in this paper, absorption spectra of both solution and films of cyano azobenzene polymer are investigated. the analysis of overlapped absorption spectra of polymer, related to trans and cis isomers, shows that the population of cis isomers is higher than trans isomers. it means that, cyano azobenzene molecules have a folded structure in polymer, in thermal equilibrium. presence of cyano molecul...

kevlar is one of the fbers which is used in heavy industrial productions such as, shipping, military and weaving for reinforcement of composites. initial polymer of kevlar or poly(para-phenylene terephthalamide) is an oriented liquid crystal polymer. existence of aromatic group in the main chain leads to formation of rigid-rod molecules in the polymer, high strength and high modulus in it is fb...

potentiometric investigation on {h2o+nano3+peg1500} mixtures were made at t=308.15k, using electrochemical cells with two ion-selective electrodes, (na+ glass) as the cation ion-selective electrode against (no3- solvent-polymer pvc) as the anion ion-selective electrode. the mean ionic activity coefficients of nano3 were measured at different concentrations of  nano3 and peg. maximum concentrati...

Up to this point we have considered polymer chains in solvent at various concentrations. In dilute solution, we observed that the segmental density is localized around the center of mass of the coils; the local concentration gradient experienced by each chain drives the swelling of the coils. By contrast, in polymer melts, this swelling force is exactly cancelled by analogous forces exerted by ...

For concentrated polymer solutions, the free energy of mixing can be described through a “regular solution” model, such as that set forth by Flory, for a mixture of nc polymers and ns solvent molecules. To understand how the model breaks down for lower concentrations, it will be helpful to review its essential features. It is convenient to derive such a model using a lattice construct, though t...

the main purpose of this study is to introduce a new method for nanofibers by bulk layer production. in the present method the effect of some parameters including take-up velocity, applied voltage, polymer solution concentration on density of produced layers is investigated. the compression characteristic of nanofiber layers produced under optimum electrospinning is also investigated. it was sh...

Dispersing nanoparticles in a polymer matrix is intrinsically challenging due to unfavorable entropic interactions between the matrix and the nanoparticle. In this research dispersion of nanoparticles in polymer matrix was studied and the effect of dispersion on properties was investigated. The properties of polymer composite depend on the type, size, shape, concentration of nanoparticles, and ...

in the past decade, electrospinning as a facile and effective means in producing nanofibers with diameters ranging from microns down to a few nanometers has been developed and considered important. in this work, electrospinning of an interesting natural biopolymer, sodium alginate, has been investigated. the results showed that water solution of sodium alginate cannot be electrospun into nanofi...