摘要:

AbstractThe behaviour in propylene polymerization of catalysts containing ethyl benzoate/methylp‐toluate (EB/MPT) or dibutyl phthalate/triethoxy(phenyl)silane (DBP/EPS) as internal/external donor pairs was investigated. Comparing catalyst composition with performance, it appears that no qualitative difference exists in the role of MPT and EPS, both acting as poisons of atactic sites and activators of isotactic sites. A higher efficiency of EPS is evident. On the contrary, a difference can be found between the internal donors EB and DBP/DBP seems not directly involved in the formation of isotactic centers as EB. These results, though obtained under conditions leading to much lower activities than usual for the catalysts considered, can be assumed to describe the general behaviour of the donor pairs investigated when the polymerization is carried out in the absence of hydroge

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930121

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of molecular weight and concentration of poly(2‐vinylnaphthalene) (PVN) on the bulk polymerization of styrene initiated by 2,2′‐azoisobutyronitrile (AIBN) was studied under UV‐irradiation in the presence of a magnetic field. It was found that in the suitable range of molecular weights (<1,7 · 103) and concentrations (1,62 to 9, 12 · 10−3mol/L) of PVN, the molecular weight and molecular weight distribution of polystyrene significantly varied with the change of the external magnetic field. A triplet energy transfer mechanism between PVN and AIBN in the PVN cages was suggested on the basis of the experimen

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930122

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractPoly(N‐isopropylacrylamide) (PIPA) with a carboxyl group at its end was coupled with amino group‐carrying porous glass beads by the active‐ester method. Gel permeation chromatography of dextran was carried out by using a column packed with the PIPA‐carrying glass beads. The chromatograms of dextrans with various molecular weights are strongly affected by temperature: the elution time of dextran is largely changed between 25 and 32°C due to a change in the effective pore size by the transition of the PIPA chains from coils to globules on the surface of the pores of the glass beads. These results suggest the usability of PIPA‐carrying glass beads as devices for thermo‐controllable ch

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930123

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractWe found that furan and alkyl‐substituted furans function as slowly reacting monomers rather than retarders or inhibitors in free‐radical copolymerization reactions with acrylonitrile. The effect of the presence of Lewis acids was examined: some cause an ionic reaction of the furan ring, one (SO2) acts as an inhibitor, and others enhance the entry of the furan into the copolymer, increase the yield and molecular weight, and for 2‐methylfuran cause a new type of furan residue to form by promoting a hydrogen abstraction rea

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930124

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

Abstract2‐Perfluoro(alkyl)ethyl vinyl ethers, F(CF2)nCH2CH2OCHCH2, (n= 6 or 8), were synthesized and polymerized by means of cationic initiators (HI/ZnI2and CF3SO3H/(CH3)2S). The perfluorohexyl‐substituted poly(vinyl ether) is completely amorphous. The polymer with perfluorooctyl segments shows side chain crystallization with a disordering transition. For the corresponding perfluorooctyl monomer a liquid‐crystalline phase was observed before melting. Copolymerization experiments of the flurocarbon‐segmented monomers with a vinyl ether containing a cyanobiphenyl group in the side chain did not give homogeneous copolymers. This is attributed to the slower rate of polymerization of the fluorinated vinyl ethers as compared with the liquid‐crystallin

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930125

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractKinetics of addition of ethylene oxide to the POH groups in phosphorous (H3PO3) and phosphoric acid (H3PO4) were studied. The reaction is catalysed by the POH groups themselves, presumably by formation of hydrogen‐bonded complexes with ethylene oxide. The values of apparent rate constants of reactions involving subsequent POH groups were determined. The apparent reactivity of POH increases with increasing number of OCH2CH2OH substituents present in the reacting molecule. This has been attributed to the formation of intramolecular hydrogen bonds influencing the reactivity of the POH groups. Mechanistic implications and the distribution of products are discussed in connection with the observed kineti

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930126

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY