Unique Curing Properties through Living Polymerization in Crosslinking Materials: Polyurethane Photopolymers from Vinyl Ether Building Blocks

Abstract

Photopolymers with unique curing capabilities were produced by combining living cationic polymerization with network formation and restricted polymer motion. A vinyl ether diol was synthesized as a functional building block and reacted with isophorone diisocyanate to form a highly functionalized vinyl ether polyurethane as a model system with high crosslinking ability. When using a cationic photoinitiator, fast polymerization is observed upon short UV irradiation. Curing proceeds in the absence of light and under ambient conditions without oxygen inhibition. Cationic active sites become trapped dormant species upon network-induced vitrification and surprisingly remain living for several days. The polymerization can be reactivated by additional UV irradiation and/or raised temperature. The curing behavior was studied in detail by using UV and FT-NIR coupled rheology and photo-DSC to simultaneously study spectroscopic and mechanical information, as well as thermal effects.

Partially Cured Photopolymer with Gradient Bingham Plastic Behaviors as a Versatile Deformable Material

“…Ultraviolet (UV)-curable polymers have been utilized extensively owing to their unique benefits such as rapid polymerization, insolubility in organic solvents, and high resistance to heat and mechanical shocks. − While traditional use of photopolymers has been limited to photoresists, coatings, and adhesives, a range of new applications is actively being pursued in the fields of micro- and nanofabrication. − It is well-known that when a UV-curable resin is exposed to UV light in air in a micro/nanofabrication process, an oxygen-induced partial curing layer is formed on its surface owing to inhibitory effects of oxygen. − Recently, this partially cured layer has been exploited to generate multiscale structures for a variety of applications in various fields including biomimetics − and microfluidics. − Despite recent interest, however, detailed studies on the rheological and mechanical behaviors of the partially cured layer have not been conducted. Furthermore, a method for the precise control of the rheological and mechanical properties of the partially cured layer has not been fully explored.…”

Phosphonic Acid-Functionalized Polyurethane Dispersions with Improved Adhesion Properties

“…They further display an extraordinarily rich chemistry due to the reversibility of isocyanate-based bonds (urethane, urea, biuret, allophanate, etc.) and allow for facile modification reactions, e.g., to integrate thermal- or UV-curing capabilities. , In the recent past, due to a rising environmental concern and increasingly stringent governmental regulations restricting the production of volatile organic compounds (VOCs), researchers have begun to shift their focus from traditional, solvent-based PUs to aqueous PUD systems. , In particular, complex structures may be obtained which provide, e.g., self-stabilization and specific surface functionalization of the dispersions and semicrystallinity in the film. , Surprisingly, only a few reports on PUDs comporting phosphorus groups (P-PUDs) can be found in the literature. For flame retardancy purposes, a polyphosphate polyol , and a phosphorus spiro compound were utilized .…”

“…and allow for facile modification reactions, e.g., to integrate thermal-or UV-curing capabilities. 24,25 In the recent past, due to a rising environmental concern and increasingly stringent governmental regulations restricting the production of volatile organic compounds (VOCs), researchers have begun to shift their focus from traditional, solvent-based PUs to aqueous PUD systems. 26,27 In particular, complex structures may be obtained which provide, e.g., self-stabilization and specific surface functionalization of the dispersions and semicrystallinity in the film.…”