Mechanistic discussion of cationic crosslinking copolymerizations of 1,2‐epoxycyclohexane with diepoxide crosslinkers accompanied by intramolecular and intermolecular chain transfer reactions

Abstract

Our previous mechanistic discussion of the free‐radical crosslinking monoallyl/diallyl copolymerizations was extended to the cationic crosslinking monoepoxide/diepoxide copolymerizations, typically including 1,2‐epoxycyclohexane (ECH) as a monoepoxide and bis[3,4‐epoxycyclohexylmethyl] adipate (BECHMA) as a diepoxide crosslinker. In the cationic polymerization, oligomer is usually obtained because of the occurrence of characteristic chain‐forming reactions. Therefore, cationic crosslinking monoepoxide/diepoxide copolymerizations could be in the category of the network formation through free‐radical crosslinking monoallyl/diallyl copolymerizations. Thus, the gelation behavior was discussed by comparing the actual gel points with the theoretical ones; the greatly delayed gelation from theory was observed. Then, the resulting network polymer precursors (NPPs) were characterized by SEC‐MALLS‐viscometry to clarify the cationic crosslinking ECH/BECHMA copolymerization mechanism. Notably, the correlation lines of molecular weight versus elution volume were specific for the NPPs obtained at a high conversion close to the gel point as compared with those obtained by the free‐radical crosslinking monoallyl/diallyl copolymerization. This may be ascribed to the occurrence of intramolecular and intermolecular chain transfer reactions characteristic of cationic polymerization; the chain transfer reactions involve the intramolecular and intermolecular nucleophilic attack of ether oxygen or terminal hydroxyl oxygen in the NPPs to a terminal growing cation that leads to the formation of not only the loop‐ but also the crosslink‐structures containing NPPs, providing fragile ultrahigh‐molecular‐weight NPP in the SEC columns. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

Control of reactions and network structures of epoxy thermosets

“…If the reaction of the first function results in the decrease of the reactivity of the remaining function, then the gelation is markedly delayed. On the contrary, it is also possible to obtain extensive crosslinking with the rapid formation of tight network structure, by avoiding chain transfer and using high amounts of crosslinker whose functions have similar reactivity [75,76,118,124]. It is interesting to note that the effect of some CTAs may be accompanied by a decrease of the polymerization rate.…”

“…13 for the chain ring-opening polymerization of epoxy monomers and diepoxide crosslinkers. The dimension and concentration of the polymer coils increase until the apparition of an interconnected structure that percolates the system resulting in macrogelation [76,77].…”

“…monoepoxy) with a tetrafunctional crosslinker BB (e.g. diepoxy), the Stockmayer's equation predicts that the gel point is reached for [76]: …”

“…In particular, intramolecular cyclizations are rapidly observed through the mechanisms of back-and end-biting [76]. Moreover, when the first functional group of a crosslinker is reacted the reactivity of the second functional group is often affected [98].…”

Self-referential holography and its applications to data storage and phase-to-intensity conversion

“…During recording, the hologram was recorded inside a photopolymer medium provided by Kyoeisha Chemical Co [20]. by focusing a beam containing the phase pattern corresponding to the signal data shown in Fig.…”