Discussion on the mechanism of alternating copolymerization of styrene and maleic anhydride

Abstract

To clear up the detailed mechanism of the alternating copolymerization of styrene (St) and maleic anhydride (MAn) concerning the initiation species, the propagation species, the tendency of the chain transfer reaction as well as the directional tendency of the reaction between copolymer radicals and monomer complexes, the role of the charge transfer complexes, characterization of end groups and additional donor effects were examined.The equilibrium constant of the St/MAn (1 : 1) complex was determined to be 0.31 by NMR spectroscopy, that suggested considerable amounts of complexes existing in the system. As expected, a small quantity of initiator (1%-azobisisobutyronitrile (AIBN)) was incorporated into the St/MAn copolymer. Chlorine atoms were scarcely incorporated into the copolymer synthesized in CCl4 with AIBN or benzoyl peroxide (BPO) as an initiator. Hence the copolymerization was considered to be induced only by attacke of initiator radicals to the monomer or the complexes, contrary to the usual conception of telomerization.When the electron donor monomer was added to the system, the terpolymerization could be treated as a copolymerization of the two complexes, i e . , St/MAn and Donor/MAn. By adding naphthalene the rate maximum point shifted from higher concentration of MAn to the equivalent concentration of St and MAn. Degradative chain transfer to N.N-dimethylaniline was observed, confirming the existance of poly-MAn radicals.It was suggested from these results that the charge transfer complex and uncomplexed MAn took part in the copolymerization of S t and MAn. This was proved kinetically. The whole mechanism was discussed. ZUSAMMENFASSUNG: Um den Mechanismus der alternierenden Copolymerisation von Styrol (St) und Maleinsaureanhydrid (MAn) in bezug auf die Art der Initiierung und des Wachstums, die Neigung zu Ketteniibertragungsreaktionen und Richtungstendenzen der Reaktion zwischen den Copolymerradikalen und den Monomerkomplexen aufzuklaren, wurden die Rolle der Elektronendonator/-akzeptor-Komplexe, die Charakterisierung der Endgruppen und Donatoreffekte untersncht. Die Gleichgewichtskonstante des St/MAn(l : 1)-Komplexes wurde durch NMR-Spektroskopie zu 0,31 bestimmt. Das bedeutet, dal3 betrachtliche Mengen von Komplexen in dem System existieren. Eine kleine Menge des Initiators (1%-Azoisobuttersaiuredinitril (AIBN)) wurde, wie erwartet, in das St/MAn-Copolymere eingebaut. Chloratome wurden so gut wie nicht in das mit AIBN oder Dibenzoylperoxid (BPO) als Initiator in C C 4 synthetisierte 265 E. TSUCHIDA and T. TOMONO Copolymere eingebaut. Es wurde daher die Copolymerisation nur als durch den AngrifT der Initiatorradikale auf das Monomere oder die Komplexe gestartet betrachtet, im Gegensatz zum iiblichen Konzept der Telomerisation. Wenn ein Elektronendonator-Monomeres dem System hinzugefiigt wurde, konnte die Terpolymerisation als Copolymerisation der beiden Komplexe St/MAn und Donator/MAn betrachtet werden. Bei Zugabe von Naphthalin wurde die maximale Copolymerisationsgeschwindigkeit von hoheren MAn-...

Tissue- and Stage-specific Expression of Two Lipophorin Receptor Variants with Seven and Eight Ligand-binding Repeats in the Adult Mosquito

“…The loading and unloading of lipids into and from fat body cells is accomplished by a shuttle mechanism involving Lp and a multiprotein complex, called a lipid transfer particle (2)(3)(4). Despite the fact that lipid transfer occurs on the fat body cell surface without apparent internalization of transfer proteins, specific Lp receptors have been described in the larval fat body of several insects (5)(6)(7)(8)(9). The larval fat body cells have been shown to internalize high density lipophorin (HDLp) by means of receptor-mediated endocytosis, suggesting HDLp turnover between the fat body and the hemolymph (6,8).…”

Isolation, Characterization, and cDNA Sequence of a Carotenoid Binding Protein from the Silk Gland of Bombyx mori Larvae

“…For example, during the larval stage lipophorin delivers diacylglycerol mainly to fat body, hydrocarbon to integument, and carotenoids to silk gland and reproductive tissues. The observed selectivity is not fully understood or characterized, although some of the proteins such as lipid transfer particle (14) and the lipophorin receptor (15) involved in lipid mobilization have been identified. It is conceivable that other cell surface components are present to facilitate the selective lipid delivery.…”

Copolymerization of Indene with N-Phenylmaleimide

“…8 -10 The change in the reactivity ratios with the solvent nature was attributed to the role of the medium polarity on the intermonomeric charge-transfer complex. 9 The heterogeneity of the reaction medium leads also to variation of the reactivity ratio values and to an enhancement of the alternating tendency. 10 The latter suggestion has also been adapted in the present study.…”