Rational design of vapor‐deposited self‐crosslinking polymer for transparent flexible oxygen barrier coatings

• Published in: Journal of applied polymer science Vol. 138; no. 21
• Main Authors: Sheng, Weijie, Chen, Ying, Mao, Haizhuo, Li, Yanshuo, Xiao, Xinle, Wang, Chunting, Ye, Yumin, Liu, Wenna
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 05.06.2021; Wiley Subscription Services, Inc
• Subjects: Chemical vapor deposition; Coatings; Copolymers; Crosslinking; Flexible components; Free surfaces; Isocyanates; Light transmittance; Materials science; Molecular structure; packaging, initiated chemical vapor deposition; Pinholes; Polyethylene terephthalate; Polymers; Substrates
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.50505

Transparent flexible barrier coatings consisting of a copolymer of 2‐isocyanatoethyl methacrylate and 4‐aminostyrene were fabricated using a facile vapor‐based initiated chemical vapor deposition (iCVD) method. The isocyanate and amino groups were well reserved during deposition and reacted on the substrate surface, inducing self‐crosslinking. The resultant coating showed a fairly smooth pinhole‐free surface with more than 99% light transmittance across the visible range. With a proper compositional ratio, the synthesized coating demonstrated oxygen permeability 26 and 8 times lower than commercial PET and PVDF barrier films, respectively. The achieved barrier performance is attributed to the designed molecular structure, where interchain crosslinks are produced between a combination of both rigid and flexible side chains. Such combination enabled efficient packing of space while avoiding loose structures with low permeation resistance. The crosslinked network with rather flexible urea linkages also imparted excellent mechanical strength and high flexibility to the coating. Furthermore, the reported method is compatible with current industrial manufacturing process, thus expecting great potential in flexible electronics encapsulation. Initiated chemical vapor deposition of self‐crosslinkable poly(2‐isocyanato ethyl methacrylate‐co‐4‐aminostyrene) resulted in highly transparent flexible barrier coatings with ultralow oxygen permeability and excellent mechanical properties. The achieved barrier and mechanical performance is attributed to the rationally designed molecular structure, where crosslinking between bulky stiff side chain and flexible long side chain resulted in effective packing of space.