Radical‐cured block copolymer‐modified thermosets

Abstract

Poly(ethylene-alt-propylene)-b-poly(ethylene oxide) (PEP-PEO) diblock copolymers were synthesized and added at 4 wt % to 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (BisGMA), a monomer that cures using free radical chemistry. In separate experiments, poly(ethylene glycol) dimethacrylate (PEGDMA) was combined as a secondary monomer with BisGMA and the monomers were loaded with 4 wt % PEP-PEO. The diblock copolymers self-assembled into well-dispersed spherical micelles with PEP cores and PEO coronas. No appreciable change in the final extent of cure of the thermosets was caused by the addition of diblock copolymer, except in the case of BisGMA, where the addition of the block copolymer increased extent of cure by 12%. Furthermore, the extent of cure was increased by 29% and 37% with the addition of 25 and 50 wt % PEGDMA, respectively. Elastic modulus and fracture resistance were also determined, and the values indicate that the addition of block copolymers does not significantly toughen the thermoset materials. This finding is surprising when compared with the large increase in fracture resistance seen in block copolymer-modified epoxies, and an explanation is proposed. V

Synergistic Toughening of Epoxy Modified by Graphene and Block Copolymer Micelles

“…Figure shows that the ternary composites exhibit increasing K Ic and G Ic with increasing theoretical M c , similar to both types of binary composites. Saturation of the improvement in the OP/epoxy binary composites at G Ic ≅ 2800 J/m 2 above M c of 3050 g/mol is consistent with previous studies on the same epoxy resin system. ,,, At M c of 6100 g/mol, the ternary composite has extraordinary mechanical properites with G Ic reaching ≈5300 J/m 2 and a modest elastic modulus of 2.5 GPa (Table S2). To the best of our knowledge, this result exceeds any previously reported toughness for this epoxy resin, and further improvements in other properties, like elastic modulus, are likely possible with continued optimization of the composition.…”

Effect of block copolymer concentration and core composition on toughening epoxies

“…% RuO 4 aqueous solution for 8 -10 minutes; based on our experience with epoxies, we believe the ruthenium preferentially stains PEO/matrix interface. 16,18,22 Specimens were examined in an FEI Technai T12 or an FEI Technai G2 Spirit BioTWIN transmission electron microscope with 120 kV accelerating voltage. All images were processed using Digital Micrograph software (Gatan).…”

Effect of Poly(ethylene oxide) Homopolymer and Two Different Poly(ethylene oxide-b-poly(propylene oxide)-b-poly(ethylene oxide) Triblock Copolymers on Morphological, Optical, and Mechanical Properties of Nanostructured Unsaturated Polyester

“…In the first case, polymerization-induced phase separation (PIPS) takes place, and in the latter, the nanoscale structure is created by “frozen” self-assembled micelles formed before cross-linking . This route to control the morphology of thermosets has been proved as an effective way to increase the toughness ,, or to modify optical properties . Due to these advantages, a considerable amount of research is still focused on modifying properties of epoxy thermosetting systems. ,− In contrast, despite UP resins are very commonly used, only a few works have been reported related to their nanostructuration employing BCPs.…”