摘要:

AbstractThe sequence distribution in random, multi‐block and alternating copolyesters based on the reaction of fumaric, maleic and phthalic acid potassium salts with 1,4‐dibromobutane were examined by1H and13C NMR spectra. Quantitative sequence distibution results were obtained from the analysis of13C NMR spectra. The different structures of synthesized copolyesters, expected from the experimental procedures used, were confirmed. In addition, it can be concluded that the esterification route used is irreversible and that no appreciable transesterification reaction between two different ester groups occurs in the course of the synthe

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910801

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe effect of the concentration of reagents on the kinetics of acceptor‐catalytic esterification is investigated for a homologous series of poly(oxyethylene)s1(number of oxyethylene units in the polymer chain:nis between 1 and 68). The reaction rate constant,k0, is found to be dependent on the concentration of the reagents and on the length of the polymer chain. The effect of concentration is most pronounced in the case of low‐molecular‐weight1(n= 1; 3). With an increase in the polymer chain length the concentration effect on the reactivity of the end groups decreases and is practically nil for oligomers containing 45 and 68 oxyethylene

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910802

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractRestriction of β‐elimination in polystyrene‐lithium (PSLi) in the block copolymerization of polystyrene with poly(ethylene‐co‐propene) catalyzed with PSLi/TiCl4(resulting in sample A‐2) by adding a spacer of a few monomeric units of isoprene (I) (PS‐InLi/TiCl4(n≤ 3)); resulting in sample A‐3), was evidenced by aM̄w/M̄n‐value of 2,67 lower than that of sample A‐2, and a crystallinity (χ) of 7,4% in the poly(ethylene‐co‐propene) (EPR) block in sample A‐3. These, together with shorter ethylene (E)‐sequences EEEn≥1, 27,6%) and a higher content of inverted propylene units (P) make the EPR‐block in A‐3 look like a polymer obtained with a soluble vanadium catalyst. This is due to the solubilization of the active centers by the PS chains. HigherM̄w/M̄n‐values (4,23) and crystallinity of the EPR block (18,3%) and longer EEEn≥1sequences (55,4%) in the case of sample A‐2 make it to look like a typical polymer as obtained with a heterogeneous Ti‐catalyst. Comparison of sample A‐3 with that obtained by E‐P copolymerization with BuLi/TiCl4(sample A‐1) corroborates the solubilization effect of PS in A‐3 and the effects of the typical heterogeneous catalyst used for the preparation of A‐1, showing up in EEEn≥1(A‐1: 63,4% A‐3

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910803

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThermotropic liquid‐crystalline polyesters with either 4,4″‐p‐terphenylylene orp‐phenylene‐oxyterephthaloyloxy‐p‐phenylene as mesogenic units and dimethylsiloxane spacers in the main chain were synthesized. The thermal behaviour was studied by means of differential scanning calorimetry, polarizing microscopy, and X‐ray diffractometry. The polymers show mainly smectic mesomorphism. The transition temperatures were found to be much lower than in the corresponding polyesters containing polymethylene or poly(oxy

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910804

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

Abstract4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione (2, PTD), like other triazolinediones, reacts with electron‐rich aromatic compounds to give an electrophilic substitution. The reaction of PTD with poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) (1, PPE) is studied by UV and IR spectroscopy. Based on the kinetic measurements, three stages of reaction can be distinguished: a slow induction period; a period with strongly increasing reaction rate associated with the formation of a strongly absorbing species, probably a charge‐transfer complex, and conversion of most of the PTD; and finally a period with a slow decay of the previously formed absorbing species. Experiments with urazole or trifluoroacetic acid added at the beginning of the reaction prove that the strong increase in the reaction rate is due to autocatalysis by the urazole groups formed during the course of the reaction. A mechanism is proposed to account for the

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910805

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractPoly(butadiene‐co‐trimethylvinylsilane) with a mole fraction of 13% trimethylvinylsilane was prepared with butyllithium as initiator. It was degraded by cross‐metathesis with (E)‐4‐octene or (Z)‐2‐butene in the presence of the catalyst WCl6/Sn(CH3)4. The mixtures of the degradation products were investigated by means of gas chromatography (GC)/mass spectrometry (MS) coupling; mass spectra of degradation products with 4‐octene are depicted and discussed. Sequences of up to six trimethylvinylsilane units inserted between 1,4‐linked butadiene were identified after degradation with 2‐butene. Trimethylvinylsilane inserted between 1,4‐ and 1,2‐linked butadiene was also found. Cyclohexenyl and cyclopentenyl compounds were the preferred cyc

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910806

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe (MoVO)3+‐containing [Fe4S4]2+agglomerate {(Ph4P)2[Fe4S4(tmbdt)2(MoVO)0,76]}n(tmbdt = 2,4,6‐trimethylbenzene‐1,3‐dithiolato) was synthesized by reaction of {(Ph4P)2[Fe4S4(tmbdt)2]}nand MoVOCl3(thf)2. The (MoVO)3+cation is coordinated to the sulfur ligands binding the [Fe4S4]2+core. The (MoVO)3+‐containing [Fe4S4]2+agglomerate exhibits catalytic activity for the reduction of azobenzene and phenylacetylene to hydrazobenzene and phenylethylene, respectively, by Et4NBH4inN,N‐dimethylformam

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910807

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractPolydepsipeptides with alternating α‐hydroxy acid and α‐amino acid residues were synthesized by ring‐opening polymerization of morpholine‐2,5‐dione derivatives. The polymerizations were performed in the melt using stannous octoate as an initiator. Molecular weights of the polydepsipeptides obtained ranged from 0,9 · 104to 7,4 · 104. Morpholine‐2,5‐dione derivatives unsubstituted at the 6‐position gave polymers with the highest molecular weights. Poly((S)‐alanine‐alt‐glycolic acid) was semi‐crystalline, whereas all other polydepsipeptides synthesized were amorphous. Morpholine‐2,5‐dione derivatives were synthesized byN‐acylation of glycine, (S)‐alanine or (S)‐valine with chloroacetyl chloride or (R,S)‐2‐bromopropionyl bromide, followed by ring‐closure ofN‐(2‐halogenacyl)‐amino acid sodium salts in the melt in 4 to 83% yield. Low yields in the cyclization reaction ofN‐(2‐halogenacyl)‐(S)‐valine were accompanied by the formation of the corresponding polydepsipeptides in 13 to 46% yield,

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910808

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractAcetylacetonato group‐bearing poly(ethylene‐co‐propene‐co‐1,4‐hexadiene) (EPDM) was prepared and its chelate by crosslinking reaction with ferric salts. The hydroiodination of residual double bonds in the EPDM terpolymer under phase‐transfer conditions and the substitution of iodine atoms in the hydroiodinated EPDM by acetylacetonato groups were studied. The ligand exchange reactions of acetylacetone with ferric trifluoromethanesulfonate (Fe(TFS)3) or ferric chloride in THF were explored by UV/Vis spectroscopy to find optimum conditions for the formation of the chelate complex ferric acetylacetonate. The results indicate that these two ligand exchange reactions are equilibrium reactions, and the addition of an organic base such as triethylamine can make the reactions go to completion. The character of the anion in the ferric salts has a significant effect on the ligand exchange reactions, which may be attributed to the different dissociation tendency of FeX bonds. The ligand exchange reactions in the polymer systems were studied, and Fe(III)‐chelate complex crosslinked EPDM elastogels with gel fractions higher than 90% were prepared. The mechanism of the chelate complex formation in the polymer systems is similar to that in model

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910809

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractModel reactions of isophorone diisocyanate (IPDI (1)) with ethanol were examined using13C NMR technique to locate the chemical shift of different urethane and isocyanate groups in the products. The reactivity of the secondary and primary isocyanate group of the IPDI isomers is catalyst‐dependent. In the presence of Lewis acids (e.g., dibutyltin dilaurate) the secondary NCO group is more reactive, while in the presence of Lewis bases (e.g., triethylamine) it is the primary one. This effect allowed the chemical shift assignment of urethane‐ and isocyanate carbonyl C atoms in adducts formed by reaction of IPDI with ethanol in mole ratio NCO:OH = 2:1. In ethyl carbamates from the main isomer the chemical shift δ = 155,93 ppm is assigned to the carbonyl C atom of the urethane group at the secondary C atom, the signal at δ = 157,07 ppm to the primary urethane group. Furthermore, it was possible to assign the signal at δ = 122,12 ppm to the primary NCO group and the signal at δ = 122,98 ppm to the secondary NCO group of isophorone diiso

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910810

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY