Synthesis and characterization of magnetite particles covered with α-trietoxysilil-polydimethylsiloxane

New silicon magnetite ferrofluids were prepared by dispersing siloxane-coated magnetite particles in polydimethylsiloxane with low or high molecular weights. Ferrofluids are stable colloidal dispersions of ultra fine covered magnetite particles, which may be selected for a specific application. We demonstrated new methods of stabilizing the magnetic particles by reacting the hydroxyl groups on the surface of magnetite particles with terminal ethoxy groups of polydimethylsiloxane, followed by their dispersion in silicon fluids. The new silicon ferrofluids were tested from the morphology, magnetic properties/losses, and rheological properties point of view.     

Disperse red 1 end capped oligoesters. Synthesis by noncatalyzed ring opening oligomerization and structural characterization

The synthesis of novel azofunctional oligoesters through bulk ring opening of ε‐caprolactone and D ,L ‐lactide (LA) at 100 and 130 °C, respectively, mediated by N‐ethyl‐N‐(2‐hydroxyethyl)‐4‐(4‐nitrophenylazo)aniline (Disperse Red 1) (DR1) is described. The synthetic procedure allows “clean” products because no catalysts were used in the reaction. Moreover, DR1 moiety is showed for the first time to promote the ring opening of cyclic esters. The molecular structure of the obtained oligoesters was established by NMR spectroscopy, MALDI ToF MS and electrospray ionization mass spectrometry (ESI MS). ESI‐MS/MS fragmentation experiments were used to demonstrate the nature of the chain end groups (hydroxyl and DR1). Intermolecular transesterification reactions were proved by mass spectrometry studies at least in the case of LA oligomerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 534–547, 2009     

Inclusion complexes of γ-cyclodextrin and carboxyl-modified γ-cyclodextrin with C60: synthesis, characterization and controlled release application via microgels

Carboxyl modified γ-cyclodextrin (CDSA) with a substitution degree of about 9.5 was prepared by the esterification of γ-cyclodextrin (CD) with succinic anhydride in pyridine at 90 °C. The chemical composition and the structure of CDSA were characterized by FT-IR, MALDI-TOF, X-ray diffraction pattern, potentiometric titration and TGA. Modified and native γ-cyclodextrin associate with fullerene (C₆₀) in DMF-toluene mixture resulting 1:1 CDSA:C₆₀ and CD:C₆₀ inclusion complexes. Aqueous solutions of native cyclodextrin, carboxyl-modified cyclodextrin and their inclusion complexes with C₆₀ were used as microgel solvent (or swelling agent) for controlled release application. The release of solutions was induced by shear stress and demonstrated using rheo-optical set-up.     

Molecular level differentiation between end‐capped and intramolecular azofunctional oligo(ε‐caprolactone) positional isomers through liquid chromatography multistage mass spectrometry

End‐capped and intramolecular azofunctional oligocaprolactones were characterized at molecular level by liquid chromatography electrospray ionization mass spectrometry (ESI MS) and NMR spectroscopy. The Disperse Red 19 (DR19) azofunctional oligomers, DC, were synthesized by ring‐opening oligomerization of ε‐caprolactone (ε‐CL) initiated by the hydroxyl groups of DR19 azo dye. The reaction products consist of a minor fraction of end‐capped azo functional oligocaprolactone (α‐DC), that is, a single CL arm oligomer, and a major fraction of intramolecular azo functional oligocaprolactone (β‐DC), that is, a two CL arms oligomer. The chromatographic separation was used to discriminate between α‐DC and β‐DC, and the results were confirmed by MS/MS performed on an ESI ion trap instrument. The results supported by accurate mass data obtained for product ions using an ESI quadrupole time of flight instrument demonstrate the qualitative discrimination at the molecular level between intramolecular and end‐capped azofunctional oligoesters isomers through a relatively simple multistage mass spectrometry experiment. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Mass spectrometry characterization of 3‐OH butyrated β‐cyclodextrin

Oligo(3‐OH butyrate)‐β‐cyclodextrin esters (PHB‐CD) were obtained through ring opening of β‐butyrolactone (β‐BL) in the presence of β‐cyclodextrin (CD) and (‐)‐sparteine (SP) as nucleophilic activator. The resulted reaction mixture was first separated in two fractions and then investigated through a deep mass spectrometry (MS) study performed on a liquid chromatography‐electrospray ionization‐quadrupole time of flight (LC‐ESI‐QTOF) instrument. LC MS and tandem MS structural assignment of the reaction products was completed by NMR. The performed analysis revealed that poly(3‐OH butyrate) homopolymers (PHB) are formed together with the PHB‐CD products. Secondary reactions resulting in the formation of crotonates were also proved to occur. A comparison between MS and NMR results demonstrated that more than one PHB oligomer is attached to the CD in the PHB‐CD product. The tandem MS fragmentation studies validated the proposed structure of CD derivatives. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Amphiphilic azopolymers capable to generate photo-sensitive micelles

Amphiphilic macromolecular micelles are advantageous for drug delivery applications due to the decrease of side-effects, ease of screening drugs against degradation, long-term stability, targeted delivery and control of the amount of the released drug. A series of amphiphilic azo-polymers having a flexible or rigid main-chain were synthesized and characterized. The presence of chlorobenzyl side-groups allowed both the easy bonding of photo-sensitive or hydrophilic groups and good control of the degree of substitution. The chemical structure was confirmed by ¹H-NMR. The critical concentration of aggregation (CCA) was calculated using the fluorescence emission spectrum of pyrene. The interest was focused on a preliminary study concerning the disaggregation capacity of micelles under UV irradiation. The presence of micellar aggregates was confirmed by DLS and SEM and different organization of the amphiphilic polymers was evidenced depending on polymers concentration and polymers structure. In low polymer concentrations in water predominantly globular aggregates were formed. The increase in concentration increased the polydispersity index due to the fusion of micelles and formation of associates of globular aggregates, inter-micellar associates (clusters) and vesicles.