Balazs Keszler

Amphiphilic networks. V: Polar/nonpolar surface characteristics, protein adsorption from human plasma and cell adhesion

The surface energetics, specifically the balance of polar/nonpolar forces on the interfaces of various amphiphilic networks comprising hydroxyethyl methacrylate (HEMA) or N,N-dimethylacrylamide (DMAAm) hydrophilic chains linked by polyisobutylene (PIB) hydrophobic chains (for brevity H and A networks) in contact with water have been studied by dynamic contact angle measurements. Both networks show large contactangle hysteresis due to surface heterogenity and surface rearrangements. The balance of the polar/nonpolar forces of the dry networks, as quantitated by the Ip/WAd ratio is much below unity; upon equilibrating in water the Ip/WAd ratio increases but remains below unity. Protein adsorption from human plasma and human monocyte adhesion to A and H amphiphilic networks possessing polar/nonpolar ratios lower than unity have been investigated. Both networks adsorb less fibrinogen, albumin and Hageman factor (factor XII) than glass, polyethylene (PE), and polydimethylsiloxane (PDMS). The extent of adsorption of factor VIII on A, H and glass are very similar. Adsorption of IgG on A was appreciable, however, on H it was less than on any of the other surfaces studied. Monocyte adhesion was significantly inhibited on both networks and glass, relative to a positive adhesive surface such as tissue culture polystyrene (TCPS). Evidently both the A and the H networks exhibit reduced protein adsorption and cell adhesion which indicates biocompatibility of these networks at blood contacting surfaces. The ratio of the polar/nonpolar forces expresed by the Ip/WAd ratio may be useful to predict low protein adsorption and cell adhesion on polymer surfaces.

Amphiphilic networks. XI. Mechanical properties and morphology

The bulk properties of two types of amphiphilic networks, poly(2-hydroxyethyl methacrylate)-l-polyisobutylene (PHEMA-l-PIB, H-network) and poly(N,N-dimethylacrylamide)-l-polyisobutylene (PDMAAm-l-PIB, A-network), have been investigated. Tensile strengths decreased considerably by swelling, and the decrease was more severe by swelling in water than in n-heptane. Elongations increased by swelling in water; however, the change was not consistent upon swelling in n-heptane. The hardness of dry networks decreased with increasing PIB content, while for wet networks it was similar to dry networks containing 85 wt % PIB. Small-angle X-ray scattering showed that average interdomain spacings decreased with increasing PIB content. According to dynamic mechanical thermal analysis (DMTA) the glass transition temperatures (T g ) of the respective hydrophobic and hydrophilic components shift toward each other with increasing PIB content. A liquid-liquid transition (T u ) above the T g of the hydrophilic component was apparent by DMTA, but could not be found by differential scanning calorimetry (DSC).

Styryl-telechelic polyisobutylenes. I. Synthesis of linear and tri-arm star styryl-telechelic polyisobutylenes

Abstract New linear and three-arm star polyisobutylenes carrying two and three terminal styryl endgroups, i.e., Fn = 2.0 and 3.0, respectively, have been prepared. The synthesis of these styryl-telechelic polyisobutylenes involved Friedel-Crafts alkylation by linear and/or three-arm star polyisobutylenes carrying tertiary chlorine endgroups of (2-bromoethyl)benzene or /β-bromoisopropylbenzene followed by de-hydrobromination. According to model studies, 1H-NMR, and UV spectroscopy, the conversions are essentially quantitative. These new terminally di- and tri-styrenated polyisobutylenes may be useful for the preparation of block copolymers and as cross-linking materials.

Styryl-Telechelic Polyisobutylenes. II. Amphiphilic Sequential Copolymers of Styryl-Telechelic Polyisobutylenes with Vinyl Acetate or N-Vinyl-2-pyrrolidone

Abstract Styryl-telechelic polyisobutylenes (i.e., linear and three-arm star polyisobutylenes capped with polymerizable p-styryl endgroups St-PIB-St and St-PIB-St) have been copolymerized with vinyl ace State VAc or N-vinyl-2-pyrrolidone VP by conventional free radical techniques. The products obtained with St-PIB-St/VAc systems were soluble, most likely branched block copolymers of isobutylene IB and VAc, whereas those prepared with St-PIB-St/VP or St-PIB-St/VP Stcombinations were networks consisting of PIB and poly(N-vinyl-2-pyrrolidone) PVP sequences. That the copolymerization of St-PIB-St with VAc results in soluble products and that with VP yields networks is due to the very different reactivities of styrene with VAc and with VP. Hydrolysis of VAc units in PID-PV Ac block copolymers gave vinyl alcohol V A units, i.e., these products are branched block copolymers consistion of random VAc/VA composition of these soluble aphiphilic materials was determined from conversion and molecular weight data and b...