The aim of this paper is to investigate how the molecular structure of linear polypropylenes can be modified by electron beam irradiation. For this purpose a linear precursor was irradiated with different doses. The samples were analyzed by size-exclusion chromatography coupled with a light scattering detector. With increasing doses, a reduction of molar mass and an increasing number of longchain branches were found. Moreover, conclusions with respect to the topography of the long-chain branches obtained were drawn from the molar mass dependence of the zero shear viscosity of the irradiated samples, which deviates significantly from that of linear polypropylenes. The experimental results can be interpreted in a way that at low doses very few but long branches occur. At higher doses more and shorter branches per molecule exist. The elongational experiments clearly exhibit a change of the strainhardening behavior with irradiation dose, which is in agreement with the structural changes concluded from the shear measurements. The results from rheology and their interpretation demonstrate two features. First, rheological experiments conducted on irradiated polypropylenes are much more sensitive with respect to long-chain branching than the classical characterization methods based on size-exclusion chromatography coupled with light scattering. Second, from a comparison of the rheological behavior of linear and irradiated polypropylenes some conclusions can be drawn regarding the topography of the long-chain branches generated.

No abstract

Protein adsorption was studied by in‐situ ATR‐FT‐IR spectroscopy of consecutively deposited polyelectrolyte multilayer systems terminated either with poly(ethyleneimine) (PEI) or polyanions, such as poly‐(acrylic acid) (PAC), poly(maleic acid‐co‐propylene) (PMA‐P) or poly(vinyl sulfate) (PVS). The influence of the polyanion type, pH and ionic strength was investigated. Negatively charged human serum albumin (HSA) was strongly repelled by multilayers terminated with weak polyanions (PAC, PMA‐P), whereas moderate attraction was observed for those terminated with the strong polyanion PVS. Changing the pH from 7.4 to 5 resulted in enhanced HSA adsorption onto PAC‐terminated multilayers. An increase in ionic strength diminished the attractive HSA adsorption onto PEI‐terminated multilayers. For the PEI/PAC system, the biomedically relevant adsorption of human fibrinogen (FGN) is determined via its isoelectric point in accordance with three other proteins.

SUMMARY In-situ attenuated total reflection (ATR)-FTIR spectroscopy was used to monitor the consecutively alternating adsorption of polyethylenimine (PEI) and poly(acry1ic acid) (PAC) onto both Si crystals (SiO) and COz plasma-treated polypropylene (PP) films. The vibration bands v,(COO-) and v(C=O) of PAC are diagnostic for the polyelectrolyte layer build-up and sensitive to protonation changes. Human serum albumine (HSA) adsorption experiments revealed a strong decrease of fouling for the PP films, which were modified with polyelectrolyte multilayers, in comparison to the unmodified ones.

No abstracts.