Polydicyclopentadiene aerogels grafted with PMMA: I. Molecular and interparticle crosslinking

Abstract

Polydicyclopentadiene (pDCPD) is a polymer of emerging technological significance from separations to armor. It is a paradigm of ring opening metathesis polymerization (ROMP) and some of its remarkable properties (e.g., strength) have been attributed to crosslinking of the pendant cyclopentenes. pDCPD should be an ideal candidate for strong nanoporous solids (aerogels), however, excessive swelling of the wet-gels precursors in toluene (up to 200% v/v), followed by de-swelling and severe deformation in acetone, renders the resulting aerogels unusable. Based on spectroscopic evidence (IR, solid state 13 C NMR and several liquid 1 H NMR controls), only 4-5% of the pendant cyclopentene double bonds of pDCPD are engaged in crosslinking, via Wagener-type olefin coupling. Deformation was rectified via free radical polymerization of methylmethacrylate (MMA) in the pores of pDCPD wet-gels. The uptake of PMMA was varied in the 13-28% w/w range by varying the concentration of MMA. Evidence (e.g., differential scanning calorimetry) though suggests that PMMA remains a linear polymer, hence the pDCPD/PMMA network resist deformation, not because of molecular-level crosslinking, but due to a synergism related to the nano-topology of the two components (see next paper of this issue). With cylindrical monoliths available, the nature of the interparticle chemical bonding in pDCPD/PMMA aerogels was probed top-down with thermal conductivity and compression testing, using linearpolynorbornene (pNB) aerogels as a control system. The latter, with no pendant cyclopentenes, has no chance for interpolymer chain crosslinking. The solid thermal conduction and stiffness of pDCPD/PMMA and pNB aerogels scale similarly, pointing to a common mechanism for interparticle bonding. That was assigned to cross-metathesis, effectively extending the polymer chains of one nanoparticle into another, and was reflected on very high polydispersities (8-13).

Thermoplastic acrylic resin with self‐healing properties

“…The exothermic curing peak obtained on the DSC scan for SH bleed. This peak can tell us that second step of polymerization is not complete and after additional heating of the pDCPD, more crosslinking between polymer chains can be created .…”

Synthesis and biomedical applications of aerogels: Possibilities and challenges

“…polyurea [144], polyimides [145], polyamide [146], polyacrylonitriles [127], polyurethanes [147], polystyrene [148], polybenzoxazine [149], poly(dicyclopentadiene) [150], etc.…”

Concurrent curing kinetics of an anhydride-cured epoxy resin and polydicyclopentadiene

“…While DCPD ROMP kinetics have been previously explored using thermal and rheokinetic analysis, (31,(51)(52)(53)(54)(55) there is little literature on the use of spectroscopy to follow the progress of the ROMP reaction. (56)(57)(58)(59) Figure 4 shows the spectra of DCPD pre-and post-curing at 30 °C. Three candidates are identified to follow the kinetics of ROMP of DCPD due to the lack of overlap with peaks in the epoxy resin spectra and strong peak intensity: 1) the peak located at 1339 cm -1 associated with the in-plane bending of the C=C-H moiety, 2) the peaks located at 754 and 727 cm -1 associated with the out-of-plane bending of the C=C-H moieties, and 3) the peak located at 484 cm -1 associated with the molecular torsion of the DCPD molecule.…”