Surface Tension, Density and Viscosity Studies on the Associative Behaviour of Oxyethylene-Oxybutylene Diblock Copolymers in Water at Different Temperatures

The associative properties of methoxy (CH3O-) ended E58B11 and hydroxyl (-OH) ended E56B19 oxyethylene-oxybuty- lene diblock copolymers in aqueous solution at different temperature are reported in this paper. For both copolymers, E represents an oxyethylene (-[CH2CH2O]-) unit and B an oxybutylene (-[CH(C2H5)CH2O]-) unit while the subscripts denote the number average block length. Surface tension measurements were used to find out surface excess concentrations (Γm), area per molecule (αs1 ) at air/water interface and Gibbs free energy for adsorption (△G0ads ) for the pre-micellar region at four temperatures. Likewise thermodynamic parameters of micellization such as, critical micelle concentrations (CMC), enthalpy of micellization (△H0mic ), standard free energy of micellization (△G0mic) and entropy of micellization (△S0mic ), were also obtained using surface tension measurements. Solution densities were used to deter-mine the partial specific volume of micelle ( Vmic) and micellar density (ρmic). Dilute solution viscosities have been used to estimate the intrinsic viscosities [η], solute-solvent interaction parameter (KH) and hydration value of micelle (Wh) at various temperatures. The effect of temperature on the micelle properties is also discussed.

A Review Featuring Fabrication, Properties and Applications of Carbon Nanotubes(CNTs) Reinforced Polymer and Epoxy Nanocomposites

Carbon nanotubes（CNTs） have long been recognized as the stiffest and strongest man-made material known to date. In addition, their high electrical conductivity has roused interest in the areas of electrical appliances and communication related applications. However, due to their miniature size, the excellent properties of these nanostructures can only be exploited if they are homogeneously embedded into light-weight matrices as those offered by a whole series of engineering polymers. In order to enhance their chemical affinity to engineering polymer matrices, chemical modification of the graphitic sidewalls and tips is necessary. The mechanical and electrical properties to date of a whole range of nanocomposites of various carbon nanotube contents are also reviewed in this attempt to facilitate progress in this emerging area. Recently, carbonaceous nano-fillers such as graphene and carbon nanotubes（CNTs） play a promising role due to their better structural and functional properties and broad range of applications in every field. Since CNTs usually form stabilized bundles due to van der Waals interactions, they are extremely difficult to disperse and align in a polymer matrix. The biggest issues in the preparation of CNTs reinforced composites reside in efficient dispersion of CNTs into a polymer matrix, the assessment of the dispersion, and the alignment and control of the CNTs in the matrix. An overview of various CNT functionalization methods is given. In particular, CNT functionalization using click chemistry and the preparation of CNT composites employing hyperbranched polymers are stressed as potential techniques to achieve good CNT dispersion. In addition, discussions on mechanical, thermal, electrical, electrochemical and applications of polymer/CNT composites are also included.

MICELLAR PARAMETERS OF DIBLOCK COPOLYMERS AND THEIR INTERACTIONS WITH IONIC SURFACTANTS

The interactions of non-ionic amphiphilic diblock copolymer poly（oxyethylene/oxybutylene） （E39B18） with anionic surfactant sodium dodecyl sulphate （SDS） and cationic surfactant hexadecyltrimethylammonium bromide （CTAB） were studied by using various techniques such as surface tension, conductivity, steady-state fluorescence and dynamic light scattering. Surface tension measurements were used to determine the critical micelle concentration （CMC） and thereby the free energy of micellization （AGmic）, free energy of adsorption （AG^ds）, surface excess concentration （F） and minimum area per molecule （A）. Conductivity measurements were used to determine the critical micelle concentration （CMC）, critical aggregation concentration （CAC）, polymer saturation point （PSP）, degree of ionization （tr） and counter ion binding （l]）. Dynamic light scattering experiments were performed to check the changes in physiochemical properties of the block copolymer micelles taken place due to the interactions of diblock copolymers with ionic surfactants. The ratio of the first and third vibronic peaks （11/Is） indicated the polarity of the pyrene micro environment and was used for the detection of micelle as well as polymer-surfactant interactions. Aggregation number （N）, number of binding sites （n） and free energy of binding （AGb） for pure surfactants as well as for polymer-surfactant mixed micellar systems were determined by the fluorescence quenching method.

GRAFTING OF POLY(SODIUM STYRENESULFONATE) ONTO GOLD SURFACE FROM NaNO_3 SOLUTION

The chemical grafting of thiol terminated poly（sodium styrenesulfonate） （HS-PSSS） chains from sodium nitrate （NaNO3） salt solution to a gold surface was investigated with a quartz crystal microbalance with dissipation monitoring （QCM-D） in different salt concentrations, It was found that at low salt concentration grafting density of HS-PSSS was low and the grafted chains adopted a mushroom conformation. With the increase of salt concentration polyelectrolyte chains underwent a transition toward coiled state due to reduction of electrostatic repulsion and as a result more chains were grafted on the surface, When the grafting density reached a certain limit after which further grafting caused repulsion between already grafted HS-PSSS chains and as a result grafted chains adopted a brush conformation.