摘要:

AbstractThe polymerization of propylene oxide (PO) was studied with an initiator prepared by the reaction of (R)‐(−)‐3,3‐dimethyl‐1,2‐butanediol (1) with aluminium hydride. When mixed with zinc chloride in a 1:1 mole ratio, the initiator was found to be highly reactive and also stereoelective in the polymerization of PO, preferentially incorporating (R)‐(+)‐PO into the polymer chain. Analysis of the polymer structure by13C NMR spectroscopy showed that chlorine, hydroxyl and alkoxy end groups, derived from the initiator, were present. Fractionation of poly(propylene oxide) (PPO) in acetone at −30°Cgave about 10% insoluble PPO, shown to be isotactic by13C NMR. The soluble, largely atactic fraction contained irregular head‐to‐head (h,h) and tail‐to‐tail (t,t) structures. In the absence of coinitiator zinc chloride the PPO product was completely soluble in acetone at −30°Cand contained a greater proportion of ir

ISSN:0025-116X    

DOI:10.1002/macp.1987.021881201

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractAiming to prove that commercial, 50°CPVC consists of a dual population of chains, has led us to the investigation of the thermal stability of low conversion (0,1–2%) PVC. Bulk polymers prepared at very low conversion levels were shown to be different to high conversion material. The former are more syndiotactic, and have a greater tendency to be less thermally stable, unzippering to long polyene sequences (withn>15). These findings are consistent with the idea that initially‐produced PVC is formed by homogeneous polymerisation and that such material is intrinsically different to PVC which is formed at subsequently higher conversions by a heterogeneous r

ISSN:0025-116X    

DOI:10.1002/macp.1987.021881202

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractThe relative reactivities of vinyl monomers in low‐temperature copolymerizations and terpolymerizations with SO2in the presence oftert‐butyl hydroperoxide as initiator were compared. The highest copolymerization rates were found in systems containing an electron‐donor monomer of low resonance stabilization, and the resulting products have an alternating structure. In reactions with monomers of high resonance stabilization and electron‐acceptor properties, mainly homopropagation of the comonomer proceeds. In the terpolymerization of SO2with two electron‐donor monomers, the relative reactivity of monomers depends mainly on their resonance stabilization. In the terpolymerization in systems SO2/electron‐donor monomer/electron‐acceptor monomer the relative reactivity of acceptor monomers decreases with increasing inductive effect in

ISSN:0025-116X    

DOI:10.1002/macp.1987.021881203

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractThe possibility of the preparation of aliphatic polyesters from dicarboxylic acids and diols by polycondensation in the presence of carbodimides under mild conditions was investigated. The following three possible routes were checked: the polycondensation of dicarboxylic acids with diols in the presence of 4‐dimethylaminopyridine, the polycondensation of dicarboxylic acids with diisourea derivatives and the polycondensation in the presence of pyridine andp‐toluenesulfonic acid. The last method was found to give polyesters with high molecular weights in good yields. This carbodiimide method can be utilized in the synthesis of biodegradable and surface active aliphatic polyest

ISSN:0025-116X    

DOI:10.1002/macp.1987.021881204

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractThe modification reaction of dextran with butyl isocyanate using 1,4‐diaza[2.2.2]bicyclooctane as catalyst was studied. The structure of the resulting polymers was determined by means of IR,1H and13C NMR spectroscopy as well as by chemical analysis. A linear dependence of the reaction rate on the concentrations of polymer, butyl isocyanate and catalyst was found. The activation energy was found to be 38,5 kJ/mol (9,2 kcal/mol). The homogeneous hydrolysis in alkaline medium was found to be first order with respect to both the base and the butyl urethane concentrations. The activation energy, obtained for the base catalyzed homogeneous hydrolysis, was 83,7 kJ/mol (20,0 kcal/mol). The heterogeneous hydrolysis of a water insoluble modified dextran (degree of substitution = 0,72) showed that no hydrolysis takes place under the applied condition

