Block copolymer (BCP) have been studied extensively in the past few decades due to their ability to self-assemble into various periodic structures at the nanometer scale. The self-assembly behaviour of BCP could further be used to direct the assembly of targeted functionalities. Among various BCP, poly(2-vinylpyridine) (P2VP) and poly(4-vinylpyridine) (P4VP) containing BCP have received considerable attention due to the ease with which nanoparticles, organic molecules and plasmonic materials could be incorporated in such BCPs. In the present study, we have investigated the self-assembly of a cylinder forming polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer blended with trioctylphosphine oxide (TOPO) capped cadmium selenide (CdSe) quantum dots (QDs). The QDs were found to be enthalpically compatible with P4VP chains via ligand displacement of TOPO from the surface of the QD which was further corroborated by the <sup>31</sup>PNMR. Interestingly, morphology transition from hexagonally closed packed cylinder to lamellar was observed with increasing weight fraction of CdSe QDs in PS-b-P4VP/QD hybrids as observed from the small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). This morphological transformation was induced by the migration of the displaced TOPO from the QD surface to polystyrene (PS) phase, effectively increases its total volume fraction. Hence, BCP with PS as the minority block showed lamellar morphology in its hybrid with CdSe QDs. Furthermore, the PS-b-P4VP/CdSe hybrid self-assembled nano-structures was isolated to produce photoluminescent nano-object containing CdSe QDs, such as nanofibers and nanosheets. The isolated nanostructures exhibited good fluorescent properties due to the presence of CdSe QDs, confirmed by the photoluminescent spectroscopy. These photoluminescent polymer nano-objects could potentially be used in a number of applications such as drug delivery, loading catalysts, medical diagnosing and fluorescent labelling.

Morphology transition in block copolymer/quantum dot hybrids <i>via</i> ligand displacement and formation of photoluminescent nano-objects

2019 Spring National Meeting

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Morphology transition in block copolymer/quantum dot hybrids via ligand displacement and formation of photoluminescent nano-objects