Polymers monolayers

Stouffer J M and McCarthy T J 1988 Polymer monolayers prepared by the spontaneous adsorption of sulphur-functionalized polystyrene on gold surfaces Macromolecules 2 1204-8... 

Koutsos V, van der Vegte E W and Hadziioannou G 1999 Direct view of structural regimes of end-grafted polymer monolayers a scanning force microscopy study Macromolecules 32 1233-6... 

H. Yu. Polymer monolayer dynamics by light scattering. In Polymer Interfaces and Adhesion. Boston Butterworth-Heinemann, 1992, p. 263. 

Loschonsky S, Shroff K, Worz A et al (2008) Surface-attached pdmaa-grgdsp hybrid polymer monolayers that promote the adhesion of living cells. Biomacromolecules 9 543-552... 

The use of a polymer monolayer to form LB films to be gas treated to form CdS nanoparticles has been reported [174]. The polymer use was poly (maleic anhydride) ester-... 

Sato, N., Ito, S. and Yamamoto, M. (1998) Molecular weight dependence of shear viscosity of a polymer monolayer evidence for the lack of chain entanglement in the two-dimensional plane. Macromolecules, 31, 2673-2675. 

The rheological properties of a fluid interface may be characterized by four parameters surface shear viscosity and elasticity, and surface dilational viscosity and elasticity. When polymer monolayers are present at such interfaces, viscoelastic behavior has been observed (1,2), but theoretical progress has been slow. The adsorption of amphiphilic polymers at the interface in liquid emulsions stabilizes the particles mainly through osmotic pressure developed upon close approach. This has become known as steric stabilization (3,4.5). In this paper, the dynamic behavior of amphiphilic, hydrophobically modified hydroxyethyl celluloses (HM-HEC), was studied. In previous studies HM-HEC s were found to greatly reduce liquid/liquid interfacial tensions even at very low polymer concentrations, and were extremely effective emulsifiers for organic liquids in water (6). 

An HM-HEC monolayer at the air/aqueous interface was formed by adsorption from an aqueous solution of the polymer placed in the Langmuir trough overnight. In "stress-jump" experiments, HM-HEC monolayers were placed under rapid compression to a large degree and surface pressure was measured as a function of time after compression was stopped. (The compressional "jumps" required a minute or two to complete, and in some cases were on the order of the polymer monolayer relaxation times. See later section for discussion). In hysteresis experiments, the adsorbed monolayers were subjected to continuous compression-expansion cycles at a specific speed, while surface pressure was determined as a function of surface area. 

An increase in the amount of hydrophobic modification restricts segmental mobility by an increase of viscosity within the monolayer for the same molecular weight (300,000) and hydrophobe chain length (C g), the polymer monolayer with the higher amount of hydrophobe has a smaller relaxation rate constant (Experiments Numbers 3 and 7). 

Test of the Mathematical Model. In the mathematical model, behavior of the polymer monolayer was related to two parameters the degree of compression, (1-A/A ), and the ratio of the relaxation rate to the compression (expansion) rate, q. The results from three typical hysteresis experiments with three different polymers were chosen for comparison to the theory. 

Figure 7.1. Surface pressure-area plot for polymer monolayer measured at 20°C and at a compression rate 2 x 10 nm/s for each side group.

Although monolayers at the gas-water interface are useful to study adsorption phenomena of e.g. proteins at membranes they are not a very good model, since they represent only one half of a biological membrane. Attempts have therefore been made to extend this concept of polymer monolayers to bilayers and particularly to liposomes. It was to prove, whether the monomers (Table I.) could form bilayers and whether a polyreaction within these bi-layers was possible under retention of the structure and the orientation of the molecules. 

Polymerization in Bilayers. Upon irradiation with UV light the monomer vesicles are transferred to polymer vesicles (Figure 12.). In the case of the diyne monomers (2,5-9,12,13,14) the polyreaction can again be followed by the color change via blue to red except phospholipids (5,6), which turn red without going through the blue intermediate as observed in monolayers. The VIS spectra of these polymer vesicle dispersions are qualitatively identical to those of the polymer monolayers (Figure 13.). 

K. Kremer Glassy States of Adsorbed Elexible Polymers and Spread Polymer Monolayers. J. Phys. (Paris) 47, 1269 (1986). 

Kusano, H. Kimura Shin, L Kitagawa, M. Kobayashi, H. Application of Cellulose Langmuir-Blodgett Films as Humidity Sensors, and Characteristics of the Sorption of Water Molecules into Polymer Monolayers. Thin Solid Films 1997, 295, 53-59. 

Studies on polymer monolayers spread at air - water interface to characterize their physical properties, as surface pressure, -it, surface potential, AV, surface viscosity, t S, and surface rigidity [39,40] have been reported abundantly. 

Polymer monolayers on the aqueous subphase are studied using the Langmuir technique as is shown in Scheme 3.2. 

As it has been remarked studies on polymer monolayers spread at the air -water interface to characterize their surface behavior as a function of area, of... 

By comparing the extrapolated area to zero surface - pressure from the surface pressure - area (it - A) isotherms with projected area of a monomer unit from molecular models of the polymer segments, it is possible to obtain information on molecular orientation and packing of these polymer monolayers. 

In the polymer monolayer spread at the air - water interface, the surface concentration can be regulated easily by compression or expansion of the monolayer. It is... 

It is very well known that different macromolecular arrangements may be induced either by changing the nature of the subphase [44, 68, 69] or by changing the spreading solvent [70], However, only a few studies describing these effects on polymer monolayer surface pressure behavior have been reported [71-73]. 

In general, there is little information available on how a change in spreading conditions can affect the behavior of polymer monolayers at the air - water interface. 

The surface behavior of poly(4-vinylpyridine) quaternized with tetradecyl bromide (P4VPCi4) as function of the quaternization degree has been reported [81], The percentage of vinylpyridine moieties quaternized was found to be 35-75%. Surface pressure-area isotherms (tt - A) at the air-water interface were determined. The polymer monolayer have shown particular shapes at different quaternization degrees. Figure 3.14 shows the (tt - A) isotherms of P4VPCi4. 

Most of the studies of insoluble polymer Langmuir monolayers have been devoted to neutral polymers, and less effort have been devoted to polymer monolayers of polyelectrolytes. 

Kawaguchi s group [82,83] have pointed out that polymer monolayers of poly(n-alkyl 4- vinylpiridinium) chains show a gas - liquid phase transition at surface pressures below 1 N.m 1. As already mentioned, this behavior is different to that of polymer monolayers of neutral and insoluble polymers. 

The dilational rheology behavior of polymer monolayers is a very interesting aspect. If a polymer film is viewed as a macroscopy continuum medium, several types of motion are possible [96], As it has been explained by Monroy et al. [59], it is possible to distinguish two main types capillary (or out of plane) and dilational (or in plane) [59,60,97], The first one is a shear deformation, while for the second one there are both a compression - dilatation motion and a shear motion. Since dissipative effects do exist within the film, each of the motions consists of elastic and viscous components. The elastic constant for the capillary motion is the surface tension y, while for the second it is the dilatation elasticity e. The latter modulus depends upon the stress applied to the monolayer. For a uniaxial stress (as it is the case for capillary waves or for compression in a single barrier Langmuir trough) the dilatational modulus is the sum of the compression and shear moduli [98]... 

It is very well known that the nature of the monolayer partially depends on the strength of interfacial interactions with substrate molecules and that of polymer in-tersegmental interactions. And it is normal to expect that the viscoelastic properties of polymer monolayer are also dependent on these factors. The static and dynamic properties of several different polymer monolayers at the air - water interface have been examined with the surface quasi-elastic Light Scattering technique combined with the static Wilhelmy plate method [101]. 

Fig. 3.19 Plots of frequency shift f versus surface concentration T for six polymer monolayers at a scattering wavevector k = 323 cm-1. (From ref. [101])...

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