Polymerization of methacrylate resins photoinitiated by camphorquinone and bulky amine-functionalized silsesquioxanes

Abstract

Polyhedral oligomeric silsesquioxanes (SSQO) functionalized with bulky amino groups were prepared by a two-stage synthesis procedure. In a first stage, a modified organotrimethoxysilane was synthesized by reacting 1 mol of N-(b-aminoethyl)-c-aminopropyltrimethoxysilane with 3 mol of 1,2-epoxy-3-phenoxypropane. The second stage consisted of the hydrolytic condensation of the modified silane catalyzed by formic acid. Methacrylate resins were activated for visible light polymerization by the addition of camphorquinone (CQ) in combination with different mass fractions of SSQO. The progress of monomer conversion versus irradiation time showed that the CQ/SSQO pair is an efficient photoinitiator system because a fast reaction and high conversion results from 60 s irradiation at 600 mW/ cm 2 . The SSQO were incorporated up to 22 wt% in the methacrylate resin without compromising the flexural or the compressive properties of the final material.

Hybrid organic–inorganic macromolecular photoinitiator system for visible-light photopolymerization

“…Resins containing a higher proportion of OI-AH should be accompanied by a higher number of nanovoids. As reported previously [25,26], the final effect is a decrease in flexural modulus and compressive strength with increasing amounts of OI-AH.…”

“…Resins containing 10 wt.% of the OI-AH reached 70% conversion after 60 s irradiation (Fig. 8) while in the previous studies, the amount of organic-inorganic oligomers needed to reach 70% conversion was 20 wt.% [25] or 30 wt.% [26]. The amino groups of the OI-AH synthesized in this study contain nitrogen atoms bonded to an aromatic ring.…”

“…In previous studies, different organic-inorganic oligomeric silsesquioxanes functionalized with bulky amino groups were prepared and used as coinitiator of CQ in the photopolmerization of methacrylate resins. In a first stage, organotriethoxysilanes were synthesized by reacting 1 mol of 3-(aminopropyl) triethoxysilane with 2 mol of 1,2-epoxy-3-phenoxypropane [25] or 1 mol of N-(␤-aminoethyl)-␥-aminopropyltrimethoxy silane with 3 mol of 1,2-epoxy-3-phenoxypropane [26]. The amino-functionalized organic-inorganic oligomeric silsesquioxanes were obtained in a second stage by the hydrolytic condensation of the modified silanes catalyzed by formic acid.…”