摘要:

AbstractThe anionic ring‐opening polymerization of mixtures of 2,2‐dimethyltrimethylene carbonate (5,5‐dimethyl‐1,3‐dioxan‐2‐one) (1) and pivalolactone (2,2‐dimethyl‐3‐propanolide) (3) in toluene as a solvent and with potassium dihydronaphthylide as initiator, results in formation of block copolymers with yields of ca. 90%. In tetrahydrofuran as a solvent the polymer yields are ca. 65% only. In toluene,1polymerizes first and subsequently3resulting in a blocky structure of the copolymer. According to a mechanistic study, the active species is first a1‐alcoholate, later a3‐alcoholate and finally a3‐carboxylate. The copolymers are soluble in deuterochloroform up to a mole fraction of pivalolactone of ca. 0,40. By means of13C NMR spectroscopy the blocky structure of the copolymers prepared in toluene was confirmed. In tetrahydrofuran as a solvent1‐3and3‐1‐diads are formed to a significant extent. The copolymers were characterized by thermoanalytical an

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910901

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe synthesis of a variety of alkyl‐chain‐substituted poly(para‐phenylene) (PPP) derivatives, including those with systematically decreased density of side chains, is described, using for their preparation the Pd‐catalyzed polymerization method recently developed in Mainz (Mainz route to PPP's). The degrees of polymerization achieved range between 30 and 50, allowing the synthesis of structurally well‐defined and soluble PPP's with more than hundred 1,4‐phenylene rings attached to

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910902

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe arylation of monomers for high‐performance polymers is described. The reaction of dibenzoyl peroxide with various 1,4‐disubstituted benzene derivatives results in phenylation. Minimization of side reactions is discussed. The Ni‐promoted reaction of Grignard compounds with iodoarenes was used to introduce the phenyl, biphenyl, and naphthyl substi

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910903

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractA not perfectly pure 1,4‐bis(trimethylsilylamino)‐2,5‐bis(trimethylsilylthio)benzene was prepared as starting material for all condensations. Condensations with 4‐chlorobenzoyl chloride under a variety of reaction conditions revealed formation of benzobisthiazoles at temperatures ≥250°C. Condensation with various aryloxy or bisalkoxyterephthaloyl chlorides in an one‐pot procedure yielded substituted poly(benzobisthiazole)s. All poly(benzobisthiazole)s were soluble in mixtures of dichloromethane or chloroform and trifluoroacetic acid (TFA). Inherent viscosities up to 2,0 dl/g were found in this solvent system. Neither homo‐ nor copoly(benzobisthiazole)s formed a freely flowing melt up to 450°C, where thermal degradation beings to affect the properties. Thermogravimetric analyses in air proved that aryloxy‐substituted polymers possess a significantly greater thermostability than alkoxy

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910904

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractBis(trimethylsilyl)bisphenol‐A was condensed with 4,4′‐dichlorodiphenyl sulfone under various reaction conditions. Satisfactory yields and molecular weights of the resulting poly(ethersulfone)s were only obtained when the condensation was conducted in amide solvents (e. g.,N‐methyl‐2‐pyrrolidone) in the presence of equimolar amounts of K2CO3. The purity of the solvent plays an important role for the molecular weights. By light scattering, weight‐average molecular weights (Mw's) up to 130000 were found. Further polycondensations were conducted with 2,6‐dichlorobenzonitrile, 2,6‐dichloropyridine or 3,6‐dichloropyridazine. For polyethers derived from 2,6‐dichlorobenzonitrileMw's up to 106000 were found and for copoly(pyridine‐ether‐sulfone)sMw's up to 220 000. The corresponding difluoroaromatics gave similar results. In contrast to the polycondensation of free diphenols with dihaloaromatics under alkaline conditions, no water is formed when sil

