Thermochromic poly(L-lactic acid) based materials and their printability on different substrates

Abstract

Ionic liquids (ILs) have been combined with different polymer matrixes to develop smart and functional materials. Due to their versatility, hybrid materials with specific tailor made properties can be obtained, including printable thermochromic materials, with a strong potential for sensing applications. In this context, the thermochromic IL bis(1-butyl-3-methylimidazolium) tetrachloronickelate ([Bmim]2[NiCl4]) was incorporated into a biopolymer derived matrix, poly(L-lactic acid) (PLLA) in distinct concentrations up to 40% wt. aiming to develop environmentally friendly screen-printable printable thermochromic materials. The addition of IL does not induce changes on the thermal properties of the material. On the other hand, the incorporation of the IL leads to the development of a porous structure in the films, a mechanical plasticizing effect in the polymer matrix, revealed by the decrease of the Young's Modulus from 1110 ± 66 MPa to 572 ± 41 MPa and a increase in the electrical conductivity from 2.89x10-14 S·cm−1 to 2.66x10-8 S·cm−1, for PLLA and the samples with 40 % wt. of IL, respectively. Finally, the thermochromic material was screen-printed on various substrates, including paper, polyethylene terephthalate (PET), textile and wood, opening the way for a wide range of applications.