Copolymer, wettability

This principle is applied not only to the PVA-PVAc composites but to other polymer composites. The composite structure does not always need to be porous but may be powders and gels designed for the wettability by solvents and the extension of the surface area in soluble polymers. From this point-of-view, the present work sheds a new light on the research on composite materials related to graft polymers and copolymers. 

Okano, T., Katayama, M., and Shinohara, 1. The influence of hydrophobic and hydrophilic domains on water wettability of 2-hydrooxyethyl methacrylate/styrene copolymers, J. Appl. Polmer Sci, 1978, 22, 361-ill. 

Research Focus Preparation of amphiphilic block copolymers to increase the wettability and printability of a plastic surface containing thermoplastic blends. Originality Thermoplastics containing amphiphilic block copolymers as antistatic... 

The effects of improved wettability, entropic repulsion, and sterical hindrance undoubtedly play a role in stabilizing dispersed solid particles by block or graft copolymers. However, since the dispersions of titanium dioxide in toluene stabilized by carboxylated styrene-butadiene block copolymers are so much more stable than dispersions stabilized by carboxylated homopolymers under otherwise identical conditions, we must assume that an additional factor comes into play when block copolymers are used. The model in Figure 1 is an attempt to explain this additional... 

In a patent dated 1965 Stowe35) laid the basis for the copolymerization of PEO macromonomer with comonomers such as acrylonitrile. It was searched for an increased wettability of polyacrylonitrile films or fibers by a permanent surface modification. ro-Styryl poly(oxyethylene) macromonomers readily copolymerize with acrylonitrile in water emulsions. They can also be copolymerized with styrene-sulfonates in the presence of poly(vinylpyrrolidone). The presence of small amounts of such copolymers in polyacrylonitrile fibers was shown to increase their wettability and their receptivity to dyes and to make them more resistant to electric loading (antistatic fibers). No characterization data on the copolymers formed have been reported. 

Wettability of Elastomers and Copolymers. The wettability of elastomers (37, 38) in terms of critical surface tension was reported previously. The elastomers commonly used for the reinforcement of brittle polymers are polybutadiene, styrene-butadiene random and block copolymers, and butadiene-acrylonitrile rubber. Critical surface tensions for several typical elastomers are 31 dyne/cm. for "Diene rubber, 33 dyne/cm. for both GR-S1006 rubber and styrene-butadiene block copolymer (25 75) and 37 dyne/cm. for butadiene-acrylonitrile rubber, ( Paracril BJLT nitrile rubber). The copolymerization of butadiene with a relatively polar monomer—e.g., styrene or acrylonitrile—generally results in an increase in critical surface tension. The increase in polarity is also reflected in the increase in the solubility parameter (34,39, 40) and in the increase of glass temperature (40). We also noted a similar increase in critical surface tensions of styrene-acrylonitrile copolymers with the... 

Table I. Comparison of the Water Wettability of AA/BM4 Copolymer Films Cast from Different Solvents...

Acrylic acid can be used as comonomer in different copolymers. The most common of these are probably poly(ethylene-co-acrylic acid) (see Section 6.1, Figure 6.1.7), poly(acrylic acid-co-acrylamide), and poly(acrylic acid-co-styrene-co-acrylonitrile) or ASA terpolymer. The acrylic acid in the poly(ethylene-co-acrylic acid) increases the wettability of the polymer. Different salts of poly(acrylic acid-co-acrylamide) are used in the water purification processes as water clarification aid and in drilling fluids. Additional -COOH groups make the polymer even more hydrophilic, and polymers such as poly(acrylic acid-co-maleic acid) are easily water soluble and used as liquid thickeners. 

To obtain information about the surface structure of the PZLL-PB-PZLL films, solvent-cast samples were investigated by means of XPS, replica electron microscopy and wettability experiments [31]. For the triblock copolymers with the smallest PB content (12mol%), these experiments also confirmed a microphase-separated structure at the surface of the films. The PB content at the surface, however, was found to be about twice as large as the bulk PB content. To account for the enhanced PB content at the film surface, the PB domains were proposed to rise above the PZLL matrix in the form of convex lenses (Fig. 3). The presence of these convex PB domains at the film surface was confirmed by replica electron microscopy experiments. Unordered amino acid sequences form an interfacial zone at the film surface between the PB domains and the PZLL matrix. Since the amide bonds in the peptide sequences in the interfacial zone are not involved in intramolecular hydrogen bonding, they are able to bind water, which explains the low water contact angles that were measured on the PZLL-PB-PZLL films. 

As stated in Chapter 1, the chemical structure of the top surface layers of a solid determines its surface properties. If these top layers consist of the same chemical groups, then the surface is called chemically homogeneous, and if they consist of different chemical groups it is called chemically heterogeneous. The presence of two or more chemically different solid substances in a surface layer enormously multiplies the possibilities for variety in the types of surface, such as copolymer surfaces and catalysts having many different atoms at the surface. The chemical heterogeneity of a surface is an important property in industry affecting catalysis, adhesion, adsorption, wettability, biocompatibility, printability and lubrication behavior of a surface, and it must be determined analytically when required. 

The change in biological response of the adsorbed fibrinogen molecule (conversion), is also noticeable with platelet adhesion studies. In confirmation of earlier studies of Zucker and Vroman (5), we found that, usually, less platelets adhered to areas of glass slides exposed to platelet-poor plasma for 3 min than areas exposed for 3 s. When, however, a gel-filtered platelet suspension was used in place of platelet-rich plasma, a dramatic difference in the number of platelets attached to the surface previously exposed to platelet-poor plasma for 3 s or 3 min occurred. Therefore, this more reproducible protocol was used to study not only the adhesion of platelets onto artificial surfaces but also as a probe of conversion. For this purpose we chose a series of block copolymers with controllable domain morphology (phase separation on a molecular scale) and different surface energies (wettability). Previous studies have shown that the degree of phase separation influences the interactions with blood components (6,7). 

The next sequence calls for the coating of a thin layer of a hydrophiUc polymer from an appropriate solvent on top of the photoresist. The polymeric HOL must have a lower glass transition temperature (7g) than the photoresist polymer it must be able to diffuse into the photoresist polymer on baking and it must be phase compatible with the photoresist polymer. Suitable hydrophilic polymers include, but are not limited to, polymers and copolymers of fluoroalkyl methacrylic acid, fluoroalkyl acrylic acid, etc. Surfactants may be used to improve the wettability of the HOL over the resist polymer layer. 

Figure 7, Wettability of copolymers of polytetrafluoroethylene and poly-chlorotrifluoroethylene [47]...

Fluorinated compoimds I, III, IV, and V were dissolved in tetra-hydrofuran solutions of the PVeC copolymer in concentrations up to 1% by weight of the polymer. Of these additives, the 3-methyl glutarate (in), ethane sulfonate (V), and tricarballylate (I) derivatives failed to modify the wettability of the polymer surface. However, the tetra-chlorophthalate derivative (IV) caused a marked decrease in the wettability of the polymer (see Table IV, last column). In Figure 3 the graph of cos 6 vs. 7lv° n-alkanes on the resulting surface shows that... 

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