Search results for "Mechanics of Materials"

The uptake of N-(2-hydroxypropyl)-methacrylamide based homo, random and block copolymers by human multi-drug resistant breast adenocarcinoma cells

2009

A series of well-defined, fluorescently labelled homopolymers, random and block copolymers based on N-(2-hydroxypropyl)-methacrylamide were prepared by reversible addition–fragmentation chain transfer polymerization (RAFT polymerization). The polydispersity indexes for all polymers were in the range of 1.2–1.3 and the number average of the molar mass (Mn) for each polymer was set to be in the range of 15–30 kDa. The cellular uptake of these polymers was investigated in the human multi-drug resistant breast adenocarcinoma cell line MCF7/ADR. The uptake greatly depended on the polymer molecular mass and structure. Specifically, smaller polymers (approx. 15 kDa) were taken up by the cells at m…

Numerical model for composite material with polymer matrix reinforced by carbon nanotubes

2008

Due to the high stiffness and strength, as well as their ability to act as conductors, carbon nanotubes are under intense investigation as fillers in polymeric materials. The nature of the carbon nanotube/polymer bonding and the curvature of the carbon nanotubes within the polymer have arisen as particular factors in the efficacy of the carbon nanotubes to actually provide any enhanced stiffness or strength to the nanocomposite. Here the effects of carbon nanotube curvature and interface interaction with the matrix on the nanocomposite stiffness are investigated using nanomechanical analysis. In particular, the effects of poor bonding and thus poor shear lag load transfer to the carbon nano…

Thermomechanical degradation of polyethylene/polyamide 6 blend-clay nanocomposites

2014

Abstract Polymer nanocomposites are gaining a growing interest both in the academia and in the industrial field, because of some specific properties they can assure. However, the rise in the attention from the industry is also leading to concerns about their processing, which can involve issues which are not present in traditional polymers processing; furthermore, additional issues can arise when nanocomposites are based on a polymer blend rather than a single polymer. In this work, a systematic study on thermomechanical degradation and reprocessing behaviour of LDPE/PA6/Cloisite 15A systems has been performed. The characterization was based on rheological, mechanical and morphological anal…

Photoluminescence waveguiding in CdSe and CdTe QDs–PMMA nanocomposite films

2011

In this paper, active planar waveguides based on the incorporation of CdSe and CdTe nanocrystal quantum dots in a polymer matrix are demonstrated. In the case of doping the polymer with both types of quantum dots, the nanocomposite film guides both emitted colors, green (550 nm, CdTe) and orange (600 nm, CdSe). The optical pumping laser can be coupled not only with a standard end-fire coupling system, but also directing the beam to the surface of the sample, indicating a good absorption cross-section and waveguide properties. To achieve these results, a study of the nanocomposite optical properties as a function of the nanocrystal concentration is presented and the optimum conditions are fo…

Metal nanoparticle/polymer superlattice films: Fabrication and control of layer structure

1997

Reversible tuning of a block-copolymer nanostructure via electric fields

2007

Block copolymers consisting of incompatible components self-assemble into microphase-separated domains yielding highly regular structures with characteristic length scales of the order of several tens of nanometres. Therefore, in the past decades, block copolymers have gained considerable potential for nanotechnological applications, such as in nanostructured networks and membranes, nanoparticle templates and high-density data storage media. However, the characteristic size of the resulting structures is usually determined by molecular parameters of the constituent polymer molecules and cannot easily be adjusted on demand. Here, we show that electric d.c. fields can be used to tune the char…

Organolanthanides, catalysts for specific olefin-diene copolymerization: access to new materials

2001

Abstract Non-hindered ansa dicyclopentadienylallyl complexes of samarium, [(CMe2C5H4)2Sm(allyl)]n, and (CMe2C5H4)2Sm(allyl)L (L=THF or allylLi) polymerize isoprene without an aluminum cocatalyst. The polymerizations are highly stereospecific, affording nearly quantitatively 1–4 trans polyisoprene. In the presence of linear 1-olefins, copolymers are formed, with 6–10% of olefin inserted; the 1–4 trans structure of the polyisoprene chain is not altered, and only one olefin molecule is inserted between two polyisoprene fragments. In the common initiator of these three catalytic systems, the (CMe2C5H4)2Sm(allyl) moiety, only one vacant site would be available. As a consequence of the presence o…

Stabilisation of LDPE cross-linked in the presence of peroxides III. Mass spectrometric study of chemical changes taking place in the n-octadecane–di…

2000

Abstract An attempt was made to identify the products of the reaction between dicumyl peroxide and Irganox 1081, carried out in n -octadecane (saturated hydrocarbon), in conditions of fast decomposition of the peroxide (180°C, 5 min). Mass spectrometry (MS) was employed to find m/z values of molecular and fragment ions in analyses of the components ( n -octadecane, dicumyl peroxide, Irganox 1081) and of the following systems: n -octadecane–dicumyl peroxide, n -octadecane–Irganox 1081 and n -octadecane–dicumyl peroxide–Irganox 1081, after holding them at a temperature of 180°C for 5 min. The tendency of sulphur in Irganox 1081 to oxidise, specifically in the presence of dicumyl peroxide, was…

Melt stabilization of wet polyamide 6

2002

Abstract Melt processing of polycondensate polymers must be carried out after careful drying in order to avoid any hydrolytic chain scission caused by the presence of water or other small molecules. In this work, the effect of two different antioxidants on the processing and flow properties of a polyamide 6 sample not dried before processing operations has been studied. One of these stabilizers seems to protect the wet polymer from hydrolytic chain scission. This action has been interpreted considering that the stabilizer hydrolyses instead of the polyamide macromolecules.

Influence of the irradiation parameters on the molecular modifications of an isotactic polypropylene gamma-irradiated under vacuum

2000

Isotactic polypropylene was irradiated under vacuum in a complete set of experimental conditions. The influence of the irradiation parameters, total absorbed dose, D, and dose rate, I, was analysed in order to verify the theoretical predictions of a simple kinetic model, already presented (Sarcinelli L, Valenza A, Spadaro G. Polymer 1997;38:2307), based on the rates of the main reactions occurring during irradiation, i.e. β-scission, addition to double bonds and termination. The concentration of free radicals and double bonds formed during irradiation is detected together with a comparison to their dependence on the irradiation parameters. A quantitative determination of the “inversion curv…