摘要:

AbstractRing‐opening polymerization of 2‐methyl‐2‐oxazoline initiated by 2‐(p‐nitrobenzenesulfonato)ethyl methacrylate follows the so‐called “living mechanism”, i.e. fast initiation compared to slow propagation and no chain transfer. Accordingly, methacryl macromonomers having homopolymers, block or random copolymers of 2‐methyl and 2‐pentyl‐2‐oxazoline backbones with narrow molecular weight distribution were obtained. Termination of the propagating species by ion‐exchange or aminolysis with triethylamine yielded hydroxyl and quaternary ammonium terminated

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970101

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe series of poly(oxyethylene)s (poly‐EO) with number‐average degrees of polymerization ranging from ≈6 to ≈80, terminated at both ends with phosphonium ion groups, was prepared by conversion of hydroxyl end groups of α‐hydro‐ω‐hydroxypoly(oxyethylene)s into bromide end groups, followed by the reaction with triphenylphosphine. The functionality of the products (diionic poly‐EO) was determined by elemental analysis,1H and31P NMR as well as mass spectroscopy (MS). The observation of the signals corresponding to individual oligomers in31P NMR spectra of short chain (DPn<10) diionic poly‐EO was explained by intramolecular aggregation of ionic end groups leading to cyclic structures. The measurements of spin lattice relaxation times and the chemical shifts of phosphorus at different conditions (temperature, solvent, concentration) confirmed, that the aggregation of ionic end groups is clearly manifested in the31P NMR spectra

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970102

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractPoly(oxyethylene)s with number‐average degrees of polymerization (DPn) ranging from ≈ 6 to ≈ 80, terminated at both ends with phosphonium ion end groups (diionic poly‐EO), have been prepared and characterized as described in the preceding paper. Viscosities of diionic poly‐EO were measured, both in solution and in bulk. In chloroform solution, at low concentration (<1 g/100 mL), the viscosity of diionic poly‐EO was lower than the viscosity of nonionic (terminated with HO‐groups) poly‐EO of the same DPn. At higher concentrations, the viscosity of diionic poly‐EO exceeded that of nonionic poly‐EO and increased sharply with increasing concentration. At the constant weight concentration of ≈4 g/100 mL, the viscosities of short‐chain diionic poly‐EO were higher and those of longer chain diionic poly‐EO were lower than the viscosities of the nonionic poly‐EO of the same chain lengths. These results were attributed to a predominant intramolecular aggregation of terminal ionic groups at low concentration of ionic groups in solution and predominant intermolecular aggregation at higher concentration of ionic groups. The results of bulk viscosity measurements as well as the results of differential scanning calorimetry measurements of the dependence of the glass transition temperature on the DPnof diionic poly‐EO indicated that in bulk physically cross‐linked networks were formed, due to intermolecular agg

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970103

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe mechanism of thermal degradation of the polymer obtained by polycondensation of ethyleneurea with formaldehyde was studied in detail using several techniques. On heating the polymer undergoes crystallisation at about 175°C. Upon melting (at 355°C) further condensation of ethyleneurea with formaldehyde takes place with elimination of water. This process overlaps with the degradation of the polymer which occurs with formation of a complex mixture of volatile products and of a charred residue. The largest fraction of the volatile products of degradation is a low boiling mixture of ethyleneurea with chain fragments containing NH, N‐methyl and unsaturated structures as end groups. A small fraction of gases such as methane, carbon dioxide, carbon monoxide etc. is also evolved. A degradation mechanism is proposed, which accounts for the experimental re

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970104

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe modification of isotactic poly(propylene) (PP) foils by reactive (O2) and inert (He) gas plasma treatment was studied with relevance to surface structure and thermo‐oxidative stability for different treatment times. The following effects were investigated: change of non‐helical (atactic or amorphous) content in the surface region and formation of vinyl and vinylidene groups by frustrated multiple internal reflection Fourier transform infrared spectroscopy (FMIR‐FTIR), formation of peroxyl redicals by electron spin resonance spectroscopy (ESR) and change of the invariant activation energy of degradation by thermogravimetric analysis (TGA). For the latter a new kinetic evaluation method was used based on a selection of multiple step model to determine the invariant Arrhenius constants, e.g., activation energy and preexponential factor, for the weight loss during thermoxidative degradation of untreated and, for the first time, of plasma‐treated PP. Several thermogravimetric curves under different temperature scanning conditions have been evaluated with different solid state models as well as with a selection of different multiple step reaction pathways. With a limitation to total weight loss of 60% of the mass for an untreated PP and applying a most probable kinetic model consisting of one consecutive and one parallel reaction step, the activation energies were found to be 84.2 ± 1.0 and 73.2 ± 1.0 kJ/mol for the initial and the consecutive reaction and 137.8 ± 3.0 kJ/mol for the parallel reaction. The corresponding data of the plasma‐treated samples are 80 ± 1.0 and 71.0 ± 1.0 kJ/mol for the initial and the consecutive reaction, while the activation energy for the parallel reaction remained almost unchanged. Unexpectedly, we found the He plasma treatment to decrease the activation energies of the first and consecutive reaction nonlinearly and within the first 600 s to a larger extent than O2plasma treatment. Based on this kinetic model, a modified mechanism for the thermo‐oxidative degradation of PP is proposed in terms of elementary degradation reactions and will be discussed with reference to

