SYNOPSISMicroporous hydrophobic polypropylene (PP) membranes (Celgard@ 2400 and 2500) were modified by the chemical modification technique to impart permanent hydrophilicity. The modification was carried out in two stages. In the first stage, the membranes were hydroxylated by treatment with aqueous potassium peroxydisulfate solution under a strong flow of nitrogen. In the second stage, the hydroxylated membranes were subjected to grafting of acrylamide using cerric ammonium nitrate as an initiator. Subsequently, acrylamide grafted PP membranes were partially hydrolyzed to have carboxyl functional groups at the membrane surfaces. Under given experimental conditions the grafting also took place within the pores of the microporous structure of hydrophobic PP Celgard@ membranes. Modified membranes exhibited permanently wettable characteristics by aqueous solutions and appeared translucent when immersed in water. Contact angle measurements showed excellent wetting properties with water. In contrast to unmodified Celgard@ membrane, the modified membranes exhibit water permeability even after repeated drying.
Acta Polymerica 38 (1987) Nr. 5 260 DONTH, KRETZSCHMAR e t al. : Influence of the chain-end mobility on the melt crystallization GOWSKI, T. M., KRYSZEWSKI, M., and PVCHERZ, J . : Acta Cryst. C 42 (1986) 172. ,Carl Schorlemmer" Leuna-Merseburg, Sektion Physik, DDR-4200 MerseburgHindering and final blocking of the normal melt crystallization in central ethylene oxide (EO) blocks by methyl methacrylate (MMA) end blocks of increasing lengths in ABA type triblock copolymers synthesized anionicallg in a new way are investigated by differential scanning calorimetry and X-ray scattering. Experimental studies of glass transitions, low temperature nucleation, and the morphologic ten-nanometer structure are included. Low percentage amounts of long homo-PEO chains can crystallize in a n ABA matrix which otherwise is not normally crystallizable. It is concluded from the experiments that in our systems with PEO molecular masses up to 50000 g/mol t h e motion of the chain ends is necessary for melt crystallization under normal conditions. DONTH, KRETZSCHMAR et al.: Influence of thr chain-end mobility on the melt crystallization Actr Polymerica 38 (1987) Nr. 5 261
EinfluP der Kettenendenbeweglichkeit auf die Schmelzkristallisation von Ethylenoxid-(B)-Sequenzen in Systemen, die Diblock AB-und Triblockcopolymere ABA mit Methylmethacrylat (A) enthaltenDie Behinderung und letztliche Blockierung der normalen Schmelzkristallisation von zentralen Ethylenoxid( E 0 ) -Blocken durch Methylmethacrylat-(MMA)-Endblocke ansteigender Lange in Triblockcopolymeren vom Typ ABA, anionisch auf einem neuen Weg synthetisiert, wurden mit Hilfe der differentiellen Scanning-Calorimetrie und der Rontgenstreuung untersucht. Experimentelle Untersuchungen des Glasiihergangs, der Keimbildung bei tiefen Temperaturen und der morphologischen Zehn-Nanometer-Struktur werden eingeschlossen. Geringe Mengen (Prozentbereich) langer Homo-PEO-Ketten konnen in einer ABA-Matrix kristallisieren, welche sonst normal nicht kristallisierbar ist. Aus den Experimenten wird geschlossen, daB in den untersuchten Systemen mit PEO-Molekiilmassen bis zu 50 000 g/mol eine Bewegung der Kettenenden notwendig ist fur die Schmelzkristallisation unter normalen Bedingungen.
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