Polydopamine nano-hybrids : interfacial and photoactive role in epoxy nanocomposites and polymerization

• Main Author: Subramanian, Alamelu Suriya
• Other Authors: Hu Xiao
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Materials; Engineering::Nanotechnology
• Online Access: https://hdl.handle.net/10356/141637
• Institution: Nanyang Technological University

Mussel foot protein biomimetic polydopamine has unique physical, chemical, photoactive and semiconducting properties and was in receipt of abundant interest during the last decade since its first inception study as an adhesive material. PDA’s facile synthesis procedures and ability to literally coat on any kind of surface increase its applicability. In this project, the mimetic molecule was used to modify nanofillers for epoxy matrices, which were studied as nanocomposite adhesives and as potential 3D printable UV curing photopolymer system. The results showed as much as 100% improvement in lap shear strength compared to unfilled epoxies bonded on aluminum substrates. Cohesive mode failure was also observed. Photopolymerization sustained research effort due to applications in adhesives, coating, printing inks and lithography but more recently renewed interest and effort due to emergence of additive manufacturing. Currently printable resins are predominantly neat polymer acrylates as the free radical polymerization route provides the reaction speeds required for the layer by layer additive manufacturing process. Advantages of epoxy compared with acrylates are reduced shrinkage; reaction not being affected by oxygen as its controlled cationic route but however it requires lower wavelengths than photoinitiators for free radical polymerization. So FRPCP approach was used, which makes use of photoinitiating system with photoinitiators sensitive in higher wavelengths (> 360 nm) and that subsequently trigger the cationic photoinitiator without requiring deep UV radiation. A novel strategy involving dual role nanophotoinitiator/ sensitizers in the photoinitiating system resulting in synergy for faster cure of epoxy has been proposed and evaluated.