Qiaobo Li

New Preparation of Structurally Symmetric, Biodegradable Poly(L‐lactide) Disulfides and PLLA–Stabilized, Photoluminescent CdSe Quantum Dots

New, biodegradable poly(L-lactide) disulfides, PLLA-SS-PLLA, were first prepared through the DMAP-catalyzed ring-opening polymerization of L-lactide with a dihydroxyethyl disulfide initiator, and were further catalytically reduced into thiol-end-functionalized poly(L-lactide)s, HO-PLLA-SH, with a tributyl phosphine catalyst (PBu3). Employing the HO-PLLA-SH as the ligand, new core-shell CdSe/PLLA quantum dots (QDs) were continuously prepared via a facile ligand-exchanging process with the CdSe/TOPO QD precursor. The chemical structures, morphologies and solvent solubility of these prepared CdSe/PLLA QDs were investigated by NMR spectroscopy, FTIR spectroscopy, XRD, TEM and excitation under either room light or UV radiation at 365 nm, demonstrating the successful ligand replacement and the new formation of core-shell CdSe/PLLA QDs (diameter:4.0 +/- 0.3 nm). Finally, UV and FL results indicate the two factors of the HO-PLLA-SH ligand molecular weight and the ligand/QD precursor feeding weight ratio were important for preparing stable and highly photoluminescent CdSe/PLLA QDs.

Solvent annealing-induced microphase-separation of polystyrene-b-polylactide block copolymer aimed at preparation of ordered nanoparticles/block copolymer hybrid thin film

A facile way to prepare a Nanoparticles/Block Copolymer (NPs/BCP) hybrid thin film with highly ordered cylindrical nanodomains of vertical orientation is presented in the current work. First, structurally well-defined polystyrene-b-poly(D-lactide) (PS-b-PDLA) and thiol-end-functionalized PDLA stabilized NPs (PDLA@CdSe) are efficiently synthesized and fully characterized. A neutral surface for PS-b-PDLA is obtained through simple hydrophobic modification on a natural Si (100) wafer. The self-assembled pattern of PS-b-PDLA thin film on the neutral surface is investigated in detail, mainly by Atomic Force Microscope (AFM) under various solvent annealing conditions. The results show that the surface morphology of the thin film is dependent not only on the film thickness, but also on the selectivity of the solvent, vapor pressure and annealing time. A small amount of NPs incorporated into the BCP thin film can promote its microphase separation, resulting in the formation of highly ordered cylindrical nanodomains of vertical orientation in the inorganic NPs/BCP hybrid thin film.