Search results for "Names"

Structure Formation of Polymeric Building Blocks: Complex Polymer Architectures

2013

This chapter describes macromolecules with a complex structure, their defined aggregation in solution, their adsorption to surfaces, and their possible aggregation on surfaces. The term “complex structure” implies that the macromolecules show different, distinct structural elements or building blocks on a supra-atomic length scale. Key to understanding the complex structure of macromolecules, their aggregation, and adsorption to surfaces are intra- and intermolecular interactions such as van der Waals, electrostatic, π–π interactions, and hydrogen bonds.

Study of interacting bands of silane: Analysis of infrared and Raman spectra

1990

Abstract The ν 1 ν 3 interacting bands of natural silane have been studied by Fourier transform spectroscopy and stimulated Raman spectroscopy, respectively, in the regions 2040–2320 and 2180–2187 cm−1. These data combined with available microwave observations have been analyzed using a reduced effective Hamiltonian developed through the fifth order for 28SiH4 and through the fourth order for 29SiH4 and 30SiH4. The observed infrared and Raman transitions have been very well reproduced with a standard deviation of about 0.0004 cm−1 for 28SiH4. Some anomalies in the Hamiltonian expansion have been found, but they did not perturb the analysis.

Structure and Chemical Bonds in Black Ti(C, N, O) Thin Films

2010

Effects of inhomogeneities of cross-links on a microphase separation of polymer mixtures

1994

We generalize de Gennes' theory of the microphase separation of cross-linked polymer mixtures to take into account the spatial fluctuations of the elasticity constant c, preventing the mixture from complete segregation. Within a mean-field analysis we found that the spatial fluctuations of c(r), which are assumed to obey the Poisson distribution, enlarge the size of the domains. The latter is obtained to be temperature dependent.


Accurately evaluating Young’s modulus of polymers through nanoindentations: a phenomenological correction factor to the Oliver and Pharr procedure

2006

The Oliver and Pharr [J. Mater. Res. 7, 1564 (1992)] procedure is a widely used tool to analyze nanoindentation force curves obtained on metals or ceramics. Its application to polymers is, however, difficult, as Young’s moduli are commonly overestimated mainly because of viscoelastic effects and pileup. However, polymers spanning a large range of morphologies have been used in this work to introduce a phenomenological correction factor. It depends on indenter geometry: sets of calibration indentations have to be performed on some polymers with known elastic moduli to characterize each indenter.

Calculation of Dependent Elastic Constants of Plastic Foams with a Pronounced Strut-Like Structure

2003

Seven dependent elastic constants of monotropic plastic foams with an expressed strut-like structure are calculated. For this purpose, the basic results of the previously elaborated mathematical model for light-weight plastic foams is used. The model includes a model cell of local structure for monotropic/isotropic plastic foams and an ensemble of structural elements, which allows one to calculate the seven dependent elastic constants, taking into account the pronounced polydispersity of the structure of plastic foams. The numerical values of the constants are compared with the available experimental data, and a satisfactory agreement is found to exist. As a final result, a full set of gene…

Modelling the hydrogen-bonding interactions in a copolymer/biodegradable homopolymer blend through excess functions

2008

A recent theoretical approach based on the coupling of both the Flory-Huggins (FH) and the Association Equilibria thermodynamic (AET) theories was modified and adapted to study the miscibility properties of a multi- component system formed by two polymers (a proton-donor and a proton-acceptor) and a proton-acceptor solvent, named copolymer(A)/solvent(B)/polymer(C). Compatibility between polymers was mainly attained by hydrogen- bonding between the hydroxyl group on the phenol unit of the poly(styrene-co-vinyl phenol) (PSVPh) and the car- bonyl group of the biodegradable and environmentally friendly poly(3-hydroxybutyrate) (PHB). However, the self- association of PSVPh and specific interacti…

Analysis of the intensities of the longitudinal acoustic vibrations inn-alkanes and polyethylene

1980

Simple theoretical considerations indicate, that the integral intensity of the „longitudinal acoustic modes” (LAM) in the Raman spectrum ofn-alkanes should be independent of the chain length. The experiment in fact confirms this expectation. Using this property it becomes possible for polyethylene samples, to derive from the measured LAM-intensity the mass fraction of all-turns sequences contributing to this band. For solution crystallized samples this fraction coincides with the crystallinity, whereas in melt crystallized samples it generally turns out as smaller. The observed difference is likely to be due to the occurrence of local conformational defects (kinks, chain torsions) which int…

Controlling the wetting properties of the Asakura-Oosawa model and applications to spherical confinement.

2012

We demonstrate for the Asakura-Oosawa model and an extension of this model that uses continuous rather than hard potentials, how wetting properties at walls can be easily controlled. By increasing the interaction range of the repulsive wall potential acting on the colloids (while keeping the polymer-wall interactions constant) polymers begin to substitute colloids at walls and the system can be driven from complete wetting of colloids via partial wetting to complete wetting of polymers. As an application, we discuss the morphology and wetting behavior of colloid-polymer mixtures in spherical confinement. We apply the recently developed 'ensemble switch method' where the Hamiltonian is exten…

On the Use of the Nanoindentation Unloading Curve to Measure the Young's Modulus of Polymers on a Nanometer Scale

2005

Summary: The nanoindentation test is a fundamental tool to assess the link between morphology and mechanical properties. The preliminary results of a more exhaustive study about the applicability to polymers of the most used procedure to determine elastic modulus by indentation are reported in this short communication. A departure of the experimental conditions from the theoretical assumptions and results that give rise to the Oliver and Pharr analysis is shown to occur under a wide range of experimental conditions, with applied loads and penetration depths covering several orders of magnitude and using different indenter geometries. Unloading curves with exponents significantly larger than…