High glass transition temperature polyester coatings for the protection of stones

Copolymers of lactic acid with mandelic or salicylic acid were synthetized through ring-opening polymerization (ROP) and tested as protective coatings for stones. Most notably, glass transition temperature (T-g), hydrophobicity, and UV barrier properties were increased, making these materials more suitable as protective coating for outdoor stones than poly(lactic acid). A T-g of 76 degrees C was obtained for the alternating copolymer lactic acid/mandelic acid and it was considerably higher than the one of poly(lactic acid) with similar molecular weight (50-55 degrees C). Furthermore, the introduction of a perfluorinated moiety as chain-end group, using a perfluoro alcohol as initiator of the ROP process, allowed to increase the hydrophobicity and stability of the new coatings. These polymers showed a good protective efficiency when applied on marble stones and preliminary stability tests under solar light showed low degradation, good stability to photo-oxidative conditions, and negligible color changes after an aging time of 1000 h. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42323.