Crosslinking and ozone degradation of thermosetting resins based on maleic anhydride/diene copolymer and polyfunctional alcohols

Abstract

Crosslinking and de-crosslinking reactions of an alternating copolymer of maleic anhydride (MAn) and 2,4-dimethyl-1,3-pentadiene (DMPD) by thermal curing with polyfunctional alcohols as the crosslinkers and subsequent ozone degradation are reported in this article. The ring-opening reaction of an anhydride group by polyfunctional alcohols produces network polymers with an ester linkage. The rate of crosslinking reaction depends on the curing conditions, i.e. the structure of the used alcohols and the curing temperature and time. The crosslinking density of the alcohol-cured copolymers is low due to a slow reaction between the anhydride and hydroxy groups, being different from the corresponding epoxy-cured copolymer with a dense network structure reported in a previous article. The insoluble resins are readily de-crosslinked and solubilized by ozone degradation. The polymer surface modification by ozone is also investigated.

Crosslinking of poly(vinyl alcohol) and poly(vinyl acetate) using poly(maleic anhydride‐alt−2,4‐dimethyl‐1,3‐pentadiene) as polyfunctional crosslinker and decrosslinking by ozone degradation

“…The ozone degradation was carried out using PVA and PVAc films in water and acetone, respectively, at 0 °C with bubbling ozone‐containing air. The degradation mechanism was similar to the ozone degradation of the epoxy and alcohol‐cured PMAD previously reported . The double bond of the PMAD repeating units were oxidized during the reaction with ozone and the subsequent treatment with triphenylphosphine.…”

“…The peak due to the ester as the reaction product was overlapped with any other peaks because the content and conversion of PMAD were much small, although it was expected to show any change for the confirmation the progress of a crosslinking reaction between hydroxy and acid anhydride groups. In the previous study on the crosslinking reaction of PMAD using ethylene glycol and glycerin as the di‐ and trifunctional crosslinkers, respectively, no change was detected in the IR spectra, suggesting the formation of a very small amount of crosslinking points by the ring‐opening reaction of the anhydride with alcohols to form the esters . The results of the TG analysis in this study can also be accounted for by the low crosslinking density.…”

“…The alternating copolymers of dienes with MAn were useful as the functional polymers, as similar to the alternating copolymers with olefins . An anhydride moiety in each repeating unit of the alternating copolymers with dienes were available for the postpolymerization reaction, such as crosslinking using epoxy compounds, alcohols, and amines . Furthermore, the DMPD repeating unit containing a carbon‐to‐carbon double bond was also reacted with ozone, leading to the polymer chain scission, decrosslinking of epoxy‐ and alcohol‐cured resins, and polymer surface modification .…”

Synthesis and Ozone Degradation of Alternating Copolymers ofN‐Substituted Maleimides with Diene Monomers

“…BMI/DMPD copolymer was synthesized by another pathway via postpolymerization reactions of MAn/DMPD copolymer according to the reactions in Scheme . We previously investigated crosslinking reactions of MAn/DMPD copolymer using various polyfunctional amines . While rapid and quantitative transformation of anhydride to the corresponding maleamic acid by ring‐opening reaction was observed at room temperature, a curing process of the products accompanying imide‐ring formation was achieved after heating at a high temperature .…”

“…We also succeeded in the synthesis of alternating copolymers of MAn and N ‐phenylmaleimide (PhMI) with 2,4‐dimethyl‐1,3‐pentadiene (DMPD) as noncyclic 1,3‐diene monomers . Anhydride moiety and carbon‐to‐carbon double bond in the repeating unit of MAn/DMPD copolymer were available for several postpolymerization reactions; for example, crosslinking using epoxy compounds, alcohols, and amines as polyfunctional crosslinkers, and oxidative ozonolysis of carbon‐to‐carbon double bonds in the main chain, leading to polymer chain scission, decrosslinking of cured resins, and polymer surface modification ( Scheme ) . More recently, radical copolymerization of PhMI with several diene monomers was carried out under various reaction conditions as an attempt for the synthesis of high‐molecular‐weight copolymers by suppression of Diels–Alder reaction .…”