Polyelectrolytes Polymer adhesion

The presence of polymers or polyelectrolytes have important effects on the Van der Waal interaction and on the electrostatic interaction. Bacterial adhesion, as discussed in Chapter 7.9 may be interpreted in terms of DLVO theory. Since the interaction in bacterial adhesion occurs at larger distances, this interaction may be looked at as occurring in the secondary minimum of the net interaction energy (Fig. 7.4). Particle Size. The DLVO theory predicts an increase of the total interaction energy with an increase in particle size. This effect cannot be verified in coagulation studies. 

This contribution will provide a review of polylectrolytes as biomaterials, with emphasis on recent developments. The first section will provide an overview of methods of synthesizing polyelectrolytes in the structures that are most commonly employed for biomedical applications linear polymers, crosslinked networks, and polymer grafts. In the remaining sections, the salient features of polyelectrolyte thermodynamics and the applications of polyelectrolytes for dental adhesives and restoratives, controlled release devices, polymeric drugs, prodrugs, or adjuvants, and biocompatibilizers will be discussed. These topics have been reviewed in the past, therefore previous reviews are cited and only the recent developments are considered here. 

Problems of desorption and loss of activity encountered with natural heparin have led numerous workers to explore synthetic heparin-like polymers or heparinoids, as reviewed by Gebelein and Murphy [475, 514, 515]. The blood compatibility of 5% blended polyelectrolyte/polyfvinly alcohol) membranes was studied by Aleyamma and Sharma [516,517]. The membranes were modified with synthetic heparinoid polyelectrolytes, and surface properties (platelet adhesion, water contact angle, protein adsorption) and bulk properties such as permeability and mechanical characteristics were evaluated. The blended membrane had a lower tendency to adhere platelets than standard cellulose membranes and were useful as dialysis grade materials. 

Electric double layer forces between polyelectrolyte and non-polymer surfaces in aqueous media have also been studied very intensively [371,394,400-402]. The adhesion between polyelectrolyte surfaces could be reduced considerably by increasing the ionic strength of the medium [400]. Using an electrochemical cell and a gold coated tip, the adhesion between electroactive layer of p oly( vinyl-ferrocene) was controlled through the selective oxidation or reduction of the polymer films [401]. 

In recent years the investigation of polymer-surfactant interactions is a rapidly growing field of interest of modem colloid science [1-4], The mixtures and multilayer structures of polyelectrolytes and surfactants are widely used for industrial application to govern the wetting, adhesion, flotation processes and so on. 

Abstract The formation of stable metal/polymer joints is an enormous challenge in material sciences. Good adhesion requires an interphase which is able to specifically interact with the metal substrate as well as with the second component. Furthermore, the interphase should compensate thermally generated mechanical tensions between the two adhering components. It will be shown that statistic copolymers of poly(vinyl formamide) and poly(vinyl amine) (PVFA-co-PVAm) are potential candidates for adhesion promoters. The polyelectrolyte character of the copolymers allows to apply them from its aqueous solutions. The primary amino groups exhibit the copolymers as highly reactive to metal surfaces as well as to the second joint partner. The... 

Modified Surfaces. It is frequently desirable to change the surface of a polymer. Nonpolar surfaces of plastics are characterized by static electricity buildup, non-wetting, poor adhesion, low printability, and poor dyeing. These disadvantages can be overcome by grafting polar vinyl monomers upon the surface by irradiation. A. S. Hoffman describes radiation grafting of polyelectrolytes upon nonpolar surfaces, and A. Chapiro and co-workers discuss radiation grafting of acrylic acid and vinyl pyridene upon Teflon films. 

The platelet adhesion and spreading was higher with bare polymer (Fig 5A), which had substantially reduced due to SPE (Fig 5B) treatments. The adhesion and spreading of platelets (finm PRP, 2 hours) on silated silicone wafer was similarly i bited by pretreatment with sulphonated polyelectrolytes (Fig 6). Regardless of treatment with SPE, all platelets adherent to polycarbonate and silicone wafer were pseudopodial (Fig 5 6). 

Lipid bilayer membranes tethered to plasma-polymerized films as hydrophilic supports were another concept introduced recently [28], The plasma polymerization of maleic anhydride (MAH-PP), e.g., has led to the synthesis of thin polymeric coatings that appear to be suitable to act as a reservoir for an aqueous phase and a cushion for lipid bilayers [29], A crucial requirement for the use of such polymers as water containing supports for lipid bilayer membranes is their adhesion to the substrate. In a previous study [30] covalent binding of MAH-PP films to gold supports was achieved by a self assembled alkylthiol adhesion layer. The previous work has shown that maleic anhydride, when polymerized at a low duty cycle, can behave as a polyelectrolyte. The thin polymer layers were found to have a very low electrical resistance (ca. lOOQcm2) after immersion and subsequent hydrolysis/swelling in aqueous buffer. 

Biomimetics is an important strategy for the fabrication of modern biomaterials that provides solutions which closely resemble those of living systems. In the area of biomimetic supramolecular chemistry, a surface-grafted PMOEP polymer has recently been found to impart mesoporous silica with switchable ion channel transport properties. This was enabled by the dual protonation and Ca chelation ability of the polymer phosphate groups. A series of studies made use of PMAEP-based copolymers in the fabrication of biomimetic adhesives which were inspired by the sandcastle worm that produces peptide polyelectrolytes rich in phosphorylated serine. These adhesives were aimed at providing molecular solutions to... 

In addition to spiropyrans, azobenzenes have also been incorporated into polymer Aims to modulate cell adhesion [273]. For instance, polyelectrolyte multilayers of poly(acrylic acid)-poly(allylamine hydrochloride) (PAA-PAH) functionalized with RGD-modified azobenzene side chains were used to produce tunable substrates with different intrinsic capacities to support cell adhesion and survival [273]. Light-driven isomerization from trans to cis of the azobenzene on the PAA-PAH-RGD polymer film resulted in an enhanced cell adhesion. 

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