The structure and properties of nanocomposites of poly(ethylene oxide), with Ag and Au nanoparticles, surface modified with a 1:1 (by volume) oleylamine/oleic acid mixture, were investigated via transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), infrared spectroscopy, dynamic mechanical analysis, and static mechanical testing. Results indicated that there was more oleylamine on Ag nanoparticles but more oleic acid on Au nanoparticles. This difference in surfactant populations on each nanoparticle led to different interfacial interactions with poly(ethylene oxide) and drastically influenced the glass transition temperature of these two nanocomposite systems. Almost all other properties were found to correlate strongly with dispersion and distribution state of Au and Ag nanoparticles, such that the property in question changed direction at the onset of agglomeration.
A facile synthetic route to poly(ethylene imine)-graft-poly(oligo(ethylene glycol methyl ether)) (PEI-graft-POEGMA) functionalised superparamagnetic magnetite nanoparticles is described. The polymerisation of OEGMA from a model molecular amide demonstrated the feasibility of POEGMA synthesis under mild ATRP conditions (20 C in ethanol) albeit with low initiator efficiencies. DFT studies suggest that the amide functionality is intrinsically of lower activity than ester functional monomers and initiators for atom transfer polymerisation (ATRP) as a consequence of higher bond dissociation energies and bond dissociation free energies (BDFE). However these studies further highlighted that use of an appropriate solvent could reduce the free energy of dissociation thereby reducing the relative difference in BDFE between the ester and amide groups. A commercial branched PEI sample was functionalised by reaction with 2-bromo-2-methylpropanoyl bromide giving an amide macroinitiator suitable for the atom transfer radical polymerisation (ATRP) of oligo(ethylene glycol methyl ether) methacrylate. The resulting PEIgraft-POEGMA copolymers were characterised by SEC, FT-IR and 1 H and 13 C NMR spectroscopy. PEIgraft-POEGMA coated magnetite nanoparticles were synthesised by a basic aqueous co-precipitation method and were characterised by transmission electron microscopy, thermogravimetric analysis and vibrating sample magnetometry and dynamic light scattering. These copolymer coated magnetite nanoparticles were demonstrated to be effectively stabilised in an aqueous medium. Overall the particle sizes and magnetic and physical properties of the coated samples were similar to those of uncoated samples. Electronic supplementary information (ESI) available: Plots of Cu(II) function with time; UV-vis absorption spectra of Cu(I)Cl, Cu(II)Cl 2 and Cu(II)Br 2 solutions with DiMePiVA; X-ray diffraction pattern of PEI-gra-POEGMA stabilised nanoparticles; high magnication TEM images of magnetite nanoparticles; pictures of particle suspensions; X-ray diffraction pattern and TEM of bare (unstabilised) nanoparticles 2D 1 H- 13 C and 1 H-15 N NMR spectra of PEI; inputs for DFT calculations; Cartesian co-ordinates of energy minimised conformations of initiators. See Scheme 3 Model structures used in DFT calculations. This journal is View Article Online a DDGG ¼ difference between DG for compound relative to DG for ester (MBriP). b K/K 0 ¼ ratio of KATRP for compound to KATRP for ester (MBriP). This journal is View Article Online a M n,theo ¼ [M]/[I] Â M n(0) Â % conversion. b SEC M n from RI response c against PMMA standards. c SEC M n from triple-detection SEC. d Conversion from 1 H NMR. 530 | Polym. Chem., 2014, 5, 524-534 This journal is
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