Contents lists available at ScienceDirect Progress in Organic Coatings journal homepage: www.elsevier.com/locate/porgcoat A designed UV–vis light curable coating nanocomposite based on colloidal TiO 2 NRs in a hybrid resin for stone protection Carola Esposito Corcione a, ⁎ ,1 , Chiara Ingrosso b, ⁎ ,1 , Francesca Petronella b , Roberto Comparelli b , Marinella Striccoli b , Angela Agostiano b,c , Mariaenrica Frigione a , M. Lucia Curri b a Department of Engineering for Innovation, University of Salento, Via Arnesano, 73100 Lecce, Italy b CNR-IPCF U.O.S. Bari, c/o Department of Chemistry, University of Bari, Via Orabona 4, 70126 Bari, Italy c Department of Chemistry, University of Bari, Via Orabona 4, 70126 Bari, Italy ARTICLE INFO Keywords: Hybrid methacrylic–siloxane resin Colloidal TiO 2 nanorods Nanocomposite Stone protection Self-cleaning UV–vis light polymerization ABSTRACT The modification of a UV–vis light curable hybrid methacrylic–siloxane resin with organic coated TiO 2 nanorods (NRs) has been carried out, in order to fabricate a functional coating for protection of stone artefacts of artistic and cultural relevance. The nanocomposite, formulated without using any harmful and high volatile monomer components, has been deposited onto the surface of stone samples made of a porous carbonate stone, namely Lecce stone. Such a building material, specifically selected as a relevant example of porous and light coloured stone, is widely used in monuments and constructions of cultural and historic interest of the Apulia region (Italy). The protective ability of the nanocomposite against the water vapour capillarity absorption and its self- cleaning properties have been investigated as a function of the TiO 2 NR loading, the applied amount of the formulation and the curing conditions. A reliable protocol for the application of the nanocomposite has been implemented, and, remarkably, a single UV–vis light curing step has resulted in a uniform and hydrophobic coating layer, able to preserve the water vapour permeability, the pristine colour and surface morphology of the stone samples. Moreover, the nanocomposite coated stone surface has demonstrated self-cleaning ability when tested for the degradation of an organic molecule, used as a model compound, under both solar light simulated and real sun irradiation. The achieved nanocomposite has ultimately proven to be technologically advantageous as a functional coating, suited to protect surfaces of artistic, archaeological monuments of historical interest, also under outdoor conditions. 1. Introduction Stone monuments, bas-reliefs and artistic artefacts are subjected to physical-chemical weathering due to rain and moisture, temperature excursions, mechanical stress and environmental pollution. Water pe- netration into pores by capillarity causes (bio)deterioration, reactions with acid rains and micro-organism actions. The application of hydro- phobic and self-cleaning coatings, based on photocatalytically active inorganic nanoparticles (NPs), dispersed in hydrophobic resin for- mulations, can be considered a suitable strategy to limit the (bio)de- terioration of valuable pieces of Cultural Heritage. TiO 2 in nanocrystalline form is widely used in exterior and interior construction furnishing materials, due to its low toxicity, commercial availability, optical transparency in the visible spectral range, photo and chemical stability and excellent antimicrobial and photocatalytic activity [1]. TiO 2 NP based coatings, achieved by dispersing commercial TiO 2 P25 NPs in water, have been applied on marble sur- faces to prevent bacterial activity [2,3], while hydrolytically pre-syn- thesized TiO 2 NPs dispersed in water, or TiO 2 NPs synthesized from titanium alkoxides through sol-gel process and then hydrothermal crystallization [4], have been applied as protective materials on tra- vertine [5,6]. This type of coatings typically suffers for a limited pho- tocatalytic efficiency, caused by NP aggregation and formation of in- homogeneous and cracked films, causing detachment of the photocatalyst from the supporting surface. The integration of colloidal nanosized TiO 2 photocatalyst in a polymer host should, in principle, overcome the problems related to catalyst aggregation and phase separation issues, leading to uniform and mechanically stable functional nanocomposites. Moreover, the polymer matrix in nanocomposites is expected to improve the hydro- phobicity of the coating, finally resulting in a suitable protective ma- terial. https://doi.org/10.1016/j.porgcoat.2018.05.020 Received 21 September 2017; Received in revised form 20 March 2018; Accepted 11 May 2018 ⁎ Corresponding authors. 1 The authors have equally contributed to the work. E-mail addresses: carola.corcione@unisalento.it (C. Esposito Corcione), c.ingrosso@ba.ipcf.cnr.it (C. Ingrosso). Progress in Organic Coatings 122 (2018) 290–301 Available online 30 June 2018 0300-9440/ © 2018 Elsevier B.V. All rights reserved. T