The synthesis, characterization, and polymerization of a new cyclic ester, γ-bromo-ε-caprolactone (γBrCL), are reported. The ring-opening polymerization (ROP) of this new monomer initiated from Al(OiPr)3 as initiator in toluene at 0 °C was found to be living and proceeds by a coordination−insertion mechanism. Random and block copolymerizations of this γBrCL with ε-caprolactone (εCL) were also found to be living as evidenced by the experimental molecular weight which is consistent with that expected from the monomer to initiator molar ratio, the narrow polydispersity, and the good agreement between the comonomers molar fraction in the comonomer feed and the copolymer. The thermal transitions (T g and T m) in the εCL/γBrCL random copolymers depend strongly on the γBrCL content. Increasing the γBrCL content in the copolymer (F BrCL) increased the T g of the copolymer from −61 °C for poly(ε-caprolactone) to −16.5 °C for the PγBrCL homopolymer but decreased the T m of the PCL to contents of ∼ 30 mol % of γBrCL (F BrCL = 0.3). Beyond this value, the copolymers were found to be amorphous and exist as viscous liquids.

New functional aliphatic polyesters were prepared by chemical modification of brominated copolyesters. Poly( -caprolactone)-co-poly(γ-(2-bromo-2-methylpropionate)--caprolactone) copolymer was prepared and successfully converted into copolyester bearing methacrylate double bonds by dehydrohalogenation of the pendant tertiary alkyl bromides, thus leading to cross-linkable polyester. The tertiary alkyl bromide groups of the original copolyester were also quaternized by reaction with pyridine, although some side reactions occurred which limited the reaction yield. Nevertheless, quaternization of the bromide groups of the poly( -caprolactone)-co-poly(γ-bromo--caprolactone) copolymer proved to be quantitative and to occur without degradation of the polyester chains. This general strategy paves the way to either amphiphilic copolyesters or water-soluble polyesters. The poly( -caprolactone)-co-poly(γ-bromo--caprolactone) copolymer was also quantitatively converted into unsaturated copolyester by dehydrohalogenation with formation of double bonds including acrylic-type double bonds. As an alternative, γ-bromo-caprolactone was first dehydrohalogenated, and the unsaturated cyclic monomer was copolymerized with -caprolactone. Finally, the nonconjugated double bonds of the copolyesters were oxidized into epoxides, except for the acrylic-type unsaturations which remained unchanged.

Fully biodegradable and surface-functionalized poly(D,L-lactide) (PLA) nanoparticles have been prepared by a co-precipitation technique. Novel amphiphilic random copolyesters P(CL-co-gammaXCL) were synthesized by controlled copolymerization of epsilon-caprolactone and epsilon-caprolactone substituted in the gamma-position by a hydrophilic X group, where X is either a cationic pyridinium (gammaPyCL) or a non-ionic hydroxyl (gammaOHCL). Nanoparticles were prepared by co-precipitation of PLA with the P(CL-co-gammaXCL) copolyester from a DMSO solution. Small amounts of cationic P(CL-co-gammaPyCL) copolymers are needed to quantitatively form stable nanoparticles (ca. 10 mg/ 100 mg PLA), although larger amounts of non-ionic P(CL-co-gammaOHCL) copolymers are needed (> or = 12.5 mg/ 100 mg PLA). Copolymers with a low degree of polymerization (ca. 40) are more efficient stabilizers, probably because of faster migration towards the nanoparticle-water interface. The nanoparticle diameter decreases with the polymer concentration in DMSO, e.g. from ca. 160 nm (16 mg/ml) to ca. 100 nm (2 mg/ml) for PLA/P(CL-co-gammaPyCL) nanoparticles. Migration of the P(CL-co-gammaXCL) copolyesters to the nanoparticle surface was confirmed by measurement of the zeta potential, i.e. ca. +65 mV for P(CL-co-gammaPCL) and -7 mV for P(CL-co-gammaOHCL). The polyamphiphilic copolyesters stabilize PLA nanoparticles by electrostatic or steric repulsions, depending on whether they are charged or not. They also impart functionality and reactivity to the surface, which opens up new opportunities for labelling and targeting purposes.

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Atomic layer deposition (ALD) on mechanically exfoliated 2D layered materials spontaneously produces network patterns of metal oxide nanoparticles in triangular and linear deposits on the basal surface. The network patterns formed under a range of ALD conditions, and were independent of the orientation of the substrate in the

Passivating defective regions on monolayer graphene with metal oxides remains an active area of research for graphene device integration. To effectively passivate these regions, a water-free atomic layer deposition (ALD) recipe was developed and yielded selective-area ALD (sa-ALD) of mixed-metal oxides onto line defects in monolayer graphene. The anisotropically deposited film targeted high-energy defect sites that were formed during synthesis or transfer of the graphene layer. The passivating layer exceeded 10 nm thickness with minimal deposition onto the basal plane of graphene. The mixed-metal oxide film was of comparable quality to films deposited using nonselective waterbased ALD methods, as shown by X-ray photoelectron spectroscopy. The development of sa-ALD techniques to target defect regions on the graphene sheet, while keeping the basal plane intact, will provide a new mechanism to passivate graphene defects and modify the electronic and physical properties of graphene.

Graphene, with its high conductivity, specific surface area, and overall chemical inertness, has been heavily researched for applications in batteries, supercapacitors, and water-splitting devices. While graphene films can be synthesized over large areas (>1 cm2) through chemical vapor deposition, graphene generated through this route exhibits a high defect density that can inhibit performance and stability in electrochemical systems. Considerable effort has been devoted to passivating, repairing, and remediating these defects for graphene-based devices to match their theoretical potential. To this end, we have developed new atomic layer deposition (ALD) processes designed to selectively passivate high energy defect sites with metal oxides. This deposition chemistry targets dangling bonds and oxidized regions on the graphene sheet based on their higher reactivity relative to the pristine basal plane. We have also demonstrated analogous chemistry on bulk highly-ordered pyrolytic graphite as well as exfoliated few-layer graphene. The efficacy of the deposition process was examined as a function of precursor dose and temperature. The selectivity of this process and metal-oxide layer thicknesses was assessed using several electron microscopy techniques. This work further illustrates an effective scheme to ameliorate the interfacial chemistry of large-area graphene and demonstrate how targeted passivation can improve device performance.