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910905

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractN‐(2‐hydroxypropyl)methacrylamide (HPMA) copolymers (11a, b) containing side chains terminating in 5‐aminosalicylic acid (5‐ASA) and fucosylamine (10) were synthesized. A reactive polymeric precursor (9), a copolymer of HPMA (7) andN‐methacryloylglycylglycinep‐nitrophenyl ester (8), was consecutively aminolyzed with 5‐[4‐(2‐aminoethylcarbamoyl)phenylazo]‐salicylic acid (6) and fucosylamine (10). The latter renders the copolymers bioadhesive in the gastrointestinal tract. The release of 5‐ASA from11a, bwas studiedin vitroby incubation with cell‐free extracts isolated from rat cecum, and factors influencing the degradation were determined. The rate of azo bond cleavage of11a, bwas similar to the rate of cleavage of low‐molecular‐weight substrates, methyl orange and compound6. Addition of benzyl viologen, a low potential electron carrier, increased the rate of cleavage. At optimal benzyl viologen and substrate concentration ratios, a zero order release was observed. At higher substrate concentration, the rate

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910906

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe influence of ethyl benzoate (E.B.) on the copolymerization of styrene with 1‐hexene, initiated by isospecific Ziegler‐Natta catalysts α‐TiCl3(H)‐AlEt3and TiCl3· 1/3 AlCl3‐AlEt3(mole ratio Al/Ti = 3), was examined. Ethyl benzoate was found to reduce the activity of the catalysts. In addition it leads, depending on the Ti catalyst, to opposite effects on the apparent reactivity order of the two monomers. Incorporation of styrene into the copolymers is reduced when E. B. is added to TiCl3· 1/3 AlCl3‐AlEt3. On the contrary, a much higher incorporation of styrene is observed with α‐TiCl3(H)‐AlEt3in the presence of E. B. For this system the calculated reactivity ratio varies strongly with increasing proportion of E. B.: for a mole ratio AlEt3/E. B. = 3,rS= 0,94 andrH= 1,46 and for AlEt3/E. B. = 2,rS= 8 andrH= 0,1. Changes in the stereoregularity of copolymers suggest that E. B. leads to an inhibition of the less stereospecific sites for TiCl3· 1/3 AlCl3‐AlEt3, whereas its addition suppresses the stereospecificity of the α‐TiCl3(H)‐AlEt3catalyst. Contributions of conventional cationic and/or radical processes to the copolymerization reaction were ex

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910907

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractA novel photosensitive multilayer film was prepared using a solid‐state photoreactive compound having four double bonds, dihexyl 5,5′‐(1,4‐phenylene)bis(2‐cyano‐2,4‐pentadienoate) (PCPAC6). PCPAC6, which forms a stable mixed monolayer on the water surface when mixed with arachidic acid, was transferred onto a substrate, thereby forming an Y‐type multilayer film. The multilayer film has an absorption maximum at 356 nm, showing a blue shift with respect to that of crystals. This indicates that the molecular arrangement of PCPAC6in the multilayer film is different from that in the crystals. The multilayer film is very sensitive to visible light and was converted into the oligomer or polymer film on irradiation. The polymer film shows a photoreversible transition between polymers and oligomers, depending on the wavelength of the irradiating light. This phenomenon is caused by the cleavage and formation of cy

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910908

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe determination of active centres concentration in ethylene polymerization using various TiCl4/MgH2‐Al(C2H5)3catalytic systems, by the14CO radio‐tagging method, is reported. It is found that with increasing the absolute titanium amount the concentration of active centres, [C*], increases, whereas the propagation rate constant,kp, decreases. In addition, using various TiCl4/MgH2catalysts in ethylene polymerization, it is found that the lower the Ti content, the higher is the surface area of the catalyst and the higher is the polymerization activity. Determination of [C*] shows consclusively that the decrease in the polymerization activity observed to occur with increasing the Ti content, and thus decreasing the surface area, is unequivocally due to a reduction in the concentration of active centres but not to any fundamental change in the value of the propagation rate const

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910909

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractL‐lactic acid (LA) was copolycondensed with various aromatic hydroxy acids such asp‐hydroxybenzoic acid (HBA),p‐hydroxyphenylacetic acid (HPAA), andp‐3‐(hydroxyphenyl)propionic acid (HPPA) in the absence of catalysts, in order to investigate the copolymerizability andin vitrodegradation. The results of1H NMR spectroscopy and gel permeation chromatography (GPC) showed that the reaction proceeds quantitatively, but the molecular weight of the copolyesters is relatively low. Thein vitrodegradation pattern of copoly(LA/HPPA) was changed into an S‐type from a parabolic‐type with increasing HPPA content in the copolyester, in contrast to only parabolic‐type for both copoly(LA/HBA) and

ISSN:0025-116X    

DOI:10.1002/macp.1990.021910910

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY