Interface polymer fraction

Starting from previous results [186, 187] the authors have ascribed this effect to the formation of a polymer layer adsorbed on the support surface where naacromolecules are less mobile and to a lower density of packing due to conformational restrictions near the interface. These conformational restrictions result in a modification of the crystallization conditions and therefore the crystalline polymer fraction is smaller, the less the film thickness. 

Structure of Adsorbed Polymers. As seen in Figure 2, the structure of the adsorbed chain can be described in terms of loops, tails, and trains (1). The relative fractions of loops, tails, and trains in an adsorbed chain depend upon the strength of interactions between the monomeric units and the interface, polymer concentration, and molecular weight. 

Diffusion and Penetration. Thermosetting condensation polymers such as phenol-formaldehyde and urea-formaldehyde resin systems generate water as a byproduct of cure. If water also is the solvent, it is a requirement that the solvent water diffuse into the wood to lower the concentration of water at the interface which might otherwise inhibit cure. Water, or other solvent(s) if present, will cany mobile lower molecular weight polymer fractions into the cell interstices and cell walls. This chromatographic effect is the initiation of penetration. 

Polyisobutylene and similar copolymers appear to "pack" well (density of 0.917 g/cm ) (86) and have fractional free volumes of 0.026 (vs 0.071 for polydimethylsiloxane). The efficient packing in PIB is attributed to the unoccupied volume in the system being largely at the intermolecular interfaces, and thus a polymer chain surface phenomenon. The thicker cross section of PIB chains results in less surface area per carbon atom. 

We present here a simple experiment, conceived to test both the reptation model and the minor chain model, by Welp et al. [50] and Agrawal et al. [51-53]. Consider the HDH/DHD interface formed with two layers of polystyrene with chain architectures shown in Fig. 5. In one of the layers, the central 50% of the chain is deuterated. This constitutes a triblock copolymer of labeled and normal polystyrene, which is, denoted HDH. In the second layer, the labeling has been reversed so that the two end fractions of the chain are deuterated, denoted by DHD. At temperatures above the glass transition temperature of the polystyrene ( 100°C), the polymer chains begin to interdiffuse across the... 

Among the various branches in colloid and interface science, polymer adsorption and its effect on the colloid stability is one of the most crucial problems. Polymer molecules are increasingly used as stabilizers in many industrial preparations, where stability is needed at a high dispersed phase volume fraction, at a high electrolyte concentration, as well as under extreme temperature and flow velocity conditions. 

Several experimental parameters have been used to describe the conformation of a polymer adsorbed at the solid-solution interface these include the thickness of the adsorbed layer (photon correlation spectroscopy(J ) (p.c.s.), small angle neutron scattering (2) (s.a.n.s.), ellipsometry (3) and force-distance measurements between adsorbed layers (A), and the surface bound fraction (e.s.r. (5), n.m.r. ( 6), calorimetry (7) and i.r. (8)). However, it is very difficult to describe the adsorbed layer with a single parameter and ideally the segment density profile of the adsorbed chain is required. Recently s.a.n.s. (9) has been used to obtain segment density profiles for polyethylene oxide (PEO) and partially hydrolysed polyvinyl alcohol adsorbed on polystyrene latex. For PEO, two types of system were examined one where the chains were terminally-anchored and the other where the polymer was physically adsorbed from solution. The profiles for these two... 

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