Photocrosslinkable unsaturated polyesters

Nine photocrosslinkable unsaturated polyesters containing pendent chalconyl and cinnamylidenemalonyl moieties have been synthesized by a route involving no water elimination. The resins are insolubilized by visible and UV irradiation. They can also be cured with styrene, MEK peroxide, and cobalt naphthenate. A study of the photoreactions reveals that the resins containing 4′‐chalconyl groups crosslink and isomerize simultaneously, whereas those containing 4‐chalconyl groups undergo crosslinking only, due to the steric suppression of isomerization. Photoinsolubility is also achieved by introducing the cinnamylidenemalonyl group into the resin structure. It is found that the resins containing both the chalconyl and cinnamylidenemalonyl groups in the repeat units do not exhibit any pronounced photofastness.