Crosslinking reaction, pendant hydroxyl group

Hydroxyl Acrylic Resins [13] AJlyl alcohol and allyl alkoxylate have l n incorporated into hydroxyl acrylic resins to provide the pendant hydroxyl groups for crosslinking reaction. The resins are crosslinked with melamine or an isocyanate to form acrylic-melamine coatings or acrylic-polyurethane coatings, respectively. The coatings can be used as automotive topcoat or other high performance industrial coatings. 

Ethyoxyline resins, now called epoxy resins, were patented by Schlack in 1939. Many of the prepolymers were versatile resins produced from the condensation of a diphenol (bisphenol A) and epichlorohydrin. Since these resins possess terminal oxirane (epoxy) groups, they can be crosslinked in reactions with polyamines at ordinary temperatures. These resins may also be crosslinked by esterifying the pendant hydroxyl groups by cyclic anydrides at elevated temperatures. 

This application of DEC chromophores requires synthesis of asymmetrically functionalized chromophores as illustrated in Fig. 1. In this example, the hydroxyl terminated end of the chromophore is capable of condensation polymerization reactions while the acrylate functionality is capable of undergoing free radical polymerization. In Fig. 2, we illustrate schematically the stepwise synthesis of a highly crosslinked polymer matrix where both ends of the chromophore are coupled to polymer main chains. The first step in the scheme shown is accomplished by free radical polymerization yielding a soluble and processible polymer with flexible pendant chromophore groups. This polymer is spin cast into an optical quality film (0.5-1.5 micron thickness) and is heated near the glass transition temperature, poled and subsequently crosslinked by a thermal crosslinking reaction involving... 

Thermosetting acrylic resins are characterized as vinyl addition polymers having pendant chemical groups capable of further reaction. The most important commercial materials used at present contain amide, carboxyl, hydroxyl, or epoxy functionality. As in other interpolymer systems, the film properties may be altered in several ways variation in backbone composition, use of curing catalyst, and variation in the amount of crosslinking agent. 

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