming peroxyl radicals; these are not reactive towards (meth)acrylate double bonds, and thus the polymerization reaction slows down until oxygen is consumed [ 30 ]. The peroxyl radicals, particularly when ether groups are present on the growing chain, may then form hydroperoxides, abstracting hydrogen atoms from the polymer backbone and thus originating a carbon-centered polymer radical that can react with the (meth)acrylate monomers, causing the re-initiation of the polymerization reaction [ 41 ]; this gives rise to a typical sigmoidal curve for the conversion as a function of time.…”

Photoinduced Processes as a Way to Sustainable Polymers and Innovation in Polymeric Materials

“…Regarding the use of innovative materials, several groups have undertaken works on biobased oligomers. We have recently synthesized and characterized a platform of methacrylic oligomers based on eugenol [ 55 ]: the reaction of the double bonds was affected by the presence and reactivity of the allyl and propenyl groups in the eugenol- and isoeugenol-derived methacrylates, respectively. It was proved that these groups are involved in radical addition, degradative chain transfer, and termination reactions, yielding crosslinked polymers.…”

Preparation of poly(eugenol-co-methyl methacrylate)/polypropylene blend by creative route approach: structural and thermal characterization

“…The development of suitable bio-based building blocks for producing polymers has increased with the need for more environmentally friendly processes and materials [1,2]. In addition, it has become important to prefer polymerization techniques with high energy efficiency [3].…”