Patterning Of Polydiacetylene/Poly(Propylene Carbonate) Plastic Films

The patterning of plastic films is an important step for plastic packaging,which is of great significance to raise the value-added to plastic packaging and to promote the brand image.Nevertheless,it still remains challenging to recycle and reuse the plastics with printed patterns due to the formidable difficulty to remove the patterns from the plastic substrate.As a consequence,mountains of plastic wastes have gone into the environment and caused severe problems.Meanwhile,the widely printed patterns on plastics are ready to illegally copy and thus hard to meet the security requirements of advanced plastic packaging.Herein,a type of rewritable and recyclable polydiacetylene(PDA)/poly(propylene carbonate)(PPC)plastic films are demonstrated,which are further integrated with upconversion nanoparticles(UCNP)with anti-counterfeiting functions,affording controllable pattern colors under the near-infrared light.First,the PDA/PPC plastic film was fabricated by homogeneously mixing PPC with the monomer pentacosadiynoic acid(PCDA),followed by host pressing and the subsequent photomediated topochemical polymerization of PCDA upon UV irradiation.The PDA can show blue color upon UV irradiation,and readily turn to red upon heating through conformational switch.Such a unique reversible photo-/thermo-response capability of the PDA allows for writing and erasing patterns on the PDA/PPC plastic film,and rewriting can be exerted more than 17 times,and each pattern is stable for 9 months under ambient conditions.It was found that the assembly and topochemical polymerization of PCDA can be greatly promoted by the hydrogen bonding interactions between the PCDA and PPC,by UVvisible spectroscopy,fluorescent spectroscopy and molecular dynamics simulations.And the thermochromic temperature of PDA in the plastic film was increased by 50% from 60 to90 ? compared with the pure PDA.Furthermore,compared with PPC,the glass transition temperature(34.1 ?)and initial decomposition temperature(262.4 ?)of the formulated PDA/PPC plastic films were increased by 33.2% and 49.9%,respectively,according to differential scanning calorimetry and thermogravimetric analysis.The prepared PDA/PPC plastic film can be recycled by hot pressing and also shows good tensile performance.Second,UCNP in the core-shell structure were synthesized with a size of 10.7 ± 1.1 nm but different upconversion emission colors(e.g.,blue,green and red),based on which the PDA/PPC/UCNP composite plastic films with upconversion emission functions were fabricated through the topochemical polymerization of PCDA.Then,the pattern color of the composite plastic films under 980 nm laser was finely tuned by virtue of the F(?)ster resonance energy transfer from the UCNP to PDA.Attractive patterning was achieved at the optimized mass ratio of 5: 50: 4 for PDA/PPC/UCNP.The proposed PDA/PPC/UCNP composite plastic films are not only able to show clear patterns under room light,but can also display controllable pattern colors upon 980 nm laser,which promise advanced security and anticounterfeiting applications of the plastic films.