Styrene Sulfonic Acid Sodium Salt Research Articles

Surface modification and functionalization of polytetrafluoroethylene films via graft copolymerization

Argon plasma pretreated polytetrafluoroethylene (PTFE) films were subjected to further surface modification by near-UV light induced graft copolymerization with hydrophilic and epoxide-containing monomers. Thus, the functional monomers used include acrylic acid (AAc), sodium salt of styrenesulfonic acid, N,N-dimethylacrylamide (DMAA) and glycidyl methacrylate (GMA). The surface composition and microstructure of the modified films were characterized by angle-resolved X-ray photoelectron spectroscopy. A stratified surface microstructure with a significantly higher substrate-to-graft chain ratio in the top surface layer than in the subsurface layer is always obtained for the PTFE surface with a substantial amount of graft. In all cases, the graft yield increases with plasma pretreatment time and monomer concentration. The PTFE films with molecularly redesigned surfaces are capable of exhibiting a number of new functionalities. These new functionalities include (i) covalent immobilization of an enzyme, such as trypsin (for AAc graft copolymerized surface), (ii) charge transfer induced coating of an electroactive polymer, such as polyaniline (for AAc and styrenesulfonic acid graft copolymerized surfaces), (iii) adhesive-free adhesion between two PTFE surfaces (for AAc, styrenesulfonic acid and DMAA graft copolymerized surfaces), and (iv) improved adhesive bonding via interfacial crosslinking of the grafted chains (for GMA graft copolymerized surfaces). © 1997 John Wiley & Sons, Ltd.

Surface Structures and Adhesive-Free Adhesion Characteristics of Polyaniline Films after Modification by Graft Copolymerization

Surface modifications of emeraldine base (EB) films have been carried out via thermally induced graft copolymerization with acrylic acid (AAc), sodium salt of styrenesulfonic acid (NaSS), N,N‘-dimethyl(methacryloylethyl)ammonium propanesulfonate (DMAPS), and acrylamide (AAm). The structure and chemical composition of each graft-copolymerized surface were studied by angle-resolved X-ray photoelectron spectroscopy (XPS). In all cases, the concentration of grafting increases with monomer concentration. Surface grafting with the four functional monomers also leads to a more hydrophilic EB film surface. Two graft-copolymerized EB film surfaces are capable of exhibiting adhesive-free adhesion when brought into direct contact in the presence of water and subsequently dried. This adhesive-free adhesion also exists between a surface-modified EB film and a similarly modified polytetrafluoroethylene (PTFE) film from graft copolymerization. The development of the lap shear adhesion strength depends on the concentrati...

Surface Modification and Functionalization of Polytetrafluoroethylene Films

Argon plasma-pretreated polytetrafluoroethylene (PTFE) films were subjected to further surface modification by near-UV light-induced graft copolymerization with acrylic acid (AAc), sodium salt of styrenesulfonic acid (NaSS), and N,N-dimethylacrylamide (DMAA). The surface compositions and microstructures of the modified films were characterized by angle-resolved X-ray photoelectron spectroscopy (XPS). A stratified surface microstructure with a significantly higher substrate-to-graft chain ratio in the top surface layer than in the subsurface layer was always obtained for PTFE surface with a substantial amount of the hydrophilic graft. The stratified surface microstructure was consistent with the observed hysteresis in advancing and receding water contact angles. The graft yield increased with Ar plasma pretreatment time and monomer concentration. Covalent immobilization of trypsin on the AAc polymer-grafted PTFE films was facilitated by water-soluble carbodiimide (WSC). The effective enzyme activities increased initially with increasing surface concentration of the grafted AAc polymer but became saturated at a moderate AAc polymer concentration. The immobilized enzyme could still retain close to 30% of its original activity. Solution-coating of the polymeric acid-modified PTFE films with the emeraldine (EM) base of polyaniline readily resulted in an interfacial charge transfer interaction and a semiconductive PTFE surface.

Practical aspects of the emulsifier-free emulsion polymerization of styrene

The influences of initiator concentration, ionic strength of the aqueous phase and styrene sulfonic acid sodium salt comonomer on the average particle size and particle uniformity of latexes generated via emulsifier-free emulsion polymerization of styrene has been studied. It was found that the average particle size increased with increasing initiator concentration in reactions where the ionic strength was not controlled. The uniformity of the latex particles decreased as the initiator concentration increased. It was also found that at a minimum initiator concentration of 1.5 × 10 −3 M at a temperature of 80°, adequate conversion could not be obtained. This limited the range of particle sizes which could be produced without adding additional surfactants. It was also found that smaller particles, 0.135 μm diameter, could be formed by copolymerizing styrene sulfonic acid sodium salt with styrene. The effects of ionic strength on particle size was also investigated and it was found that the particle size increased with increasing ionic strength. At constant ionic strength, it was found that particle size decreased with increasing initiator concentration as expected theoretically.