Transparent ultraviolet‐barrier coatings

Abstract

Division, Spring$eld, Massachusetts 011 01 synopsisA number of phenyl polyesters have been synthesized to furnish molecules whose backbones rearrange under ultraviolet irradiation to an o-hydroxybenzophenone structure.This photochemical Fries rearrangement produces ultraviolet opacity in the irradiated film while maintainiig visual transparency. Thin coatings of these polyesters completely protect substrates ordinarily sensitive to ultraviolet light. Spectroscopic analysis of various rearranged films and coatings clearly shows that the o-hydroxybenzophenone polymer formed is concentrated at the irradiated surface of the original polyester coating as a "skin". Such a skin, formed in situ during the irradiation, functions to protect both the original polyester coating as well as the coated substrate from degradation by ultraviolet irradiation. Furthermore, a significant "healing" mechanism appears inherent in these coatings, for as the exposed skin ultimately degrades under extended ultraviolet irradiation, more of the underlying polyester layer apparently rearranges to compensate for the loss. Thus the clear coating functions both as a protective skin and a rearrangeable reservoir. Modified structures of the polyesters have been prepared which possess, in addition to their protective fdm properties, a useful solubility spectrum and a good solution shelf life.

One-pot melt synthesis of resorcinol based polyarylates for UV-stable coatings

“…5). Such composition was chosen according to the procedure reported in the literature for ITR block co-polymers with high UV stability [12][13][14].…”

Photostabilizing of bisphenol A polycarbonate by using UV-absorbers and self protective block copolymers based on resorcinol polyarylate blocks

“…A relatively new way to stabilize polymers is to incorporate moieties in the polymer chain that rearrange into UV-absorbers under the influence of sunlight [10]. This can be done by incorporation of (block)polymers, such as polyarylates.…”

“…These polymers can undergo a photo-Fries rearrangement which gives o-hydroxybenzophenones which can act as a protective, UV blocking layer to the underlying resin. These resins have very good retention of gloss and mechanical properties, however, a major drawback is that the polymer rapidly turns yellow after the photo-Fries rearrangements [10].…”

Photo-Induced Micellization of Block Copolymers

“…We chose three kinds of the irreversible photoreactions of the photolysis, photoelectron transfer, and photorearrangement. The photolysis and photorearrangement of pendant groups attached to polymers are important methods often used in the field of photoresist [48,49], while the photoelectron transfer is envisaged to be a new technique, without mass transfer and volume shrinkage, for optical data storage. To attain the self-assembly induced by these photoirreversible reactions, three different block copolymers supporting photoreactive groups were prepared; poly(4-tert-butoxystyrene)-block-polystyrene diblock copolymer (PBSt-b-PSt) for the photolysis-induced micellization, poly(4-pyridinemethoxymethylstyrene)-block-polystyrene (PPySt-b-PSt) for the photoelectron transfer-induced micellization, and poly(4-allyloxystyrene)-block-polystyrene (PASt-b-PSt) for the photorearrangement-induced micellization.…”