Thermo-mechanical/thermal properties of photo-cationic polymerized cyclo-aliphatic epoxy hybrid materials

Abstract

Cyclo-aliphatic epoxy and methacrylate hybrimers were fabricated via the photocationic polymerization of cycloaliphatic epoxy oligosiloxanes and photoradical polymerization of methacrylate oligosiloxanes, respectively. The thermomechanical/thermal properties of these two hybrimers using different photo-polymerization mechanisms were compared. Although both oligosiloxanes showed similar degrees of condensation, siloxane network structures, and sizes, the cycloaliphatic epoxy hybrimer showed improved thermomechanical/thermal properties as compared to the methacrylate hybrimer. This was attributable to a highly crosslinked network structure developing from the living characteristics of photocationic polymerization and the short, compact organic chains of the cycloaliphatic epoxy hybrimer as compared to the methacrylate hybrimer.

Heat- and water-proof quantum dot/siloxane composite film: Effect of quantum dot-siloxane linkage

“…We fabricated the QD/siloxane (methacryl) film via UV‐induced cross‐linking of free radical addition reaction to solidify the CdSe/ZnS QDs in oligosiloxane (methacryl) resin (concentration of QDs: 0.5 wt%) which was synthesized by sol–gel condensation reaction between silane precursors of MPTS and DPSD . Similarly, the QD/siloxane (epoxy) film was fabricated via UV‐induced cross‐linking of epoxy ring opening cationic reaction to solidify the same batch of CdSe/ZnS QDs in oligosiloxane (epoxy) resin which was synthesized by sol–gel condensation reaction between silane precursors of ECTS and DPSD . Figure a shows traces of PL QY of QD/siloxane (methacryl) film and QD/siloxane (epoxy) film observed for 40 days of aging in air at 85°C and 5% RH for 40 days.…”

“…b, the free radical addition reaction of the QD/oligosiloxane (methacryl) resin results in the formation of carbon single bonds by two cross‐linking reaction pathways: the one is the reaction between C═C bonds of methacryl groups of siloxane matrix (i.e., cross‐linked bonds between siloxane matrix), and another is the reaction between C═C bonds of the methacryl group and OA (i.e., cross‐linked bonds between QD and siloxane matrix) . While, the epoxy ring opening cationic reaction of the QD/oligosiloxane (epoxy) resin results in the formation of only ether bonds of between epoxy groups of siloxane matrix . Therefore, the long‐term PL QY stability of the QD/siloxane (methacryl) film attributed to cross‐linked bonding forms between QD and siloxane matrix responsible for robust encapsulation of QDs, whereas the QD/siloxane (epoxy) film has no bonding forms between QD and siloxane matrix.…”

“…22 Similarly, the QD/siloxane (epoxy) film was fabricated via UV-induced cross-linking of epoxy ring opening cationic reaction to solidify the same batch of CdSe/ZnS QDs in oligosiloxane (epoxy) resin which was synthesized by sol-gel condensation reaction between silane precursors of ECTS and DPSD. 23 Figure 1a shows traces of PL QY of QD/siloxane (methacryl) film and QD/siloxane (epoxy) film observed for 40 days of aging in air at 85°C and 5% RH for 40 days. The QD/siloxane (methacryl) film retains the initial PL QY (~61%), while the QD/siloxane (epoxy) film exhibits severe decrease of PL QY from~61 to~9%, during aging for 40 days.…”

“…21,22,27 While, the epoxy ring opening cationic reaction of the QD/oligosiloxane (epoxy) resin results in the formation of only ether bonds of between epoxy groups of siloxane matrix. 23 Therefore, the long-term PL QY stability of the QD/siloxane (methacryl) film attributed to cross-linked bonding forms between QD and siloxane matrix responsible for robust encapsulation of QDs, whereas the QD/siloxane (epoxy) film has no bonding forms between QD and siloxane matrix.…”

Low temperature curable epoxy siloxane hybrid materials for LED encapsulant

“…These higher thermal stability results of the CAEO/oxetane (L‐epoxy and UV‐epoxy) hybrimers originated from high density cross‐linking in the oxetane hardener, which has difunctional reactive sites and low molecular weight . Similarly, epoxy rings in the CAEO resin have high density cross‐linking because of the multifunctional structure and short siloxane bonds in the CAEO resin . Therefore, the thermal stability of the L‐epoxy hybrimer is much higher than those of other siloxane based LED encapsulants (around 350°C) …”