Varying the Core Topology in All-Glycidol Hyperbranched Polyglycerols: Synthesis and Physical Characterization.

In the present study, low molecular weight cyclic polyglycidol is used as a macroinitiator for hypergrafting glycidol and producing cyclic graft hyperbranched polyglycerol (cPG-g-hbPG) in the molecular weight range of 10-10 g mol. Linear graft hyperbranched polyglycerol (linPG-g-hbPG) and hyperbranched polyglycerol (hbPG) are prepared as reference samples. This creates a family of hbPG structures with cyclic, linear, and star cores, allowing to evaluate their properties in solution and in bulk.

Biocompatibility and Endothelial Permeability of Branched Polyglycidols Generated by Ring-Opening Polymerization of Glycidol with B(CF) under Dry and Wet Conditions.

Polyglycidol or polyglycerol (PG), a polyether widely used in biomedical applications, has not been extensively studied in its branched cyclic form (PG), despite extensive research on hyperbranched PG (HPG). This study explores the biomedical promise of PG, particularly its ability to cross the blood-brain barrier (BBB). We evaluate biocompatibility, endothelial permeability, and formation of branched linear PG (PG) as topological impurities in the presence of water.

Synthesis and Characterization of a Luminescent Cyclic Poly(ethylene oxide)-Polypyridyl Ruthenium Complex.

We report the synthesis of a macrocyclic poly(ethylene oxide) (PEO) connected by one [Ru(bpy)] unit (where bpy = 2,2'-bipyridine), a photoactive metal complex that provides photosensitivity and potential biomedical applications to this polymer structure. The PEO chain provides biocompatibility, water solubility, and topological play. The macrocycles were successfully synthesized by copper-free click cycloaddition between a bifunctional dibenzocyclooctyne (DBCO)-PEO precursor and 4,4'-diazido-2,2'-bipyridine, followed by complexation with [Ru(bpy)Cl].

Flavin-Conjugated Pt(IV) Anticancer Agents.

In situ activation of Pt(IV) to Pt(II) species is a promising strategy to control the anticancer activity and overcome the off-target toxicity linked to classic platinum chemotherapeutic agents. Herein, we present the design and synthesis of two new asymmetric Pt(IV) derivatives of cisplatin and oxaliplatin ( and , respectively) bearing a covalently bonded 2',3',4',5'-tetraacetylriboflavin moiety (). H and Pt NMR spectroscopy shows that and can be effectively activated into toxic Pt(II) species, when incubated with nicotinamide adenine dinucleotide, sodium ascorbate, and glutathione in the dark and under light irradiation.

Separation, identification, and confirmation of cyclic and tadpole macromolecules UPLC-MS/MS.

Macrocyclic poly(glycidyl phenyl ether) (pGPE) synthesized zwitterionic ring opening polymerization is typically contaminated by chains with linear and tadpole architecture. Although mass spectrometry (MS) analysis can readily confirm the presence of the linear byproduct, due to its unique mass, it is unable to differentiate between the cyclic and tadpole structures, which are constitutional isomers produced by backbiting reactions in monomeric or dimeric chains, respectively. To overcome this problem, ultraperformance reversed-phase liquid chromatography interfaced with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) was employed.

Gold nanoparticles endowed with low-temperature colloidal stability by cyclic polyethylene glycol in ethanol.

The colloidal stability of metal nanoparticles is tremendously dependent on the thermal behavior of polymer brushes. Neat polyethylene glycol (PEG) presents an unconventional upper critical solution temperature in ethanol, where phase segregation and crystallization coexist. This thermal behavior translated to a PEG brush has serious consequences on the colloidal stability in ethanol of gold nanoparticles (AuNPs) modified with PEG brushes upon cooling.

Cyclic Polyethylene Glycol as Nanoparticle Surface Ligand.

Cyclic polymers behave different than linear polymers due to the lack of end groups and smaller coil dimensions. Herein, we demonstrate that cyclic polyethylene glycol (PEG) can be used as an alternative of classical linear PEG ligands for gold nanoparticle (AuNP) stabilization. We observed that the brush height of cyclic PEG on AuNPs of diameter 4.

Broadband dielectric spectroscopy to validate architectural features in Type-A polymers: Revisiting the poly(glycidyl phenyl ether) case.

