J. Sledz

Modification of the biocompatible and haemocompatible properties of polymer substrates by plasma-deposited fluorocarbon coatings

The polymerization of gases present in a low temperature plasma is a technique particularly well suited for biomedical material processing. Therefore, the possibilities this technique offers to increase the biocompatibility and haemocompatibility of polysulphone and poly(hydroxybutyrate) membranes to be used in a new bioartificial pancreas device were studied. The deposition of thin fluorocarbon coatings from an argon plasma containing perfluorohexane gave very smooth and hydrophobic surfaces without affecting the filtering properties of the treated membranes. Adding hydrogen increased the reaction yield, but gave rougher and less hydrophobic coatings. We characterized the biological properties of the treated surfaces and discussed the influence of the modified surface properties on the biological behaviour of the treated polymers. The good biocompatibility of the deposited coatings was established by following in vitro the insulin secretion of Langerhans islets cultured on the treated membranes and by examining the fibrous capsule that developed on plasma-treated polymer disks after three months of in vivo incubation in the peritoneum of Wistar rats. Rough and haemocompatible films of poly(hydroxybutyrate) and smoother, but more thrombogenic, polysulphone films were treated by perfluorohexane and perfluorohexane + H2 plasmas to study the relative influence of surface roughness and surface energy on polymer thrombogenicity. In vitro protein adsorption and total blood clotting tests proved that the surface roughness influences the thrombogenicity more than the other surface properties. This study seems to show that the plasma deposition of smooth and hydrophobic fluorocarbon coatings can increase the biocompatibility and reduce the surface thrombogenicity of the treated membranes without affecting their filtering properties.

E.s.r. study of the Ti(OBu)4 catalyst mixture in silicone oil with regard to the synthesis of homogeneous and highly conducting (CH)x

Abstract E.s.r. spectra of a homogeneous catalyst system based on n -butyltitanate and triethylaluminium in a Al/Ti molar ratio of four were recorded in silicone oil at temperatures ranging from 22 – 130 °C. They contained signals with G values of 1.954, 1.972, 1.977, and 1.986, whose intensities varied with the ageing temperature. It is shown that increasing the catalyst ageing temperature above 100 °C favours only the active species with G value 1.954. This could be related to the initial rate of polymerization and to the synthesis of a more homogeneous, regular and highly conducting (CH) x film after doping with a 0.25 M FeCl 3 -nitromethane solution.

Plasma deposition of thin fluorocarbon films for increased membrane hemocompatibility

Abstract Plasma polymerization of gases present in a low temperature plasma is a “clean” technique that is particularly well suited for biomedical material processing. This paper presents the first results of a project which studies the possibilities offered by this technique to prepare commercial lowcost membranes with the required bio- and hemocompatibility to be implanted in an organism. The deposition on polysulfone of films from a plasma containing a mixture of ethylene oxide and perfluorohexane in order to obtain very hydrophobic, less hydrophobic and intermediate coatings was studied. Results obtained by adding hydrogen to perfluorohexane are also discussed. The deposition of a thin coating from a perfluorohexane and hydrogen plasma was studied in order to optimize the surface properties of the treated membranes without affecting their filtering properties. The treated substrates have been characterized by measuring mass variations, by surface profilometry and contact angle techniques as well as by scanning electron microscopy and electron spectroscopy for chemical analysis.

A new asymmetric membrane having blood compatibility

A new asymmetric membrane has been synthesized from an ABA poly(styrene-bisoprene) (SIS) block copolymer (Mn = 89,000; 30 mol% polyisoprene with 68% 1,4 links and 32% 3,4 links). The asymmetric structure of the membrane obtained by casting the collodium (block copolymer in THF/DMF mixture) has been evidenced by scanning electron microscopy. A chemical modification of the membrane by reaction with gaseous chlorosulfonylisocyanate leads to a heparin-like compound with enhanced blood compatibility properties. Elemental analysis and infrared measurements show the presence of sulfamate and carboxylate groups on the modified block copolymer. These functional groups increase the hydrophilicity of the membrane and therefore enhance its water permeability.

Polymerization of acetylene in the presence of a tungsten-based catalyst, and geometric structure, electrical properties and morphology of the polymer

A new metathesis catalyst, WCl6n-BuLi, was investigated for its catalytic activity in the polymerization of acetylene. The structure, electrical properties and morphology of the doped polyacetylene were also studied.

Some Observations About Polysilane Synthesis

Abstract Three polysilanes have been synthesized by Wurtz coupling of various organomethyl dichlorosilanes, GPC, u.v. and i.r. analyses were performed. The i.r. spectra reveal hydrosilanes and siloxanes groups in the oligomer fractions. Possible sources of these unusual groups are discussed.

Anionic polymerization of isoprene by the complexes oligoisoprenyllithium/tertiary polyamines in cyclohexane: 3. Structural study of the polymers by 1H n.m.r. at 100 MHz

Abstract The microstructure of polyisoprene prepared anionically in the presence of catalytic amounts of N,N,N′,N′-tetramethylethylenediamine (TMEDA) and pentamethyldiethylenetriamine (PMDT) has been studied as a function of r = [ TMEDA ] [ living ends ] and r = [ PMDT ] [ living ends ] . No significant effect is observed for r ⩽ 0.5. The structure varies drastically for r > 0.5. The 4,3 addition increases mainly at the expense of the cis4,1 addition and a plateau is reached for r ⩾ 1.0. The results are discussed on the basis of the nature of the living species.

Synthesis of aminotelechelic polymers with the redox system TiCl3NH2OH in hydrochloric aqueous phase: 3. Polymerization of methylacrylate. relation functionality/molecular weight/yield

Abstract Aminotelechelic poly(methylmethacrylates) of which number average molecular weight M n is less than 7 × 103 are synthesized with the redox system TiCl 3 NH 2 OH in hydrochloric aqueous phase. Functionality, molecular weight and yield are discussed on the basis of initiation, propagation and termination reactions. These considerations justify the influence of various factors such as the addition time of the TiCl3 solution, the molar ration MMA TiCl 3 and the nature of the reducing ions. The evolution of molecular weights determined by g.p.c. confirms the interpretation of the results.

Polymerization of Acetylene with New Catalytic Systems and Optimization of the Properties of the Polymers

Abstract This paper reports a comparative study of different catalytic systems for the synthesis of novel polyacetylene films. That the morphology could be optimized by the use of a highly viscous complexing solvent together with thermal treatment [1,2] encouraged us to study the catalytic systems with the aid of ESR spectroscopy. The different samples were characterized with the aid of IR and ESR spectroscopic methods, conductivity measurements, and scanning electron microscopy before and after doping.

Polymerization of (R, S)-β-butyrolactone from tetraisobutyldialuminoxane (TIBAO) catalyst

Poly-β-hydroxybutyrate (PHB) was prepared by ring-opening polymerization reactions of racemic β-butyrolactone ((R,S)-β-BL) using tetraisobutyldialuminoxane (TIBAO). A study was conducted on the effects of catalyst concentration, polymerization time, polymerization temperature, nature of solvent, modifications of the catalyst by water addition and TIBAO purification on the yield and molecular weights of the polymer obtained. Optimal conditions for the synthesis of highest yield and molecular weights of the polymer were determined. By adding water to TIBAO, molecular weights increased but also polydispersities. Quantitative yields of crude PHB were obtained but reaction times required were long, molecular weights were quite low and molecular weight distributions were broad. A study of the TIBAO stereospecificity, the polymers structure and morphology and their biodegradation will be considered in future papers.