Aeta Polymerica 40 (1989) Nr. 9 602 SPANGE, HORTSCHANSKY und HEUBLEIN: Untersuchungen zum Donator-Acceptor-Verhalten von Reaktionskompositen intensity of t h e processes i n different PEI suggests t h a t t h e weakest moiety (under investigation) is (SOz is isolated beginning from 320°C). This is t h e case of PEI-1.A slightly more stable moiety is (PEI-2)Imide rings are opened beginning from 360°C ( C 0 2 and CO are intensively isolated).
The most stable moiety isThis m a y be due t o t h e presence of S-bonds. PEI-3 begins t o degrade at 360°C. Hence, t h e crosslinking of PEI-3 is difficult.
Thus t h e first stage of crosslinking of t h e PEI chains ist h e formation of free radicals i n t h e reaction of decarboxylation a n d degradation of terminal anhydride groups with subsequent recombination of radicals. T h e second stage is t h e degradation of t h e main chains following random recombination of these fragments.
AcknowlegementW e a r e grateful t o Dr. L. M. KALUZHNAYA for sorption d a t a a n d I. L. USHAKOVA for EPR data.
Der Feststoffanteil der mit Peroxodisulfat initiierten Vinylacetat‐Emulsionspolymerisation mit Polyvinylalkohol als Schutzkolloid besteht aus einem wasserlöslichen Anteil (unumgesetzter Polyvinylalkohol, Pfropfprodukte mit niedrigem Pfropfgrad), einem acetonlöslichen Anteil (Polyvinylacetat, Pfropfprodukte mit hohem Pfropfgrad) und einem unlöslichen Anteil (vernetzte Produkte). Der Einfluß der Reaktionszeit auf die Mengen dieser Anteile wird untersucht. Die löslichen Anteile werden IR‐spektroskopisch charakterisiert.
In unpolaren und stark polaren aprotischen Lösungsmitteln wird die Bromaddition an cis‐ und trans‐Stilben quantitativ verfolgt. Die Ergebnisse erlauben Hinweise auf die unterschiedliche Stabilisierung des Zwischenzustandes der elektrophilen Addition, die im unpolaren Lösungsmittel mehr über Halonium‐Ionen und im polaren Lösungsmittel über solvatstabilisierte klassische Carbonium‐Ionen verläuft.
ABSTRACT:Living cationic copolymerization of isobutyl vinyl ether with p-methoxystyrene was effected by an equimolar mixture of hydrogen iodide and iodine (HIII2 initiator) at -l5°C in nonpolar solvents (carbon tetrachloride and toluene). Isobutyl vinyl ether reacted faster than pmethoxystyrene. The products were random copolymers with a nearly monodisperse molecular weight distribution (MWD) (MwiM.= 1.1-1.2). Their number-average molecular weight (M.) increased in proportion to total monomer conversion. The iodine-initiated copolymerization under similar conditions led to long-lived (but not perfectly living) copolymers with a narrow MWD (MwiM.= 1.2-1.3). In contrast, boron trifluoride etherate induced a conventional transferdominant copolymerization. TheM. of the copolymers obtained with the HIII2 initiator was almost independent of the monomer feed ratio, but in the BF30Et2-initiated non-living process, the polymer molecular weight decreased sharply with increasing isobutyl vinyl ether content in the feed. These findings show the living copolymerization by HIII2 to be free from the cross-transfer usually involved in the conventional cationic copolymerization of vinyl monomers.
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