Laura Ricco

Free radical grafting onto cellulose in homogeneous conditions 1. Modified cellulose-acrylonitrile system

Abstract Synthesis of cellulose–polyacrylonitrile copolymers has been studied in a homogeneous solution of N,N-dimethylacetamide/LiCl. The method is based on the preliminary reaction of a portion of OH cellulosic groups with acryloyl chloride to give cellulose with a certain number of pendant double bonds. Successively, acrylonitrile is grafted onto the unsaturated groups by free radical polymerization using azobisisobutyronitrile as initiator. The optimum grafting conditions are evaluated by changing reaction temperature, as well as monomer/initiator and monomer/unsaturated group molar ratios. The products are characterized by size exclusion chromatography, i.r. and 13C n.m.r. spectroscopy and a possible reaction mechanism is deduced.

Caprolactam-laurolactam copolymers : Fast activated anionic synthesis, thermal properties and structural investigations

Anionic poly(caprolactam-co-laurolactam) has been isothermally synthesized at 155°C by hexamethylene dicarbomoylcaprolactam as fast activation agent and two Na lactamates (from the mixed monomers or neat caprolactam, respectively) as initiators. The specific roles of both the chosen initiator and the laurolactam content in the feed have been investigated in terms of high polymer yield, structural defects of the polymer chains due to side reactions, T g and T m values, degree of cyrstallinity, molecular and superlattice order of the copolyamides. Namely, structural and thermal peculiarities of the latter have been brought into evidence on as-polymerized samples as well as on high polymers after the deoligomerization process. Interesting differences among the various materials have been found and some possible explanations of the above behavior are given.

Enhancement of Photoelectrical Properties in Polymer Nanocomposites Containing Modified Single-walled Carbon Nanotubes by Conducting Dendrimer

We report the photoinduced conductivity changes measured on a system composed of single-wall carbon nanotubes (SWNTs) modified by a semiconducting poly(amidoamine) dendrimer (PAMAMC) characterized by highly aromatic end groups. Under illumination hole injection into SWNTs prevails over the photoinjection of electrons from PAMAMC to SWNT holes, and film photoconductivity is observed. This system was incorporated as an electroactive component within a conducting polymer [poly(3-octylthiophene)], providing improvements in the photoelectrical properties of the composite. Such supramolecular structures consisting of dendrimer-functionalized carbon nanotubes provide the means for an approach toward the preparation of photoactive materials of high current interest.

Fast‐activated anionic polymerization of ε‐caprolactam in suspension, 1. Role of the continuous phase on characteristics and properties of powdered PA6

The fast-activated anionic polymerization of e- caprolactam has been performed in suspension in order not only to efficiently dissipate the heat of polymerization, but also to directly synthesize powdered polyamide 6. The continuous phase of the system is composed of polyisobutene oils: five fractions, different in their molecular weights and viscosities, have been used and thoroughly studied in terms of their influence on polymerization yield, as well as on polyamide 6 chemical and physical properties, and on shape and size of the polymer particles. The above characterizations have been performed on samples synthesized varying the weight ratio between the suspending medium and the droplets made of monomer, initiator (sodium caprolactamate) and ultra-fast activator (cyclohexyl carbamoyl caprolactam).

Interpenetrating polydicyclopentadiene/polyacrylate networks obtained by simultaneous non-interfering frontal polymerization

Abstract Interpenetrating polymer networks made of dicyclopentadiene and methyl methacrylate or tri(ethylene glycol) dimethacrylate have been successfully prepared by non-interfering frontal polymerization. The role of catalyst and free radical initiator relative amounts, as well as of monomer ratio, has been thoroughly studied. The conditions under which a pure frontal polymerization occurs, and the related values of both front velocity and maximum temperature reached by the reaction, are presented and discussed.

Synthesis and characterization of a polyester/styrene resin obtained by frontal polymerization

Abstract The frontal polymerization technique has been successfully applied, for the first time, to obtain an unsaturated polyester/styrene resin. The effect of the ratio of the two aforementioned components, as well as of the type and amount of free-radical initiator on both front velocity and maximum temperature reached by the front, has been thoroughly studied. The resulting products have been characterized in terms of their thermal and dynamic-mechanical behaviour. A comparison of such products with the corresponding materials obtained by the classical batch polymerization technique has evidenced that frontal polymerization allows to reach a higher degree of crosslinking with respect to batch copolymerization and hence a better thermal and mechanical behaviour.