Polylactide/Perfluoropolyether Block Copolymers: Potential Candidates for Protective and Surface Modifiers

Abstract

Perfluoropolyethers are a well known and widely used family of polymers, suitable as protectives. Their main drawback is the lack of solubility, which is complete only in chlorofluorocarbons. In this work a series of A‐B‐A block copolymers (FluoPLA), with a relative low molecular weight, were prepared by ROP of L‐ and D,L‐lactide (PLA) in the presence of a hydroxy‐terminated perfluoropolyether as macroinitiator. In fact the use of block copolymers leads to different advantages, i.e. a limited segregation phenomena and higher polymer solubility. The resulting polymers were characterized (by NMR, IR, HPLC‐SEC, DSC, LS) and tested as potential protective and surface modifiers for cultural heritage (ESEM‐EDS, solar‐box technique, colorimeter analysis).magnified image

High glass transition temperature polyester coatings for the protection of stones

“…19 F‐NMR spectra of these copolymers (reported as Supporting Information) showed the resonances of fluorine atoms, with chemical shifts very close to those detected for the starting alcohol, confirming the insertion of a perfluoroalkyl moiety in the polymers . The invariance of the 19 F‐NMR spectra of the fluorinated polymers with respect of the starting alcohols was in agreement with previous study on the synthesis of end‐capped perfluoroalkyl PLA …”

“…The products, selected from those reported in Table , were a poly(PMGLY) (run 1), a chain‐end perfluorinated alkyl containing poly(PMGLY) [poly(PMGLY)‐F] (run 3), a poly(SALD) (run 6) and a chain‐end perfluorinated alkyl containing poly(SALD) [poly(SALD)‐F] (run 8). PLA and PLA‐F were synthesized as reference materials and employed to correlate the results with those previously reported …”

“…Monomers were polymerized in the melt phase through ROP using benzyl alcohol as chain initiator (conditions are reported in Table ), obtaining two classes of copolymers of lactic acid with mandelic acid (poly(PMGLY)) or salicylic acid (poly(SALD)) (Scheme ). The homopolymer of lactic acid (PLA) was also synthesized as previously reported for comparative purposes. In some polymerizations, PFoct was used as chain initiator obtaining end‐capped copolymers with a perfluoroalkyl moiety (poly(PMGLY)‐F, poly(SALD)‐F, and PLA‐F).…”

“…White calcitic marble with low porosity was chosen as stone substrate to evaluate the performances of the coatings. Products were applied by solution casting, a common practice for film formation, successfully employed to form thin polymer coatings of acrylates, methacrylates, fluorinated acrylic resins, polysiloxanes, polyolefins, and polylactic acid . Taking into account the goals of this study, two sets of samples were prepared: (a) polymer coatings on glass slides and NaCl disks, for the characterization of films and to study their stability after an aging process under solar radiations (coating were checked by optical microscopy, FT‐IR, 1 H‐NMR, GPC, DSC, and weight loss), and (b) polymer coatings on marble surfaces, to evaluate the protective efficiency, as well as color change, that is the performances as stone protective.…”

“…Hydrorepellence of the protective was improved through copolymerization with a perfluoroalkyl moiety. Good results were obtained either with a block copolymer containing PLA and perfluoropolyether (FLK) moieties (PLA–FLK–PLA) or with a chain‐end perfluoroalkyl‐functionalized PLA (PLA‐F) . However, the T g of these copolymers ranged from 25 to 55°C, depending on the degree of crystallinity and molecular weight.…”