Implementation of two distinct wavelengths to induce multistage polymerization in shape memory materials and nanoimprint lithography. (7th November 2018)

• Record Type: Journal Article
• Authors: Zhang, Xinpeng; Cox, Lewis; Wen, Zhibin; Xi, Weixian; Ding, Yifu; Bowman, Christopher N.
• Is Part Of: Polymer. Volume 156(2018)
• Page Start: 162
• Page End: 168
• Publication Date: 2018-11-07
• Subjects: Photopolymerization -- Thiol-michael polymerization -- Step-growth polymerization -- "Click" chemistry; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2018.09.032
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Here, a process is introduced for forming dual stage thiol-Michael/acrylate hybrid networks photocured by two different wavelengths, demonstrating its use in nanoimprint lithography (NIL) and shape memory materials. Initiated with a visible light sensitive photobase and a UV-sensitive radical initiator, thiol-Michael-acrylate hybrid polymerizations were programmed to proceed sequentially and orthogonally, with base-catalyzed thiol-Michael photopolymerization as the first stage and radical mediated acrylate photopolymerization as the second stage. By regulating the photopolymerization formulations, i.e. thiol-to-acrylate ratios, initiator loadings and irradiation conditions, a series of materials with highly tunable mechanical performance was achieved, with ultimate Tg values ranging from 23 to 70 °C. With a photopatternable first stage and a readily reconfigurable second stage, its implementation in nanoimprint lithography (NIL) enabled surface features on the scale of 10 nm to be formed on a photopatterned substrate. Additionally, the dual stage polymer results in a relatively homogenous polymer network with a narrow glass transition temperature (Tg), which enables rapid response in applications as shape memory materials, with shape-fixity values above 95% and shape-recovery values above 99%. With its unique photocuring process and programmable mechanical properties, the two color light controlled photopolymerization can be exploited as a useful tool in a wide range of materials science applications. Graphical abstract: Highlights: A photo-induced multistage polymerization was achieved in the thiol-Michael/acrylate hybrid polymer system. Nanoscale features (<10 nm) were created on the photopatterned surfaces by this multistage polymerization. The multistage polymers were used to produce shape memory materials with simple, three-dimensional structures.