Broadband dielectric spectroscopy (BDS) is a powerful technique that allows studying the molecular dynamics of materials containing polar entities. Among a vast set of different applications, BDS can be used as a complementary tool in polymer synthesis. In this work, we will show how BDS can be used to validate architectural features in Type-A polymers, those having a net dipole moment component along the chain contour.

Endowing Single-Chain Polymer Nanoparticles with Enzyme-Mimetic Activity.

The development of simple, efficient, and robust strategies affording the facile construction of biomimetic organocatalytic nano-objects is currently a subject of great interest. Herein, a new pathway to artificial organocatalysts based on partially collapsed individual soft nano-objects displaying useful and diverse biomimetic catalytic functions is reported. Single-chain polymer nanoparticles endowed with enzyme-mimetic activity synthesized following this new route display (i) a relatively extended morphology under good solvent conditions, as revealed by small angle neutron scattering and coarse-grained molecular dynamics simulation results, (ii) multiple, compartmentalized, and accessible catalytic sites in which borane catalytic units are retained via B···O interactions, and (iii) unprecedented reductase and polymerase enzyme-mimetic properties.

Subsurface imaging of carbon nanotube networks in polymers with DC-biased multifrequency dynamic atomic force microscopy.

The characterization of dispersion and connectivity of carbon nanotube (CNT) networks inside polymers is of great interest in polymer nanocomposites in new material systems, organic photovoltaics, and in electrodes for batteries and supercapacitors. We focus on a technique using amplitude modulation atomic force microscopy (AM-AFM) in the attractive regime of operation, using both single and dual mode excitation, which upon the application of a DC tip bias voltage allows, via the phase channel, the in situ, nanoscale, subsurface imaging of CNT networks dispersed in a polymer matrix at depths of 10-100 nm. We present an in-depth study of the origins of phase contrast in this technique and demonstrate that an electrical energy dissipation mechanism in the Coulomb attractive regime is key to the formation of the phase contrast which maps the spatial variations in the local capacitance and resistance due to the CNT network.

Macromolecular Structure and Vibrational Dynamics of Confined Poly(ethylene oxide): From Subnanometer 2D-Intercalation into Graphite Oxide to Surface Adsorption onto Graphene Sheets.

In this work, high-resolution inelastic neutron scattering (INS) has been used to provide novel insights into the properties of confined poly(ethylene oxide) (PEO) chains. Two limits have been explored in detail, namely, single-layer 2D-polymer intercalation into graphite oxide (GO) and surface polymer adsorption onto thermally reduced and exfoliated graphite oxide, that is, graphene (G) sheets. Careful control over the degree of GO oxidation and exfoliation reveals three distinct cases of spatial confinement: (i) subnanometer 2D-confinement; (ii) frustrated absorption; and (iii) surface immobilization.

Easy-dispersible poly(glycidyl phenyl ether)-functionalized graphene sheets obtained by reaction of "living" anionic polymer chains.

Excellent dispersion of functionalized graphene (FG) sheets in polystyrene was achieved relying on the reaction of "living" poly(glycidyl phenyl ether) chains onto graphene sheets. The physical aging of polystyrene was substantially accelerated by the presence of FG sheets at low filler content, retaining film transparency and increasing the electrical conductivity.

Grafting of poly(acrylic acid) onto an aluminum surface.

Grafting of poly(acrylic acid) (PAA) onto an aluminum surface was successfully achieved by free radical polymerization of acrylic acid using typical radical initiators, benzoyl peroxide and 2,2'-azobisisobutyronitrile. Both spotlike and brush morphologies were achieved. A complete coverage of PAA on an aluminum surface was then achieved by using a thermal chemical vapor deposition process.

Grafting of poly(methyl vinyl ketone) onto aluminum surface.

Polymers were grafted on aluminum surfaces in order to modify the chemical and physical properties of the interface. The properly cleaned and activated surface of the aluminum substrate was first "silanized" either with 3-(trimethoxysilyl)propylamine or allyltrimethoxysilane. The grafting was carried out following two methods: (i) by the reaction of preformed poly(methyl vinyl ketone) with the aminosilane-modified surface; and (ii) by polymerization of methyl vinyl ketone with the vinylsilane-modified surface.