Novel synthesis of covalently linked silicon quantum dot-polystyrene hybrid materials: Silicon quantum dot-polystyrene polymers of tunable refractive index

We present a new material design concept, silicon quantum dot (Si QD) polymers, for which surface-functionalized Si QDs can be regarded as a large monomer in the polymers. As a prototypical example, vinyl-functionalized Si QDs, i.e., divinylbenzene-capped Si QDs (DVB-Si QDs) synthesized by adopting divinylbenzene (DVB) capping molecule to the hydride-terminated Si QD (H-Si QD) via Pt-catalyzed hydrosilylation was introduced and polymerized with a styrene monomer to yield Si QD -polystyrene (Si QD-PS) polymers. To demonstrate controllability of the content of Si QDs in the polymers as in conventional polymers, three Si QD content varied Si QD-PS polymers were systematically prepared, named as Si QD-PS-A, Si QD-PS-B, and Si QD-PS-C. It has been demonstrated that the content of the Si QDs in the Si QD-PS polymers was well controlled by the amount of the DVB-Si QD used, as found to be 3.8 wt% (Si QD-PS-A), 10.0 wt% (Si QD-PS-B), 20.0 wt% (Si QD-PS-A), and 37.4 wt% (DVB-Si QD), which was deduced from TGA results. Thin films of the Si QD-PS polymers and the freestanding DVB-Si QDs were successfully fabricated by a spin-coating method and it was found that the refractive index of the thin films dried at 40 degrees C was linearly increased as the content of the Si QD in the polymers was increased from 1.586 (0 wt%), to 1.590 (3.8 wt%), to 1.592 (10.0 wt%), to 1.592 (20.0 wt%), and to 1.614 (37.4 wt%). (C) 2014 Elsevier B.V. All rights reserved.