One- and Two-Photon Induced Polymerization of Methylmethacrylate Using Colloidal CdS Semiconductor Quantum Dots.
The development of one- and two-photon induced polymerization using CdS semiconductor quantum dots (QDs) and amine co-initiators to promote radical generation and subsequent polymerization is presented. Two-photon absorption (TPA) cross-section measurements, linear absorption, and transmission electron microscopy are used to characterize the QDs. The effectiveness of the co-initiators in increasing the efficiency of photopolymerization (polymer chains formed per excitation) is examined. Triethylamine was observed to be most effective, yielding quantum efficiencies of initiation of >5%. The interactions between the co-initiators and QDs are investigated with steady-state photoluminescence and infrared spectroscopies. Possible initiation mechanisms are discussed and supported by electrochemical data. Making use of the surface chemistry developed here and the large QD TPA cross-sections, two-photon induced polymerization is demonstrated. The large TPA cross-sections coupled with modest quantum efficiencies for initiation reveal the unique potential of molecularly passivated QDs as efficient two-photon photosensitizers for polymerization.