ISSN:0025-116X    

DOI:10.1002/macp.1987.021881205

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractThree activep‐aminobenzenesulfonic acid derivatives, 1‐(p‐aminobenzenesulfonyl)imidazole (4a), 1‐(p‐aminobenzenesulfonyloxy)benzotriazole (4b), and 2‐phenyl‐4‐(p‐aminobenzenesulfonyl)‐1,3,4‐oxadiazoline‐5‐thione (4c) were synthesized by reactingp‐isocyanatobenzenesulfonyl chloride (1) with stoichiometrical quantities of water in the presence of dibutyltin didodecanoate and subsequently with imidazole, 1‐hydroxybenzotriazole and 2‐phenyl‐1,3,4‐oxadiazoline‐5‐thione, respectively. The self‐polycondensation of4a–c, leading to poly(p‐benzenesulfonamide) (7), was carried out in solution using polar aprotic solvents,N‐methyl‐2‐pyrrolidone (NMP) and hexamethylphosphoric triamide (HMPA), and acidic media, dimethyl sulfoxide (DMSO) andm‐cresol, with or without an appropriate acid catalyst or acid acceptor under mild conditions. Poly(p‐benzenesulfonamide) having the highest reduced viscosity of 0,14 dl·−1was obtained almost quantitatively from4cby usingm‐cresol as a solvent without any acid catalyst and acid acceptor at 25°C. The polymers are soluble in polar aprotic solvents such as NMP, HMPA and DMSO and in aqueous sodium hydroxide. These poly(p‐benzenesulfonamide)s are less thermally stable than completely aromatic polyamides, because the initial weight‐loss started at 250–350°C. Aminolysis of three benzenesulfonic acid derivatives, 1‐benzenesulfonylimidazole (5a), 1‐benzenesulfonyloxybenzotriazole (5b), and 2‐phenyl‐4‐benzenesulfonyl‐1,3,4‐oxadiazoline‐5‐thione (5c), with the same leaving groups was also carried

ISSN:0025-116X    

DOI:10.1002/macp.1987.021881206

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractOptically active poly(styrene‐co‐methyl methacrylate) and poly(styrene‐co‐methacrylonitrile) were obtained by means of asymmetric copolymerization of 3,4‐cyclohexylidene‐D‐mannitol‐1,2; 5,6‐bis{O‐[(4‐vinylphenyl)boronate]} (1) with methyl methacrylate and methacrylonitrile, respectively, removal of the D‐mannitol template and splitting off boric acid from the resulting copolymers. By polymer analogous reactions, various functional groups were introduced to obtain optically active functional vinyl copolymers. The polymers were characterized by spectral and o

ISSN:0025-116X    

DOI:10.1002/macp.1987.021881207

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractDuring the reaction of 1‐phenoxy‐2,3‐epoxypropane (1) with catalytic amounts of Mg(ClO4)2a variety of reaction products are formed which do not correpond to a normally distributed oligomer range. Essentially, three reaction paths can be distinguished which lead to oligo‐(hydroxyether)s of similar structure (6and8) and to cyclic, isomeric dimers (9and10) of very low reactivity. During the reaction of bifunctional 2,3‐epoxypropyl ethers, cyclic products act as nonreactive diluents decreasing the network density of the final crosslinke

ISSN:0025-116X    

DOI:10.1002/macp.1987.021881208

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractA series of rigid rod polyimides1a–fderived from pyromellitic anhydride (PMDA) and 2,5‐di‐n‐alkoxy‐1,4‐phenylenediamine containing flexible alkoxy side chains with 4 to 16 carbon atoms was prepared by solution polycondensation. As demonstrated by model experiments full conversion to the imide structure is achieved by reaction of PMDA with 2,5‐dialkoxyphenylene diisocyanate, the latter compound being blocked by imidazole. The best solvent for the polycondensation, found in the course of the model reaction, is 1,3‐dimethyl‐2‐oxo‐perhydro‐pyrimidine together with 4‐dimethylaminopyridine as an accelerator. Wide‐angle X‐ray diffractograms showed that all polyimides under consideration here are highly crystalline at room temperature. The occurrence of a sharp reflection at the region of low angles together with its higher orders demonstrates the presence of a layered structure. The layer spacing was found to increase linearly with the length of the alkyl side chains. Polyimides bearing long side chains (n≥ 10) exhibit two broad endotherms in the DSC analysis. As is revealed by wide‐angle X‐ray analysis the first transition is related to a disordering process of the side chains. The second transition leads to a layered high‐temperature phase akin to the modification (B) found in a recent study of a similar rigid p

ISSN:0025-116X    

DOI:10.1002/macp.1987.021881209

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractQuaternization reactions of poly(2‐dimethylaminoethyl methacrylate) using methyl iodide were carried out up to 50% conversion in 18 chemically different solvents. Copolymers which contain moderate hydrophilic 2‐dimethylaminoethoxycarbonyl groups and strongly hydrophilic 2‐trimethylammoniumethoxycarbonyl iodide groups were obtained. Potentiometric titration showed that in some solvents the reaction proceeds by the zip mechanism, i.e. copolymers with a predominantly block structure are formed, while in other solvents the reaction proceeds along the macromolecular chain randomly, that is, giving rise to statistical copol

ISSN:0025-116X    

DOI:10.1002/macp.1987.021881210

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY