Polyurethanes with long fluorinated side chains

Abstract

AbstractCopolymer triols were prepared from propylene oxide and glycidyl (α,α,ω‐trihydrododecafluoroheptyl) ether or pentadecafluoroheptylepoxyethane. Cationic polymerization was used and block copolymers were obtained in the molecular weight range of 1,000 to 3,000. These copolymer triols were reacted with an 80/20 mixture of 2,4‐/2,6‐tolylene diisocyanate, giving polyurethanes with the same polymer backbone as the conventional polyurethanes based on polyoxypropylene triols and tolylene diisocyanate. It was found that these polyurethanes, containing between 0% and 45% fluorine, showed increasing adhesion to anodized aluminum with increasing urea bond content of the polymer. However, the fluorine content did not show the expected effect on adhesion. Isothermal gravimetric analysis showed that the heat stability of the fluorourethanes was lower than for conventional urethanes on a weight basis, only because the segments split off in heat degradation were heavier for the fluorourethane. This phenomenon might possibly also apply to urethanes with a fluorinated backbone. On a mole basis fluorourethanes might be as stable as nonfluorourethanes. It was also found that the thermostability, as measured by weight loss, increased with an increasing degree of crosslink density in the polymers.