Rocío Cuervo-Rodríguez

Solvent effects on the free-radical copolymerization of styrene with butyl acrylate. I. Monomer reactivity ratios

The free-radical copolymerization of styrene with butyl acrylate was carried out in benzene and benzonitrile at 50°C. Differences between the apparent reactivity ratios determined in this work and those previously reported in bulk indicated noticeable solvent effects. This is explained by a qualitative bootstrap effect.

Antimicrobial films obtained from latex particles functionalized with quaternized block copolymers.

New amphiphilic block copolymers with antimicrobial properties were obtained by atom transfer radical polymerization (ATRP) and copper catalyzed cycloaddition following two approaches, a simultaneous strategy or a two-step synthesis, which were proven to be very effective methods. These copolymers were subsequently quaternized using two alkyl chains, methyl and butyl, to amplify their antimicrobial properties and to investigate the effect of alkyl length. Antimicrobial experiments in solution were performed with three types of bacteria, two gram-positive and one gram-negative, and a fungus. Those copolymers quaternized with methyl iodide showed better selectivities on gram-positive bacteria, Staphylococcus aureus and Staphylococcus epidermidis, against red blood cells, demonstrating the importance of the quaternizing agent chosen. Once the solution studies were performed, we prepared poly(butyl methacrylate) latex particles functionalized with the antimicrobial copolymers by emulsion polymerization of butyl methacrylate using such copolymers as surfactants. The characterization by various techniques served to test their effectiveness as surfactants. Finally, films were prepared from these emulsions, and their antimicrobial activity was studied against the gram-positive bacteria. The results indicate that the antimicrobial efficiency of the films depends not only on the copolymer activity but also on other factors such as the surface segregation of the antimicrobial agent to the interface.

A kinetic study on the radical copolymerization of dimethyl itaconate and methyl methacrylate in benzene

Abstract The copolymerization of dimethyl itaconate and methyl methacrylate with 2,2′-azobisisobutyronitrile was investigated kinetically at 50°C in benzene. The copolymer composition conforms to the terminal model within experimental error, but the variation of the copolymerization rate shows a penultimate effect on the propagation reaction. Homopolymerization kinetic coefficients for dimethyl itaconate monomer were also determined.

Preparation of amphiphilic glycopolymers with flexible long side chain and their use as stabilizer for emulsion polymerization.

A glycomonomer was synthesized from poly(ethylene glycol) methacrylate (PEGMA). The terminal hydroxyl moieties were activated with ester groups and subsequently the glucosamine was incorporated forming urethane linkages. The obtained glycomonomer was copolymerized with methyl acrylate by free radical polymerization varying the initial feed composition to produce different amphiphilic glycopolymers. The glycopolymers were then characterized and compared with the homologous glycopolymers based on 2-{[(D-glucosamin-2-N-yl)carbonyl]oxy}ethyl methacrylate. Both series of glycopolymers were used in emulsion polymerization of methyl acrylate as stabilizers without the addition of any cosurfactant. Although high conversions were not achieved with any of the employed surfactant, the glycopolymers provide good colloidal stability, spherical, monodisperse and small latex particles in comparison with the surfactant-free emulsion polymerization. The latex particles stabilized with the glycosurfactant based on PEGMA, containing a flexible spacer between the backbone and the glucosamine, lead to smooth films whereas the short side chain surfactant from 2-hydroxyethyl methacrylate (HEMA), with higher glass transition temperature, restricts the coalescence of particles and, therefore, the film formation. Moreover, the surface bioactivity of these polymer coatings was examined by analyzing their specific interaction with the lectin, Concanavalin A, Canavalia ensiformis. The specific and successful binding to the Concanavalin A was demonstrated by fluorescence microscopy for both series being more intense with increasing amount of glycounits in the glycopolymer stabilizers. Interestingly, the incorporation of a flexible spacer in the glycopolymer structures enhances the binding activity.

Amphiphilic polymers bearing gluconolactone moieties: synthesis and long side-chain crystalline behavior.

The synthesis and characterization of amphiphilic polymers bearing gluconolactone moieties has been described. In a first step, an unprotected glycomonomer 2-[({[4-(d-gluconamid-N-yl)butyl]amino}carbonyl)oxy]ethyl acrylate, HEAG, has been synthesized. Posterior, this glycomonomer has been copolymerized with methyl methacrylate at different compositions and the kinetic behavior has been also studied calculating the monomer reactivity ratios by Kelen-Tüdös extended equation. In addition, the long side-chain crystalline behavior of these carbohydrate-based copolymers with high composition of glycomonomer has been examined by using conventional and modulated differential scanning calorimetry and X-ray diffraction measurements. At the same time, the phase separation behavior of carbohydrate-based copolymers with lower HEAG content has been determined by their glass transition temperature measurements. Finally, the thermal stability of all these amphiphilic copolymers has been evaluated by thermogravimetric analysis.

Thermal properties of ethyl α-hydroxymethylacrylate-methyl methacrylate copolymers

Abstract The degradation and glass transition temperatures of a series of methyl methacrylate (MMA)-ethyl α-hydroxymethylacrylate (EHMA) copolymers have been studied by t.g.a./i.r. and d.s.c. Thermal degradation yielded intramolecular lactone and intermolecular crosslinking formation, with concurrent loss of ethanol and/or methanol involving adjacent or near-neighbour EHMA or MMA units. Glass transitions of copolymers have been analysed as a function of sequence distribution and their values compared to the theoretical ones derived using Johnstons equation. The partially degraded copolymers increased their glass transition temperatures as a consequence of the above mentioned lactone and crosslinking formation.

Sequence Distribution and Stereoregularity in Styrene/Butyl Methacrylate Copolymers Obtained at High Conversion by Stable Free-Radical Polymerization

13 C NMR spectra of styrene/butyl methacrylate copolymers prepared in bulk at 125°C using 2,2,6,6-tetramethyl-1-(1-phenylethoxy)piperidine as the initiator were analyzed. After assignment of the carbon resonances of the aromatic C-1 region, the Mayo-Lewis terminal model (MLTM) was tested by comparison of experimental and predicted values of configurational triad sequences. It follows that MLTM provides an excellent prediction across a wide conversion range for all comonomer feeds.

Antimicrobial Porous Surfaces Prepared by Breath Figures Approach

Herein, efficient antimicrobial porous surfaces were prepared by breath figures approach from polymer solutions containing low content of block copolymers with high positive charge density. In brief, those block copolymers, which were used as additives, are composed of a polystyrene segment and a large antimicrobial block bearing flexible side chain with 1,3-thiazolium and 1,2,3-triazolium groups, PS54-b-PTTBM-M44, PS54-b-PTTBM-B44, having different alkyl groups, methyl or butyl, respectively. The antimicrobial block copolymers were blended with commercial polystyrene in very low proportions, from 3 to 9 wt %, and solubilized in THF. From these solutions, ordered porous films functionalized with antimicrobial cationic copolymers were fabricated, and the influence of alkylating agent and the amount of copolymer in the blend was investigated. Narrow pore size distribution was obtained for all the samples with pore diameters between 5 and 11 µm. The size of the pore decreased as the hydrophilicity of the system increased; thus, either as the content of copolymer was augmented in the blend or as the copolymers were quaternized with methyl iodide. The resulting porous polystyrene surfaces functionalized with low content of antimicrobial copolymers exhibited remarkable antibacterial efficiencies against Gram positive bacteria Staphylococcus aureus, and Candida parapsilosis fungi as microbial models.