ACTIVE-BAPO - A Versatile Transfer Agent for Photoactive Bis(acyl)phosphane Oxide Units

Area of Science:

• Polymer Chemistry
• Materials Science
• Organic Synthesis

Background:

• Bis(acyl)phosphine oxides (BAPOs) are efficient photoinitiators for radical polymerization.
• Developing new photoinitiators with improved properties and functionalities is crucial for advanced material applications.
• Poly(amidoamine) (PAMAM) dendrimers offer a versatile platform for creating polymeric materials due to their branched structure and numerous functional groups.

Purpose of the Study:

• To synthesize a novel N-hydroxy succinimide (NHS) ester substituted bis(acyl)phosphane oxide (ACTIVE-BAPO).
• To utilize ACTIVE-BAPO for facile conjugation with primary amino groups on various substrates, including biomolecules and dendrimers.
• To evaluate the performance of the resulting polymeric photoinitiators, particularly poly(amidoamine) (PAMAM) BAPOs, in free radical polymerization and crosslinking applications.

Main Methods:

• Synthesis of ACTIVE-BAPO via phospha-Michael addition.
• One-step BAPO ligation with amino-functionalized substrates (amino acids, proteins, PAMAM dendrimers).
• Real-time photo-rheology experiments to assess photoinitiator efficiency.
• Characterization of thermosetting networks formed by PAMAM BAPOs.

Main Results:

• A range of new molecular and polymeric photoinitiators were successfully prepared.
• PAMAM BAPOs demonstrated outstanding efficiency as photoinitiators in free radical polymerization.
• PAMAM BAPOs acted as crosslinking agents, converting monofunctional methacrylate monomers into thermosetting networks without additional crosslinkers.
• The degree of crosslinking and swelling capability of the thermosets could be tuned by varying the number of attached BAPOs.

Conclusions:

• The developed ACTIVE-BAPO is a versatile building block for creating novel photoinitiators.
• PAMAM BAPOs are highly efficient photoinitiators and effective crosslinking agents for creating thermosets.
• This approach offers a facile method for synthesizing functional polymeric materials with tunable properties.