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970105

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe termination reaction of the cationic polymerization of 2‐phenyl‐ and 2‐nonyl‐2‐oxazolines was examined by reacting the corresponding model oxazolinium salts having tosylate and trifluoromethansulfonate counterions with various nucleophiles. The reaction was monitored by1H NMR spectroscopy. Piperidine and KOH react with the oxazolinium salts very fast and quantitatively. In the case of piperidine, the use of a double molar amount of piperidine is necessary to achieve complete conversion. The addition of piperidine, pyridine, 4‐dimethylaminopyridine and morpholine takes place in position 5 of the oxazolinium ring, whereas water and KOH add in position 2. The rate of the termination reaction depends on the electron density of the nucleophile which can be correlated with the pKavalue. With CF3SO 3−as counterion the addition of nucleophiles in position 5 is distinctly faster, whereas the addition of water in position 2 is much slower than with TsO−as counterion. The ring‐opening of the nonyl oxazolinium ion is slower than that of the phe

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970106

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe polymerization of 5‐vinyl‐2‐norbornene (VNB) with TiCl3‐alkylaluminium catalysts proceeded selectively via the vinyl group; the vinylene group in the bicyclic ring did not participate in the polymerization. The rate of polymerization of VNB was slow due to the steric effect of the side chain, but effects of the types of TiCl3and alkylaluminiums on the polymerization were observed. Hydrogen‐activated TiCl3plus Al(C2H5)3revealed the highest catalytic activities among the catalysts examined. The monomer‐isomerization copolymerization of VNB andtrans‐2‐butene with TiCl3/Al(i‐C4H9)3afforded a copolymer consisting of VNB and 1‐butene units. The rate of copolymerization of VNB and 1‐butene was larger than the monomer‐isomerization copolymerization of VNB andtrans‐2‐butene. Copolymers rich in VNB units were produced easily by monomerisomerization copolymerizati

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970107

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe complexation of poly(4‐vinylpyridine)(1), poly(2‐methyl‐5‐vinylpyridine)(2)and poly(2‐vinylpyridine)(3)with bromides, perchlorates and tetraphenylborates of alkali metals in organic solvents was investigated by means of electroconductivity, viscometry and nuclear magnetic resonance spectroscopy. The influence of the nature of the polymer, the low‐molecular‐weight salt and the solvent, salt and polymer concentration as well as the temperature on complexation was studied. The fraction of cations and that of polymer units bound were determined. The compositions of the complexes were found by means of viscometry. It was established that the mechanism of binding of the polymers with alkali metal salts is of the io

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970108

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWell defined oligo(arylenevinylene)s were prepared by Pd‐catalyzed coupling of dibromoarenes and styrenes. The mixing behavior of these oligo(arylenevinylene)s with polymers is significantly influenced by the structure of the oligo(arylenevinylene)s. Potential consequences for optical properties are discussed. Segmented polymers with arylenevinylene segments in the main chain are presented and discussed in detail. Light‐emitting thermotropic polymers were obtained with modified distyrylbenzene segments in the main chain. These thermotropic light‐emitting polymers show polarized photoluminescence on orientation on rubbed polyimide substrates. Light‐emitting amorphous polymers with high fluorophore concentrations and high glass transition temperatures were obtained by polymers with arylenevinylene segments in the sid

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970109

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractPolyurethanes with saccharide moieties in their repeating units (8and9) were prepared by polyaddition of methyl α‐ and β‐D‐glucofuranosidurono‐6,3‐lactones (3α and3β, respectively) and 1,4:3,6‐dianhydro‐D‐glucitol (4) with hexamethylene diisocyanate (5a) and methyl (S)‐2,6‐diisocyanatohexanoate (5b), which was derived from L‐lysine, inN,N‐dimethylformamide at 25°C using dibutyltin dilaurate as a catalyst. Their properties were compared with those of the polyurethanes (6and7) prepared from D‐glucaro‐1,4:6,3‐dilactone (1) and D‐mannaro‐1,4:6,3‐dilactone (2), respectively, in our previous work. Hydrolyzability of the polyurethanes containing1, 2, or3αunits in buffer solutions was found to be higher than th

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970110

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY