46 / 2023-08-14 09:54:29

A general strategy for sustainable 3D printing based on a multifunctional photoinitiator

3D printing; thermosets; photocurable materials; photoinitiator; cleavable

Phosphorus Material Chemistry and Applied Science > 1) Phosphorus chemistry in material science

Thermosetting photoresins comprise almost half of the polymeric materials consumed by 3D printing. The high density of crosslinks that gives thermosets their useful properties (for example, chemical and thermal resistance and tensile strength) comes at the expense of degradability and recyclability. Most of them will be burned or landfilled in the end. To tackle this issue, researchers have used alternative materials such as thermoplastic polymers, Vitrimers, and cleavable crosslinkers in the printing process. However, current research is focused on specific monomers or crosslinkers. A general strategy to realize the recycling and reuse of photoresins is still missing.

Based on the previous research of bisacylphosphane oxide photoinitiators, we aim to build a new and universal strategy for the development of recyclable photoresins. This is achieved with an initiable, cross-linkable, and cleavable multifunctional photoinitiator, which is prepared by immobilizing a photoinitiator with an additional cleavable group on the surface of γ-Cyclodextrin. It has been verified that the multifunctional photoinitiator can initiate polymerization at 450 nm and cleavage at 365 nm, and the polymerization and cleavage are carried out independently without cross-talk. It is suitable for the polymerization of various monomers such as short-chain aliphatic acrylates, long-chain aliphatic acrylates, aromatic acrylates, and heterocyclic acrylates. Based on the spatially controllable properties of photodegradation, specific patterns or shapes can be degraded on cured materials. The cleaved linear polymers were purified and dissolved in new monomers, which can be reused for photocuring. With a self-developed 450 nm blue light DLP printer, high-precision printing is realized.